CheckExpressions.fs

// Copyright (c) Microsoft Corporation. All Rights Reserved. See License.txt in the project root for license information.

/// The typechecker. Left-to-right constrained type checking
/// with generalization at appropriate points.
module internal FSharp.Compiler.CheckExpressions

open System
open System.Collections.Generic
open System.Text.RegularExpressions

open Internal.Utilities.Collections
open Internal.Utilities.Library
open Internal.Utilities.Library.Extras
open Internal.Utilities.Library.ResultOrException
open Internal.Utilities.Rational
open FSharp.Compiler
open FSharp.Compiler.AbstractIL.IL
open FSharp.Compiler.AccessibilityLogic
open FSharp.Compiler.AttributeChecking
open FSharp.Compiler.CheckBasics
open FSharp.Compiler.CheckExpressionsOps
open FSharp.Compiler.CheckRecordSyntaxHelpers
open FSharp.Compiler.ConstraintSolver
open FSharp.Compiler.DiagnosticsLogger
open FSharp.Compiler.Features
open FSharp.Compiler.Infos
open FSharp.Compiler.InfoReader
open FSharp.Compiler.CodeAnalysis
open FSharp.Compiler.MethodCalls
open FSharp.Compiler.MethodOverrides
open FSharp.Compiler.NameResolution
open FSharp.Compiler.PatternMatchCompilation
open FSharp.Compiler.Syntax
open FSharp.Compiler.SyntaxTrivia
open FSharp.Compiler.Syntax.PrettyNaming
open FSharp.Compiler.SyntaxTreeOps
open FSharp.Compiler.TcGlobals
open FSharp.Compiler.Text
open FSharp.Compiler.Text.Position
open FSharp.Compiler.Text.Range
open FSharp.Compiler.Xml
open FSharp.Compiler.TypedTree
open FSharp.Compiler.TypedTreeBasics
open FSharp.Compiler.TypedTreeOps
open FSharp.Compiler.TypeHierarchy
open FSharp.Compiler.TypeRelations
open Import

#if !NO_TYPEPROVIDERS
open FSharp.Compiler.TypeProviders
#endif

//-------------------------------------------------------------------------
// Errors.
//-------------------------------------------------------------------------

exception BakedInMemberConstraintName of string * range

exception FunctionExpected of DisplayEnv * TType * range

exception NotAFunction of DisplayEnv * TType * range * range

exception NotAFunctionButIndexer of DisplayEnv * TType * string option * range * range * bool

exception Recursion of DisplayEnv * Ident * TType * TType * range

exception RecursiveUseCheckedAtRuntime of DisplayEnv * ValRef * range

exception LetRecEvaluatedOutOfOrder of DisplayEnv * ValRef * ValRef * range

exception LetRecCheckedAtRuntime of range

exception LetRecUnsound of DisplayEnv * ValRef list * range

exception TyconBadArgs of DisplayEnv * TyconRef * int * range

exception UnionCaseWrongArguments of DisplayEnv * int * int * range

exception UnionCaseWrongNumberOfArgs of DisplayEnv * int * int * range

exception FieldsFromDifferentTypes of DisplayEnv * RecdFieldRef * RecdFieldRef * range

exception FieldGivenTwice of DisplayEnv * RecdFieldRef * range

exception MissingFields of string list * range

exception FunctionValueUnexpected of DisplayEnv * TType * range

exception UnitTypeExpected of DisplayEnv * TType * range

exception UnitTypeExpectedWithEquality of DisplayEnv * TType * range

exception UnitTypeExpectedWithPossibleAssignment of DisplayEnv * TType * bool * string * range

exception UnitTypeExpectedWithPossiblePropertySetter of DisplayEnv * TType * string * string * range

exception UnionPatternsBindDifferentNames of range

exception VarBoundTwice of Ident

exception ValueRestriction of DisplayEnv * InfoReader * Val * Typar * range

exception ValNotMutable of DisplayEnv * ValRef * range

exception ValNotLocal of DisplayEnv * ValRef * range

exception InvalidRuntimeCoercion of DisplayEnv * TType * TType * range

exception IndeterminateRuntimeCoercion of DisplayEnv * TType * TType * range

exception IndeterminateStaticCoercion of DisplayEnv * TType * TType * range

exception RuntimeCoercionSourceSealed of DisplayEnv * TType * range

exception CoercionTargetSealed of DisplayEnv * TType * range

exception UpcastUnnecessary of range

exception TypeTestUnnecessary of range

exception StaticCoercionShouldUseBox of DisplayEnv * TType * TType * range

exception SelfRefObjCtor of bool * range

exception VirtualAugmentationOnNullValuedType of range

exception NonVirtualAugmentationOnNullValuedType of range

exception UseOfAddressOfOperator of range

exception DeprecatedThreadStaticBindingWarning of range

exception IntfImplInIntrinsicAugmentation of range

exception IntfImplInExtrinsicAugmentation of range

exception OverrideInIntrinsicAugmentation of range

exception OverrideInExtrinsicAugmentation of range

exception NonUniqueInferredAbstractSlot of TcGlobals * DisplayEnv * string * MethInfo * MethInfo * range

exception StandardOperatorRedefinitionWarning of string * range

exception InvalidInternalsVisibleToAssemblyName of badName: string * fileName: string option

exception InvalidAttributeTargetForLanguageElement of elementTargets: string array * allowedTargets: string array * range: range

//----------------------------------------------------------------------------------------------
// Helpers for determining if/what specifiers a string has.
// Used to decide if interpolated string can be lowered to a concat call.
// We don't care about single- vs multi-$ strings here, because lexer took care of that already.
//----------------------------------------------------------------------------------------------
[<return: Struct>]
let (|HasFormatSpecifier|_|) (s: string) =
    if
        Regex.IsMatch(
            s,
            // Regex pattern for something like: %[flags][width][.precision][type]
            """
            (^|[^%])                # Start with beginning of string or any char other than '%'
            (%%)*%                  # followed by an odd number of '%' chars
            [+-0 ]{0,3}             # optionally followed by flags
            (\d+)?                  # optionally followed by width
            (\.\d+)?                # optionally followed by .precision
            [bscdiuxXoBeEfFgGMOAat] # and then a char that determines specifier's type
            """,
            RegexOptions.Compiled ||| RegexOptions.IgnorePatternWhitespace)
    then
        ValueSome HasFormatSpecifier
    else
        ValueNone

// Removes trailing "%s" unless it was escaped by another '%' (checks for odd sequence of '%' before final "%s")
let (|WithTrailingStringSpecifierRemoved|) (s: string) =
    if s.EndsWith "%s" then
        let i = s.AsSpan(0, s.Length - 2).LastIndexOfAnyExcept '%'
        let diff = s.Length - 2 - i
        if diff &&& 1 <> 0 then
            s[..s.Length - 3]
        else
            s
    else
        s

/// Compute the available access rights from a particular location in code
let ComputeAccessRights eAccessPath eInternalsVisibleCompPaths eFamilyType =
    AccessibleFrom (eAccessPath :: eInternalsVisibleCompPaths, eFamilyType)

//-------------------------------------------------------------------------
// Helpers related to determining if we're in a constructor and/or a class
// that may be able to access "protected" members.
//-------------------------------------------------------------------------

let EnterFamilyRegion tcref env =
    let eFamilyType = Some tcref
    { env with
        eAccessRights = ComputeAccessRights env.eAccessPath env.eInternalsVisibleCompPaths eFamilyType // update this computed field
        eFamilyType = eFamilyType }

let ExitFamilyRegion env =
    let eFamilyType = None
    match env.eFamilyType with
    | None -> env // optimization to avoid reallocation
    | _ ->
        { env with
            eAccessRights = ComputeAccessRights env.eAccessPath env.eInternalsVisibleCompPaths eFamilyType // update this computed field
            eFamilyType = eFamilyType }

let AreWithinCtorShape env = match env.eCtorInfo with None -> false | Some ctorInfo -> ctorInfo.ctorShapeCounter > 0

let GetCtorShapeCounter env = match env.eCtorInfo with None -> 0 | Some ctorInfo -> ctorInfo.ctorShapeCounter

let GetRecdInfo env = match env.eCtorInfo with None -> RecdExpr | Some ctorInfo -> if ctorInfo.ctorShapeCounter = 1 then RecdExprIsObjInit else RecdExpr

let AdjustCtorShapeCounter f env = {env with eCtorInfo = Option.map (fun ctorInfo -> { ctorInfo with ctorShapeCounter = f ctorInfo.ctorShapeCounter }) env.eCtorInfo }

let ExitCtorShapeRegion env = AdjustCtorShapeCounter (fun _ -> 0) env

/// Add a type to the TcEnv, i.e. register it as ungeneralizable.
let addFreeItemOfTy ty eUngeneralizableItems =
    let fvs = freeInType CollectAllNoCaching ty
    if isEmptyFreeTyvars fvs then eUngeneralizableItems
    else UngeneralizableItem(fun () -> freeInType CollectAllNoCaching ty) :: eUngeneralizableItems

/// Add the contents of a module type to the TcEnv, i.e. register the contents as ungeneralizable.
/// Add a module type to the TcEnv, i.e. register it as ungeneralizable.
let addFreeItemOfModuleTy mtyp eUngeneralizableItems =
    let fvs = freeInModuleTy mtyp
    if isEmptyFreeTyvars fvs then eUngeneralizableItems
    else UngeneralizableItem(fun () -> freeInModuleTy mtyp) :: eUngeneralizableItems

/// Add a table of values to the name resolution environment.
let AddValMapToNameEnv g vs nenv =
    NameMap.foldBackRange (fun v nenv -> AddValRefToNameEnv g nenv (mkLocalValRef v)) vs nenv

/// Add a list of values to the name resolution environment.
let AddValListToNameEnv g vs nenv =
    List.foldBack (fun v nenv -> AddValRefToNameEnv g nenv (mkLocalValRef v)) vs nenv

/// Add a local value to TcEnv
let AddLocalValPrimitive g (v: Val) env =
    { env with
        eNameResEnv = AddValRefToNameEnv g env.eNameResEnv (mkLocalValRef v)
        eUngeneralizableItems = addFreeItemOfTy v.Type env.eUngeneralizableItems }

/// Add a table of local values to TcEnv
let AddLocalValMap g tcSink scopem (vals: Val NameMap) env =
    if vals.IsEmpty then
        env
    else
        let env =
            { env with
                eNameResEnv = AddValMapToNameEnv g vals env.eNameResEnv
                eUngeneralizableItems = NameMap.foldBackRange (typeOfVal >> addFreeItemOfTy) vals env.eUngeneralizableItems }
        CallEnvSink tcSink (scopem, env.NameEnv, env.AccessRights)
        env

/// Add a list of local values to TcEnv and report them to the sink
let AddLocalVals g tcSink scopem (vals: Val list) env =
    if isNil vals then
        env
    else
        let env =
            { env with
                eNameResEnv = AddValListToNameEnv g vals env.eNameResEnv
                eUngeneralizableItems = List.foldBack (typeOfVal >> addFreeItemOfTy) vals env.eUngeneralizableItems }
        CallEnvSink tcSink (scopem, env.NameEnv, env.AccessRights)
        env

/// Add a local value to TcEnv and report it to the sink
let AddLocalVal g tcSink scopem v env =
    let env = { env with
                    eNameResEnv = AddValRefToNameEnv g env.eNameResEnv (mkLocalValRef v)
                    eUngeneralizableItems = addFreeItemOfTy v.Type env.eUngeneralizableItems }
    CallEnvSink tcSink (scopem, env.NameEnv, env.eAccessRights)
    env

/// Add a set of explicitly declared type parameters as being available in the TcEnv
let AddDeclaredTypars check typars env =
    if isNil typars then
        env
    else
        { env with
            eUngeneralizableItems = List.foldBack (mkTyparTy >> addFreeItemOfTy) typars env.eUngeneralizableItems
            eNameResEnv = AddDeclaredTyparsToNameEnv check env.eNameResEnv typars}

/// Environment of implicitly scoped type parameters, e.g. 'a in "(x: 'a)"

let emptyUnscopedTyparEnv: UnscopedTyparEnv = UnscopedTyparEnv Map.empty

let AddUnscopedTypar name typar (UnscopedTyparEnv tab) = UnscopedTyparEnv (Map.add name typar tab)

let TryFindUnscopedTypar name (UnscopedTyparEnv tab) = Map.tryFind name tab

let HideUnscopedTypars typars (UnscopedTyparEnv tab) =
    UnscopedTyparEnv (List.fold (fun acc (tp: Typar) -> Map.remove tp.Name acc) tab typars)

type OverridesOK =
    | OverridesOK
    | WarnOnOverrides
    | ErrorOnOverrides

let permitInferTypars = ExplicitTyparInfo ([], [], true)
let dontInferTypars = ExplicitTyparInfo ([], [], false)

let noArgOrRetAttribs = ArgAndRetAttribs ([], [])

[<RequireQualifiedAccess>]
type LiteralArgumentType =
    /// Literal defined at call site
    ///
    /// call "literal"
    | Inline

    /// F# literal value or IL constant
    ///
    /// let [<Literal>] lit = "x"
    /// call lit
    | StaticField

/// A flag to represent the sort of bindings are we processing.
/// Processing "declaration" and "class" bindings that make up a module (such as "let x = 1 let y = 2")
/// shares the same code paths (e.g. TcLetBinding and TcLetrecBindings) as processing expression bindings (such as "let x = 1 in ...")
/// Member bindings also use this path.
//
// However there are differences in how different bindings get processed,
// i.e. module bindings get published to the implicitly accumulated module type, but expression 'let' bindings don't.
type DeclKind =
    | ModuleOrMemberBinding

    /// Extensions to a type within the same module or namespace fragment
    | IntrinsicExtensionBinding

    /// Extensions to a type not within the same module or namespace fragment
    | ExtrinsicExtensionBinding

    | ClassLetBinding of isStatic: bool

    | ObjectExpressionOverrideBinding

    | ExpressionBinding

    member x.IsModuleOrMemberOrExtensionBinding =
        match x with
        | ModuleOrMemberBinding -> true
        | IntrinsicExtensionBinding -> true
        | ExtrinsicExtensionBinding -> true
        | ClassLetBinding _ -> false
        | ObjectExpressionOverrideBinding -> false
        | ExpressionBinding -> false

    member x.MustHaveValReprInfo = x.IsModuleOrMemberOrExtensionBinding

    member x.CanBeDllImport =
        match x with
        | ModuleOrMemberBinding -> true
        | IntrinsicExtensionBinding -> true
        | ExtrinsicExtensionBinding -> true
        | ClassLetBinding _ -> true
        | ObjectExpressionOverrideBinding -> false
        | ExpressionBinding -> false

    member x.IsAccessModifierPermitted = x.IsModuleOrMemberOrExtensionBinding

    member x.AllowedAttribTargets (memberFlagsOpt: SynMemberFlags option) =
        match x with
        | ModuleOrMemberBinding | ObjectExpressionOverrideBinding ->
            match memberFlagsOpt with
            | Some flags when flags.MemberKind = SynMemberKind.Constructor -> AttributeTargets.Constructor
            | Some flags when flags.MemberKind = SynMemberKind.PropertyGetSet -> AttributeTargets.Event ||| AttributeTargets.Property
            | Some flags when flags.MemberKind = SynMemberKind.PropertyGet -> AttributeTargets.Event ||| AttributeTargets.Property ||| AttributeTargets.ReturnValue
            | Some flags when flags.MemberKind = SynMemberKind.PropertySet -> AttributeTargets.Property
            | Some _ -> AttributeTargets.Method ||| AttributeTargets.ReturnValue
            | None -> AttributeTargets.Field ||| AttributeTargets.Method ||| AttributeTargets.Property ||| AttributeTargets.ReturnValue
        | IntrinsicExtensionBinding -> AttributeTargets.Method ||| AttributeTargets.Property ||| AttributeTargets.ReturnValue
        | ExtrinsicExtensionBinding -> AttributeTargets.Method ||| AttributeTargets.Property ||| AttributeTargets.ReturnValue
        | ClassLetBinding _ -> AttributeTargets.Field ||| AttributeTargets.Method ||| AttributeTargets.ReturnValue
        | ExpressionBinding -> enum 0 // indicates attributes not allowed on expression 'let' bindings

    // Note: now always true
    member x.CanGeneralizeConstrainedTypars =
        match x with
        | ModuleOrMemberBinding -> true
        | IntrinsicExtensionBinding -> true
        | ExtrinsicExtensionBinding -> true
        | ClassLetBinding _ -> true
        | ObjectExpressionOverrideBinding -> true
        | ExpressionBinding -> true

    member x.IsConvertToLinearBindings =
        match x with
        | ModuleOrMemberBinding -> true
        | IntrinsicExtensionBinding -> true
        | ExtrinsicExtensionBinding -> true
        | ClassLetBinding _ -> true
        | ObjectExpressionOverrideBinding -> true
        | ExpressionBinding -> false

    member x.CanOverrideOrImplement =
        match x with
        | ModuleOrMemberBinding -> OverridesOK
        | IntrinsicExtensionBinding -> WarnOnOverrides
        | ExtrinsicExtensionBinding -> ErrorOnOverrides
        | ClassLetBinding _ -> ErrorOnOverrides
        | ObjectExpressionOverrideBinding -> OverridesOK
        | ExpressionBinding -> ErrorOnOverrides

/// The results of applying let-style generalization after type checking.
// We should make this a record for cleaner code
type PrelimVal2 =
    PrelimVal2 of
        id: Ident *
        prelimType: GeneralizedType *
        prelimValReprInfo: PrelimValReprInfo option *
        memberInfoOpt: PrelimMemberInfo option *
        isMutable: bool *
        inlineFlag: ValInline *
        baseOrThisInfo: ValBaseOrThisInfo *
        argAttribs: ArgAndRetAttribs *
        visibility: SynAccess option *
        isCompGen: bool *
        hasDeclaredTypars: bool

/// The results of applying arity inference to PrelimVal2
type ValScheme =
    | ValScheme of
        id: Ident *
        typeScheme: GeneralizedType *
        valReprInfo: ValReprInfo option *
        valReprInfoForDisplay: ValReprInfo option *
        memberInfo: PrelimMemberInfo option *
        isMutable: bool *
        inlineInfo: ValInline *
        baseOrThisInfo: ValBaseOrThisInfo *
        visibility: SynAccess option *
        isCompGen: bool *
        isIncrClass: bool *
        isTyFunc: bool *
        hasDeclaredTypars: bool

    member x.GeneralizedTypars = let (ValScheme(typeScheme=GeneralizedType(gtps, _))) = x in gtps

    member x.GeneralizedType = let (ValScheme(typeScheme=ts)) = x in ts

    member x.ValReprInfo = let (ValScheme(valReprInfo=valReprInfo)) = x in valReprInfo

/// The first phase of checking and elaborating a binding leaves a goop of information.
/// This is a bit of a mess: much of this information is also carried on a per-value basis by the
/// "NameMap<PrelimVal1>".
type CheckedBindingInfo =
    | CheckedBindingInfo of
       inlineFlag: ValInline *
       valAttribs: Attribs *
       xmlDoc: XmlDoc *
       tcPatPhase2: (TcPatPhase2Input -> Pattern) *
       explicitTyparInfo: ExplicitTyparInfo *
       nameToPrelimValSchemeMap: NameMap<PrelimVal1> *
       rhsExprChecked: Expr *
       argAndRetAttribs: ArgAndRetAttribs *
       overallPatTy: TType *
       mBinding: range *
       debugPoint: DebugPointAtBinding *
       isCompilerGenerated: bool *
       literalValue: Const option *
       isFixed: bool

    member x.Expr = let (CheckedBindingInfo(rhsExprChecked=expr)) = x in expr

    member x.DebugPoint = let (CheckedBindingInfo(debugPoint=debugPoint)) = x in debugPoint

type cenv = TcFileState

// Extract nullness-specific context, filtering out all other context kinds to avoid side effects on non-nullness diagnostics.
let nullnessContextOnly (env: TcEnv) =
    match env.eContextInfo with
    | ContextInfo.NullnessCheckOfCapturedArg _ -> env.eContextInfo
    | _ -> ContextInfo.NoContext

// If the overall type admits subsumption or type directed conversion, and the original unify would have failed,
// then allow subsumption or type directed conversion.
//
// Any call to UnifyOverallType MUST have a matching call to TcAdjustExprForTypeDirectedConversions
// to actually build the expression for any conversion applied.
let UnifyOverallType (cenv: cenv) (env: TcEnv) m overallTy actualTy =
    let g = cenv.g
    match overallTy with
    | MustConvertTo(isMethodArg, reqdTy) when g.langVersion.SupportsFeature LanguageFeature.AdditionalTypeDirectedConversions ->
        let actualTy = tryNormalizeMeasureInType g actualTy
        let reqdTy = tryNormalizeMeasureInType g reqdTy
        let reqTyForUnification = reqTyForArgumentNullnessInference g actualTy reqdTy
        let nullnessContext = nullnessContextOnly env
        if AddCxTypeEqualsTypeUndoIfFailedWithContext nullnessContext env.DisplayEnv cenv.css m reqTyForUnification actualTy then
            ()
        else
            // try adhoc type-directed conversions
            let reqdTy2, usesTDC, eqn = AdjustRequiredTypeForTypeDirectedConversions cenv.infoReader env.eAccessRights isMethodArg false reqdTy actualTy m

            match eqn with
            | Some (ty1, ty2, msg) ->
                UnifyTypes cenv env m ty1 ty2
                msg env.DisplayEnv
            | None -> ()

            match usesTDC with
            | TypeDirectedConversionUsed.Yes(warn, _, _) -> warning(warn env.DisplayEnv)
            | TypeDirectedConversionUsed.No -> ()

            if AddCxTypeMustSubsumeTypeUndoIfFailed env.DisplayEnv cenv.css m reqdTy2 actualTy then
                let reqdTyText, actualTyText, _cxs = NicePrint.minimalStringsOfTwoTypes env.DisplayEnv reqdTy actualTy
                warning (Error(FSComp.SR.tcSubsumptionImplicitConversionUsed(actualTyText, reqdTyText), m))
            else
                // report the error
                UnifyTypes cenv env m reqdTy actualTy
    | _ ->
        UnifyTypes cenv env m overallTy.Commit actualTy

let UnifyOverallTypeAndRecover (cenv: cenv) env m overallTy actualTy =
    try
        UnifyOverallType cenv env m overallTy actualTy
    with RecoverableException exn ->
        errorRecovery exn m

/// Make an environment suitable for a module or namespace. Does not create a new accumulator but uses one we already have/
let MakeInnerEnvWithAcc addOpenToNameEnv env nm moduleTyAcc moduleKind =
    let path = env.ePath @ [nm]
    let cpath = env.eCompPath.NestedCompPath nm.idText moduleKind
    let nenv =
        if addOpenToNameEnv then
            { env.NameEnv with eDisplayEnv = env.DisplayEnv.AddOpenPath (pathOfLid path) }
        else
            env.NameEnv
    let ad = ComputeAccessRights cpath env.eInternalsVisibleCompPaths env.eFamilyType
    { env with
        ePath = path
        eCompPath = cpath
        eAccessPath = cpath
        eAccessRights = ad
        eNameResEnv = nenv
        eModuleOrNamespaceTypeAccumulator = moduleTyAcc }

/// Make an environment suitable for a module or namespace, creating a new accumulator.
let MakeInnerEnv addOpenToNameEnv env nm moduleKind =
    // Note: here we allocate a new module type accumulator
    let moduleTyAcc = ref (Construct.NewEmptyModuleOrNamespaceType moduleKind)
    MakeInnerEnvWithAcc addOpenToNameEnv env nm moduleTyAcc moduleKind, moduleTyAcc

/// Make an environment suitable for processing inside a type definition
let MakeInnerEnvForTyconRef env tcref isExtrinsicExtension =
    if isExtrinsicExtension then
        // Extension members don't get access to protected stuff
        env
    else
        // Regular members get access to protected stuff
        let env = EnterFamilyRegion tcref env
        // Note: assumes no nesting
        let eAccessPath = env.eCompPath.NestedCompPath tcref.LogicalName ModuleOrType
        { env with
             eAccessRights = ComputeAccessRights eAccessPath env.eInternalsVisibleCompPaths env.eFamilyType // update this computed field
             eAccessPath = eAccessPath }

/// Make an environment suitable for processing inside a member definition
let MakeInnerEnvForMember env (v: Val) =
    match v.MemberInfo with
    | None -> env
    | Some _ -> MakeInnerEnvForTyconRef env v.MemberApparentEntity v.IsExtensionMember

/// Get the current accumulator for the namespace/module we're in
let GetCurrAccumulatedModuleOrNamespaceType env =
    env.eModuleOrNamespaceTypeAccumulator.Value

/// Set the current accumulator for the namespace/module we're in, updating the inferred contents
let SetCurrAccumulatedModuleOrNamespaceType env x =
    env.eModuleOrNamespaceTypeAccumulator.Value <- x

/// Set up the initial environment accounting for the enclosing "namespace X.Y.Z" definition
let LocateEnv isModule ccu env enclosingNamespacePath =
    let cpath = compPathOfCcu ccu
    let env =
        {env with
            ePath = []
            eCompPath = cpath
            eAccessPath = cpath
            // update this computed field
            eAccessRights = ComputeAccessRights cpath env.eInternalsVisibleCompPaths env.eFamilyType }
    let isExplicitNamespace = not isModule
    let env = List.fold (fun env id -> MakeInnerEnv false env id (Namespace isExplicitNamespace) |> fst) env enclosingNamespacePath
    let env = { env with eNameResEnv = { env.NameEnv with eDisplayEnv = env.DisplayEnv.AddOpenPath (pathOfLid env.ePath) } }
    env

//-------------------------------------------------------------------------
// Helpers for unification
//-------------------------------------------------------------------------

/// When the context is matching the oldRange then this function shrinks it to newRange.
/// This can be used to change context over no-op expressions like parens.
let ShrinkContext env oldRange newRange =
    match env.eContextInfo with
    | ContextInfo.NoContext
    | ContextInfo.RecordFields
    | ContextInfo.TupleInRecordFields
    | ContextInfo.ReturnInComputationExpression
    | ContextInfo.YieldInComputationExpression
    | ContextInfo.RuntimeTypeTest _
    | ContextInfo.DowncastUsedInsteadOfUpcast _
    | ContextInfo.SequenceExpression _
    | ContextInfo.NullnessCheckOfCapturedArg _ ->
        env
    | ContextInfo.CollectionElement (b,m) ->
        if not (equals m oldRange) then env else
        { env with eContextInfo = ContextInfo.CollectionElement(b,newRange) }
    | ContextInfo.FollowingPatternMatchClause m ->
        if not (equals m oldRange) then env else
        { env with eContextInfo = ContextInfo.FollowingPatternMatchClause newRange }
    | ContextInfo.PatternMatchGuard m ->
        if not (equals m oldRange) then env else
        { env with eContextInfo = ContextInfo.PatternMatchGuard newRange }
    | ContextInfo.IfExpression m ->
        if not (equals m oldRange) then env else
        { env with eContextInfo = ContextInfo.IfExpression newRange }
    | ContextInfo.OmittedElseBranch m ->
        if not (equals m oldRange) then env else
        { env with eContextInfo = ContextInfo.OmittedElseBranch newRange }
    | ContextInfo.ElseBranchResult m ->
        if not (equals m oldRange) then env else
        { env with eContextInfo = ContextInfo.ElseBranchResult newRange }

/// Allow the inference of structness from the known type, e.g.
///    let (x: struct (int * int)) = (3,4)
let UnifyTupleTypeAndInferCharacteristics contextInfo (cenv: cenv) denv m knownTy isExplicitStruct ps =
    let g = cenv.g
    let tupInfo, ptys =
        if isAnyTupleTy g knownTy then
            let tupInfo, ptys = destAnyTupleTy g knownTy
            let tupInfo = (if isExplicitStruct then tupInfoStruct else tupInfo)
            let ptys =
                if List.length ps = List.length ptys then ptys
                else NewInferenceTypes g ps
            tupInfo, ptys
        else
            mkTupInfo isExplicitStruct, NewInferenceTypes g ps

    let contextInfo =
        match contextInfo with
        | ContextInfo.RecordFields -> ContextInfo.TupleInRecordFields
        | _ -> contextInfo

    let ty2 = TType_tuple (tupInfo, ptys)
    AddCxTypeEqualsType contextInfo denv cenv.css m knownTy ty2
    tupInfo, ptys

// Allow inference of assembly-affinity and structness from the known type - even from another assembly. This is a rule of
// the language design and allows effective cross-assembly use of anonymous types in some limited circumstances.
let UnifyAnonRecdTypeAndInferCharacteristics contextInfo (cenv: cenv) denv m ty isExplicitStruct unsortedNames =
    let g = cenv.g
    let anonInfo, ptys =
        match tryDestAnonRecdTy g ty with
        | ValueSome (anonInfo, ptys) ->
            // Note: use the assembly of the known type, not the current assembly
            // Note: use the structness of the known type, unless explicit
            // Note: use the names of our type, since they are always explicit
            let tupInfo = (if isExplicitStruct then tupInfoStruct else anonInfo.TupInfo)
            let anonInfo = AnonRecdTypeInfo.Create(anonInfo.Assembly, tupInfo, unsortedNames)
            let ptys =
                if List.length ptys = Array.length unsortedNames then ptys
                else NewInferenceTypes g (Array.toList anonInfo.SortedNames)
            anonInfo, ptys
        | ValueNone ->
            // Note: no known anonymous record type - use our assembly
            let anonInfo = AnonRecdTypeInfo.Create(cenv.thisCcu, mkTupInfo isExplicitStruct, unsortedNames)
            anonInfo, NewInferenceTypes g (Array.toList anonInfo.SortedNames)
    let ty2 = TType_anon (anonInfo, ptys)
    AddCxTypeEqualsType contextInfo denv cenv.css m ty ty2
    anonInfo, ptys


/// Optimized unification routine that avoids creating new inference
/// variables unnecessarily
let UnifyFunctionTypeUndoIfFailed (cenv: cenv) denv m ty =
    let g = cenv.g
    match tryDestFunTy g ty with
    | ValueNone ->
        let domainTy = NewInferenceType g
        let resultTy = NewInferenceType g
        if AddCxTypeEqualsTypeUndoIfFailed denv cenv.css m ty (mkFunTy g domainTy resultTy) then
            ValueSome(domainTy, resultTy)
        else
            ValueNone
    | r -> r

/// Optimized unification routine that avoids creating new inference
/// variables unnecessarily
let UnifyFunctionType extraInfo (cenv: cenv) denv mFunExpr ty =
    match UnifyFunctionTypeUndoIfFailed cenv denv mFunExpr ty with
    | ValueSome res -> res
    | ValueNone ->
        match extraInfo with
        | Some argm -> error (NotAFunction(denv, ty, mFunExpr, argm))
        | None -> error (FunctionExpected(denv, ty, mFunExpr))

let UnifyFunctionTypeAndRecover extraInfo (cenv: cenv) denv mFunExpr ty =
    match UnifyFunctionTypeUndoIfFailed cenv denv mFunExpr ty with
    | ValueSome res -> res
    | ValueNone ->
        match extraInfo with
        | Some argm -> errorR (NotAFunction(denv, ty, mFunExpr, argm))
        | None -> errorR (FunctionExpected(denv, ty, mFunExpr))

        let g = cenv.g
        let domainTy = NewInferenceType g
        let resultTy = NewInferenceType g
        domainTy, resultTy

/// Extract the localized warning message from a WarnOnWithoutNullArgumentAttribute, if present.
let tryGetWarnOnWithoutNullMessage (g: TcGlobals) (attribs: Attrib list) =
    match attribs with
    | ValAttrib g WellKnownValAttributes.WarnOnWithoutNullArgumentAttribute (Attrib(_, _, [ AttribStringArg b ], namedArgs, _, _, _)) ->
        match namedArgs with
        | ExtractAttribNamedArg "Localize" (AttribBoolArg true) -> FSComp.SR.GetTextOpt(b)
        | _ -> Some b
    | _ -> Option.None

let ReportImplicitlyIgnoredBoolExpression denv m ty expr =
    let checkExpr m expr =
        match stripDebugPoints expr with
        | Expr.App (Expr.Val (vref, _, _), _, _, exprs, _) when vref.LogicalName = opNameEquals ->
            match List.map stripDebugPoints exprs with
            | Expr.App (Expr.Val (propRef, _, _), _, _, Expr.Val (vref, _, _) :: _, _) :: _ ->
                if propRef.IsPropertyGetterMethod then
                    let propertyName = propRef.PropertyName
                    let hasCorrespondingSetter =
                        match propRef.TryDeclaringEntity with
                        | Parent entityRef ->
                            entityRef.MembersOfFSharpTyconSorted
                            |> List.exists (fun vref -> vref.IsPropertySetterMethod && vref.PropertyName = propertyName)
                        | _ -> false

                    if hasCorrespondingSetter then
                        UnitTypeExpectedWithPossiblePropertySetter (denv, ty, vref.DisplayName, propertyName, m)
                    else
                        UnitTypeExpectedWithEquality (denv, ty, m)
                else
                    UnitTypeExpectedWithEquality (denv, ty, m)
            | Expr.Op (TOp.ILCall (_, _, _, _, _, _, _, ilMethRef, _, _, _), _, Expr.Val (vref, _, _) :: _, _) :: _ when ilMethRef.Name.StartsWithOrdinal("get_") ->
                UnitTypeExpectedWithPossiblePropertySetter (denv, ty, vref.DisplayName, ChopPropertyName(ilMethRef.Name), m)
            | Expr.Val (vref, _, _) :: _ ->
                UnitTypeExpectedWithPossibleAssignment (denv, ty, vref.IsMutable, vref.DisplayName, m)
            | _ -> UnitTypeExpectedWithEquality (denv, ty, m)
        | _ -> UnitTypeExpected (denv, ty, m)

    match stripDebugPoints expr with
    | Expr.Let (_, DebugPoints(Expr.Sequential (_, inner, _, _), _), _, _)
    | Expr.Sequential (_, inner, _, _) ->
        let rec extractNext expr =
            match stripDebugPoints expr with
            | Expr.Sequential (_, inner, _, _) -> extractNext inner
            | _ -> checkExpr expr.Range expr
        extractNext inner
    | expr -> checkExpr m expr

let UnifyUnitType (cenv: cenv) (env: TcEnv) m ty expr =
    let g = cenv.g
    let denv = env.DisplayEnv
    if AddCxTypeEqualsTypeUndoIfFailed denv cenv.css m ty g.unit_ty then
        true
    else
        let domainTy = NewInferenceType g
        let resultTy = NewInferenceType g
        if AddCxTypeEqualsTypeUndoIfFailed denv cenv.css m ty (mkFunTy g domainTy resultTy) then
            warning (FunctionValueUnexpected(denv, ty, m))
        else
            let reportImplicitlyDiscardError() =
                if typeEquiv g g.bool_ty ty then
                    warning (ReportImplicitlyIgnoredBoolExpression denv m ty expr)
                else
                    warning (UnitTypeExpected (denv, ty, m))

            match env.eContextInfo with
            | ContextInfo.SequenceExpression seqTy ->
                let liftedTy = mkSeqTy g ty
                if typeEquiv g seqTy liftedTy then
                    warning (Error (FSComp.SR.implicitlyDiscardedInSequenceExpression(NicePrint.prettyStringOfTy denv ty), m))
                else
                    if isListTy g ty || isArrayTy g ty || typeEquiv g seqTy ty then
                        warning (Error (FSComp.SR.implicitlyDiscardedSequenceInSequenceExpression(NicePrint.prettyStringOfTy denv ty), m))
                    else
                        reportImplicitlyDiscardError()
            | _ ->
                reportImplicitlyDiscardError()

        false

let TryUnifyUnitTypeWithoutWarning (cenv: cenv) (env:TcEnv) m ty =
    let g = cenv.g
    let denv = env.DisplayEnv
    AddCxTypeEqualsTypeUndoIfFailedOrWarnings denv cenv.css m ty g.unit_ty

// Logically extends System.AttributeTargets
module AttributeTargets =
    let FieldDecl = AttributeTargets.Field ||| AttributeTargets.Property
    let FieldDeclRestricted = AttributeTargets.Field
    let UnionCaseDecl = AttributeTargets.Method ||| AttributeTargets.Property
    let TyconDecl = AttributeTargets.Class ||| AttributeTargets.Interface ||| AttributeTargets.Delegate ||| AttributeTargets.Struct ||| AttributeTargets.Enum
    let ExnDecl = AttributeTargets.Class
    let ModuleDecl = AttributeTargets.Class
    let Top = AttributeTargets.Assembly ||| AttributeTargets.Module ||| AttributeTargets.Method

let ForNewConstructors tcSink (env: TcEnv) mObjTy methodName meths =
    let origItem = Item.CtorGroup(methodName, meths)
    let callSink (item, minst) = CallMethodGroupNameResolutionSink tcSink (mObjTy, env.NameEnv, item, origItem, minst, ItemOccurrence.Use, env.AccessRights)
    let sendToSink minst refinedMeths = 
        callSink (Item.CtorGroup(methodName, refinedMeths), minst)
    match meths with
    | [] ->
        AfterResolution.DoNothing
    | [_] ->
        sendToSink emptyTyparInst meths
        AfterResolution.DoNothing
    | _ ->
        AfterResolution.RecordResolution (None, (fun tpinst -> callSink (origItem, tpinst)), (fun (minfo, _, minst) -> sendToSink minst [minfo]), (fun () -> callSink (origItem, emptyTyparInst)))

/// Typecheck rational constant terms in units-of-measure exponents
let rec TcSynRationalConst c =
  match c with
  | SynRationalConst.Integer(value = i) -> intToRational i
  | SynRationalConst.Negate(rationalConst = c2) -> NegRational (TcSynRationalConst c2)
  | SynRationalConst.Rational(numerator = p; denominator = q) -> DivRational (intToRational p) (intToRational q)
  | SynRationalConst.Paren(rationalConst = c) -> TcSynRationalConst c

/// Typecheck constant terms in expressions and patterns
let TcConst (cenv: cenv) (overallTy: TType) m env synConst =
    let g = cenv.g
    let rec tcMeasure ms =
        match ms with
        | SynMeasure.One m -> Measure.One m
        | SynMeasure.Named(tc, m) ->
            let ad = env.eAccessRights
            let _, tcref, _ = ForceRaise(ResolveTypeLongIdent cenv.tcSink cenv.nameResolver ItemOccurrence.Use OpenQualified env.eNameResEnv ad tc TypeNameResolutionStaticArgsInfo.DefiniteEmpty PermitDirectReferenceToGeneratedType.No)
            match tcref.TypeOrMeasureKind with
            | TyparKind.Type -> error(Error(FSComp.SR.tcExpectedUnitOfMeasureNotType(), m))
            | TyparKind.Measure -> Measure.Const(tcref, ms.Range)

        | SynMeasure.Power(measure = ms; power = exponent) -> Measure.RationalPower (tcMeasure ms, TcSynRationalConst exponent)
        | SynMeasure.Product(measure1 = ms1; measure2 = ms2; range= m) ->
            Measure.Prod(tcMeasure ms1, tcMeasure ms2, m)
        | SynMeasure.Divide(ms1, _, (SynMeasure.Seq (_ :: _ :: _, _) as ms2), m) ->
            warning(Error(FSComp.SR.tcImplicitMeasureFollowingSlash(), m))
            let factor1 = ms1 |> Option.defaultValue (SynMeasure.One range0)
            Measure.Prod(tcMeasure factor1, Measure.Inv (tcMeasure ms2), ms.Range)
        | SynMeasure.Divide(measure1 = ms1; measure2 = ms2) ->
            let factor1 = ms1 |> Option.defaultValue (SynMeasure.One range0)
            Measure.Prod(tcMeasure factor1, Measure.Inv (tcMeasure ms2), ms.Range)
        | SynMeasure.Seq(mss, _) -> ProdMeasures (List.map tcMeasure mss)
        | SynMeasure.Anon _ -> error(Error(FSComp.SR.tcUnexpectedMeasureAnon(), m))
        | SynMeasure.Var(range= m) -> error(Error(FSComp.SR.tcNonZeroConstantCannotHaveGenericUnit(), m))
        | SynMeasure.Paren(measure= measure) -> tcMeasure measure

    let unif expectedTy = UnifyTypes cenv env m overallTy expectedTy

    let unifyMeasureArg iszero tcr =
        let measureTy =
            match synConst with
            | SynConst.Measure(synMeasure = SynMeasure.Anon _) ->
              (mkWoNullAppTy tcr [TType_measure (Measure.Var (NewAnonTypar (TyparKind.Measure, m, TyparRigidity.Anon, (if iszero then TyparStaticReq.None else TyparStaticReq.HeadType), TyparDynamicReq.No)))])

            | SynConst.Measure(synMeasure = ms) -> mkWoNullAppTy tcr [TType_measure (tcMeasure ms)]
            | _ -> mkWoNullAppTy tcr [TType_measure(Measure.One m)]
        unif measureTy

    let expandedMeasurablesEnabled =
        g.langVersion.SupportsFeature LanguageFeature.ExpandedMeasurables

    match synConst with
    | SynConst.Unit ->
        unif g.unit_ty
        Const.Unit
    | SynConst.Bool i ->
        unif g.bool_ty
        Const.Bool i
    | SynConst.Single f ->
        unif g.float32_ty
        Const.Single f
    | SynConst.Double f ->
        unif g.float_ty
        Const.Double f
    | SynConst.Decimal f ->
        unif (mkWoNullAppTy g.decimal_tcr [])
        Const.Decimal f
    | SynConst.SByte i ->
        unif g.sbyte_ty
        Const.SByte i
    | SynConst.Int16 i ->
        unif g.int16_ty
        Const.Int16 i
    | SynConst.Int32 i ->
        unif g.int_ty
        Const.Int32 i
    | SynConst.Int64 i ->
        unif g.int64_ty
        Const.Int64 i
    | SynConst.IntPtr i ->
        unif g.nativeint_ty
        Const.IntPtr i
    | SynConst.Byte i ->
        unif g.byte_ty
        Const.Byte i
    | SynConst.UInt16 i ->
        unif g.uint16_ty
        Const.UInt16 i
    | SynConst.UInt32 i ->
        unif g.uint32_ty
        Const.UInt32 i
    | SynConst.UInt64 i ->
        unif g.uint64_ty
        Const.UInt64 i
    | SynConst.UIntPtr i ->
        unif g.unativeint_ty
        Const.UIntPtr i
    | SynConst.Measure(constant = SynConst.Single f) ->
        unifyMeasureArg (f=0.0f) g.pfloat32_tcr
        Const.Single f
    | SynConst.Measure(constant = SynConst.Double f) ->
        unifyMeasureArg (f=0.0) g.pfloat_tcr
        Const.Double f
    | SynConst.Measure(constant = SynConst.Decimal f) ->
        unifyMeasureArg false g.pdecimal_tcr
        Const.Decimal f
    | SynConst.Measure(constant = SynConst.SByte i)->
        unifyMeasureArg (i=0y) g.pint8_tcr
        Const.SByte i
    | SynConst.Measure(constant = SynConst.Int16 i) ->
        unifyMeasureArg (i=0s) g.pint16_tcr
        Const.Int16 i
    | SynConst.Measure(constant = SynConst.Int32 i) ->
        unifyMeasureArg (i=0) g.pint_tcr
        Const.Int32 i
    | SynConst.Measure(constant = SynConst.Int64 i) ->
        unifyMeasureArg (i=0L) g.pint64_tcr
        Const.Int64 i
    | SynConst.Measure(constant = SynConst.IntPtr i) when expandedMeasurablesEnabled ->
        unifyMeasureArg (i=0L) g.pnativeint_tcr
        Const.IntPtr i
    | SynConst.Measure(constant = SynConst.Byte i) when expandedMeasurablesEnabled ->
        unifyMeasureArg (i=0uy) g.puint8_tcr
        Const.Byte i
    | SynConst.Measure(constant = SynConst.UInt16 i) when expandedMeasurablesEnabled ->
        unifyMeasureArg (i=0us) g.puint16_tcr
        Const.UInt16 i
    | SynConst.Measure(constant = SynConst.UInt32 i) when expandedMeasurablesEnabled ->
        unifyMeasureArg (i=0u) g.puint_tcr
        Const.UInt32 i
    | SynConst.Measure(constant = SynConst.UInt64 i) when expandedMeasurablesEnabled ->
        unifyMeasureArg (i=0UL) g.puint64_tcr
        Const.UInt64 i
    | SynConst.Measure(constant = SynConst.UIntPtr i) when expandedMeasurablesEnabled ->
        unifyMeasureArg (i=0UL) g.punativeint_tcr
        Const.UIntPtr i
    | SynConst.Char c ->
        unif g.char_ty
        Const.Char c
    | SynConst.String (s, _, _) ->
        unif g.string_ty
        Const.String s
    | SynConst.SourceIdentifier (i, s, m) ->
        unif g.string_ty
        let s = applyLineDirectivesToSourceIdentifier i s m
        Const.String s
    | SynConst.UserNum _ -> error (InternalError(FSComp.SR.tcUnexpectedBigRationalConstant(), m))
    | SynConst.Measure _ -> error (Error(FSComp.SR.tcInvalidTypeForUnitsOfMeasure(), m))
    | SynConst.UInt16s _ -> error (InternalError(FSComp.SR.tcUnexpectedConstUint16Array(), m))
    | SynConst.Bytes _ -> error (InternalError(FSComp.SR.tcUnexpectedConstByteArray(), m))

/// Convert an Abstract IL ILFieldInit value read from .NET metadata to a TAST constant
let TcFieldInit (_m: range) lit = ilFieldToTastConst lit

//-------------------------------------------------------------------------
// Arities. These serve two roles in the system:
// 1. syntactic arities come from the syntactic forms found
//     signature files and the syntactic forms of function and member definitions.
// 2. compiled arities representing representation choices w.r.t. internal representations of
//     functions and members.
//-------------------------------------------------------------------------

// Adjust the arities that came from the parsing of the toptyp (arities) to be a valSynData.
// This means replacing the "[unitArg]" arising from a "unit -> ty" with a "[]".
let AdjustValSynInfoInSignature g ty (SynValInfo(argsData, retData) as sigMD) =
    match argsData with
    | [[_]] when isFunTy g ty && typeEquiv g g.unit_ty (domainOfFunTy g ty) ->
        SynValInfo(argsData.Head.Tail :: argsData.Tail, retData)
    | _ ->
        sigMD


let TranslateTopArgSynInfo (cenv: cenv) isArg (m: range) tcAttributes (SynArgInfo(Attributes attrs, isOpt, nm)) =
    // Synthesize an artificial "OptionalArgument" attribute for the parameter
    let optAttrs: SynAttribute list =
        if isOpt then
            let m = m.MakeSynthetic()
            [ { TypeName = SynLongIdent(pathToSynLid m ["Microsoft"; "FSharp"; "Core"; "OptionalArgument"], [], [None; None; None; None])
                ArgExpr = mkSynUnit m
                Target = None
                AppliesToGetterAndSetter = false
                Range = m } ]
        else
            []

    if isArg && not (isNil attrs) && Option.isNone nm then
        errorR(Error(FSComp.SR.tcParameterRequiresName(), m))

    if not isArg && Option.isSome nm then
        errorR(Error(FSComp.SR.tcReturnValuesCannotHaveNames(), m))

    let attribs = tcAttributes (optAttrs @ attrs)

    let key = nm |> Option.map (fun id -> id.idText, id.idRange)

    let argInfo =
        key
        |> Option.map cenv.argInfoCache.TryGetValue
        |> Option.bind (fun (found, info) ->
            if found then
                Some info
            else None)
        |> Option.defaultValue ({ Attribs = WellKnownValAttribs.Create(attribs); Name = nm; OtherRange = None }: ArgReprInfo)

    match key with
    | Some k -> cenv.argInfoCache.[k] <- argInfo
    | None -> ()

    // Set freshly computed attribs in case they are different in the cache
    argInfo.Attribs <- WellKnownValAttribs.Create(attribs)

    argInfo

/// Members have an arity inferred from their syntax. This "valSynData" is not quite the same as the arities
/// used in the middle and backends of the compiler ("valReprInfo").
/// "0" in a valSynData (see arity_of_pat) means a "unit" arg in a valReprInfo
/// Hence remove all "zeros" from arity and replace them with 1 here.
/// Note we currently use the compiled form for choosing unique names, to distinguish overloads because this must match up
/// between signature and implementation, and the signature just has "unit".
let TranslateSynValInfo (cenv: cenv) m tcAttributes (SynValInfo(argsData, retData)) =
    PrelimValReprInfo (argsData |> List.mapSquared (TranslateTopArgSynInfo cenv true m (tcAttributes AttributeTargets.Parameter)),
                       retData |> TranslateTopArgSynInfo cenv false m (tcAttributes AttributeTargets.ReturnValue))

let TranslatePartialValReprInfo tps (PrelimValReprInfo (argsData, retData)) =
    ValReprInfo(ValReprInfo.InferTyparInfo tps, argsData, retData)

//-------------------------------------------------------------------------
// Members
//-------------------------------------------------------------------------


[<RequireQualifiedAccess>]
type TcCanFail =
    | IgnoreMemberResoutionError
    | IgnoreAllErrors
    | ReportAllErrors
    
[<RequireQualifiedAccess>]
[<Struct>]
type TcTrueMatchClause =
    | Yes
    | No

let TcAddNullnessToType (warn: bool) (cenv: cenv) (env: TcEnv) nullness innerTyC m =
    let g = cenv.g
    if g.langFeatureNullness then
        if TypeNullNever g innerTyC then
            let tyString = NicePrint.minimalStringOfType env.DisplayEnv innerTyC
            errorR(Error(FSComp.SR.tcTypeDoesNotHaveAnyNull(tyString), m))

        match tryAddNullnessToTy nullness innerTyC with

        | None ->
            let tyString = NicePrint.minimalStringOfType env.DisplayEnv innerTyC
            errorR(Error(FSComp.SR.tcTypeDoesNotHaveAnyNull(tyString), m))
            innerTyC

        | Some innerTyCWithNull ->
            // The inner type is not allowed to support null or use null as a representation value.
            // For example "int option?" is not allowed, nor "string??".
            //
            // For variable types in FSharp.Core we make an exception because we must allow
            //    val toObj: value: 'T option -> 'T | null when 'T : not struct (* and 'T : not null *)
            // without implying 'T is not null.  This is because it is legitimate to use this
            // function to "collapse" null and obj-null-coming-from-option using such a function.

            if not g.compilingFSharpCore || not (isTyparTy g innerTyC) then
                AddCxTypeDefnNotSupportsNull env.DisplayEnv cenv.css m NoTrace innerTyC
                AddCxTypeIsReferenceType env.DisplayEnv cenv.css m NoTrace innerTyC

            if not g.compilingFSharpCore && isTyparTy g innerTyC then
                // A typar might be later inferred into a type not supporting `| null|, like tuple or anon.
                // Repeat the check in post inference
                AddCxTypeCanCarryNullnessInfo env.DisplayEnv cenv.css m innerTyC nullness

            innerTyCWithNull

    else
        if warn then
            warning(Error(FSComp.SR.tcNullnessCheckingNotEnabled(), m))
        innerTyC

//-------------------------------------------------------------------------
// Members
//-------------------------------------------------------------------------

let ComputeLogicalName (id: Ident) (memberFlags: SynMemberFlags) =
    match memberFlags.MemberKind with
    | SynMemberKind.ClassConstructor -> ".cctor"
    | SynMemberKind.Constructor -> ".ctor"
    | SynMemberKind.Member ->
        match id.idText with
        | ".ctor" | ".cctor" as r -> errorR(Error(FSComp.SR.tcInvalidMemberNameCtor(), id.idRange)); r
        | r -> r
    | SynMemberKind.PropertyGetSet -> error(InternalError(FSComp.SR.tcMemberKindPropertyGetSetNotExpected(), id.idRange))
    | SynMemberKind.PropertyGet -> "get_" + id.idText
    | SynMemberKind.PropertySet -> "set_" + id.idText

/// Make the unique "name" for a member.
//
// optImplSlotTy = None (for classes) or Some ty (when implementing interface type ty)
let MakeMemberDataAndMangledNameForMemberVal(g, tcref, isExtrinsic, attrs, implSlotTys, memberFlags, valSynData, id, isCompGen) =
    let logicalName = ComputeLogicalName id memberFlags

    let intfSlotTys = if implSlotTys |> List.forall (isInterfaceTy g) then implSlotTys else []

    let memberInfo: ValMemberInfo =
        { ApparentEnclosingEntity=tcref
          MemberFlags=memberFlags
          IsImplemented=false
          // NOTE: This value is initially only set for interface implementations and those overrides
          // where we manage to pre-infer which abstract is overridden by the method. It is filled in
          // properly when we check the allImplemented implementation checks at the end of the inference scope.
          ImplementedSlotSigs=implSlotTys |> List.map (fun intfTy -> TSlotSig(logicalName, intfTy, [], [], [], None)) }

    let isInstance = MemberIsCompiledAsInstance g tcref isExtrinsic memberInfo attrs

    let hasUseNullAsTrueAttr = TyconHasUseNullAsTrueValueAttribute g tcref.Deref

    if hasUseNullAsTrueAttr then
        if (memberFlags.IsDispatchSlot || not (isNil intfSlotTys)) then
            if not isInstance then
              errorR(VirtualAugmentationOnNullValuedType(id.idRange))

        elif not memberFlags.IsOverrideOrExplicitImpl && memberFlags.IsInstance then
            if not isExtrinsic && not isInstance then
                warning(NonVirtualAugmentationOnNullValuedType(id.idRange))

    let compiledName =
        if isExtrinsic then
             let tname = tcref.LogicalName
             let text = tname + "." + logicalName
             let text = if memberFlags.MemberKind <> SynMemberKind.Constructor && memberFlags.MemberKind <> SynMemberKind.ClassConstructor && not memberFlags.IsInstance then text + ".Static" else text
             let text = if memberFlags.IsOverrideOrExplicitImpl then text + ".Override" else text
             text
        elif not intfSlotTys.IsEmpty then
            // interface implementation
            if intfSlotTys.Length > 1 then
                failwithf "unexpected: intfSlotTys.Length > 1 (== %i) in MakeMemberDataAndMangledNameForMemberVal for '%s'" intfSlotTys.Length logicalName
            qualifiedInterfaceImplementationName g intfSlotTys.Head logicalName
        else
            List.foldBack (fun x -> qualifiedMangledNameOfTyconRef (tcrefOfAppTy g x)) intfSlotTys logicalName

    if not isCompGen && IsLogicalInfixOpName id.idText then
        let m = id.idRange
        let logicalName = id.idText
        let displayName = ConvertValLogicalNameToDisplayNameCore logicalName
        // Check symbolic members. Expect valSynData implied arity to be [[2]].
        match SynInfo.AritiesOfArgs valSynData with
        | [] | [0] -> warning(Error(FSComp.SR.memberOperatorDefinitionWithNoArguments displayName, m))
        | n :: otherArgs ->
            let opTakesThreeArgs = IsLogicalTernaryOperator logicalName
            if n<>2 && not opTakesThreeArgs then warning(Error(FSComp.SR.memberOperatorDefinitionWithNonPairArgument(displayName, n), m))
            if n<>3 && opTakesThreeArgs then warning(Error(FSComp.SR.memberOperatorDefinitionWithNonTripleArgument(displayName, n), m))
            if not (isNil otherArgs) then warning(Error(FSComp.SR.memberOperatorDefinitionWithCurriedArguments displayName, m))

    if isExtrinsic && IsLogicalOpName id.idText then
        warning(Error(FSComp.SR.tcMemberOperatorDefinitionInExtrinsic(), id.idRange))

    PrelimMemberInfo(memberInfo, logicalName, compiledName)

/// Return the generalized type for a type scheme
let GeneralizedTypeForTypeScheme typeScheme =
    let (GeneralizedType(generalizedTypars, tau)) = typeScheme
    mkForallTyIfNeeded generalizedTypars tau

/// Create a type scheme for something that is not generic
let NonGenericTypeScheme ty = GeneralizedType([], ty)

//-------------------------------------------------------------------------
// Helpers related to publishing values, types and members into the
// elaborated representation.
//-------------------------------------------------------------------------

let UpdateAccModuleOrNamespaceType (cenv: cenv) env f =
    // When compiling FSharp.Core, modify the fslib CCU to ensure forward stable references used by
    // the compiler can be resolved ASAP. Not at all pretty but it's hard to
    // find good ways to do references from the compiler into a term graph.
    if cenv.compilingCanonicalFslibModuleType then
        let nleref = mkNonLocalEntityRef cenv.thisCcu (arrPathOfLid env.ePath)
        let modul = nleref.Deref
        modul.entity_modul_type <- MaybeLazy.Strict (f true modul.ModuleOrNamespaceType)
    SetCurrAccumulatedModuleOrNamespaceType env (f false (GetCurrAccumulatedModuleOrNamespaceType env))

let PublishModuleDefn (cenv: cenv) env mspec =
    UpdateAccModuleOrNamespaceType cenv env (fun intoFslibCcu mty ->
       if intoFslibCcu then mty
       else mty.AddEntity mspec)
    let item = Item.ModuleOrNamespaces([mkLocalModuleRef mspec])
    CallNameResolutionSink cenv.tcSink (mspec.Range, env.NameEnv, item, emptyTyparInst, ItemOccurrence.Binding, env.AccessRights)

let PublishTypeDefn (cenv: cenv) env mspec =
    UpdateAccModuleOrNamespaceType cenv env (fun _ mty ->
       mty.AddEntity mspec)

let PublishValueDefnPrim (cenv: cenv) env (vspec: Val) =
    UpdateAccModuleOrNamespaceType cenv env (fun _ mty ->
        mty.AddVal vspec)

let PublishValueDefnMaybeInclCompilerGenerated (cenv: cenv) env inclCompilerGenerated declKind (vspec: Val) =
    let g = cenv.g
    let isNamespace =
        let kind = (GetCurrAccumulatedModuleOrNamespaceType env).ModuleOrNamespaceKind
        match kind with
        | Namespace _ -> true
        | _ -> false

    if (declKind = ModuleOrMemberBinding) &&
       isNamespace &&
       (Option.isNone vspec.MemberInfo) then
           errorR(Error(FSComp.SR.tcNamespaceCannotContainValues(), vspec.Range))

    if (declKind = ExtrinsicExtensionBinding) &&
       isNamespace then
           errorR(Error(FSComp.SR.tcNamespaceCannotContainExtensionMembers(), vspec.Range))

    // Publish the value to the module type being generated.
    match declKind with
    | ModuleOrMemberBinding
    | ExtrinsicExtensionBinding
    | IntrinsicExtensionBinding -> PublishValueDefnPrim cenv env vspec
    | _ -> ()

    match vspec.MemberInfo with
    | Some _ when
        ((not vspec.IsCompilerGenerated || inclCompilerGenerated) &&
         // Extrinsic extensions don't get added to the tcaug
         declKind <> ExtrinsicExtensionBinding) ->
         // // Static initializers don't get published to the tcaug
         // not (memberInfo.MemberFlags.MemberKind = SynMemberKind.ClassConstructor)) ->

        let tcaug = vspec.MemberApparentEntity.TypeContents
        let vref = mkLocalValRef vspec
        tcaug.tcaug_adhoc <- NameMultiMap.add vspec.LogicalName vref tcaug.tcaug_adhoc
        tcaug.tcaug_adhoc_list.Add (ValRefIsExplicitImpl g vref, vref)
    | _ -> ()

let PublishValueDefn cenv env declKind vspec =
    PublishValueDefnMaybeInclCompilerGenerated cenv env false declKind vspec

let CombineVisibilityAttribs vis1 vis2 m =
    match vis1 with
    | Some _ ->
        if Option.isSome vis2 then
            errorR(Error(FSComp.SR.tcMultipleVisibilityAttributes(), m))
        vis1
    | _ -> vis2

let ComputeAccessAndCompPath (g:TcGlobals) env (declKindOpt: DeclKind option) m vis overrideVis actualParent =
    let accessPath = env.eAccessPath
    let accessModPermitted =
        match declKindOpt with
        | None -> true
        | Some declKind -> declKind.IsAccessModifierPermitted

    if Option.isSome vis && not accessModPermitted then
        errorR(Error(FSComp.SR.tcMultipleVisibilityAttributesWithLet(), m))

    let vis =
        match declKindOpt, overrideVis, vis with
        | _, Some v, _ -> v
        | Some (DeclKind.ClassLetBinding _), _, None when g.realsig -> taccessPrivate accessPath  // a type binding defaults to "private"
        | _, _, None ->  taccessPublic                                                  // a module or member binding defaults to "public"
        | _, _, Some (SynAccess.Public _) -> taccessPublic
        | _, _, Some (SynAccess.Private _) -> taccessPrivate accessPath
        | _, _, Some (SynAccess.Internal _) -> taccessInternal

    let vis =
        match actualParent with
        | ParentNone -> vis
        | Parent tcref -> combineAccess vis tcref.Accessibility

    let cpath = if accessModPermitted then Some env.eCompPath else None
    vis, cpath

let CheckForAbnormalOperatorNames (cenv: cenv) (idRange: range) coreDisplayName (memberInfoOpt: ValMemberInfo option) =
    let g = cenv.g
    if (idRange.EndColumn - idRange.StartColumn <= 5) &&
        not g.compilingFSharpCore
    then
        let opName = ConvertValLogicalNameToDisplayNameCore coreDisplayName
        let isMember = memberInfoOpt.IsSome
        match opName with
        | Relational ->
            if isMember then
                warning(StandardOperatorRedefinitionWarning(FSComp.SR.tcInvalidMethodNameForRelationalOperator(opName, coreDisplayName), idRange))
            else
                warning(StandardOperatorRedefinitionWarning(FSComp.SR.tcInvalidOperatorDefinitionRelational opName, idRange))
        | Equality ->
            if isMember then
                warning(StandardOperatorRedefinitionWarning(FSComp.SR.tcInvalidMethodNameForEquality(opName, coreDisplayName), idRange))
            else
                warning(StandardOperatorRedefinitionWarning(FSComp.SR.tcInvalidOperatorDefinitionEquality opName, idRange))
        | Control ->
            if isMember then
                warning(StandardOperatorRedefinitionWarning(FSComp.SR.tcInvalidMemberName(opName, coreDisplayName), idRange))
            else
                warning(StandardOperatorRedefinitionWarning(FSComp.SR.tcInvalidOperatorDefinition opName, idRange))
        | Indexer ->
            if not isMember then
                error(StandardOperatorRedefinitionWarning(FSComp.SR.tcInvalidIndexOperatorDefinition opName, idRange))
        | FixedTypes ->
            if isMember then
                warning(StandardOperatorRedefinitionWarning(FSComp.SR.tcInvalidMemberNameFixedTypes opName, idRange))
        | Other -> ()

let CheckInitProperties (g: TcGlobals) (minfo: MethInfo) methodName mItem =
    if g.langVersion.SupportsFeature(LanguageFeature.InitPropertiesSupport) then
        // Check, whether this method has external init, emit an error diagnostic in this case.
        if minfo.HasExternalInit then
            errorR (Error (FSComp.SR.tcSetterForInitOnlyPropertyCannotBeCalled1 methodName, mItem))

let CheckRequiredProperties (g:TcGlobals) (env: TcEnv) (cenv: TcFileState) (minfo: MethInfo) finalAssignedItemSetters mMethExpr =
    // Make sure, if apparent type has any required properties, they all are in the `finalAssignedItemSetters`.
    // If it is a constructor, and it is not marked with `SetsRequiredMembersAttributeAttribute`, then:
    // 1. Get all properties of the type.
    // 2. Check if any of them has `IsRequired` set.
    //      2.1. If there are none, proceed as usual
    //      2.2. If there are any, make sure all of them (or their setters) are in `finalAssignedItemSetters`.
    // 3. If some are missing, produce a diagnostic which missing ones.
    if g.langVersion.SupportsFeature(LanguageFeature.RequiredPropertiesSupport)
        && minfo.IsConstructor
        && not (minfo.GetCustomAttrs().HasWellKnownAttribute(WellKnownILAttributes.SetsRequiredMembersAttribute))
        then

        let requiredProps =
            [
                let props = GetImmediateIntrinsicPropInfosOfType (None, AccessibleFromSomeFSharpCode) g cenv.amap range0 minfo.ApparentEnclosingType
                for prop in props do
                    if prop.IsRequired then
                        prop
             ]

        if requiredProps.Length > 0 then
            let setterPropNames =
                finalAssignedItemSetters
                |> List.choose (function | AssignedItemSetter(_, AssignedPropSetter (_, pinfo, _, _), _) -> Some pinfo.PropertyName  | _ -> None)
                |> Set.ofList

            let missingProps =
                requiredProps
                |> List.filter (fun pinfo -> not (Set.contains pinfo.PropertyName setterPropNames))
            if missingProps.Length > 0 then
                let details = NicePrint.multiLineStringOfPropInfos g cenv.amap mMethExpr env.DisplayEnv missingProps
                errorR(Error(FSComp.SR.tcMissingRequiredMembers details, mMethExpr))

let private HasMethodImplNoInliningAttribute g attrs =
    match attrs with
    // NO_INLINING = 8
    | ValAttribInt g WellKnownValAttributes.MethodImplAttribute flags -> (flags &&& 0x8) <> 0x0
    | _ -> false

let MakeAndPublishVal (cenv: cenv) env (altActualParent, inSig, declKind, valRecInfo, vscheme, attrs, xmlDoc, konst, isGeneratedEventVal) =

    let g = cenv.g

    let (ValScheme(id, typeScheme, valReprInfo, valReprInfoForDisplay, memberInfoOpt, isMutable, inlineFlag, baseOrThis, vis, isCompGen, isIncrClass, isTyFunc, hasDeclaredTypars)) = vscheme

    let ty = GeneralizedTypeForTypeScheme typeScheme

    let m = id.idRange

    let isTopBinding =
        match declKind with
        | ModuleOrMemberBinding -> true
        | ExtrinsicExtensionBinding -> true
        | IntrinsicExtensionBinding -> true
        | _ -> false

    let isExtrinsic = (declKind = ExtrinsicExtensionBinding)

    let actualParent, overrideVis =
        // Use the parent of the member if it's available
        // If it's an extrinsic extension member or not a member then use the containing module.
        match memberInfoOpt with
        | Some (PrelimMemberInfo(memberInfo, _, _)) when not isExtrinsic ->
            if memberInfo.ApparentEnclosingEntity.IsModuleOrNamespace then
                errorR(InternalError(FSComp.SR.tcExpectModuleOrNamespaceParent(id.idText), m))

            // Members of interface implementations have the accessibility of the interface
            // they are implementing.
            let vis =
                if MemberIsExplicitImpl g memberInfo then
                    let slotSig = List.head memberInfo.ImplementedSlotSigs
                    match slotSig.DeclaringType with
                    | TType_app (tcref, _, _) -> Some tcref.Accessibility
                    | _ -> None
                else
                    None
            Parent(memberInfo.ApparentEnclosingEntity), vis
        | _ -> altActualParent, None

    let vis, _ = ComputeAccessAndCompPath g env (Some declKind) id.idRange vis overrideVis actualParent

    let valFlags = computeValWellKnownFlags g attrs

    let inlineFlag =
        if hasFlag valFlags WellKnownValAttributes.DllImportAttribute then
            if inlineFlag = ValInline.Always then
              errorR(Error(FSComp.SR.tcDllImportStubsCannotBeInlined(), m))
            ValInline.Never
        else
            if HasMethodImplNoInliningAttribute g attrs
            then ValInline.Never
            else inlineFlag


    // CompiledName not allowed on virtual/abstract/override members
    let compiledNameAttrib =
        match attrs with
        | ValAttribString g WellKnownValAttributes.CompiledNameAttribute s -> Some s
        | _ -> None
    if Option.isSome compiledNameAttrib then
        match memberInfoOpt with
        | Some (PrelimMemberInfo(memberInfo, _, _)) ->
            if memberInfo.MemberFlags.IsDispatchSlot || memberInfo.MemberFlags.IsOverrideOrExplicitImpl then
                errorR(Error(FSComp.SR.tcCompiledNameAttributeMisused(), m))
        | None ->
            match altActualParent with
            | ParentNone -> errorR(Error(FSComp.SR.tcCompiledNameAttributeMisused(), m))
            | _ -> ()

    let compiledNameIsOnProp =
        match memberInfoOpt with
        | Some (PrelimMemberInfo(memberInfo, _, _)) ->
            memberInfo.MemberFlags.MemberKind = SynMemberKind.PropertyGet ||
            memberInfo.MemberFlags.MemberKind = SynMemberKind.PropertySet ||
            memberInfo.MemberFlags.MemberKind = SynMemberKind.PropertyGetSet
        | _ -> false

    let compiledName =
        match compiledNameAttrib with
        // We fix up CompiledName on properties during codegen
        | Some _ when not compiledNameIsOnProp -> compiledNameAttrib
        | _ ->
            match memberInfoOpt with
            | Some (PrelimMemberInfo(_, _, compiledName)) ->
                Some compiledName
            | None ->
                None

    let logicalName =
        match memberInfoOpt with
        | Some (PrelimMemberInfo(_, logicalName, _)) ->
            logicalName
        | None ->
            id.idText

    let memberInfoOpt =
        match memberInfoOpt with
        | Some (PrelimMemberInfo(memberInfo, _, _)) ->
            Some memberInfo
        | None ->
            None

    let mut = if isMutable then Mutable else Immutable
    let vspec =
        Construct.NewVal
            (logicalName, id.idRange, compiledName, ty, mut,
             isCompGen, valReprInfo, vis, valRecInfo, memberInfoOpt, baseOrThis, attrs, inlineFlag,
             xmlDoc, isTopBinding, isExtrinsic, isIncrClass, isTyFunc,
             (hasDeclaredTypars || inSig), isGeneratedEventVal, konst, actualParent)

    match valReprInfoForDisplay with
    | Some info when not (ValReprInfo.IsEmpty info) ->
        vspec.SetValReprInfoForDisplay valReprInfoForDisplay
    | _ -> ()

    CheckForAbnormalOperatorNames cenv id.idRange vspec.DisplayNameCoreMangled memberInfoOpt

    PublishValueDefn cenv env declKind vspec

    let shouldNotifySink (vspec: Val) =
        match vspec.MemberInfo with
        // `this` reference named `__`. It's either:
        // * generated by compiler for auto properties or
        // * provided by source code (i.e. `member _.Method = ...`)
        // We don't notify sink about it to prevent generating `FSharpSymbol` for it and appearing in completion list.
        | None when
            vspec.IsBaseVal ||
            vspec.IsMemberThisVal && vspec.LogicalName = "__" -> false
        | _ -> true

    match cenv.tcSink.CurrentSink with
    | Some _ when not vspec.IsCompilerGenerated && shouldNotifySink vspec ->
        let nenv = AddFakeNamedValRefToNameEnv vspec.DisplayName env.NameEnv (mkLocalValRef vspec)
        CallEnvSink cenv.tcSink (vspec.Range, nenv, env.eAccessRights)
        let vref = mkLocalValRef vspec
        let item = Item.Value(vref)
        CallNameResolutionSink cenv.tcSink (vspec.Range, nenv, item, emptyTyparInst, ItemOccurrence.Binding, env.eAccessRights)
        
        // (#14969, #19173) For active patterns in signature files, also report each case as Item.ActivePatternResult
        // so that Find All References can find them. In implementation files, this is done during 
        // TcLetBinding, but signature files don't go through that path.
        if inSig then
            match TryGetActivePatternInfo vref with
            | Some apinfo ->
                apinfo.ActiveTagsWithRanges |> List.iteri (fun i (_tag, tagRange) ->
                    let apItem = Item.ActivePatternResult(apinfo, vspec.TauType, i, tagRange)
                    CallNameResolutionSink cenv.tcSink (tagRange, nenv, apItem, emptyTyparInst, ItemOccurrence.Binding, env.eAccessRights))
            | None -> ()
    | _ -> ()

    vspec

let MakeAndPublishVals (cenv: cenv) env (altActualParent, inSig, declKind, valRecInfo, valSchemes, attrs, xmlDoc, literalValue) =
    Map.foldBack
        (fun name (valscheme: ValScheme) values ->
          Map.add name (MakeAndPublishVal cenv env (altActualParent, inSig, declKind, valRecInfo, valscheme, attrs, xmlDoc, literalValue, false), valscheme.GeneralizedType) values)
        valSchemes
        Map.empty

/// Create a Val node for "base" in a class
let MakeAndPublishBaseVal (cenv: cenv) env baseIdOpt ty =
    baseIdOpt
    |> Option.map (fun (id: Ident) ->
       let valscheme = ValScheme(id, NonGenericTypeScheme ty, None, None, None, false, ValInline.Never, BaseVal, None, false, false, false, false)
       MakeAndPublishVal cenv env (ParentNone, false, ExpressionBinding, ValNotInRecScope, valscheme, [], XmlDoc.Empty, None, false))

// Make the "delayed reference" value where the this pointer will reside after calling the base class constructor
// Make the value for the 'this' pointer for use within a constructor
let MakeAndPublishSafeThisVal (cenv: cenv) env (thisIdOpt: Ident option) thisTy =
    let g = cenv.g
    match thisIdOpt with
    | Some thisId ->
        // for structs, thisTy is a byref
        if not (isFSharpObjModelTy g thisTy) then
            errorR(Error(FSComp.SR.tcStructsCanOnlyBindThisAtMemberDeclaration(), thisId.idRange))

        let valScheme = ValScheme(thisId, NonGenericTypeScheme(mkRefCellTy g thisTy), None, None, None, false, ValInline.Never, CtorThisVal, None, false, false, false, false)
        Some(MakeAndPublishVal cenv env (ParentNone, false, ExpressionBinding, ValNotInRecScope, valScheme, [], XmlDoc.Empty, None, false))

    | None ->
        None


//-------------------------------------------------------------------------
// Helpers for type inference for recursive bindings
//-------------------------------------------------------------------------

/// Fixup the type instantiation at recursive references. Used after the bindings have been
/// checked. The fixups are applied by using mutation.
let AdjustAndForgetUsesOfRecValue (cenv: cenv) (vrefTgt: ValRef) (valScheme: ValScheme) =
    let (GeneralizedType(generalizedTypars, _)) = valScheme.GeneralizedType
    let valTy = GeneralizedTypeForTypeScheme valScheme.GeneralizedType
    let lvrefTgt = vrefTgt.Deref
    if not (isNil generalizedTypars) then
        // Find all the uses of this recursive binding and use mutation to adjust the expressions
        // at those points in order to record the inferred type parameters.
        let recUses = cenv.recUses.Find lvrefTgt
        for fixupPoint, m, isComplete in recUses do
            if not isComplete then
                // Keep any values for explicit type arguments
                let fixedUpExpr =
                    let vrefFlags, tyargs0 =
                        match stripDebugPoints fixupPoint.Value with
                        | Expr.App (Expr.Val (_, vrefFlags, _), _, tyargs0, [], _) -> vrefFlags, tyargs0
                        | Expr.Val (_, vrefFlags, _) -> vrefFlags, []
                        | _ ->
                            errorR(Error(FSComp.SR.tcUnexpectedExprAtRecInfPoint(), m))
                            NormalValUse, []

                    let ityargs = generalizeTypars (List.skip (List.length tyargs0) generalizedTypars)
                    primMkApp (Expr.Val (vrefTgt, vrefFlags, m), valTy) (tyargs0 @ ityargs) [] m
                fixupPoint.Value <- fixedUpExpr

    vrefTgt.Deref.SetValRec ValNotInRecScope
    cenv.recUses <- cenv.recUses.Remove vrefTgt.Deref

/// Set the properties of recursive values that are only fully known after inference is complete
let AdjustRecType (v: Val) vscheme =
    let (ValScheme(typeScheme=typeScheme; valReprInfo=valReprInfo)) = vscheme
    let valTy = GeneralizedTypeForTypeScheme typeScheme
    v.SetType valTy
    v.SetValReprInfo valReprInfo
    v.SetValRec (ValInRecScope true)

/// Record the generated value expression as a place where we will have to
/// adjust using AdjustAndForgetUsesOfRecValue at a letrec point. Every use of a value
/// under a letrec gets used at the _same_ type instantiation.
let RecordUseOfRecValue (cenv: cenv) valRecInfo (vrefTgt: ValRef) vExpr m =
    match valRecInfo with
    | ValInRecScope isComplete ->
        let fixupPoint = ref vExpr
        cenv.recUses <- cenv.recUses.Add (vrefTgt.Deref, (fixupPoint, m, isComplete))
        Expr.Link fixupPoint
    | ValNotInRecScope ->
        vExpr

type RecursiveUseFixupPoints = RecursiveUseFixupPoints of (Expr ref * range) list

/// Get all recursive references, for fixing up delayed recursion using laziness
let GetAllUsesOfRecValue (cenv: cenv) vrefTgt =
    RecursiveUseFixupPoints (cenv.recUses.Find vrefTgt |> List.map (fun (fixupPoint, m, _) -> (fixupPoint, m)))


//-------------------------------------------------------------------------
// Helpers for Generalization
//-------------------------------------------------------------------------

let ChooseCanonicalDeclaredTyparsAfterInference g denv declaredTypars m =
    declaredTypars |> List.iter (fun tp ->
      let ty = mkTyparTy tp
      if not (isAnyParTy g ty) then
          error(Error(FSComp.SR.tcLessGenericBecauseOfAnnotation(tp.Name, NicePrint.prettyStringOfTy denv ty), tp.Range)))

    let declaredTypars = NormalizeDeclaredTyparsForEquiRecursiveInference g declaredTypars

    if ListSet.hasDuplicates typarEq declaredTypars then
        errorR(Error(FSComp.SR.tcConstrainedTypeVariableCannotBeGeneralized(), m))

    declaredTypars

let ChooseCanonicalValSchemeAfterInference g denv vscheme m =
    let (ValScheme(id, typeScheme, valReprInfo, valReprInfoForDisplay, memberInfoOpt, isMutable, inlineFlag, baseOrThis, vis, isCompGen, isIncrClass, isTyFunc, hasDeclaredTypars)) = vscheme
    let (GeneralizedType(generalizedTypars, ty)) = typeScheme
    let generalizedTypars = ChooseCanonicalDeclaredTyparsAfterInference g denv generalizedTypars m
    let typeScheme = GeneralizedType(generalizedTypars, ty)
    let valscheme = ValScheme(id, typeScheme, valReprInfo, valReprInfoForDisplay, memberInfoOpt, isMutable, inlineFlag, baseOrThis, vis, isCompGen, isIncrClass, isTyFunc, hasDeclaredTypars)
    valscheme

let PlaceTyparsInDeclarationOrder declaredTypars generalizedTypars =
    declaredTypars @ (generalizedTypars |> List.filter (fun tp -> not (ListSet.contains typarEq tp declaredTypars)))

let SetTyparRigid denv m (tp: Typar) =
    match tp.Solution with
    | None -> ()
    | Some ty ->
        if tp.IsCompilerGenerated then
            errorR(Error(FSComp.SR.tcGenericParameterHasBeenConstrained(NicePrint.prettyStringOfTy denv ty), m))
        else
            errorR(Error(FSComp.SR.tcTypeParameterHasBeenConstrained(NicePrint.prettyStringOfTy denv ty), tp.Range))
    tp.SetRigidity TyparRigidity.Rigid

let GeneralizeVal (cenv: cenv) denv enclosingDeclaredTypars generalizedTyparsForThisBinding prelimVal =

    let g = cenv.g

    let (PrelimVal1(id, explicitTyparInfo, ty, prelimValReprInfo, memberInfoOpt, isMutable, inlineFlag, baseOrThis, argAttribs, vis, isCompGen)) = prelimVal
    let (ExplicitTyparInfo(_rigidCopyOfDeclaredTypars, declaredTypars, _)) = explicitTyparInfo

    let m = id.idRange

    let allDeclaredTypars = enclosingDeclaredTypars@declaredTypars
    let allDeclaredTypars = ChooseCanonicalDeclaredTyparsAfterInference g denv allDeclaredTypars m

    // Trim out anything not in type of the value (as opposed to the type of the r.h.s)
    // This is important when a single declaration binds
    // multiple generic items, where each item does not use all the polymorphism
    // of the r.h.s., e.g. let x, y = None, []
    let computeRelevantTypars thruFlag =
        let ftps = freeInTypeLeftToRight g thruFlag ty
        let generalizedTypars = generalizedTyparsForThisBinding |> List.filter (fun tp -> ListSet.contains typarEq tp ftps)
        // Put declared typars first
        let generalizedTypars = PlaceTyparsInDeclarationOrder allDeclaredTypars generalizedTypars
        generalizedTypars

    let generalizedTypars = computeRelevantTypars false

    // Check stability of existence and ordering of type parameters under erasure of type abbreviations
    let generalizedTyparsLookingThroughTypeAbbreviations = computeRelevantTypars true
    if not (generalizedTypars.Length = generalizedTyparsLookingThroughTypeAbbreviations.Length &&
            List.forall2 typarEq generalizedTypars generalizedTyparsLookingThroughTypeAbbreviations)
    then
        warning(Error(FSComp.SR.tcTypeParametersInferredAreNotStable(), m))

    let hasDeclaredTypars = not (isNil declaredTypars)

    // This is just about the only place we form a GeneralizedType
    let tyScheme = GeneralizedType(generalizedTypars, ty)

    PrelimVal2(id, tyScheme, prelimValReprInfo, memberInfoOpt, isMutable, inlineFlag, baseOrThis, argAttribs, vis, isCompGen, hasDeclaredTypars)

let GeneralizeVals (cenv: cenv) denv enclosingDeclaredTypars generalizedTypars types =
    NameMap.map (GeneralizeVal cenv denv enclosingDeclaredTypars generalizedTypars) types

let DontGeneralizeVals types =
    let dontGeneralizeVal (PrelimVal1(id, _, ty, partialValReprInfoOpt, memberInfoOpt, isMutable, inlineFlag, baseOrThis, argAttribs, vis, isCompGen)) =
        PrelimVal2(id, NonGenericTypeScheme ty, partialValReprInfoOpt, memberInfoOpt, isMutable, inlineFlag, baseOrThis, argAttribs, vis, isCompGen, false)
    NameMap.map dontGeneralizeVal types

let InferGenericArityFromTyScheme (GeneralizedType(generalizedTypars, _)) prelimValReprInfo =
    TranslatePartialValReprInfo generalizedTypars prelimValReprInfo

let ComputeIsTyFunc(id: Ident, hasDeclaredTypars, arityInfo: ValReprInfo option) =
    hasDeclaredTypars &&
    (match arityInfo with
     | None -> error(Error(FSComp.SR.tcExplicitTypeParameterInvalid(), id.idRange))
     | Some info -> info.NumCurriedArgs = 0)

let UseSyntacticValReprInfo (declKind: DeclKind) typeScheme prelimValReprInfo =
    let valReprInfo = InferGenericArityFromTyScheme typeScheme prelimValReprInfo
    if declKind.MustHaveValReprInfo then
        Some valReprInfo, None
    else
        None, Some valReprInfo

/// Combine the results of InferSynValData and InferValReprInfoOfExpr.
//
// The F# spec says that we infer arities from declaration forms and types.
//
// For example
//     let f (a, b) c = 1                  // gets arity [2;1]
//     let f (a: int*int) = 1              // gets arity [2], based on type
//     let f () = 1                       // gets arity [0]
//     let f = (fun (x: int) (y: int) -> 1) // gets arity [1;1]
//     let f = (fun (x: int*int) y -> 1)   // gets arity [2;1]
//
// Some of this arity inference is purely syntax directed and done in InferSynValData in ast.fs
// Some is done by InferValReprInfoOfExpr.
//
// However, there are some corner cases in this specification. In particular, consider
//   let f () () = 1             // [0;1] or [0;0]? Answer: [0;1]
//   let f (a: unit) = 1          // [0] or [1]? Answer: [1]
//   let f = (fun () -> 1)       // [0] or [1]? Answer: [0]
//   let f = (fun (a: unit) -> 1) // [0] or [1]? Answer: [1]
//
// The particular choice of [1] for
//   let f (a: unit) = 1
// is intended to give a disambiguating form for members that override methods taking a single argument
// instantiated to type "unit", e.g.
//    type Base<'a> =
//        abstract M: 'a -> unit
//
//    { new Base<int> with
//        member x.M(v: int) = () }
//
//    { new Base<unit> with
//        member x.M(v: unit) = () }
//
let CombineSyntacticAndInferredValReprInfo g rhsExpr prelimScheme =
    let (PrelimVal2(_, typeScheme, partialValReprInfoOpt, memberInfoOpt, isMutable, _, _, ArgAndRetAttribs(argAttribs, retAttribs), _, _, _)) = prelimScheme
    match partialValReprInfoOpt with
    | None -> Some(PrelimValReprInfo([], ValReprInfo.unnamedRetVal))
    // Don't use any expression information for members, where syntax dictates the arity completely
    | _ when memberInfoOpt.IsSome ->
        partialValReprInfoOpt
    // Don't use any expression information for 'let' bindings where return attributes are present
    | _ when retAttribs.Length > 0 ->
        partialValReprInfoOpt
    | Some partialValReprInfoFromSyntax ->
        let (PrelimValReprInfo(curriedArgInfosFromSyntax, retInfoFromSyntax)) = partialValReprInfoFromSyntax
        let partialArityInfo =
            if isMutable then
                PrelimValReprInfo ([], retInfoFromSyntax)
            else

                let (ValReprInfo (_, curriedArgInfosFromExpression, _)) =
                    InferValReprInfoOfExpr g AllowTypeDirectedDetupling.Yes (GeneralizedTypeForTypeScheme typeScheme) argAttribs retAttribs rhsExpr

                // Choose between the syntactic arity and the expression-inferred arity
                // If the syntax specifies an eliminated unit arg, then use that
                let choose ai1 ai2 =
                    match ai1, ai2 with
                    | [], _ -> []
                    // Dont infer eliminated unit args from the expression if they don't occur syntactically.
                    | ai, [] -> ai
                    // If we infer a tupled argument from the expression and/or type then use that
                    | _ when ai1.Length < ai2.Length -> ai2
                    | _ -> ai1
                let rec loop ais1 ais2 =
                    match ais1, ais2 with
                    // If the expression infers additional arguments then use those (this shouldn't happen, since the
                    // arity inference done on the syntactic form should give identical results)
                    | [], ais | ais, [] -> ais
                    | h1 :: t1, h2 :: t2 -> choose h1 h2 :: loop t1 t2
                let curriedArgInfos = loop curriedArgInfosFromSyntax curriedArgInfosFromExpression
                PrelimValReprInfo (curriedArgInfos, retInfoFromSyntax)

        Some partialArityInfo

let BuildValScheme (declKind: DeclKind) partialValReprInfoOpt prelimScheme =
    let (PrelimVal2(id, typeScheme, _, memberInfoOpt, isMutable, inlineFlag, baseOrThis, _, vis, isCompGen, hasDeclaredTypars)) = prelimScheme
    let valReprInfoOpt =
        partialValReprInfoOpt
        |> Option.map (InferGenericArityFromTyScheme typeScheme)

    let valReprInfo, valReprInfoForDisplay =
        if declKind.MustHaveValReprInfo then
            valReprInfoOpt, None
        else
            None, valReprInfoOpt

    let isTyFunc = ComputeIsTyFunc(id, hasDeclaredTypars, valReprInfo)
    ValScheme(id, typeScheme, valReprInfo, valReprInfoForDisplay, memberInfoOpt, isMutable, inlineFlag, baseOrThis, vis, isCompGen, false, isTyFunc, hasDeclaredTypars)

let UseCombinedValReprInfo g declKind rhsExpr prelimScheme =
    let partialValReprInfoOpt = CombineSyntacticAndInferredValReprInfo g rhsExpr prelimScheme
    BuildValScheme declKind partialValReprInfoOpt prelimScheme

let UseNoValReprInfo prelimScheme =
    BuildValScheme ExpressionBinding None prelimScheme

/// Make and publish the Val nodes for a collection of simple (non-generic) value specifications
let MakeAndPublishSimpleVals (cenv: cenv) env names =
    let tyschemes = DontGeneralizeVals names
    let valSchemes = NameMap.map UseNoValReprInfo tyschemes
    let values = MakeAndPublishVals cenv env (ParentNone, false, ExpressionBinding, ValNotInRecScope, valSchemes, [], XmlDoc.Empty, None)
    let vspecMap = NameMap.map fst values
    values, vspecMap

/// Make and publish the Val nodes for a collection of value specifications at Lambda and Match positions
///
/// We merge the additions to the name resolution environment into one using a merged range so all values are brought
/// into scope simultaneously. The technique used to do this is a disturbing and unfortunate hack that
/// intercepts `NotifyNameResolution` calls being emitted by `MakeAndPublishSimpleVals`

let MakeAndPublishSimpleValsForMergedScope (cenv: cenv) env m (names: NameMap<_>) =

    let g = cenv.g

    let values, vspecMap =
        if names.Count <= 1 then
            MakeAndPublishSimpleVals cenv env names
        else
            let nameResolutions = ResizeArray()

            let notifyNameResolution (pos, item, itemGroup, itemTyparInst, occurrence, nenv, ad, m: range, replacing) =
                if not m.IsSynthetic then
                    nameResolutions.Add(pos, item, itemGroup, itemTyparInst, occurrence, nenv, ad, m, replacing)

            let values, vspecMap =
                let sink =
                    { new ITypecheckResultsSink with
                        member _.NotifyEnvWithScope(_, _, _) = () // ignore EnvWithScope reports

                        member _.NotifyNameResolution(pos, item, itemTyparInst, occurrence, nenv, ad, m, replacing) =
                            notifyNameResolution (pos, item, item, itemTyparInst, occurrence, nenv, ad, m, replacing)

                        member _.NotifyMethodGroupNameResolution(pos, item, itemGroup, itemTyparInst, occurrence, nenv, ad, m, replacing) =
                            notifyNameResolution (pos, item, itemGroup, itemTyparInst, occurrence, nenv, ad, m, replacing)

                        member _.NotifyExprHasType(_, _, _, _) = assert false // no expr typings in MakeAndPublishSimpleVals
                        member _.NotifyExprHasTypeSynthetic(_, _, _, _) =  assert false // no expr typings in MakeAndPublishSimpleVals

                        member _.NotifyFormatSpecifierLocation(_, _) = ()

                        member _.NotifyRelatedSymbolUse(_, _, _) = ()

                        member _.NotifyOpenDeclaration _ = ()

                        member _.CurrentSourceText = None

                        member _.FormatStringCheckContext = None }

                use _h = WithNewTypecheckResultsSink(sink, cenv.tcSink)
                MakeAndPublishSimpleVals cenv env names

            if nameResolutions.Count <> 0 then
                let _, _, _, _, _, _, ad, m1, _replacing = nameResolutions[0]
                // mergedNameEnv - name resolution env that contains all names
                // mergedRange - union of ranges of names
                let mergedNameEnv, mergedRange =
                    ((env.NameEnv, m1), nameResolutions) ||> Seq.fold (fun (nenv, merged) (_, item, _, _, _, _, _, m, _) ->
                        // MakeAndPublishVal creates only Item.Value
                        let item = match item with Item.Value item -> item | _ -> failwith "impossible"
                        (AddFakeNamedValRefToNameEnv item.DisplayName nenv item), (unionRanges m merged)
                        )
                // send notification about mergedNameEnv
                CallEnvSink cenv.tcSink (mergedRange, mergedNameEnv, ad)
                // call CallNameResolutionSink for all captured name resolutions using mergedNameEnv
                for _, item, itemGroup, itemTyparInst, occurrence, _nenv, ad, m, _replacing in nameResolutions do
                    CallMethodGroupNameResolutionSink cenv.tcSink (m, mergedNameEnv, item, itemGroup, itemTyparInst, occurrence, ad)

            values, vspecMap

    let envinner = AddLocalValMap g cenv.tcSink m vspecMap env
    envinner, values, vspecMap

//-------------------------------------------------------------------------
// Helpers to freshen existing types and values, i.e. when a reference
// to C<_> occurs then generate C<?ty> for a fresh type inference variable ?ty.
//-------------------------------------------------------------------------

let FreshenTyconRef (g: TcGlobals) m rigid (tcref: TyconRef) declaredTyconTypars =
    let origTypars = declaredTyconTypars
    let clearStaticReq = g.langVersion.SupportsFeature LanguageFeature.InterfacesWithAbstractStaticMembers
    let freshTypars = copyTypars clearStaticReq origTypars
    if rigid <> TyparRigidity.Rigid then
        for tp in freshTypars do
            tp.SetRigidity rigid

    let renaming, tinst = FixupNewTypars m [] [] origTypars freshTypars
    let origTy = TType_app(tcref, List.map mkTyparTy origTypars, g.knownWithoutNull)
    let freshTy = TType_app(tcref, tinst, g.knownWithoutNull)
    origTy, freshTypars, renaming, freshTy

let FreshenPossibleForallTy g m rigid ty =
    let origTypars, tau = tryDestForallTy g ty
    if isNil origTypars then
        [], [], [], tau
    else
        // tps may be have been equated to other tps in equi-recursive type inference and units-of-measure type inference. Normalize them here
        let origTypars = NormalizeDeclaredTyparsForEquiRecursiveInference g origTypars
        let tps, renaming, tinst = CopyAndFixupTypars g m rigid origTypars
        origTypars, tps, tinst, instType renaming tau

let FreshenTyconRef2 (g: TcGlobals) m (tcref: TyconRef) =
    let tps, renaming, tinst = FreshenTypeInst g m (tcref.Typars m)
    tps, renaming, tinst, TType_app (tcref, tinst, g.knownWithoutNull)

/// Given a abstract method, which may be a generic method, freshen the type in preparation
/// to apply it as a constraint to the method that implements the abstract slot
let FreshenAbstractSlot g amap m synTyparDecls absMethInfo =

    // Work out if an explicit instantiation has been given. If so then the explicit type
    // parameters will be made rigid and checked for generalization. If not then auto-generalize
    // by making the copy of the type parameters on the virtual being overridden rigid.

    let typarsFromAbsSlotAreRigid =

        match synTyparDecls with
        | ValTyparDecls(synTypars, _, infer) ->
            if infer && not (isNil synTypars) then
                errorR(Error(FSComp.SR.tcOverridingMethodRequiresAllOrNoTypeParameters(), m))

            isNil synTypars

    let (CompiledSig (argTys, retTy, fmtps, _)) = CompiledSigOfMeth g amap m absMethInfo

    // If the virtual method is a generic method then copy its type parameters
    let typarsFromAbsSlot, typarInstFromAbsSlot, _ =
        let ttps = absMethInfo.GetFormalTyparsOfDeclaringType m
        let ttinst = argsOfAppTy g absMethInfo.ApparentEnclosingType
        let rigid = if typarsFromAbsSlotAreRigid then TyparRigidity.Rigid else TyparRigidity.Flexible
        FreshenAndFixupTypars g m rigid ttps ttinst fmtps

    // Work out the required type of the member
    let argTysFromAbsSlot = argTys |> List.mapSquared (instType typarInstFromAbsSlot)

    let retTyFromAbsSlot = 
        retTy 
        |> GetFSharpViewOfReturnType g        
        |> instType typarInstFromAbsSlot
    typarsFromAbsSlotAreRigid, typarsFromAbsSlot, argTysFromAbsSlot, retTyFromAbsSlot

let CheckRecdExprDuplicateFields (elems: Ident list) =
    elems |> List.iteri (fun i (uc1: Ident) ->
        elems |> List.iteri (fun j (uc2: Ident) ->
            if j > i && uc1.idText = uc2.idText then
               errorR (Error(FSComp.SR.tcMultipleFieldsInRecord(uc1.idText), uc1.idRange))))

//-------------------------------------------------------------------------
// Helpers to typecheck expressions and patterns
//-------------------------------------------------------------------------

/// Helper used to check record expressions and record patterns
let BuildFieldMap (cenv: cenv) env isPartial ty (flds: ((Ident list * Ident) * 'T) list) m =
    let g = cenv.g
    let ad = env.eAccessRights

    let allFields = flds |> List.map (fun ((_, ident), _) -> ident)
    if allFields.Length > 1 then
        // In the case of nested record fields on the same level in record copy-and-update.
        // We need to reverse the list to get the correct order of fields.
        let idents = if isPartial then allFields |> List.rev else allFields
        CheckRecdExprDuplicateFields idents

    let fldResolutions =
        flds
        |> List.choose (fun (fld, fldExpr) ->
            try
                let fldPath, fldId = fld
                let frefSet = ResolveField cenv.tcSink cenv.nameResolver env.eNameResEnv ad ty fldPath fldId allFields
                Some(fld, frefSet, fldExpr)
            with e ->
                errorRecoveryNoRange e
                None
        )

    if fldResolutions.IsEmpty then None else

    let relevantTypeSets =
        fldResolutions |> List.map (fun (_, frefSet, _) ->
            frefSet |> List.map (fun (FieldResolution(rfinfo, _)) ->
                rfinfo.TypeInst, rfinfo.TyconRef))

    let tinst, tcref =
        let first, rest = List.headAndTail relevantTypeSets
        match (first, rest) ||> List.fold (ListSet.intersect (fun (_, tcref1) (_, tcref2) -> tyconRefEq g tcref1 tcref2)) with
        | [ (tinst, tcref) ] ->
            tinst, tcref
        | tcrefs ->
            if isPartial then
                warning (Error(FSComp.SR.tcFieldsDoNotDetermineUniqueRecordType(), m))

            // try finding a record type with the same number of fields as the ones that are given.
            match tcrefs |> List.tryFind (fun (_, tc) -> tc.TrueFieldsAsList.Length =  flds.Length) with
            | Some (tinst, tcref) -> tinst, tcref
            | _ ->
                // OK, there isn't a unique, good type dictated by the intersection for the field refs.
                // We're going to get an error of some kind below.
                // Just choose one field ref and let the error come later
                let _, frefSet1, _ = List.head fldResolutions
                let (FieldResolution(rfinfo1, _)) = List.head frefSet1
                rfinfo1.TypeInst, rfinfo1.TyconRef

    let fldsmap, rfldsList =
        ((Map.empty, []), fldResolutions) ||> List.fold (fun (fs, rfldsList) ((_, ident), frefs, fldExpr) ->
                match frefs |> List.filter (fun (FieldResolution(rfinfo2, _)) -> tyconRefEq g tcref rfinfo2.TyconRef) with
                | [FieldResolution(rfinfo2, showDeprecated)] ->

                    // Record the precise resolution of the field for intellisense
                    let item = Item.RecdField(rfinfo2)
                    CallNameResolutionSink cenv.tcSink (ident.idRange, env.NameEnv, item, emptyTyparInst, ItemOccurrence.Use, ad)

                    let fref2 = rfinfo2.RecdFieldRef

                    CheckRecdFieldAccessible cenv.amap m env.eAccessRights fref2 |> ignore

                    CheckFSharpAttributes g fref2.PropertyAttribs ident.idRange |> CommitOperationResult

                    if showDeprecated then
                        let diagnostic = Deprecated(FSComp.SR.nrRecordTypeNeedsQualifiedAccess(fref2.FieldName, fref2.Tycon.DisplayName) |> snd, m)
                        if g.langVersion.SupportsFeature(LanguageFeature.ErrorOnDeprecatedRequireQualifiedAccess) then
                            errorR(diagnostic)
                        else
                            warning(diagnostic)

                    if not (tyconRefEq g tcref fref2.TyconRef) then
                        let _, frefSet1, _ = List.head fldResolutions
                        let (FieldResolution(rfinfo1, _)) = List.head frefSet1
                        errorR (FieldsFromDifferentTypes(env.DisplayEnv, rfinfo1.RecdFieldRef, fref2, m))
                        fs, rfldsList
                    else
                        Map.add fref2.FieldName fldExpr fs, (fref2.FieldName, fldExpr) :: rfldsList

                | _ -> error(Error(FSComp.SR.tcRecordFieldInconsistentTypes(), m)))
    Some(tinst, tcref, fldsmap, List.rev rfldsList)

let ApplyUnionCaseOrExn (makerForUnionCase, makerForExnTag) m (cenv: cenv) env overallTy item =
    let g = cenv.g
    let ad = env.eAccessRights
    match item with
    | Item.ExnCase ecref ->
        CheckEntityAttributes g ecref m |> CommitOperationResult
        UnifyTypes cenv env m overallTy g.exn_ty
        CheckTyconAccessible cenv.amap m ad ecref |> ignore
        let mkf = makerForExnTag ecref
        mkf, recdFieldTysOfExnDefRef ecref, [ for f in (recdFieldsOfExnDefRef ecref) -> f.Id ]

    | Item.UnionCase(ucinfo, showDeprecated) ->
        if showDeprecated then
            let diagnostic = Deprecated(FSComp.SR.nrUnionTypeNeedsQualifiedAccess(ucinfo.DisplayName, ucinfo.Tycon.DisplayName) |> snd, m)
            if g.langVersion.SupportsFeature(LanguageFeature.ErrorOnDeprecatedRequireQualifiedAccess) then
                errorR(diagnostic)
            else
                warning(diagnostic)

        let ucref = ucinfo.UnionCaseRef
        CheckUnionCaseAttributes g ucref m |> CommitOperationResult
        CheckUnionCaseAccessible cenv.amap m ad ucref |> ignore
        let resTy = actualResultTyOfUnionCase ucinfo.TypeInst ucref
        let inst = mkTyparInst ucref.TyconRef.TyparsNoRange ucinfo.TypeInst
        UnifyTypes cenv env m overallTy resTy
        let mkf = makerForUnionCase(ucref, ucinfo.TypeInst)
        mkf, actualTysOfUnionCaseFields inst ucref, [ for f in ucref.AllFieldsAsList -> f.Id ]
    | _ -> invalidArg "item" "not a union case or exception reference"

let ApplyUnionCaseOrExnTypes m (cenv: cenv) env overallTy c =
  ApplyUnionCaseOrExn ((fun (a, b) mArgs args -> mkUnionCaseExpr(a, b, args, unionRanges m mArgs)),
                       (fun a mArgs args -> mkExnExpr (a, args, unionRanges m mArgs))) m cenv env overallTy c

let UnionCaseOrExnCheck (env: TcEnv) numArgTys numArgs m =
  if numArgs <> numArgTys then error (UnionCaseWrongArguments(env.DisplayEnv, numArgTys, numArgs, m))

let TcUnionCaseOrExnField (cenv: cenv) (env: TcEnv) ty1 m longId fieldNum funcs =
    let ad = env.eAccessRights

    let mkf, argTys, _argNames =
        match ResolvePatternLongIdent cenv.tcSink cenv.nameResolver AllIdsOK false m ad env.eNameResEnv TypeNameResolutionInfo.Default longId ExtraDotAfterIdentifier.No with
        | Item.UnionCase _ | Item.ExnCase _ as item ->
            ApplyUnionCaseOrExn funcs m cenv env ty1 item
        | _ -> error(Error(FSComp.SR.tcUnknownUnion(), m))

    if fieldNum >= argTys.Length then
        errorR (UnionCaseWrongNumberOfArgs(env.DisplayEnv, argTys.Length, fieldNum, m))

    let ty2 = List.item fieldNum argTys
    mkf, ty2

//-------------------------------------------------------------------------
// Helpers for generalizing type variables
//-------------------------------------------------------------------------

type GeneralizeConstrainedTyparOptions =
    | CanGeneralizeConstrainedTypars
    | DoNotGeneralizeConstrainedTypars


module GeneralizationHelpers =
    let ComputeUngeneralizableTypars env =

        let acc = List()

        for item in env.eUngeneralizableItems do
            if not item.WillNeverHaveFreeTypars then
                let ftps = item.GetFreeTyvars().FreeTypars
                if not ftps.IsEmpty then
                    for ftp in ftps do
                        acc.Add ftp

        Zset.Create(typarOrder, acc)


    let ComputeUnabstractableTycons env =
        let accInFreeItem acc (item: UngeneralizableItem) =
            let ftycs =
                if item.WillNeverHaveFreeTypars then item.CachedFreeLocalTycons else
                let ftyvs = item.GetFreeTyvars()
                ftyvs.FreeTycons
            if ftycs.IsEmpty then acc else unionFreeTycons ftycs acc

        List.fold accInFreeItem emptyFreeTycons env.eUngeneralizableItems

    let ComputeUnabstractableTraitSolutions env =
        let accInFreeItem acc (item: UngeneralizableItem) =
            let ftycs =
                if item.WillNeverHaveFreeTypars then item.CachedFreeTraitSolutions else
                let ftyvs = item.GetFreeTyvars()
                ftyvs.FreeTraitSolutions
            if ftycs.IsEmpty then acc else unionFreeLocals ftycs acc

        List.fold accInFreeItem emptyFreeLocals env.eUngeneralizableItems

    let rec IsGeneralizableValue g t =
        match t with
        | Expr.Lambda _ | Expr.TyLambda _ | Expr.Const _ -> true

        // let f(x: byref<int>) = let v = &x in ... shouldn't generalize "v"
        | Expr.Val (vref, _, m) -> not (isByrefLikeTy g m vref.Type)

        // Look through coercion nodes corresponding to introduction of subsumption
        | Expr.Op (TOp.Coerce, [inputTy;actualTy], [expr1], _) when isFunTy g actualTy && isFunTy g inputTy ->
            IsGeneralizableValue g expr1

        | Expr.Op (op, _, args, _) ->

            let canGeneralizeOp =
                match op with
                | TOp.Tuple _ -> true
                | TOp.UnionCase uc -> not (isUnionCaseRefDefinitelyMutable uc)
                | TOp.Recd (ctorInfo, tcref) ->
                    match ctorInfo with
                    | RecdExpr -> not (isRecdOrUnionOrStructTyconRefDefinitelyMutable tcref)
                    | RecdExprIsObjInit -> false
                | TOp.Array -> isNil args
                | TOp.ExnConstr ec -> not (isExnDefinitelyMutable ec)
                | TOp.ILAsm ([], _) -> true
                | _ -> false

            canGeneralizeOp && List.forall (IsGeneralizableValue g) args

        | Expr.LetRec (binds, body, _, _) ->
            binds |> List.forall (fun b -> not b.Var.IsMutable) &&
            binds |> List.forall (fun b -> IsGeneralizableValue g b.Expr) &&
            IsGeneralizableValue g body

        | Expr.Let (bind, body, _, _) ->
            not bind.Var.IsMutable &&
            IsGeneralizableValue g bind.Expr &&
            IsGeneralizableValue g body

        // Applications of type functions are _not_ normally generalizable unless explicitly marked so
        | Expr.App (Expr.Val (vref, _, _), _, _, [], _) when vref.IsTypeFunction ->
            ValHasWellKnownAttribute g WellKnownValAttributes.GeneralizableValueAttribute vref.Deref

        | Expr.App (expr1, _, _, [], _) -> IsGeneralizableValue g expr1
        | Expr.TyChoose (_, b, _) -> IsGeneralizableValue g b
        | Expr.Obj (_, ty, _, _, _, _, _) -> isInterfaceTy g ty || isDelegateTy g ty
        | Expr.Link eref -> IsGeneralizableValue g eref.Value
        | Expr.DebugPoint (_, innerExpr) -> IsGeneralizableValue g innerExpr

        | _ -> false

    let CanGeneralizeConstrainedTyparsForDecl (declKind: DeclKind) =
        if declKind.CanGeneralizeConstrainedTypars then
            CanGeneralizeConstrainedTypars
        else
            DoNotGeneralizeConstrainedTypars

    /// Recursively knock out typars we can't generalize.
    /// For non-generalized type variables be careful to iteratively knock out
    /// both the typars and any typars free in the constraints of the typars
    /// into the set that are considered free in the environment.
    let rec TrimUngeneralizableTypars genConstrainedTyparFlag inlineFlag (generalizedTypars: Typar list) freeInEnv =
        // Do not generalize type variables with a static requirement unless function is marked 'inline'
        let generalizedTypars, ungeneralizableTypars1 =
            if inlineFlag = ValInline.Always then generalizedTypars, []
            else generalizedTypars |> List.partition (fun tp -> tp.StaticReq = TyparStaticReq.None)

        // Do not generalize type variables which would escape their scope
        // because they are free in the environment
        let generalizedTypars, ungeneralizableTypars2 =
            List.partition (fun x -> not (Zset.contains x freeInEnv)) generalizedTypars

        // Some situations, e.g. implicit class constructions that represent functions as fields,
        // do not allow generalisation over constrained typars. (since they cannot be represented as fields)
        //
        // Don't generalize IsCompatFlex type parameters to avoid changing inferred types.
        let generalizedTypars, ungeneralizableTypars3 =
            generalizedTypars
            |> List.partition (fun tp ->
                (genConstrainedTyparFlag = CanGeneralizeConstrainedTypars || tp.Constraints.IsEmpty) &&
                not tp.IsCompatFlex)

        if isNil ungeneralizableTypars1 && isNil ungeneralizableTypars2 && isNil ungeneralizableTypars3 then
            generalizedTypars, freeInEnv
        else
            let freeInEnv =
                unionFreeTypars
                    (accFreeInTypars CollectAllNoCaching ungeneralizableTypars1
                        (accFreeInTypars CollectAllNoCaching ungeneralizableTypars2
                            (accFreeInTypars CollectAllNoCaching ungeneralizableTypars3 emptyFreeTyvars))).FreeTypars
                    freeInEnv
            TrimUngeneralizableTypars genConstrainedTyparFlag inlineFlag generalizedTypars freeInEnv

    /// Condense type variables in positive position
    let CondenseTypars (cenv: cenv, denv: DisplayEnv, generalizedTypars: Typars, tauTy, m) =

        let g = cenv.g

        // The type of the value is ty11 * ... * ty1N -> ... -> tyM1 * ... * tyMM -> retTy
        // This is computed REGARDLESS of the arity of the expression.
        let curriedArgTys, retTy = stripFunTy g tauTy
        let allUntupledArgTys = curriedArgTys |> List.collect (tryDestRefTupleTy g)

        // Compute the type variables in 'rettyR
        let returnTypeFreeTypars = freeInTypeLeftToRight g false retTy
        let allUntupledArgTysWithFreeVars = allUntupledArgTys |> List.map (fun ty -> (ty, freeInTypeLeftToRight g false ty))

        let relevantUniqueSubtypeConstraint (tp: Typar) =
            // Find a single subtype constraint
            match tp.Constraints |> List.partition _.IsCoercesTo with
            | [TyparConstraint.CoercesTo(tgtTy, _)], others ->
                 // Throw away null constraints if they are implied
                 if others |> List.exists (function TyparConstraint.SupportsNull _ -> not (TypeNullIsExtraValue g m tgtTy) | _ -> true)
                 then None
                 else Some tgtTy
            | _ -> None


        // Condensation typars can't be used in the constraints of any candidate condensation typars. So compute all the
        // typars free in the constraints of tyIJ

        let lhsConstraintTypars =
            allUntupledArgTys |> List.collect (fun ty ->
                match tryDestTyparTy g ty with
                | ValueSome tp ->
                    match relevantUniqueSubtypeConstraint tp with
                    | Some cxty -> freeInTypeLeftToRight g false cxty
                    | None -> []
                | _ -> [])

        let IsCondensationTypar (tp: Typar) =
            // A condensation typar may not a user-generated type variable nor has it been unified with any user type variable
            (tp.DynamicReq = TyparDynamicReq.No) &&
            // A condensation typar must have a single constraint "'a :> A"
            Option.isSome (relevantUniqueSubtypeConstraint tp) &&
            // This is type variable is not used on the r.h.s. of the type
            not (ListSet.contains typarEq tp returnTypeFreeTypars) &&
            // A condensation typar can't be used in the constraints of any candidate condensation typars
            not (ListSet.contains typarEq tp lhsConstraintTypars) &&
            // A condensation typar must occur precisely once in tyIJ, and must not occur free in any other tyIJ
            (match allUntupledArgTysWithFreeVars |> List.partition (fun (ty, _) -> match tryDestTyparTy g ty with ValueSome destTypar -> typarEq destTypar tp | _ -> false) with
             | [_], rest -> not (rest |> List.exists (fun (_, fvs) -> ListSet.contains typarEq tp fvs))
             | _ -> false)

        let condensationTypars, generalizedTypars = generalizedTypars |> List.partition IsCondensationTypar

        // Condensation solves type variables eagerly and removes them from the generalization set
        for tp in condensationTypars do
            ChooseTyparSolutionAndSolve cenv.css denv tp

        generalizedTypars

    let ComputeAndGeneralizeGenericTypars (cenv: cenv,
            denv: DisplayEnv,
            m,
            freeInEnv: FreeTypars,
            canInferTypars,
            genConstrainedTyparFlag,
            inlineFlag,
            exprOpt,
            allDeclaredTypars: Typars,
            maxInferredTypars: Typars,
            tauTy,
            resultFirst) =

        let g = cenv.g
        let allDeclaredTypars = NormalizeDeclaredTyparsForEquiRecursiveInference g allDeclaredTypars

        let typarsToAttemptToGeneralize =
            if (match exprOpt with None -> true | Some e -> IsGeneralizableValue g e)
            then (ListSet.unionFavourLeft typarEq allDeclaredTypars maxInferredTypars)
            else allDeclaredTypars

        // Update the StaticReq of type variables prior to assessing generalization
        for typar in typarsToAttemptToGeneralize do
            UpdateStaticReqOfTypar denv cenv.css m NoTrace typar

        let generalizedTypars, freeInEnv =
            TrimUngeneralizableTypars genConstrainedTyparFlag inlineFlag typarsToAttemptToGeneralize freeInEnv

        for tp in allDeclaredTypars do
            if Zset.memberOf freeInEnv tp then
                let ty = mkTyparTy tp
                error(Error(FSComp.SR.tcNotSufficientlyGenericBecauseOfScope(NicePrint.prettyStringOfTy denv ty), m))

        let generalizedTypars = CondenseTypars(cenv, denv, generalizedTypars, tauTy, m)

        let generalizedTypars =
            if canInferTypars then generalizedTypars
            else generalizedTypars |> List.filter (fun tp -> ListSet.contains typarEq tp allDeclaredTypars)

        let allConstraints = List.collect (fun (tp: Typar) -> tp.Constraints) generalizedTypars
        let generalizedTypars = SimplifyMeasuresInTypeScheme g resultFirst generalizedTypars tauTy allConstraints

        // Generalization turns inference type variables into rigid, quantified type variables,
        // (they may be rigid already)
        generalizedTypars |> List.iter (SetTyparRigid denv m)

        // Generalization removes constraints related to generalized type variables
        EliminateConstraintsForGeneralizedTypars denv cenv.css m NoTrace generalizedTypars

        generalizedTypars

    //-------------------------------------------------------------------------
    // Helpers to freshen existing types and values, i.e. when a reference
    // to C<_> occurs then generate C<?ty> for a fresh type inference variable ?ty.
    //-------------------------------------------------------------------------

    let CheckDeclaredTyparsPermitted (memFlagsOpt: SynMemberFlags option, declaredTypars: Typars, m) =
        match memFlagsOpt with
        | None -> ()
        | Some memberFlags ->
            match memberFlags.MemberKind with
            // can't infer extra polymorphism for properties
            | SynMemberKind.PropertyGet
            | SynMemberKind.PropertySet
            | SynMemberKind.PropertyGetSet ->
                 if not (isNil declaredTypars) then
                    let declaredTyparsRange = 
                        declaredTypars 
                        |> List.map(fun typar ->  typar.Range)
                            
                    let m = declaredTyparsRange |> List.fold (fun r a -> unionRanges r a) range0
                        
                    errorR(Error(FSComp.SR.tcPropertyRequiresExplicitTypeParameters(), m))
            | SynMemberKind.Constructor ->
                 if not (isNil declaredTypars) then
                     errorR(Error(FSComp.SR.tcConstructorCannotHaveTypeParameters(), m))
            | _ -> ()

    /// Properties and Constructors may only generalize the variables associated with the containing class (retrieved from the 'this' pointer)
    /// Also check they don't declare explicit typars.
    let ComputeCanInferExtraGeneralizableTypars (parentRef, canInferTypars, memFlagsOpt: SynMemberFlags option) =
        canInferTypars &&
        (match memFlagsOpt with
         | None -> true
         | Some memberFlags ->
            match memberFlags.MemberKind with
            // can't infer extra polymorphism for properties
            | SynMemberKind.PropertyGet
            | SynMemberKind.PropertySet
            | SynMemberKind.PropertyGetSet -> false
            // can't infer extra polymorphism for class constructors
            | SynMemberKind.ClassConstructor -> false
            // can't infer extra polymorphism for constructors
            | SynMemberKind.Constructor -> false
            // feasible to infer extra polymorphism
            | _ -> true) &&
        (match parentRef with
         | Parent tcref -> not tcref.IsFSharpDelegateTycon
         | _ -> true) // no generic parameters inferred for 'Invoke' method

//-------------------------------------------------------------------------
// ComputeInlineFlag
//-------------------------------------------------------------------------

let ComputeInlineFlag (memFlagsOption: SynMemberFlags option) isInline isMutable g attrs m =
    let valFlags = computeValWellKnownFlags g attrs

    let hasNoCompilerInliningAttribute () =
        hasFlag valFlags WellKnownValAttributes.NoCompilerInliningAttribute

    let isCtorOrAbstractSlot () =
        match memFlagsOption with
        | None -> false
        | Some x -> (x.MemberKind = SynMemberKind.Constructor) || x.IsDispatchSlot || x.IsOverrideOrExplicitImpl

    let isExtern () =
        hasFlag valFlags WellKnownValAttributes.DllImportAttribute

    let inlineFlag, reportIncorrectInlineKeywordUsage =
        // Mutable values may never be inlined
        // Constructors may never be inlined
        // Calls to virtual/abstract slots may never be inlined
        // Values marked with NoCompilerInliningAttribute or [<MethodImpl(MethodImplOptions.NoInlining)>] may never be inlined
        if isMutable || isCtorOrAbstractSlot() || hasNoCompilerInliningAttribute() || isExtern () then
            ValInline.Never, errorR
        elif HasMethodImplNoInliningAttribute g attrs then
            ValInline.Never,
                if g.langVersion.SupportsFeature LanguageFeature.WarningWhenInliningMethodImplNoInlineMarkedFunction
                then warning
                else ignore
        elif isInline then
            ValInline.Always, ignore
        else
            ValInline.Optional, ignore

    if isInline && (inlineFlag <> ValInline.Always) then
        reportIncorrectInlineKeywordUsage (Error(FSComp.SR.tcThisValueMayNotBeInlined(), m))

    inlineFlag


//-------------------------------------------------------------------------
// Binding normalization.
//
// Determine what sort of value is being bound (normal value, instance
// member, normal function, static member etc.) and make some
// name-resolution-sensitive adjustments to the syntax tree.
//
// One part of this "normalization" ensures:
//        "let SynPat.LongIdent(f) = e" when f not a datatype constructor --> let Pat_var(f) = e"
//        "let SynPat.LongIdent(f) pat = e" when f not a datatype constructor --> let Pat_var(f) = \pat. e"
//        "let (SynPat.LongIdent(f) : ty) = e" when f not a datatype constructor --> let (Pat_var(f) : ty) = e"
//        "let (SynPat.LongIdent(f) : ty) pat = e" when f not a datatype constructor --> let (Pat_var(f) : ty) = \pat. e"
//
// This is because the first lambda in a function definition "let F x = e"
// now looks like a constructor application, i.e. let (F x) = e ...
// also let A.F x = e ...
// also let f x = e ...
//
// The other parts turn property definitions into method definitions.
//-------------------------------------------------------------------------


// NormalizedBindingRhs records the r.h.s. of a binding after some munging just before type checking.
// NOTE: This is a bit of a mess. In the early implementation of F# we decided
// to have the parser convert "let f x = e" into
// "let f = fun x -> e". This is called "pushing" a pattern across to the right hand side. Complex
// patterns (e.g. non-tuple patterns) result in a computation on the right.
// However, this approach really isn't that great - especially since
// the language is now considerably more complex, e.g. we use
// type information from the first (but not the second) form in
// type inference for recursive bindings, and the first form
// may specify .NET attributes for arguments. There are still many
// relics of this approach around, e.g. the expression in BindingRhs
// below is of the second form. However, to extract relevant information
// we keep a record of the pats and optional explicit return type already pushed
// into expression so we can use any user-given type information from these
type NormalizedBindingRhs =
    | NormalizedBindingRhs of
        simplePats: SynSimplePats list *
        returnTyOpt: SynBindingReturnInfo option *
        rhsExpr: SynExpr

let PushOnePatternToRhs (cenv: cenv) isMember synPat (NormalizedBindingRhs(simplePatsList, retTyOpt, rhsExpr)) =
    let simplePats, rhsExpr = PushPatternToExpr cenv.synArgNameGenerator isMember synPat rhsExpr
    NormalizedBindingRhs(simplePats :: simplePatsList, retTyOpt, rhsExpr)

type NormalizedBindingPatternInfo =
    NormalizedBindingPat of SynPat * NormalizedBindingRhs * SynValData * SynValTyparDecls

/// Represents a syntactic, unchecked binding after the resolution of the name resolution status of pattern
/// constructors and after "pushing" all complex patterns to the right hand side.
type NormalizedBinding =
  | NormalizedBinding of
      visibility: SynAccess option *
      kind: SynBindingKind *
      shouldInline: bool *
      isMutable: bool *
      attribs: SynAttribute list *
      xmlDoc: XmlDoc *
      typars: SynValTyparDecls *
      valSynData: SynValData *
      pat: SynPat *
      rhsExpr: NormalizedBindingRhs *
      mBinding: range *
      spBinding: DebugPointAtBinding

type IsObjExprBinding =
    | ObjExprBinding
    | ValOrMemberBinding

module BindingNormalization =
    /// Push a bunch of pats at once. They may contain patterns, e.g. let f (A x) (B y) = ...
    /// In this case the semantics is let f a b = let A x = a in let B y = b
    let private PushMultiplePatternsToRhs (cenv: cenv) isMember pats (NormalizedBindingRhs(spatsL, rtyOpt, rhsExpr)) =
        let spatsL2, rhsExpr = PushCurriedPatternsToExpr cenv.synArgNameGenerator rhsExpr.Range isMember pats None rhsExpr
        NormalizedBindingRhs(spatsL2@spatsL, rtyOpt, rhsExpr)


    let private MakeNormalizedStaticOrValBinding (cenv: cenv) isObjExprBinding id vis typars args rhsExpr valSynData =
        let (SynValData(memberFlags = memberFlagsOpt)) = valSynData
        NormalizedBindingPat(mkSynPatVar vis id, PushMultiplePatternsToRhs cenv ((isObjExprBinding = ObjExprBinding) || Option.isSome memberFlagsOpt) args rhsExpr, valSynData, typars)

    let private MakeNormalizedInstanceMemberBinding (cenv: cenv) thisId memberId toolId vis m typars args rhsExpr valSynData =
        NormalizedBindingPat(SynPat.InstanceMember(thisId, memberId, toolId, vis, m), PushMultiplePatternsToRhs cenv true args rhsExpr, valSynData, typars)

    let private NormalizeStaticMemberBinding (cenv: cenv) (memberFlags: SynMemberFlags) valSynData id vis typars args m rhsExpr =
        let (SynValData(valInfo = valSynInfo; thisIdOpt = thisIdOpt)) = valSynData
        if memberFlags.IsInstance then
            // instance method without adhoc "this" argument
            error(Error(FSComp.SR.tcInstanceMemberRequiresTarget(), m))
        match args, memberFlags.MemberKind with
        | _, SynMemberKind.PropertyGetSet -> error(Error(FSComp.SR.tcUnexpectedPropertyInSyntaxTree(), m))
        | [], SynMemberKind.ClassConstructor -> error(Error(FSComp.SR.tcStaticInitializerRequiresArgument(), m))
        | [], SynMemberKind.Constructor -> error(Error(FSComp.SR.tcObjectConstructorRequiresArgument(), m))
        | [_], SynMemberKind.ClassConstructor
        | [_], SynMemberKind.Constructor -> MakeNormalizedStaticOrValBinding cenv ValOrMemberBinding id vis typars args rhsExpr valSynData
        // Static property declared using 'static member P = expr': transformed to a method taking a "unit" argument
        // static property: these transformed into methods taking one "unit" argument
        | [], SynMemberKind.Member ->
            let memberFlags = {memberFlags with MemberKind = SynMemberKind.PropertyGet}
            let valSynData = SynValData(Some memberFlags, valSynInfo, thisIdOpt)
            NormalizedBindingPat(mkSynPatVar vis id,
                                 PushOnePatternToRhs cenv true (SynPat.Const(SynConst.Unit, m)) rhsExpr,
                                 valSynData,
                                 typars)
        | _ -> MakeNormalizedStaticOrValBinding cenv ValOrMemberBinding id vis typars args rhsExpr valSynData

    let private NormalizeInstanceMemberBinding (cenv: cenv) (memberFlags: SynMemberFlags) valSynData thisId memberId (toolId: Ident option) vis typars args m rhsExpr =
        let (SynValData(_, valSynInfo, thisIdOpt)) = valSynData

        if not memberFlags.IsInstance then
            // static method with adhoc "this" argument
            error(Error(FSComp.SR.tcStaticMemberShouldNotHaveThis(), m))

        match args, memberFlags.MemberKind with
        | _, SynMemberKind.ClassConstructor ->
            error(Error(FSComp.SR.tcExplicitStaticInitializerSyntax(), m))

        | _, SynMemberKind.Constructor ->
            error(Error(FSComp.SR.tcExplicitObjectConstructorSyntax(), m))

        | _, SynMemberKind.PropertyGetSet ->
            error(Error(FSComp.SR.tcUnexpectedPropertySpec(), m))

        // Instance property declared using 'x.Member': transformed to methods taking a "this" and a "unit" argument
        // We push across the 'this' arg in mk_rec_binds
        | [], SynMemberKind.Member ->
            let memberFlags = {memberFlags with MemberKind = SynMemberKind.PropertyGet}
            NormalizedBindingPat
                (SynPat.InstanceMember(thisId, memberId, toolId, vis, m),
                 PushOnePatternToRhs cenv true (SynPat.Const(SynConst.Unit, m)) rhsExpr,
                 // Update the member info to record that this is a SynMemberKind.PropertyGet
                 SynValData(Some memberFlags, valSynInfo, thisIdOpt),
                 typars)

        | _ ->
            MakeNormalizedInstanceMemberBinding cenv thisId memberId toolId vis m typars args rhsExpr valSynData

    let private NormalizeBindingPattern (cenv: cenv) nameResolver isObjExprBinding (env: TcEnv) valSynData headPat rhsExpr =
        let ad = env.AccessRights
        let (SynValData(memberFlags = memberFlagsOpt)) = valSynData
        let rec normPattern pat =
            // One major problem with versions of F# prior to 1.9.x was that data constructors easily 'pollute' the namespace
            // of available items, to the point that you can't even define a function with the same name as an existing union case.
            match pat with
            | SynPat.FromParseError(innerPat, _) ->
                normPattern innerPat

            | SynPat.LongIdent (SynLongIdent(longId, _, _) as synLongId, toolId, tyargs, SynArgPats.Pats args, vis, m) ->
                let typars = match tyargs with None -> inferredTyparDecls | Some typars -> typars
                match memberFlagsOpt with
                | None ->
                    let extraDot = if synLongId.ThereIsAnExtraDotAtTheEnd then ExtraDotAfterIdentifier.Yes else ExtraDotAfterIdentifier.No
                    let warnOnUpper =
                        if not args.IsEmpty then
                            WarnOnUpperUnionCaseLabel
                        else AllIdsOK  
                    
                    match ResolvePatternLongIdent cenv.tcSink nameResolver warnOnUpper true m ad env.NameEnv TypeNameResolutionInfo.Default longId extraDot with
                    | Item.NewDef id ->
                        if id.idText = opNameCons then
                            NormalizedBindingPat(pat, rhsExpr, valSynData, typars)
                        else
                            if isObjExprBinding = ObjExprBinding then
                                errorR(Deprecated(FSComp.SR.tcObjectExpressionFormDeprecated(), m))
                            MakeNormalizedStaticOrValBinding cenv isObjExprBinding id vis typars args rhsExpr valSynData
                    | _ ->
                        error(Error(FSComp.SR.tcInvalidDeclaration(), m))

                | Some memberFlags ->
                    match longId with
                    // x.Member in member binding patterns.
                    | [thisId;memberId] -> NormalizeInstanceMemberBinding cenv memberFlags valSynData thisId memberId toolId vis typars args m rhsExpr
                    | [memberId] ->
                        if memberFlags.IsInstance then
                            // instance method without adhoc "this" argument
                            errorR(Error(FSComp.SR.tcInstanceMemberRequiresTarget(), memberId.idRange))
                            let thisId = ident ("_", m)
                            NormalizeInstanceMemberBinding cenv memberFlags valSynData thisId memberId toolId vis typars args m rhsExpr
                        else
                            NormalizeStaticMemberBinding cenv memberFlags valSynData memberId vis typars args m rhsExpr
                    | _ ->
                        NormalizedBindingPat(pat, rhsExpr, valSynData, typars)

            // Object constructors are normalized in TcLetrecBindings
            // Here we are normalizing member definitions with simple (not long) ids,
            // e.g. "static member x = 3" and "member x = 3" (instance with missing "this." comes through here. It is trapped and generates a warning)
            | SynPat.Named(SynIdent(id,_), false, vis, m)
                when
                   (match memberFlagsOpt with
                    | None -> false
                    | Some memberFlags ->
                         memberFlags.MemberKind <> SynMemberKind.Constructor &&
                         memberFlags.MemberKind <> SynMemberKind.ClassConstructor) ->

                NormalizeStaticMemberBinding cenv (Option.get memberFlagsOpt) valSynData id vis inferredTyparDecls [] m rhsExpr

            | SynPat.Typed(innerPat, x, y) ->
                let (NormalizedBindingPat(innerPatR, rhsExpr, valSynData, typars)) = normPattern innerPat
                NormalizedBindingPat(SynPat.Typed(innerPatR, x, y), rhsExpr, valSynData, typars)

            | SynPat.Attrib(_, _, m) ->
                error(Error(FSComp.SR.tcAttributesInvalidInPatterns(), m))

            | _ ->
                NormalizedBindingPat(pat, rhsExpr, valSynData, inferredTyparDecls)
        normPattern headPat

    let NormalizeBinding isObjExprBinding (cenv: cenv) (env: TcEnv) binding =
        match binding with
        | SynBinding (vis, kind, isInline, isMutable, Attributes attrs, xmlDoc, valSynData, headPat, retInfo, rhsExpr, mBinding, debugPoint, _) ->
            let (NormalizedBindingPat(pat, rhsExpr, valSynData, typars)) =
                NormalizeBindingPattern cenv cenv.nameResolver isObjExprBinding env valSynData headPat (NormalizedBindingRhs ([], retInfo, rhsExpr))
            let paramNames = Some valSynData.SynValInfo.ArgNames
            let checkXmlDocs = cenv.diagnosticOptions.CheckXmlDocs
            let xmlDoc = xmlDoc.ToXmlDoc(checkXmlDocs, paramNames)
            NormalizedBinding(vis, kind, isInline, isMutable, attrs, xmlDoc, typars, valSynData, pat, rhsExpr, mBinding, debugPoint)

//-------------------------------------------------------------------------
// input is:
//    [<CompileAsEvent>]
//    member x.P with get = fun () -> e
// -->
//    member x.add_P< >(argName) = (e).AddHandler(argName)
//    member x.remove_P< >(argName) = (e).RemoveHandler(argName)

module EventDeclarationNormalization =
    let ConvertSynInfo m (SynValInfo(argInfos, retInfo)) =
       // reconstitute valSynInfo by adding the argument
       let argInfos =
           match argInfos with
           | [[thisArgInfo];[]] -> [[thisArgInfo];SynInfo.unnamedTopArg] // instance property getter
           | [[]] -> [SynInfo.unnamedTopArg] // static property getter
           | _ -> error(BadEventTransformation m)

       // reconstitute valSynInfo
       SynValInfo(argInfos, retInfo)

    // The property x.P becomes methods x.add_P and x.remove_P
    let ConvertMemberFlags (memberFlags: SynMemberFlags) = { memberFlags with MemberKind = SynMemberKind.Member }

    let private ConvertMemberFlagsOpt m memberFlagsOpt =
        match memberFlagsOpt with
        | Some memberFlags -> Some (ConvertMemberFlags memberFlags)
        | _ -> error(BadEventTransformation m)

    let private ConvertSynData m valSynData =
        let (SynValData(memberFlagsOpt, valSynInfo, thisIdOpt)) = valSynData
        let memberFlagsOpt = ConvertMemberFlagsOpt m memberFlagsOpt
        let valSynInfo = ConvertSynInfo m valSynInfo
        SynValData(memberFlagsOpt, valSynInfo, thisIdOpt)

    let rec private RenameBindingPattern f declPattern =
        match declPattern with
        | SynPat.FromParseError(innerPat, _) -> RenameBindingPattern f innerPat
        | SynPat.Typed(innerPat, _, _) -> RenameBindingPattern f innerPat
        | SynPat.Named (SynIdent(id,_), x2, vis2, m) -> SynPat.Named (SynIdent(ident(f id.idText, id.idRange), None), x2, vis2, m)
        | SynPat.InstanceMember(thisId, id, toolId, vis2, m) -> SynPat.InstanceMember(thisId, ident(f id.idText, id.idRange), toolId, vis2, m)
        | _ -> error(Error(FSComp.SR.tcOnlySimplePatternsInLetRec(), declPattern.Range))

    /// Some F# bindings syntactically imply additional bindings, notably properties
    /// annotated with [<CLIEvent>]
    let GenerateExtraBindings (cenv: cenv) (bindingAttribs, binding) =
        let g = cenv.g

        let (NormalizedBinding(vis1, bindingKind, isInline, isMutable, _, bindingXmlDoc, _synTyparDecls, valSynData, declPattern, bindingRhs, mBinding, debugPoint)) = binding

        if CompileAsEvent g bindingAttribs then

            let MakeOne (prefix, target) =
                let declPattern = RenameBindingPattern (fun s -> prefix + s) declPattern
                let argName = "handler"
                let mBinding = mBinding.MakeSynthetic()

                // modify the rhs and argument data
                let bindingRhs, valSynData =
                   let (NormalizedBindingRhs(_, _, rhsExpr)) = bindingRhs
                   let m = rhsExpr.Range
                   // reconstitute valSynInfo by adding the argument
                   let valSynData = ConvertSynData m valSynData

                   match rhsExpr with
                   // Detect 'fun () -> e' which results from the compilation of a property getter
                   | SynExpr.Lambda (args=SynSimplePats.SimplePats(pats = []); body=trueRhsExpr; range=m) ->
                       let m = m.MakeSynthetic()
                       let rhsExpr = mkSynApp1 (SynExpr.DotGet (SynExpr.Paren (trueRhsExpr, range0, None, m), range0, SynLongIdent([ident(target, m)], [], [None]), m)) (SynExpr.Ident (ident(argName, m))) m

                       // reconstitute rhsExpr
                       let bindingRhs = NormalizedBindingRhs([], None, rhsExpr)

                       // add the argument to the expression
                       let bindingRhs = PushOnePatternToRhs cenv true (mkSynPatVar None (ident (argName, mBinding))) bindingRhs

                       bindingRhs, valSynData
                   | _ ->
                       error(BadEventTransformation m)

                // reconstitute the binding
                NormalizedBinding(vis1, bindingKind, isInline, isMutable, [], bindingXmlDoc, noInferredTypars, valSynData, declPattern, bindingRhs, mBinding, debugPoint)

            [ MakeOne ("add_", "AddHandler"); MakeOne ("remove_", "RemoveHandler") ]
        else
            []

/// Make a copy of the "this" type for a generic object type, e.g. List<'T> --> List<'?> for a fresh inference variable.
/// Also adjust the "this" type to take into account whether the type is a struct.
let FreshenObjectArgType (cenv: cenv) m rigid tcref isExtrinsic declaredTyconTypars =
    let g = cenv.g

    let tcrefObjTy, enclosingDeclaredTypars, renaming, objTy =
        FreshenTyconRef g m rigid tcref declaredTyconTypars

    // Struct members have a byref 'this' type (unless they are extrinsic extension members)
    let thisTy =
        if not isExtrinsic && tcref.IsStructOrEnumTycon then
            if isRecdOrStructTyReadOnly g m objTy then
                mkInByrefTy g objTy
            else
                mkByrefTy g objTy
        else
            objTy

    tcrefObjTy, enclosingDeclaredTypars, renaming, objTy, thisTy

// The early generalization rule of F# 2.0 can be unsound for members in generic types (Bug DevDiv2 10649).
// It gives rise to types like "Forall T. ?X -> ?Y" where ?X and ?Y are later discovered to involve T.
//
// For example:
//      type C<'T>() =
//          let mutable x = Unchecked.defaultof<_> // unknown inference variable ?X
//          static member A() = x
//                     // At this point A is generalized early to "Forall T. unit -> ?X"
//          static member B1() = C<string>.A()
//                     // At this point during type inference, the return type of C<string>.A() is '?X'
//                     // After type inference, the return type of C<string>.A() is 'string'
//          static member B2() = C<int>.A()
//                     // At this point during type inference, the return type of C<int>.A() is '?X'
//                     // After type inference, the return type of C<int>.A() is 'int'
//          member this.C() = (x: 'T)
//                     // At this point during type inference the type of 'x' is inferred to be 'T'
//
// Here "A" is generalized too early.
//
// Ideally we would simply generalize "A" later, when it is known to be
// sound. However, that can lead to other problems (e.g. some programs that typecheck today would no longer
// be accepted). As a result, we deal with this unsoundness by an adhoc post-type-checking
// consistency check for recursive uses of "A" with explicit instantiations within the recursive
// scope of "A".
let TcValEarlyGeneralizationConsistencyCheck (cenv: cenv) (env: TcEnv) (v: Val, valRecInfo, tinst, vTy, tau, m) =
    let g = cenv.g

    match valRecInfo with
    | ValInRecScope isComplete when isComplete && not (isNil tinst) ->
        cenv.css.PushPostInferenceCheck (preDefaults=false, check=fun () ->
            let vTypars, vTauTy = tryDestForallTy g vTy
            if not (isNil vTypars) then
              let vTypars = NormalizeDeclaredTyparsForEquiRecursiveInference g vTypars
              let vTauTy = instType (mkTyparInst vTypars tinst) vTauTy
              if not (AddCxTypeEqualsTypeUndoIfFailed env.DisplayEnv cenv.css m tau vTauTy) then
                  let txt = buildString (fun buf -> NicePrint.outputQualifiedValSpec env.DisplayEnv cenv.infoReader buf (mkLocalValRef v))
                  error(Error(FSComp.SR.tcInferredGenericTypeGivesRiseToInconsistency(v.DisplayName, txt), m)))
    | _ -> ()


/// TcVal. "Use" a value, normally at a fresh type instance (unless instantiationInfoOpt is
/// given). instantiationInfoOpt is set when an explicit type instantiation is given, e.g.
///     Seq.empty<string>
/// In this case the vrefFlags inside instantiationInfoOpt are just NormalValUse.
///
/// instantiationInfoOpt is is also set when building the final call for a reference to an
/// F# object model member, in which case the instantiationInfoOpt is the type instantiation
/// inferred by member overload resolution.
let TcVal (cenv: cenv) env (tpenv: UnscopedTyparEnv) (vref: ValRef) instantiationInfoOpt optAfterResolution (m: range) =
    let g = cenv.g

    let tpsorig, _, _, _, tinst, _ as res =
        let v = vref.Deref
        let valRecInfo = v.RecursiveValInfo

        // Don't count compiler-generated refs (synthetic range) for FS1182
        if not m.IsSynthetic then v.SetHasBeenReferenced()

        CheckValAccessible m env.eAccessRights vref

        CheckValAttributes g vref m |> CommitOperationResult

        let vTy = vref.Type

        // byref-typed values get dereferenced
        if isByrefTy g vTy then
            let isSpecial = true
            [], mkAddrGet m vref, isSpecial, destByrefTy g vTy, [], tpenv
        else
          match v.LiteralValue with
          | Some c ->
              // Literal values go to constants
              let isSpecial = true
              // The value may still be generic, e.g.
              //   [<Literal>]
              //   let Null = null
              let tpsorig, _, tinst, tauTy = FreshenPossibleForallTy g m TyparRigidity.Flexible vTy
              tpsorig, Expr.Const (c, m, tauTy), isSpecial, tauTy, tinst, tpenv

          | None ->
                // References to 'this' in classes get dereferenced from their implicit reference cell and poked
              if v.IsCtorThisVal && isRefCellTy g vTy then
                  let exprForVal = exprForValRef m vref
                  //if AreWithinCtorPreConstruct env then
                  //    warning(SelfRefObjCtor(AreWithinImplicitCtor env, m))

                  let ty = destRefCellTy g vTy
                  let isSpecial = true
                  [], mkCallCheckThis g m ty (mkRefCellGet g m ty exprForVal), isSpecial, ty, [], tpenv
              else
                  // Instantiate the value
                  let tpsorig, vrefFlags, tinst, tau, tpenv =
                      // Have we got an explicit instantiation?
                      match instantiationInfoOpt with
                      // No explicit instantiation (the normal case)
                      | None ->
                          if ValHasWellKnownAttribute g WellKnownValAttributes.RequiresExplicitTypeArgumentsAttribute v then
                               errorR(Error(FSComp.SR.tcFunctionRequiresExplicitTypeArguments(v.DisplayName), m))

                          match valRecInfo with
                          | ValInRecScope false ->
                              let tpsorig, tau = vref.GeneralizedType
                              let tinst = tpsorig |> List.map mkTyparTy
                              tpsorig, NormalValUse, tinst, tau, tpenv
                          | ValInRecScope true
                          | ValNotInRecScope ->
                              let tpsorig, _, tinst, tau = FreshenPossibleForallTy g m TyparRigidity.Flexible vTy
                              tpsorig, NormalValUse, tinst, tau, tpenv

                      // If we have got an explicit instantiation then use that
                      | Some(vrefFlags, checkTys) ->
                            let checkInst (tinst: TypeInst) =
                                if not v.IsMember && not v.PermitsExplicitTypeInstantiation && not (List.isEmpty tinst) && not (List.isEmpty v.Typars) then
                                    warning(Error(FSComp.SR.tcDoesNotAllowExplicitTypeArguments(v.DisplayName), m))
                            match valRecInfo with
                            | ValInRecScope false ->
                                let vTypars, vTauTy = vref.GeneralizedType
                                let tinst, tpenv = checkTys tpenv (vTypars |> List.map (fun tp -> tp.Kind))

                                checkInst tinst

                                if vTypars.Length <> tinst.Length then error(Error(FSComp.SR.tcTypeParameterArityMismatch(vTypars.Length, tinst.Length), m))

                                let vRecTauTy = instType (mkTyparInst vTypars tinst) vTauTy

                                (vTypars, tinst) ||> List.iter2 (fun tp ty ->
                                    try UnifyTypes cenv env m (mkTyparTy tp) ty
                                    with _ -> error (Recursion(env.DisplayEnv, v.Id, vRecTauTy, vTauTy, m)))

                                vTypars, vrefFlags, tinst, vRecTauTy, tpenv

                            | ValInRecScope true
                            | ValNotInRecScope ->
                                let vTypars, tps, tpTys, vTauTy = FreshenPossibleForallTy g m TyparRigidity.Flexible vTy

                                let tinst, tpenv = checkTys tpenv (tps |> List.map (fun tp -> tp.Kind))

                                checkInst tinst

                                if tpTys.Length <> tinst.Length then error(Error(FSComp.SR.tcTypeParameterArityMismatch(tps.Length, tinst.Length), m))

                                List.iter2 (UnifyTypes cenv env m) tpTys tinst

                                TcValEarlyGeneralizationConsistencyCheck cenv env (v, valRecInfo, tinst, vTy, vTauTy, m)

                                vTypars, vrefFlags, tinst, vTauTy, tpenv

                  let exprForVal = Expr.Val (vref, vrefFlags, m)
                  let exprForVal = mkTyAppExpr m (exprForVal, vTy) tinst
                  let isSpecial =
                      (match vrefFlags with NormalValUse | PossibleConstrainedCall _ -> false | _ -> true) || g.isSpliceOperator vref
                  let exprForVal = RecordUseOfRecValue cenv valRecInfo vref exprForVal m

                  tpsorig, exprForVal, isSpecial, tau, tinst, tpenv

    match optAfterResolution with
    | Some (AfterResolution.RecordResolution(_, callSink, _, _)) -> callSink (mkTyparInst tpsorig tinst)
    | Some AfterResolution.DoNothing | None -> ()
    res

/// Mark points where we decide whether an expression will support automatic
/// decondensation or not.
type ApplicableExpr =
    | ApplicableExpr of
           // context
           ctxt: cenv *
           // the function-valued expression
           expr: Expr *
           // is this the first in an application series
           isFirst: bool *
           // Is this a traitCall, where we don't build a lambda
           traitCallInfo: (Val list * Expr) option

    member x.Range =
        let (ApplicableExpr (_, expr, _, _)) = x
        expr.Range

    member x.Type =
        match x with
        | ApplicableExpr (cenv, expr, _, _) -> tyOfExpr cenv.g expr

    member x.SupplyArgument(expr2, m) =
        let (ApplicableExpr (cenv, funcExpr, first, traitCallInfo)) = x
        let g = cenv.g

        let combinedExpr =
            match funcExpr with
            | Expr.App (funcExpr0, funcExpr0Ty, tyargs0, args0, m0) when
                       (not first || isNil args0) &&
                       (not (isForallTy g funcExpr0Ty) || isFunTy g (applyTys g funcExpr0Ty (tyargs0, args0))) ->
                Expr.App (funcExpr0, funcExpr0Ty, tyargs0, args0@[expr2], unionRanges m0 m)
            | _ ->
                // Trait calls do not build a lambda if applied immediately to a tuple of arguments or a unit argument
                match traitCallInfo, tryDestRefTupleExpr expr2 with
                | Some (vs, traitCall), exprs when vs.Length = exprs.Length ->
                    mkLetsBind m (mkCompGenBinds vs exprs) traitCall
                | _ ->
                    Expr.App (funcExpr, tyOfExpr g funcExpr, [], [expr2], m)

        ApplicableExpr(cenv, combinedExpr, false, None)

    member x.Expr =
        let (ApplicableExpr (_, expr, _, _)) = x
        expr

let MakeApplicableExprNoFlex (cenv: cenv) expr =
    ApplicableExpr (cenv, expr, true, None)

let MakeApplicableExprForTraitCall (cenv: cenv) expr traitCallInfo =
    ApplicableExpr (cenv, expr, true, Some traitCallInfo)

/// This function reverses the effect of condensation for a named function value (indeed it can
/// work for any expression, though we only invoke it immediately after a call to TcVal).
///
/// De-condensation is determined BEFORE any arguments are checked. Thus
///      let f (x:'a) (y:'a) = ()
///
///      f (new obj()) "string"
///
/// does not type check (the argument instantiates 'a to "obj" but there is no flexibility on the
/// second argument position.
///
/// De-condensation is applied AFTER taking into account an explicit type instantiation. This
///      let f<'a> (x:'a) = ()
///
///      f<obj>("string)"
///
/// will type check but
///
/// Sealed types and 'obj' do not introduce generic flexibility when functions are used as first class
/// values.
///
/// For 'obj' this is because introducing this flexibility would NOT be the reverse of condensation,
/// since we don't condense
///     f: 'a -> unit
/// to
///     f: obj -> unit
///
/// We represent the flexibility in the TAST by leaving a function-to-function coercion node in the tree
/// This "special" node is immediately eliminated by the use of IteratedFlexibleAdjustArityOfLambdaBody as soon as we
/// first transform the tree (currently in optimization)

let isNonFlexibleTy g ty = isSealedTy g ty

let MakeApplicableExprWithFlex (cenv: cenv) (env: TcEnv) expr =
    let g = cenv.g
    let exprTy = tyOfExpr g expr
    let m = expr.Range

    let argTys, retTy = stripFunTy g exprTy
    let curriedActualTys = argTys |> List.map (tryDestRefTupleTy g)
    if (curriedActualTys.IsEmpty ||
        curriedActualTys |> List.exists (List.exists (isByrefTy g)) ||
        curriedActualTys |> List.forall (List.forall (isNonFlexibleTy g))) then

        ApplicableExpr (cenv, expr, true, None)
    else
        let curriedFlexibleTys =
            curriedActualTys |> List.mapSquared (fun actualTy ->
                if isNonFlexibleTy g actualTy then
                    actualTy
                else
                    let flexibleTy = NewInferenceType g
                    AddCxTypeMustSubsumeType ContextInfo.NoContext env.DisplayEnv cenv.css m NoTrace actualTy flexibleTy
                    flexibleTy)

        // Create a coercion to represent the expansion of the application
        let expr = mkCoerceExpr (expr, mkIteratedFunTy g (List.map (mkRefTupledTy g) curriedFlexibleTys) retTy, m, exprTy)
        ApplicableExpr (cenv, expr, true, None)

///  Checks, warnings and constraint assertions for downcasts
let TcRuntimeTypeTest isCast isOperator (cenv: cenv) denv m tgtTy srcTy =
    let g = cenv.g
    if TypeDefinitelySubsumesTypeNoCoercion 0 g cenv.amap m tgtTy srcTy then
      warning(TypeTestUnnecessary m)

    if isTyparTy g srcTy && not (destTyparTy g srcTy).IsCompatFlex then
        error(IndeterminateRuntimeCoercion(denv, srcTy, tgtTy, m))

    if isSealedTy g srcTy then
        error(RuntimeCoercionSourceSealed(denv, srcTy, m))

    if (isSealedTy g tgtTy || isTyparTy g tgtTy || not (isInterfaceTy g srcTy)) && not (isObjTyAnyNullness g srcTy) then
        let context = if isCast then ContextInfo.RuntimeTypeTest isOperator else ContextInfo.NoContext
        AddCxTypeMustSubsumeType context denv cenv.css m NoTrace srcTy tgtTy

    if isErasedType g tgtTy then
        if isCast then
            warning(Error(FSComp.SR.tcTypeCastErased(NicePrint.minimalStringOfType denv tgtTy, NicePrint.minimalStringOfType denv (stripTyEqnsWrtErasure EraseAll g tgtTy)), m))
        else
            error(Error(FSComp.SR.tcTypeTestErased(NicePrint.minimalStringOfType denv tgtTy, NicePrint.minimalStringOfType denv (stripTyEqnsWrtErasure EraseAll g tgtTy)), m))
    else
        let checkTrgtNullness = 
            match (srcTy,g),(tgtTy,g) with
            | (NullableRefType|NullTrueValue|NullableTypar), WithoutNullRefType when g.checkNullness && isCast -> 
                let srcNice = NicePrint.minimalStringOfTypeWithNullness denv srcTy
                let tgtNice = NicePrint.minimalStringOfTypeWithNullness denv tgtTy
                warning(Error(FSComp.SR.tcDowncastFromNullableToWithoutNull(srcNice,tgtNice,tgtNice), m))
                false
            | (NullableRefType|NullTrueValue|NullableTypar), (NullableRefType|NullTrueValue|NullableTypar) -> not isCast //a type test (unlike type cast) will never return true for  null in the source, therefore adding |null to target does not help => keep the erasure warning
            | _ -> true
        for ety in getErasedTypes g tgtTy checkTrgtNullness do
            if isMeasureTy g ety then
                warning(Error(FSComp.SR.tcTypeTestLosesMeasures(NicePrint.minimalStringOfType denv ety), m))
            else
                warning(Error(FSComp.SR.tcTypeTestLossy(NicePrint.minimalStringOfTypeWithNullness denv ety, NicePrint.minimalStringOfType denv (stripTyEqnsWrtErasure EraseAll g ety)), m))

///  Checks, warnings and constraint assertions for upcasts
let TcStaticUpcast (cenv: cenv) denv mSourceExpr mUpcastExpr tgtTy srcTy =
    let g = cenv.g
    if isTyparTy g tgtTy then
        if not (destTyparTy g tgtTy).IsCompatFlex then
            error(IndeterminateStaticCoercion(denv, srcTy, tgtTy, mUpcastExpr))

    if isSealedTy g tgtTy && not (isTyparTy g tgtTy) then
        warning(CoercionTargetSealed(denv, tgtTy, mUpcastExpr))

    if typeEquiv g srcTy tgtTy then
        warning(UpcastUnnecessary mUpcastExpr)

    AddCxTypeMustSubsumeType ContextInfo.NoContext denv cenv.css mSourceExpr NoTrace tgtTy srcTy

let BuildPossiblyConditionalMethodCall (cenv: cenv) env isMutable m isProp minfo valUseFlags minst objArgs args staticTyOpt =

    let g = cenv.g

    let shouldEraseCall =
        match cenv.conditionalDefines with
        | None -> false
        | Some defines ->

        match TryFindMethInfoStringAttribute g m g.attrib_ConditionalAttribute minfo with
        | None -> false
        | Some d -> not (List.contains d defines)

    if shouldEraseCall then
        // Methods marked with 'Conditional' must return 'unit'
        UnifyTypes cenv env m g.unit_ty (minfo.GetFSharpReturnType(cenv.amap, m, minst))
        mkUnit g m, g.unit_ty
    else
#if !NO_TYPEPROVIDERS
        match minfo with
        | ProvidedMeth(_, mi, _, _) ->
            // BuildInvokerExpressionForProvidedMethodCall converts references to F# intrinsics back to values
            // and uses TcVal to do this. However we don't want to check attributes again for provided references to values,
            // so we pass 'false' for 'checkAttributes'.
            let tcVal = LightweightTcValForUsingInBuildMethodCall g
            let _, retExpr, retTy = ProvidedMethodCalls.BuildInvokerExpressionForProvidedMethodCall tcVal (g, cenv.amap, mi, objArgs, isMutable, isProp, valUseFlags, args, m)
            retExpr, retTy

        | _ ->
#endif
        let tcVal valref valUse ttypes m =
            let _, exprForVal, _, tau, _, _ = TcVal cenv env emptyUnscopedTyparEnv valref (Some (valUse, (fun x _ -> ttypes, x))) None m
            exprForVal, tau

        BuildMethodCall tcVal g cenv.amap isMutable m isProp minfo valUseFlags minst objArgs args staticTyOpt


let TryFindIntrinsicOrExtensionMethInfo collectionSettings (cenv: cenv) (env: TcEnv) m ad nm ty =
    AllMethInfosOfTypeInScope collectionSettings cenv.infoReader env.NameEnv (Some nm) ad IgnoreOverrides m ty

let TryFindFSharpSignatureInstanceGetterProperty (cenv: cenv) (env: TcEnv) m nm ty (sigTys: TType list) =
    let g = cenv.g
    TryFindIntrinsicPropInfo cenv.infoReader m env.AccessRights nm ty
    |> List.tryFind (fun propInfo ->
        not propInfo.IsStatic && propInfo.HasGetter &&
        (
            match propInfo.GetterMethod.GetParamTypes(cenv.amap, m, []) with
            | [] -> false
            | argTysList ->

                let argTys = (argTysList |> List.reduce (@)) @ [ propInfo.GetterMethod.GetFSharpReturnType(cenv.amap, m, []) ] in
                if argTys.Length <> sigTys.Length then
                    false
                else
                    (argTys, sigTys)
                    ||> List.forall2 (typeEquiv g)
        )
    )

/// Build the 'test and dispose' part of a 'use' statement
let BuildDisposableCleanup (cenv: cenv) env m (v: Val) =
    let g = cenv.g
    let ad = env.eAccessRights

    v.SetHasBeenReferenced()

    let disposeMethod =
        match TryFindIntrinsicOrExtensionMethInfo ResultCollectionSettings.AllResults cenv env m ad "Dispose" g.system_IDisposable_ty with
        | [x] -> x
        | _ -> error(InternalError(FSComp.SR.tcCouldNotFindIDisposable(), m))

    // For struct types the test is simpler: we can determine if IDisposable is supported, and even when it is, we can avoid doing the type test
    // Note this affects the elaborated form seen by quotations etc.
    if isStructTy g v.Type then
        if TypeFeasiblySubsumesType 0 g cenv.amap m g.system_IDisposable_ty CanCoerce v.Type then
            // We can use NeverMutates here because the variable is going out of scope, there is no need to take a defensive
            // copy of it.
            let disposeExpr, _ = BuildPossiblyConditionalMethodCall cenv env NeverMutates m false disposeMethod NormalValUse [] [exprForVal v.Range v] [] None
            disposeExpr
        else
            mkUnit g m
    else
        let disposeObjVar, disposeObjExpr = mkCompGenLocal m "objectToDispose" g.system_IDisposableNull_ty
        let disposeExpr, _ = BuildPossiblyConditionalMethodCall cenv env PossiblyMutates m false disposeMethod NormalValUse [] [disposeObjExpr] [] None
        let inputExpr = mkCoerceExpr(exprForVal v.Range v, g.obj_ty_ambivalent, m, v.Type)
        mkIsInstConditional g m g.system_IDisposable_ty inputExpr disposeObjVar disposeExpr (mkUnit g m)

/// Build call to get_OffsetToStringData as part of 'fixed'
let BuildOffsetToStringData (cenv: cenv) env m =
    let g = cenv.g
    let ad = env.eAccessRights

    let offsetToStringDataMethod =
        match TryFindIntrinsicOrExtensionMethInfo ResultCollectionSettings.AllResults cenv env m ad "get_OffsetToStringData" g.system_RuntimeHelpers_ty with
        | [x] -> x
        | _ -> error(Error(FSComp.SR.tcCouldNotFindOffsetToStringData(), m))

    let offsetExpr, _ = BuildPossiblyConditionalMethodCall cenv env NeverMutates m false offsetToStringDataMethod NormalValUse [] [] [] None
    offsetExpr

let BuildILFieldGet g amap m objExpr (finfo: ILFieldInfo) =
    let fref = finfo.ILFieldRef
    let isStruct = finfo.IsValueType
    let boxity = if isStruct then AsValue else AsObject
    let tinst = finfo.TypeInst
    let fieldTy = finfo.FieldType (amap, m)
#if !NO_TYPEPROVIDERS
    let ty = tyOfExpr g objExpr
    match finfo with
    | ProvidedField _ when (isErasedType g ty) ->
        // we know it's accessible, and there are no attributes to check for now...
        match finfo.LiteralValue with
        | None ->
            error (Error(FSComp.SR.tcTPFieldMustBeLiteral(), m))
        | Some lit ->
            Expr.Const (TcFieldInit m lit, m, fieldTy)
    | _ ->
#endif
    let wrap, objExpr, _readonly, _writeonly = mkExprAddrOfExpr g isStruct false NeverMutates objExpr None m
      // The empty instantiation on the AbstractIL fspec is OK, since we make the correct fspec in IlxGen.GenAsm
      // This ensures we always get the type instantiation right when doing this from
      // polymorphic code, after inlining etc. *
    let fspec = mkILFieldSpec(fref, mkILNamedTy boxity fref.DeclaringTypeRef [])
    // Add an I_nop if this is an initonly field to make sure we never recognize it as an lvalue. See mkExprAddrOfExpr.
    wrap (mkAsmExpr (([ mkNormalLdfld fspec ] @ (if finfo.IsInitOnly then [ AI_nop ] else [])), tinst, [objExpr], [fieldTy], m))

/// Checks that setting a field value does not set a literal or initonly field
let private CheckFieldLiteralArg (finfo: ILFieldInfo) argExpr m =
    finfo.LiteralValue |> Option.iter (fun _ ->
        match stripDebugPoints argExpr with
        | Expr.Const (v, _, _) ->
            let literalValue = string v
            error (Error(FSComp.SR.tcLiteralFieldAssignmentWithArg literalValue, m))
        | _ ->
            error (Error(FSComp.SR.tcLiteralFieldAssignmentNoArg(), m))
    )
    if finfo.IsInitOnly then error (Error (FSComp.SR.tcFieldIsReadonly(), m))

let BuildILFieldSet g m objExpr (finfo: ILFieldInfo) argExpr =
    let fref = finfo.ILFieldRef
    let isStruct = finfo.IsValueType
    let boxity = if isStruct then AsValue else AsObject
    let tinst = finfo.TypeInst
      // The empty instantiation on the AbstractIL fspec is OK, since we make the correct fspec in IlxGen.GenAsm
      // This ensures we always get the type instantiation right when doing this from
      // polymorphic code, after inlining etc. *
    let fspec = mkILFieldSpec(fref, mkILNamedTy boxity fref.DeclaringTypeRef [])
    CheckFieldLiteralArg finfo argExpr m
    let wrap, objExpr, _readonly, _writeonly = mkExprAddrOfExpr g isStruct false DefinitelyMutates objExpr None m
    wrap (mkAsmExpr ([ mkNormalStfld fspec ], tinst, [objExpr; argExpr], [], m))

let BuildILStaticFieldSet m (finfo: ILFieldInfo) argExpr =
    let fref = finfo.ILFieldRef
    let isStruct = finfo.IsValueType
    let boxity = if isStruct then AsValue else AsObject
    let tinst = finfo.TypeInst
      // The empty instantiation on the AbstractIL fspec is OK, since we make the correct fspec in IlxGen.GenAsm
      // This ensures we always get the type instantiation right when doing this from
      // polymorphic code, after inlining etc.
    let fspec = mkILFieldSpec(fref, mkILNamedTy boxity fref.DeclaringTypeRef [])
    CheckFieldLiteralArg finfo argExpr m
    mkAsmExpr ([ mkNormalStsfld fspec ], tinst, [argExpr], [], m)

let BuildRecdFieldSet g m objExpr (rfinfo: RecdFieldInfo) argExpr =
    let tgtTy = rfinfo.DeclaringType
    let boxity = isStructTy g tgtTy
    let objExpr = if boxity then objExpr else mkCoerceExpr(objExpr, tgtTy, m, tyOfExpr g objExpr)
    let wrap, objExpr, _readonly, _writeonly = mkExprAddrOfExpr g boxity false DefinitelyMutates objExpr None m
    wrap (mkRecdFieldSetViaExprAddr (objExpr, rfinfo.RecdFieldRef, rfinfo.TypeInst, argExpr, m) )

// This is used to check the target of an attribute with the form of
// Long Form: [<target:attribute-name(arguments)>]
// Short Form: [<attribute-name(arguments)>]
let (|LongFormAttrTarget|UnrecognizedLongAttrTarget|ShortFormAttributeTarget|) (targetIndicator: Ident option) =
    match targetIndicator with
    | Some id when id.idText = "assembly" -> LongFormAttrTarget AttributeTargets.Assembly
    | Some id when id.idText = "module" -> LongFormAttrTarget AttributeTargets.Module
    | Some id when id.idText = "return" -> LongFormAttrTarget AttributeTargets.ReturnValue
    | Some id when id.idText = "field" -> LongFormAttrTarget AttributeTargets.Field
    | Some id when id.idText = "property" -> LongFormAttrTarget AttributeTargets.Property
    | Some id when id.idText = "method" -> LongFormAttrTarget AttributeTargets.Method
    | Some id when id.idText = "param" -> LongFormAttrTarget AttributeTargets.Parameter
    | Some id when id.idText = "type" -> LongFormAttrTarget AttributeTargets.TyconDecl
    | Some id when id.idText = "constructor" -> LongFormAttrTarget AttributeTargets.Constructor
    | Some id when id.idText = "event" -> LongFormAttrTarget AttributeTargets.Event
    | Some id -> UnrecognizedLongAttrTarget id
    | None -> ShortFormAttributeTarget

//-------------------------------------------------------------------------
// Helpers dealing with named and optional args at callsites
//-------------------------------------------------------------------------

[<return: Struct>]
let (|BinOpExpr|_|) expr =
    match expr with
    | SynExpr.App (_, _, SynExpr.App (_, _, SingleIdent opId, a, _), b, _) -> ValueSome (opId, a, b)
    | _ -> ValueNone

[<return: Struct>]
let (|SimpleEqualsExpr|_|) expr =
    match expr with
    | BinOpExpr(opId, a, b) when opId.idText = opNameEquals -> ValueSome (a, b)
    | _ -> ValueNone

/// Detect a named argument at a callsite
let TryGetNamedArg expr =
    match expr with
    | SimpleEqualsExpr(LongOrSingleIdent(isOpt, SynLongIdent([a], _, _), None, _), b) -> Some(isOpt, a, b)
    | _ -> None

let inline IsNamedArg expr =
    match expr with
    | SimpleEqualsExpr(LongOrSingleIdent(_, SynLongIdent([_], _, _), None, _), _) -> true
    | _ -> false

/// Get the method arguments at a callsite, taking into account named and optional arguments
let GetMethodArgs arg =
    let argExprs =
        match arg with
        | SynExpr.Const (SynConst.Unit, _) -> []
        | SynExprParen(SynExpr.Tuple (false, args, _, _), _, _, _) | SynExpr.Tuple (false, args, _, _) -> args
        | SynExprParen(arg, _, _, _)
        | arg -> [arg]

    let unnamedCallerArgs, namedCallerArgs =
        argExprs |> List.takeUntil IsNamedArg

    let namedCallerArgs =
        namedCallerArgs
        |> List.choose (fun argExpr ->
              match TryGetNamedArg argExpr with
              | None ->
                  // ignore errors to avoid confusing error messages in cases like foo(a = 1, )
                  // do not abort overload resolution in case if named arguments are mixed with errors
                  match argExpr with
                  | SynExpr.ArbitraryAfterError _ -> None
                  | _ -> error(Error(FSComp.SR.tcNameArgumentsMustAppearLast(), argExpr.Range))
              | namedArg -> namedArg)

    unnamedCallerArgs, namedCallerArgs

//-------------------------------------------------------------------------
// Helpers dealing with sequence expressions
//-------------------------------------------------------------------------

/// Get the fragmentary expressions resulting from turning
/// an expression into an enumerable value, e.g. at 'for' loops

// localAlloc is relevant if the enumerator is a mutable struct and indicates
// if the enumerator can be allocated as a mutable local variable
let AnalyzeArbitraryExprAsEnumerable (cenv: cenv) (env: TcEnv) localAlloc m exprTy expr =
    let ad = env.AccessRights
    let g = cenv.g

    let err k ty =
        let txt = NicePrint.minimalStringOfType env.DisplayEnv ty
        let msg = if k then FSComp.SR.tcTypeCannotBeEnumerated txt else FSComp.SR.tcEnumTypeCannotBeEnumerated txt
        Exception(Error(msg, m))

    let findMethInfo k m nm ty =
        match TryFindIntrinsicOrExtensionMethInfo ResultCollectionSettings.AtMostOneResult cenv env m ad nm ty with
        | [] -> err k ty
        | res :: _ -> Result res

    // Ensure there are no curried arguments, and indeed no arguments at all
    let hasArgs (minfo: MethInfo) minst =
        match minfo.GetParamTypes(cenv.amap, m, minst) with
        | [[]] -> false
        | _ -> true

    let tryType (exprToSearchForGetEnumeratorAndItem, tyToSearchForGetEnumeratorAndItem) =
        match findMethInfo true m "GetEnumerator" tyToSearchForGetEnumeratorAndItem with
        | Exception exn -> Exception exn
        | Result getEnumeratorMethInfo ->

        let getEnumeratorMethInst = FreshenMethInfo m getEnumeratorMethInfo
        let getEnumeratorRetTy = getEnumeratorMethInfo.GetFSharpReturnType(cenv.amap, m, getEnumeratorMethInst)
        if hasArgs getEnumeratorMethInfo getEnumeratorMethInst then err true tyToSearchForGetEnumeratorAndItem else

        match findMethInfo false m "MoveNext" getEnumeratorRetTy with
        | Exception exn -> Exception exn
        | Result moveNextMethInfo ->

        let moveNextMethInst = FreshenMethInfo m moveNextMethInfo
        let moveNextRetTy = moveNextMethInfo.GetFSharpReturnType(cenv.amap, m, moveNextMethInst)
        if not (typeEquiv g g.bool_ty moveNextRetTy) then err false getEnumeratorRetTy else
        if hasArgs moveNextMethInfo moveNextMethInst then err false getEnumeratorRetTy else

        match findMethInfo false m "get_Current" getEnumeratorRetTy with
        | Exception exn -> Exception exn
        | Result getCurrentMethInfo ->

        let getCurrentMethInst = FreshenMethInfo m getCurrentMethInfo
        if hasArgs getCurrentMethInfo getCurrentMethInst then err false getEnumeratorRetTy else
        let enumElemTy = getCurrentMethInfo.GetFSharpReturnType(cenv.amap, m, getCurrentMethInst)

        // Compute the element type of the strongly typed enumerator
        //
        // Like C#, we detect the 'GetEnumerator' pattern for .NET version 1.x abstractions that don't
        // support the correct generic interface. However unlike C# we also go looking for a 'get_Item' or 'Item' method
        // with a single integer indexer argument to try to get a strong type for the enumeration should the Enumerator
        // not provide anything useful. To enable interop with some legacy COM APIs,
        // the single integer indexer argument is allowed to have type 'object'.

        let enumElemTy =

            if isObjTyAnyNullness g enumElemTy then
                // Look for an 'Item' property, or a set of these with consistent return types
                let allEquivReturnTypes (minfo: MethInfo) (others: MethInfo list) =
                    let returnTy = minfo.GetFSharpReturnType(cenv.amap, m, [])
                    others |> List.forall (fun other -> typeEquiv g (other.GetFSharpReturnType(cenv.amap, m, [])) returnTy)

                let isInt32OrObjectIndexer (minfo: MethInfo) =
                    match minfo.GetParamTypes(cenv.amap, m, []) with
                    | [[ty]] ->
                        // e.g. MatchCollection
                        typeEquiv g g.int32_ty ty ||
                        // e.g. EnvDTE.Documents.Item
                        typeEquiv g g.obj_ty_ambivalent ty
                    | _ -> false

                match TryFindIntrinsicOrExtensionMethInfo ResultCollectionSettings.AllResults cenv env m ad "get_Item" tyToSearchForGetEnumeratorAndItem with
                | minfo :: others when (allEquivReturnTypes minfo others &&
                                          List.exists isInt32OrObjectIndexer (minfo :: others)) ->
                    minfo.GetFSharpReturnType(cenv.amap, m, [])

                | _ ->

                // Some types such as XmlNodeList have only an Item method
                match TryFindIntrinsicOrExtensionMethInfo ResultCollectionSettings.AllResults cenv env m ad "Item" tyToSearchForGetEnumeratorAndItem with
                | minfo :: others when (allEquivReturnTypes minfo others &&
                                          List.exists isInt32OrObjectIndexer (minfo :: others)) ->
                    minfo.GetFSharpReturnType(cenv.amap, m, [])

                | _ -> enumElemTy
            else
                enumElemTy

        let isEnumeratorTypeStruct = isStructTy g getEnumeratorRetTy
        let originalRetTypeOfGetEnumerator = getEnumeratorRetTy

        let (enumeratorVar, enumeratorExpr), getEnumeratorRetTy =
            if isEnumeratorTypeStruct then
               if localAlloc then
                  mkMutableCompGenLocal m "enumerator" getEnumeratorRetTy, getEnumeratorRetTy
               else
                  let refCellTyForRetTypeOfGetEnumerator = mkRefCellTy g getEnumeratorRetTy
                  let v, e = mkMutableCompGenLocal m "enumerator" refCellTyForRetTypeOfGetEnumerator
                  (v, mkRefCellGet g m getEnumeratorRetTy e), refCellTyForRetTypeOfGetEnumerator

            else
               mkCompGenLocal m "enumerator" getEnumeratorRetTy, getEnumeratorRetTy

        let getEnumExpr, getEnumTy =
            let getEnumExpr, getEnumTy as res = BuildPossiblyConditionalMethodCall cenv env PossiblyMutates m false getEnumeratorMethInfo NormalValUse getEnumeratorMethInst [exprToSearchForGetEnumeratorAndItem] [] None
            if not isEnumeratorTypeStruct || localAlloc then res
            else
                // wrap enumerators that are represented as mutable structs into ref cells
                let getEnumExpr = mkRefCell g m originalRetTypeOfGetEnumerator getEnumExpr
                let getEnumTy = mkRefCellTy g getEnumTy
                getEnumExpr, getEnumTy

        let guardExpr, guardTy = BuildPossiblyConditionalMethodCall cenv env DefinitelyMutates m false moveNextMethInfo NormalValUse moveNextMethInst [enumeratorExpr] [] None
        let currentExpr, currentTy = BuildPossiblyConditionalMethodCall cenv env DefinitelyMutates m true getCurrentMethInfo NormalValUse getCurrentMethInst [enumeratorExpr] [] None
        let currentExpr = mkCoerceExpr(currentExpr, enumElemTy, currentExpr.Range, currentTy)
        let currentExpr, enumElemTy =
            // Implicitly dereference byref for expr 'for x in ...'
            if isByrefTy g enumElemTy then
                let expr = mkDerefAddrExpr m currentExpr currentExpr.Range enumElemTy
                expr, destByrefTy g enumElemTy
            else
                currentExpr, enumElemTy

        Result(enumeratorVar, enumeratorExpr, getEnumeratorRetTy, enumElemTy, getEnumExpr, getEnumTy, guardExpr, guardTy, currentExpr)

    // First try the original known static type
    match (if isArray1DTy g exprTy then Exception (Failure "") else tryType (expr, exprTy)) with
    | Result res -> res
    | Exception exn ->

    let probe ty =
        if (AddCxTypeMustSubsumeTypeUndoIfFailed env.DisplayEnv cenv.css m ty exprTy) then
            match tryType (mkCoerceExpr(expr, ty, expr.Range, exprTy), ty) with
            | Result res -> Some res
            | Exception exn ->
                PreserveStackTrace exn
                raise exn
        else None

    // Next try to typecheck the thing as a sequence
    let enumElemTy = NewInferenceType g
    let exprTyAsSeq = mkSeqTy g enumElemTy

    match probe exprTyAsSeq with
    | Some res -> res
    | None ->
    let ienumerable = mkWoNullAppTy g.tcref_System_Collections_IEnumerable []
    match probe ienumerable with
    | Some res -> res
    | None ->
    PreserveStackTrace exn
    raise exn

// Used inside sequence expressions
let ConvertArbitraryExprToEnumerable (cenv: cenv) ty (env: TcEnv) (expr: Expr) =
    let g = cenv.g
    let m = expr.Range
    let enumElemTy = NewInferenceType g
    if AddCxTypeMustSubsumeTypeUndoIfFailed env.DisplayEnv cenv.css m (mkSeqTy g enumElemTy) ty then
        expr, enumElemTy
    else
        let enumerableVar, enumerableExpr = mkCompGenLocal m "inputSequence" ty
        let enumeratorVar, _, getEnumeratorRetTy, enumElemTy, getEnumExpr, _, guardExpr, guardTy, betterCurrentExpr =
            AnalyzeArbitraryExprAsEnumerable cenv env false m ty enumerableExpr

        let expr =
           mkCompGenLet m enumerableVar expr
               (mkCallSeqOfFunctions g m getEnumeratorRetTy enumElemTy
                   (mkUnitDelayLambda g m getEnumExpr)
                   (mkLambda m enumeratorVar (guardExpr, guardTy))
                   (mkLambda m enumeratorVar (betterCurrentExpr, enumElemTy)))
        expr, enumElemTy

//-------------------------------------------------------------------------
// Post-transform initialization graphs using the 'lazy' interpretation.
// See ML workshop paper.
//-------------------------------------------------------------------------

type InitializationGraphAnalysisState =
    | Top
    | InnerTop
    | DefinitelyStrict
    | MaybeLazy
    | DefinitelyLazy

type PreInitializationGraphEliminationBinding =
    { FixupPoints: RecursiveUseFixupPoints
      Binding: Binding }

/// Check for safety and determine if we need to insert lazy thunks
let EliminateInitializationGraphs
      g
      mustHaveValReprInfo
      denv
      (bindings: 'Bindings list)
      (iterBindings: (PreInitializationGraphEliminationBinding list -> unit) -> 'Bindings list -> unit)
      (buildLets: Binding list -> 'Result)
      (mapBindings: (PreInitializationGraphEliminationBinding list -> Binding list) -> 'Bindings list -> 'Result list)
      bindsm =

    let recursiveVals =
        let hash = ValHash<Val>.Create()
        let add (pgrbind: PreInitializationGraphEliminationBinding) = let c = pgrbind.Binding.Var in hash.Add(c, c)
        bindings |> iterBindings (List.iter add)
        hash

    // The output of the analysis
    let mutable outOfOrder = false
    let mutable runtimeChecks = false
    let mutable directRecursiveData = false
    let mutable reportedEager = false
    let mutable definiteDependencies = []

    let rec stripChooseAndExpr e =
        match stripDebugPoints (stripExpr e) with
        | Expr.TyChoose (_, b, _) -> stripChooseAndExpr b
        | e -> e

    let availIfInOrder = ValHash<_>.Create()
    let check boundv expr =
        let strict = function
            | MaybeLazy -> MaybeLazy
            | DefinitelyLazy -> DefinitelyLazy
            | Top | DefinitelyStrict | InnerTop -> DefinitelyStrict
        let lzy = function
            | Top | InnerTop | DefinitelyLazy -> DefinitelyLazy
            | MaybeLazy | DefinitelyStrict -> MaybeLazy
        let fixable = function
            | Top | InnerTop -> InnerTop
            | DefinitelyStrict -> DefinitelyStrict
            | MaybeLazy -> MaybeLazy
            | DefinitelyLazy -> DefinitelyLazy

        let rec CheckExpr st e =
            match stripChooseAndExpr e with
              // Expressions with some lazy parts
            | Expr.Lambda (_, _, _, _, b, _, _) -> checkDelayed st b

            // Type-lambdas are analyzed as if they are strict.
            //
            // This is a design decision (See bug 6496), so that generalized recursive bindings such as
            //   let rec x = x
            // are analyzed. Although we give type "x: 'T" to these, from the users point of view
            // any use of "x" will result in an infinite recursion. Type instantiation is implicit in F#
            // because of type inference, which makes it reasonable to check generic bindings strictly.
            | Expr.TyLambda (_, _, b, _, _) -> CheckExpr st b

            | Expr.Obj (_, ty, _, e, overrides, extraImpls, _) ->
                // NOTE: we can't fixup recursive references inside delegates since the closure delegee of a delegate is not accessible
                // from outside. Object expressions implementing interfaces can, on the other hand, be fixed up. See FSharp 1.0 bug 1469
                if isInterfaceTy g ty then
                    List.iter (fun (TObjExprMethod(_, _, _, _, e, _)) -> checkDelayed st e) overrides
                    List.iter (snd >> List.iter (fun (TObjExprMethod(_, _, _, _, e, _)) -> checkDelayed st e)) extraImpls
                else
                    CheckExpr (strict st) e
                    List.iter (fun (TObjExprMethod(_, _, _, _, e, _)) -> CheckExpr (lzy (strict st)) e) overrides
                    List.iter (snd >> List.iter (fun (TObjExprMethod(_, _, _, _, e, _)) -> CheckExpr (lzy (strict st)) e)) extraImpls

              // Expressions where fixups may be needed
            | Expr.Val (v, _, m) -> CheckValRef st v m

             // Expressions where subparts may be fixable
            | Expr.Op ((TOp.Tuple _ | TOp.UnionCase _ | TOp.Recd _), _, args, _) ->
                List.iter (CheckExpr (fixable st)) args

              // Composite expressions
            | Expr.Const _ -> ()
            | Expr.LetRec (binds, e, _, _) ->
                binds |> List.iter (CheckBinding (strict st))
                CheckExpr (strict st) e
            | Expr.Let (bind, e, _, _) ->
                CheckBinding (strict st) bind
                CheckExpr (strict st) e
            | Expr.Match (_, _, pt, targets, _, _) ->
                CheckDecisionTree (strict st) pt
                Array.iter (CheckDecisionTreeTarget (strict st)) targets
            | Expr.App (expr1, _, _, args, _) ->
                CheckExpr (strict st) expr1
                List.iter (CheckExpr (strict st)) args
          // Binary expressions
            | Expr.Sequential (expr1, expr2, _, _)
            | Expr.StaticOptimization (_, expr1, expr2, _) ->
                 CheckExpr (strict st) expr1; CheckExpr (strict st) expr2
          // n-ary expressions
            | Expr.Op (op, _, args, m) -> CheckExprOp st op m; List.iter (CheckExpr (strict st)) args
          // misc
            | Expr.Link eref -> CheckExpr st eref.Value
            | Expr.DebugPoint (_, expr2) -> CheckExpr st expr2
            | Expr.TyChoose (_, b, _) -> CheckExpr st b
            | Expr.Quote _ -> ()
            | Expr.WitnessArg (_witnessInfo, _m) -> ()

        and CheckBinding st (TBind(_, e, _)) = CheckExpr st e

        and CheckDecisionTree st dt =
            match dt with
            | TDSwitch(expr1, csl, dflt, _) -> CheckExpr st expr1; List.iter (fun (TCase(_, d)) -> CheckDecisionTree st d) csl; Option.iter (CheckDecisionTree st) dflt
            | TDSuccess (es, _) -> es |> List.iter (CheckExpr st)
            | TDBind(bind, e) -> CheckBinding st bind; CheckDecisionTree st e

        and CheckDecisionTreeTarget st (TTarget(_, e, _)) = CheckExpr st e

        and CheckExprOp st op m =
            match op with
            | TOp.LValueOp (_, lvr) -> CheckValRef (strict st) lvr m
            | _ -> ()

        and CheckValRef st (v: ValRef) m =
            match st with
            | MaybeLazy ->
                if recursiveVals.TryFind v.Deref |> Option.isSome then
                    warning (RecursiveUseCheckedAtRuntime (denv, v, m))
                    if not reportedEager then
                      (warning (LetRecCheckedAtRuntime m); reportedEager <- true)
                    runtimeChecks <- true

            | Top | DefinitelyStrict ->
                if recursiveVals.TryFind v.Deref |> Option.isSome then
                    if availIfInOrder.TryFind v.Deref |> Option.isNone then
                        warning (LetRecEvaluatedOutOfOrder (denv, boundv, v, m))
                        outOfOrder <- true
                        if not reportedEager then
                          (warning (LetRecCheckedAtRuntime m); reportedEager <- true)
                    definiteDependencies <- (boundv, v) :: definiteDependencies
            | InnerTop ->
                if recursiveVals.TryFind v.Deref |> Option.isSome then
                    directRecursiveData <- true
            | DefinitelyLazy -> ()
        and checkDelayed st b =
            match st with
            | MaybeLazy | DefinitelyStrict -> CheckExpr MaybeLazy b
            | DefinitelyLazy | Top | InnerTop -> ()


        CheckExpr Top expr


    // Check the bindings one by one, each w.r.t. the previously available set of binding
    begin
        let checkBind (pgrbind: PreInitializationGraphEliminationBinding) =
            let (TBind(v, e, _)) = pgrbind.Binding
            check (mkLocalValRef v) e
            availIfInOrder.Add(v, 1)
        bindings |> iterBindings (List.iter checkBind)
    end

    // ddg = definiteDependencyGraph
    let ddgNodes = recursiveVals.Values |> Seq.toList |> List.map mkLocalValRef
    let ddg = Graph<ValRef, Stamp>((fun v -> v.Stamp), ddgNodes, definiteDependencies )
    ddg.IterateCycles (fun path -> error (LetRecUnsound (denv, path, path.Head.Range)))

    let requiresLazyBindings = runtimeChecks || outOfOrder
    if directRecursiveData && requiresLazyBindings then
        error(Error(FSComp.SR.tcInvalidMixtureOfRecursiveForms(), bindsm))

    if requiresLazyBindings then
        let morphBinding (pgrbind: PreInitializationGraphEliminationBinding) =
            let (RecursiveUseFixupPoints fixupPoints) = pgrbind.FixupPoints
            let (TBind(v, e, seqPtOpt)) = pgrbind.Binding
            match stripChooseAndExpr e with
            | Expr.Lambda _ | Expr.TyLambda _ ->
                [], [mkInvisibleBind v e]
            | _ ->
                let ty = v.Type
                let m = v.Range
                let vTy = mkLazyTy g ty

                let fty = mkFunTy g g.unit_ty ty
                let flazy, felazy = mkCompGenLocal m v.LogicalName fty
                let frhs = mkUnitDelayLambda g m e

                if mustHaveValReprInfo then
                    flazy.SetValReprInfo (Some(InferValReprInfoOfExpr g AllowTypeDirectedDetupling.Yes fty [] [] frhs))

                let vlazy, velazy = mkCompGenLocal m v.LogicalName vTy
                let vrhs = (mkLazyDelayed g m ty felazy)

                if mustHaveValReprInfo then
                    vlazy.SetValReprInfo (Some(InferValReprInfoOfExpr g AllowTypeDirectedDetupling.Yes vTy [] [] vrhs))

                for fixupPoint, _ in fixupPoints do
                    fixupPoint.Value <- mkLazyForce g fixupPoint.Value.Range ty velazy

                [mkInvisibleBind flazy frhs; mkInvisibleBind vlazy vrhs],
                [mkBind seqPtOpt v (mkLazyForce g m ty velazy)]

        let newTopBinds = ResizeArray<_>()
        let morphBindings pgrbinds = pgrbinds |> List.map morphBinding |> List.unzip |> (fun (a, b) -> newTopBinds.Add (List.concat a); List.concat b)

        let res = bindings |> mapBindings morphBindings
        if newTopBinds.Count = 0 then res
        else buildLets (List.concat newTopBinds) :: res
    else
        let noMorph (pgrbinds: PreInitializationGraphEliminationBinding list) = pgrbinds |> List.map (fun pgrbind -> pgrbind.Binding)
        bindings |> mapBindings noMorph

//-------------------------------------------------------------------------
// Check the shape of an object constructor and rewrite calls
//-------------------------------------------------------------------------

let CheckAndRewriteObjectCtor g env (ctorLambdaExpr: Expr) =

    let m = ctorLambdaExpr.Range
    let tps, vsl, body, returnTy = stripTopLambda (ctorLambdaExpr, tyOfExpr g ctorLambdaExpr)

    // Rewrite legitimate self-construction calls to CtorValUsedAsSelfInit
    let error (expr: Expr) =
        errorR(Error(FSComp.SR.tcInvalidObjectConstructionExpression(), expr.Range))
        expr

    // Build an assignment into the safeThisValOpt mutable reference cell that holds recursive references to 'this'
    // Build an assignment into the safeInitInfo mutable field that indicates that partial initialization is successful
    let rewriteConstruction recdExpr =
       match env.eCtorInfo with
       | None -> recdExpr
       | Some ctorInfo ->
           let recdExpr =
               match ctorInfo.safeThisValOpt with
               | None -> recdExpr
               | Some safeInitVal ->
                   let ty = tyOfExpr g recdExpr
                   let thisExpr = mkGetArg0 m ty
                   let setExpr = mkRefCellSet g m ty (exprForValRef m (mkLocalValRef safeInitVal)) thisExpr
                   Expr.Sequential (recdExpr, setExpr, ThenDoSeq, m)
           let recdExpr =
               match ctorInfo.safeInitInfo with
               | NoSafeInitInfo -> recdExpr
               | SafeInitField (rfref, _) ->
                   let thisTy = tyOfExpr g recdExpr
                   let thisExpr = mkGetArg0 m thisTy
                   let thisTyInst = argsOfAppTy g thisTy
                   let setExpr = mkRecdFieldSetViaExprAddr (thisExpr, rfref, thisTyInst, mkOne g m, m)
                   Expr.Sequential (recdExpr, setExpr, ThenDoSeq, m)
           recdExpr


    let rec checkAndRewrite (expr: Expr) =
        match expr with
        // <ctor-body> = { fields }
        // The constructor ends in an object initialization expression - good
        | Expr.Op (TOp.Recd (RecdExprIsObjInit, _), _, _, _) -> rewriteConstruction expr

        // <ctor-body> = "a; <ctor-body>"
        | Expr.Sequential (a, body, NormalSeq, b) ->
            Expr.Sequential (a, checkAndRewrite body, NormalSeq, b)

        // <ctor-body> = "<ctor-body> then <expr>"
        | Expr.Sequential (body, a, ThenDoSeq, b) ->
            Expr.Sequential (checkAndRewrite body, a, ThenDoSeq, b)

        // <ctor-body> = "let pat = expr in <ctor-body>"
        | Expr.Let (bind, body, m, _) -> mkLetBind m bind (checkAndRewrite body)

        // The constructor is a sequence "let pat = expr in <ctor-body>"
        | Expr.Match (debugPoint, a, b, targets, c, d) ->
            let targets = targets |> Array.map (fun (TTarget(vs, body, flags)) -> TTarget(vs, checkAndRewrite body, flags))
            Expr.Match (debugPoint, a, b, targets, c, d)

        // <ctor-body> = "let rec binds in <ctor-body>"
        | Expr.LetRec (a, body, _, _) ->
            Expr.LetRec (a, checkAndRewrite body, m, Construct.NewFreeVarsCache())

        // <ctor-body> = "new C(...)"
        | Expr.App (f, b, c, d, m) ->
            // The application had better be an application of a ctor
            let f = checkAndRewriteCtorUsage f
            let expr = Expr.App (f, b, c, d, m)
            rewriteConstruction expr

        | Expr.DebugPoint (dp, innerExpr) ->
            Expr.DebugPoint (dp, checkAndRewrite innerExpr)

        | _ ->
            error expr

    and checkAndRewriteCtorUsage expr =
        match expr with
        | Expr.Link eref ->
            let e = checkAndRewriteCtorUsage eref.Value
            eref.Value <- e
            expr

        // Type applications are ok, e.g.
        //     type C<'a>(x: int) =
        //         new() = C<'a>(3)
        | Expr.App (f, fty, tyargs, [], m) ->
            let f = checkAndRewriteCtorUsage f
            Expr.App (f, fty, tyargs, [], m)

        // Self-calls are OK and get rewritten.
        | Expr.Val (vref, NormalValUse, a) ->
           let isCtor =
               match vref.MemberInfo with
               | None -> false
               | Some memberInfo -> memberInfo.MemberFlags.MemberKind = SynMemberKind.Constructor

           if not isCtor then
               error expr
           else
               Expr.Val (vref, CtorValUsedAsSelfInit, a)

        | Expr.DebugPoint (dp, innerExpr) ->
            Expr.DebugPoint (dp, checkAndRewriteCtorUsage innerExpr)

         | _ ->
            error expr

    let body = checkAndRewrite body
    mkMultiLambdas g m tps vsl (body, returnTy)

/// Post-typechecking normalizations to enforce semantic constraints
/// lazy and, lazy or, rethrow, address-of
let buildApp (cenv: cenv) expr resultTy arg m =
    let g = cenv.g
    match expr, arg with

    // Special rule for building applications of the 'x && y' operator
    | ApplicableExpr(expr=Expr.App (Expr.Val (vref, _, _), _, _, [x0], _)), _
         when valRefEq g vref g.and2_vref ->
        MakeApplicableExprNoFlex cenv (mkLazyAnd g m x0 arg), resultTy

    // Special rule for building applications of the 'x || y' operator
    | ApplicableExpr(expr=Expr.App (Expr.Val (vref, _, _), _, _, [x0], _)), _
         when valRefEq g vref g.or2_vref ->
        MakeApplicableExprNoFlex cenv (mkLazyOr g m x0 arg ), resultTy

    // Special rule for building applications of the 'reraise' operator
    | ApplicableExpr(expr=Expr.App (Expr.Val (vref, _, _), _, _, [], _)), _
         when valRefEq g vref g.reraise_vref ->

        // exprTy is of type: "unit -> 'a". Break it and store the 'a type here, used later as return type.
        MakeApplicableExprNoFlex cenv (mkCompGenSequential m arg (mkReraise m resultTy)), resultTy

    // Special rules for NativePtr.ofByRef to generalize result.
    // See RFC FS-1053.md
    | ApplicableExpr(expr=Expr.App (Expr.Val (vref, _, _), _, _, [], _)), _
         when (valRefEq g vref g.nativeptr_tobyref_vref) ->

        let argTy = NewInferenceType g
        let resultTy = mkByrefTyWithInference g argTy (NewByRefKindInferenceType g m)
        expr.SupplyArgument (arg, m), resultTy

    // Special rules for building applications of the '&expr' operator, which gets the
    // address of an expression.
    //
    // See also RFC FS-1053.md
    | ApplicableExpr(expr=Expr.App (Expr.Val (vref, _, _), _, _, [], _)), _
         when valRefEq g vref g.addrof_vref ->

        let wrap, e1a', readonly, _writeonly = mkExprAddrOfExpr g true false AddressOfOp arg (Some vref) m
        // Assert the result type to be readonly if we couldn't take the address
        let resultTy =
            let argTy = tyOfExpr g arg
            if readonly then
                mkInByrefTy g argTy

            // "`outref<'T>` types are never introduced implicitly by F#.", see rationale in RFC FS-1053
            //
            // We do _not_ introduce outref here, e.g. '&x' where 'x' is outref<_> is _not_ outref.
            // This effectively makes 'outref<_>' documentation-only. There is frequently a need to pass outref
            // pointers to .NET library functions whose signatures are not tagged with [<Out>]
            //elif writeonly then
            //    mkOutByrefTy g argTy

            else
                mkByrefTyWithInference g argTy (NewByRefKindInferenceType g m)

        MakeApplicableExprNoFlex cenv (wrap(e1a')), resultTy

    // Special rules for building applications of the &&expr' operators, which gets the
    // address of an expression.
    | ApplicableExpr(expr=Expr.App (Expr.Val (vref, _, _), _, _, [], _)), _
         when valRefEq g vref g.addrof2_vref ->

        warning(UseOfAddressOfOperator m)
        let wrap, e1a', _readonly, _writeonly = mkExprAddrOfExpr g true false AddressOfOp arg (Some vref) m
        MakeApplicableExprNoFlex cenv (wrap(e1a')), resultTy

    | _ when isByrefTy g resultTy ->
        // Handle byref returns, byref-typed returns get implicitly dereferenced
        let expr = expr.SupplyArgument (arg, m)
        let expr = mkDerefAddrExpr m expr.Expr m resultTy
        let resultTy = destByrefTy g resultTy
        MakeApplicableExprNoFlex cenv expr, resultTy

    | _ ->
        expr.SupplyArgument (arg, m), resultTy

//-------------------------------------------------------------------------
// Additional data structures used by type checking
//-------------------------------------------------------------------------

type DelayedItem =
  /// Represents the <tyargs> in "item<tyargs>"
  | DelayedTypeApp of
      typeArgs: SynType list *
      mTypeArgs: range *
      mExprAndTypeArgs: range

  /// Represents the args in "item args", or "item.Property(args)".
  | DelayedApp of
      isAtomic: ExprAtomicFlag *
      isSugar: bool *
      synLeftExprOpt: SynExpr option *
      argExpr: SynExpr *
      mFuncAndArg: range

  /// Represents the long identifiers in "item.Ident1", or "item.Ident1.Ident2" etc.
  | DelayedDotLookup of
      idents: Ident list *
      range

  /// Represents an incomplete "item."
  | DelayedDot

  /// Represents the valueExpr in "item <- valueExpr", also "item.[indexerArgs] <- valueExpr" etc.
  | DelayedSet of SynExpr * range

module DelayedItem =
    let maybeAppliedArgForPreferExtensionOverProperty delayed =
        match delayed with
        | [] -> None
        | DelayedItem.DelayedApp(argExpr=argExpr) :: _ -> Some argExpr
        | _ -> None

let MakeDelayedSet(e: SynExpr, m) =
    // We have longId <- e. Wrap 'e' in another pair of parentheses to ensure it's never interpreted as
    // a named argument, e.g. for "el.Checked <- (el = el2)"
    DelayedSet (SynExpr.Paren (e, range0, None, e.Range), m)

/// Indicates if member declarations are allowed to be abstract members.
type NewSlotsOK =
    | NewSlotsOK
    | NoNewSlots

/// Indicates whether the position being checked is precisely the r.h.s. of a "'T :> ***" constraint or a similar
/// places where IWSAM types do not generate a warning
[<RequireQualifiedAccess>]
type WarnOnIWSAM =
    | Yes
    | No

/// Represents information about the module or type in which a member or value is declared.
type MemberOrValContainerInfo =
    | MemberOrValContainerInfo of
        tcref: TyconRef *
        intfSlotTyOpt: (TType * SlotImplSet) option *
        baseValOpt: Val option *
        safeInitInfo: SafeInitData *
        declaredTyconTypars: Typars

/// Provides information about the context for a value or member definition
type ContainerInfo =
    | ContainerInfo of
          // The nearest containing module. Used as the 'actual' parent for extension members and values
          ParentRef *
          // For members:
          MemberOrValContainerInfo option
    member x.ParentRef =
        let (ContainerInfo(v, _)) = x
        v

/// Indicates a declaration is contained in an expression
let ExprContainerInfo = ContainerInfo(ParentNone, None)

type NormalizedRecBindingDefn =
    | NormalizedRecBindingDefn of
        containerInfo: ContainerInfo *
        newslotsOk: NewSlotsOK *
        declKind: DeclKind *
        binding: NormalizedBinding

type ValSpecResult =
    | ValSpecResult of
        altActualParent: ParentRef *
        memberInfoOpt: PrelimMemberInfo option *
        id: Ident *
        enclosingDeclaredTypars: Typars *
        declaredTypars: Typars *
        ty: TType *
        prelimValReprInfo: PrelimValReprInfo *
        declKind: DeclKind

type DecodedIndexArg =
    | IndexArgRange of (SynExpr * bool) option * (SynExpr * bool) option * range * range
    | IndexArgItem of SynExpr * bool * range
//-------------------------------------------------------------------------
// Additional data structures used by checking recursive bindings
//-------------------------------------------------------------------------

type RecDefnBindingInfo =
    | RecDefnBindingInfo of
        containerInfo: ContainerInfo *
        newslotsOk: NewSlotsOK *
        declKind: DeclKind *
        synBinding: SynBinding

/// RecursiveBindingInfo - flows through initial steps of TcLetrecBindings
type RecursiveBindingInfo =
    | RecursiveBindingInfo of
          recBindIndex: int * // index of the binding in the recursive group
          containerInfo: ContainerInfo *
          enclosingDeclaredTypars: Typars *
          inlineFlag: ValInline *
          vspec: Val *
          explicitTyparInfo: ExplicitTyparInfo *
          prelimValReprInfo: PrelimValReprInfo *
          memberInfoOpt: PrelimMemberInfo option *
          baseValOpt: Val option *
          safeThisValOpt: Val option *
          safeInitInfo: SafeInitData *
          visibility: SynAccess option *
          ty: TType *
          declKind: DeclKind

    member x.EnclosingDeclaredTypars = let (RecursiveBindingInfo(_, _, enclosingDeclaredTypars, _, _, _, _, _, _, _, _, _, _, _)) = x in enclosingDeclaredTypars
    member x.Val = let (RecursiveBindingInfo(_, _, _, _, vspec, _, _, _, _, _, _, _, _, _)) = x in vspec
    member x.ExplicitTyparInfo = let (RecursiveBindingInfo(_, _, _, _, _, explicitTyparInfo, _, _, _, _, _, _, _, _)) = x in explicitTyparInfo
    member x.DeclaredTypars = let (ExplicitTyparInfo(_, declaredTypars, _)) = x.ExplicitTyparInfo in declaredTypars
    member x.Index = let (RecursiveBindingInfo(i, _, _, _, _, _, _, _, _, _, _, _, _, _)) = x in i
    member x.ContainerInfo = let (RecursiveBindingInfo(_, c, _, _, _, _, _, _, _, _, _, _, _, _)) = x in c
    member x.DeclKind = let (RecursiveBindingInfo(_, _, _, _, _, _, _, _, _, _, _, _, _, declKind)) = x in declKind

type PreCheckingRecursiveBinding =
    { SyntacticBinding: NormalizedBinding
      RecBindingInfo: RecursiveBindingInfo }

type PreGeneralizationRecursiveBinding =
    { ExtraGeneralizableTypars: Typars
      CheckedBinding: CheckedBindingInfo
      RecBindingInfo: RecursiveBindingInfo }

type PostGeneralizationRecursiveBinding =
    { ValScheme: ValScheme
      CheckedBinding: CheckedBindingInfo
      RecBindingInfo: RecursiveBindingInfo }
    member x.GeneralizedTypars = x.ValScheme.GeneralizedTypars

type PostSpecialValsRecursiveBinding =
    { ValScheme: ValScheme
      Binding: Binding }

let CanInferExtraGeneralizedTyparsForRecBinding (pgrbind: PreGeneralizationRecursiveBinding) =
    let explicitTyparInfo = pgrbind.RecBindingInfo.ExplicitTyparInfo
    let (ExplicitTyparInfo(_, _, canInferTypars)) = explicitTyparInfo
    let memFlagsOpt = pgrbind.RecBindingInfo.Val.MemberInfo |> Option.map (fun memInfo -> memInfo.MemberFlags)
    let canInferTypars = GeneralizationHelpers.ComputeCanInferExtraGeneralizableTypars (pgrbind.RecBindingInfo.ContainerInfo.ParentRef, canInferTypars, memFlagsOpt)
    canInferTypars

/// Get the "this" variable from an instance member binding
let GetInstanceMemberThisVariable (vspec: Val, expr) =
    // Skip over LAM tps. Choose 'a.
    if vspec.IsInstanceMember then
        let rec firstArg e =
            match stripDebugPoints e with
            | Expr.TyLambda (_, _, b, _, _) -> firstArg b
            | Expr.TyChoose (_, b, _) -> firstArg b
            | Expr.Lambda (_, _, _, [v], _, _, _) -> Some v
            | _ -> failwith "GetInstanceMemberThisVariable: instance member did not have expected internal form"

        firstArg expr
    else
        None

/// c.atomicLeftMethExpr[idx] and atomicLeftExpr[idx] as applications give warnings
let checkHighPrecedenceFunctionApplicationToList (g: TcGlobals) args atomicFlag exprRange =
    match args, atomicFlag with
    | ([SynExpr.ArrayOrList (false, _, _)] | [SynExpr.ArrayOrListComputed (false, _, _)]), ExprAtomicFlag.Atomic ->
        if g.langVersion.SupportsFeature LanguageFeature.IndexerNotationWithoutDot then
            informationalWarning(Error(FSComp.SR.tcHighPrecedenceFunctionApplicationToListDeprecated(), exprRange))
        elif not (g.langVersion.IsExplicitlySpecifiedAs50OrBefore()) then
            informationalWarning(Error(FSComp.SR.tcHighPrecedenceFunctionApplicationToListReserved(), exprRange))
    | _ -> ()

/// Indicates whether a syntactic type is allowed to include new type variables
/// not declared anywhere, e.g. `let f (x: 'T option) = x.Value`
type ImplicitlyBoundTyparsAllowed =
    | NewTyparsOKButWarnIfNotRigid
    | NewTyparsOK
    | NoNewTypars

//-------------------------------------------------------------------------
// Checking types and type constraints
//-------------------------------------------------------------------------
/// Check specifications of constraints on type parameters
let rec TcTyparConstraint ridx (cenv: cenv) newOk checkConstraints occ (env: TcEnv) tpenv c =
    let g = cenv.g

    match c with
    | SynTypeConstraint.WhereTyparDefaultsToType(tp, ty, m) ->
        let tyR, tpenv = TcTypeAndRecover cenv newOk checkConstraints occ WarnOnIWSAM.Yes env tpenv ty
        let tpR, tpenv = TcTypar cenv env newOk tpenv tp
        AddCxTyparDefaultsTo env.DisplayEnv cenv.css m env.eContextInfo tpR ridx tyR
        tpenv

    | SynTypeConstraint.WhereTyparSubtypeOfType(tp, ty, m) ->
        let tyR, tpenv = TcTypeAndRecover cenv newOk checkConstraints ItemOccurrence.UseInType WarnOnIWSAM.No env tpenv ty
        let tpR, tpenv = TcTypar cenv env newOk tpenv tp
        if newOk = NoNewTypars && isSealedTy g tyR then
            errorR(Error(FSComp.SR.tcInvalidConstraintTypeSealed(), m))
        AddCxTypeMustSubsumeType ContextInfo.NoContext env.DisplayEnv cenv.css m NoTrace tyR (mkTyparTy tpR)
        tpenv

    | SynTypeConstraint.WhereTyparSupportsNull(tp, m) ->
        TcSimpleTyparConstraint cenv env newOk tpenv tp m AddCxTypeUseSupportsNull

    | SynTypeConstraint.WhereTyparNotSupportsNull(tp, m, _) ->
        if g.langFeatureNullness then
            TcSimpleTyparConstraint cenv env newOk tpenv tp m AddCxTypeDefnNotSupportsNull
        else
            warning(Error(FSComp.SR.tcNullnessCheckingNotEnabled(), m))
            tpenv

    | SynTypeConstraint.WhereTyparIsComparable(tp, m) ->
        TcSimpleTyparConstraint cenv env newOk tpenv tp m AddCxTypeMustSupportComparison

    | SynTypeConstraint.WhereTyparIsEquatable(tp, m) ->
        TcSimpleTyparConstraint cenv env newOk tpenv tp m AddCxTypeMustSupportEquality

    | SynTypeConstraint.WhereTyparIsReferenceType(tp, m) ->
        TcSimpleTyparConstraint cenv env newOk tpenv tp m AddCxTypeIsReferenceType

    | SynTypeConstraint.WhereTyparIsValueType(tp, m) ->
        TcSimpleTyparConstraint cenv env newOk tpenv tp m AddCxTypeIsValueType

    | SynTypeConstraint.WhereTyparIsUnmanaged(tp, m) ->
        TcSimpleTyparConstraint cenv env newOk tpenv tp m AddCxTypeIsUnmanaged

    | SynTypeConstraint.WhereTyparIsEnum(tp, synUnderlingTys, m) ->
        TcConstraintWhereTyparIsEnum cenv env newOk checkConstraints tpenv tp synUnderlingTys m

    | SynTypeConstraint.WhereTyparIsDelegate(tp, synTys, m) ->
        TcConstraintWhereTyparIsDelegate cenv env newOk checkConstraints occ tpenv tp synTys m

    | SynTypeConstraint.WhereTyparSupportsMember(TypesForTypar synSupportTys, synMemberSig, m) ->
        TcConstraintWhereTyparSupportsMember cenv env newOk tpenv synSupportTys synMemberSig m

    | SynTypeConstraint.WhereSelfConstrained(ty, m) ->
        checkLanguageFeatureAndRecover g.langVersion LanguageFeature.SelfTypeConstraints m
        let tyR, tpenv = TcTypeAndRecover cenv newOk checkConstraints ItemOccurrence.UseInType WarnOnIWSAM.No env tpenv ty
        match tyR with
        | TType_app(tcref, tinst, _) when (tcref.IsTypeAbbrev && (isTyparTy g tcref.TypeAbbrev.Value) && tinst |> List.forall (isTyparTy g)) ->
            match checkConstraints with
            | NoCheckCxs ->
                //let formalEnclosingTypars = []
                let tpsorig = tcref.Typars(m) //List.map (destTyparTy g) inst //, _, tinst, _ = FreshenTyconRef2 g m tcref
                let tps = List.map (destTyparTy g) tinst //, _, tinst, _ = FreshenTyconRef2 g m tcref
                let tprefInst, _tptys = mkTyparToTyparRenaming tpsorig tps
                //let tprefInst = mkTyparInst formalEnclosingTypars tinst @ renaming
                (tpsorig, tps) ||> List.iter2 (fun tporig tp -> tp.SetConstraints (tp.Constraints @ CopyTyparConstraints  m tprefInst tporig))
            | CheckCxs -> ()
        | AppTy g (_tcref, selfTy :: _rest) when isTyparTy g selfTy && isInterfaceTy g tyR ->
            AddCxTypeMustSubsumeType ContextInfo.NoContext env.DisplayEnv cenv.css m NoTrace tyR selfTy
        | _ ->
            errorR(Error(FSComp.SR.tcInvalidSelfConstraint(), m))
        tpenv

and TcConstraintWhereTyparIsEnum cenv env newOk checkConstraints tpenv tp synUnderlingTys m =
    let tpR, tpenv = TcTypar cenv env newOk tpenv tp
    let tpenv =
        match synUnderlingTys with
        | [synUnderlyingTy] ->
            let underlyingTy, tpenv = TcTypeAndRecover cenv newOk checkConstraints ItemOccurrence.UseInType WarnOnIWSAM.Yes env tpenv synUnderlyingTy
            AddCxTypeIsEnum env.DisplayEnv cenv.css m NoTrace (mkTyparTy tpR) underlyingTy
            tpenv
        | _ ->
            errorR(Error(FSComp.SR.tcInvalidEnumConstraint(), m))
            tpenv
    tpenv

and TcConstraintWhereTyparIsDelegate cenv env newOk checkConstraints occ tpenv tp synTys m =
    let tpR, tpenv = TcTypar cenv env newOk tpenv tp
    match synTys with
    | [a;b] ->
        let a', tpenv = TcTypeAndRecover cenv newOk checkConstraints occ WarnOnIWSAM.Yes env tpenv a
        let b', tpenv = TcTypeAndRecover cenv newOk checkConstraints occ WarnOnIWSAM.Yes env tpenv b
        AddCxTypeIsDelegate env.DisplayEnv cenv.css m NoTrace (mkTyparTy tpR) a' b'
        tpenv
    | _ ->
        errorR(Error(FSComp.SR.tcInvalidEnumConstraint(), m))
        tpenv

and TcConstraintWhereTyparSupportsMember cenv env newOk tpenv synSupportTys synMemberSig m =
    let g = cenv.g
    let traitInfo, tpenv = TcPseudoMemberSpec cenv newOk env synSupportTys tpenv synMemberSig m
    match traitInfo with
    | TTrait(tys=objTys; memberName=".ctor"; memberFlags=memberFlags; objAndArgTys=argTys; returnTyOpt=returnTy)
      when memberFlags.MemberKind = SynMemberKind.Constructor ->
        match objTys, argTys with
        | [ty], [] when typeEquiv g ty (GetFSharpViewOfReturnType g returnTy) ->
            AddCxTypeMustSupportDefaultCtor env.DisplayEnv cenv.css m NoTrace ty
            tpenv
        | _ ->
            errorR(Error(FSComp.SR.tcInvalidNewConstraint(), m))
            tpenv
    | _ ->
        AddCxMethodConstraint env.DisplayEnv cenv.css m NoTrace traitInfo
        tpenv

and TcSimpleTyparConstraint cenv env newOk tpenv tp m constraintAdder =
    let tpR, tpenv = TcTypar cenv env newOk tpenv tp
    constraintAdder env.DisplayEnv cenv.css m NoTrace (mkTyparTy tpR)
    tpenv

and TcPseudoMemberSpec cenv newOk env synTypes tpenv synMemberSig m =
    let g = cenv.g

    let tys, tpenv = List.mapFold (TcTypeAndRecover cenv newOk CheckCxs ItemOccurrence.UseInType WarnOnIWSAM.Yes env) tpenv synTypes

    match synMemberSig with
    | SynMemberSig.Member (synValSig, memberFlags, m, _) ->
        // REVIEW: Test pseudo constraints cannot refer to polymorphic methods.
        // REVIEW: Test pseudo constraints cannot be curried.
        let members, tpenv = TcValSpec cenv env ModuleOrMemberBinding newOk ExprContainerInfo (Some memberFlags) (Some (List.head tys)) tpenv synValSig []
        match members with
        | [ValSpecResult(_, _, id, _, _, memberConstraintTy, prelimValReprInfo, _)] ->

            match synValSig with
            | SynValSig(accessibility = access) ->
                match access with
                | SynValSigAccess.Single(Some access)
                | SynValSigAccess.GetSet(Some access, _, _)
                | SynValSigAccess.GetSet(_, Some access, _)
                | SynValSigAccess.GetSet(_, _, Some access) ->
                    if g.langVersion.SupportsFeature(LanguageFeature.AllowAccessModifiersToAutoPropertiesGettersAndSetters) then
                        errorR(Error(FSComp.SR.tcAccessModifiersNotAllowedInSRTPConstraint(), access.Range))
                    else
                        warning(Error(FSComp.SR.tcAccessModifiersNotAllowedInSRTPConstraint(), access.Range))
                | _ -> ()

            let memberConstraintTypars, _ = tryDestForallTy g memberConstraintTy
            let valReprInfo = TranslatePartialValReprInfo memberConstraintTypars prelimValReprInfo
            let _, _, curriedArgInfos, returnTy, _ = GetValReprTypeInCompiledForm g valReprInfo 0 memberConstraintTy m
            //if curriedArgInfos.Length > 1 then  error(Error(FSComp.SR.tcInvalidConstraint(), m))
            let argTys = List.concat curriedArgInfos
            let argTys = List.map fst argTys
            let logicalCompiledName = ComputeLogicalName id memberFlags
            for argInfos in curriedArgInfos do
                for argInfo in argInfos do
                    let info = CrackParamAttribsInfo g argInfo
                    let (ParamAttribs(isParamArrayArg, isInArg, isOutArg, optArgInfo, callerInfo, reflArgInfo)) = info
                    if isParamArrayArg || isInArg || isOutArg || optArgInfo.IsOptional || callerInfo <> CallerInfo.NoCallerInfo || reflArgInfo <> ReflectedArgInfo.None then
                        if g.langVersion.SupportsFeature(LanguageFeature.InterfacesWithAbstractStaticMembers) then
                            errorR(Error(FSComp.SR.tcTraitMayNotUseComplexThings(), m))
                        else
                            warning(Error(FSComp.SR.tcTraitMayNotUseComplexThings(), m))

            let item = Item.OtherName (Some id, memberConstraintTy, None, None, id.idRange)
            CallNameResolutionSink cenv.tcSink (id.idRange, env.NameEnv, item, emptyTyparInst, ItemOccurrence.Use, env.AccessRights)

            TTrait(tys, logicalCompiledName, memberFlags, argTys, returnTy, ref None, ref None), tpenv

        | _ -> error(Error(FSComp.SR.tcInvalidConstraint(), m))

    | _ -> error(Error(FSComp.SR.tcInvalidConstraint(), m))

/// Check a value specification, e.g. in a signature, interface declaration or a constraint
and TcValSpec (cenv: cenv) env declKind newOk containerInfo memFlagsOpt thisTyOpt tpenv synValSig attrs =
    let g = cenv.g
    let (SynValSig(ident=SynIdent(id,_); explicitTypeParams=ValTyparDecls (synTypars, synTyparConstraints, _); synType=ty; arity=valSynInfo; range=m)) = synValSig
    let declaredTypars = TcTyparDecls cenv env synTypars
    let (ContainerInfo(altActualParent, tcrefContainerInfo)) = containerInfo

    let enclosingDeclaredTypars, memberContainerInfo, thisTyOpt, declKind =
        match tcrefContainerInfo with
        | Some(MemberOrValContainerInfo(tcref, _, _, _, declaredTyconTypars)) ->
            let isExtrinsic = (declKind = ExtrinsicExtensionBinding)
            let _, enclosingDeclaredTypars, _, _, thisTy =
                FreshenObjectArgType cenv m TyparRigidity.Rigid tcref isExtrinsic declaredTyconTypars

            // An implemented interface type is in terms of the type's type parameters.
            // We need a signature in terms of the values' type parameters.
            enclosingDeclaredTypars, Some tcref, Some thisTy, declKind

        | None ->
            [], None, thisTyOpt, ModuleOrMemberBinding

    let allDeclaredTypars = enclosingDeclaredTypars @ declaredTypars
    let envinner = AddDeclaredTypars NoCheckForDuplicateTypars allDeclaredTypars env
    let checkConstraints = CheckCxs
    let tpenv = TcTyparConstraints cenv newOk checkConstraints ItemOccurrence.UseInType envinner tpenv synTyparConstraints

    // Treat constraints at the "end" of the type as if they are declared.
    // This is by far the most convenient place to locate the constraints.
    // e.g.
    //    val FastGenericComparer<'T>: IComparer<'T> when 'T: comparison
    let tpenv =
        match ty with
        | SynType.WithGlobalConstraints(_, synConstraints, _) ->
            TcTyparConstraints cenv newOk checkConstraints ItemOccurrence.UseInType envinner tpenv synConstraints
        | _ ->
            tpenv

    // Enforce "no undeclared constraints allowed on declared typars"
    allDeclaredTypars |> List.iter (SetTyparRigid env.DisplayEnv m)

    // Process the type, including any constraints
    let declaredTy, tpenv = TcTypeAndRecover cenv newOk checkConstraints ItemOccurrence.UseInType WarnOnIWSAM.Yes envinner tpenv ty

    match memFlagsOpt, thisTyOpt with
    | Some memberFlags, Some thisTy ->
        let generateOneMember (memberFlags: SynMemberFlags) =

            // Decode members in the signature
            let tyR, valSynInfo =
                match memberFlags.MemberKind with
                | SynMemberKind.ClassConstructor
                | SynMemberKind.Constructor
                | SynMemberKind.Member ->
                    declaredTy, valSynInfo
                | SynMemberKind.PropertyGet
                | SynMemberKind.PropertySet ->
                    let fakeArgReprInfos = [ for n in SynInfo.AritiesOfArgs valSynInfo do yield [ for _ in 1 .. n do yield ValReprInfo.unnamedTopArg1 ] ]
                    let arginfos, returnTy = GetTopTauTypeInFSharpForm g fakeArgReprInfos declaredTy m
                    if arginfos.Length > 1 then error(Error(FSComp.SR.tcInvalidPropertyType(), m))
                    match memberFlags.MemberKind with
                    | SynMemberKind.PropertyGet ->
                        if SynInfo.HasNoArgs valSynInfo then
                            let getterTy = mkFunTy g g.unit_ty declaredTy
                            getterTy, (SynInfo.IncorporateEmptyTupledArgForPropertyGetter valSynInfo)
                        else
                            declaredTy, valSynInfo
                    | _ ->
                        let setterArgTys = List.map fst (List.concat arginfos) @ [returnTy]
                        let setterArgTy = mkRefTupledTy g setterArgTys
                        let setterTy = mkFunTy g setterArgTy cenv.g.unit_ty
                        let synInfo = SynInfo.IncorporateSetterArg valSynInfo
                        setterTy, synInfo
                | SynMemberKind.PropertyGetSet ->
                    error(InternalError("Unexpected SynMemberKind.PropertyGetSet from signature parsing", m))

            // Take "unit" into account in the signature
            let valSynInfo = AdjustValSynInfoInSignature g tyR valSynInfo

            let tyR, valSynInfo =
                if memberFlags.IsInstance then
                    (mkFunTy cenv.g thisTy tyR), (SynInfo.IncorporateSelfArg valSynInfo)
                else
                    tyR, valSynInfo

            let reallyGenerateOneMember(id: Ident, valSynInfo, tyR, memberFlags) =
                let PrelimValReprInfo(argsData, _) as prelimValReprInfo =
                    TranslateSynValInfo cenv id.idRange (TcAttributes cenv env) valSynInfo


                // Fold in the optional argument information
                // Resort to using the syntactic argument information since that is what tells us
                // what is optional and what is not.
                let tyR =

                    if SynInfo.HasOptionalArgs valSynInfo then
                        let curriedArgTys, returnTy = GetTopTauTypeInFSharpForm g argsData tyR m
                        let curriedArgTys =
                            ((List.mapSquared fst curriedArgTys), valSynInfo.CurriedArgInfos)
                            ||> List.map2 (fun argTys argInfos ->
                                 (argTys, argInfos)
                                 ||> List.map2 (fun argTy (SynArgInfo(attribs, _, _) as argInfo) ->
                                     if SynInfo.IsOptionalArg argInfo then mkOptionalParamTyBasedOnAttribute g argTy attribs
                                     else argTy))
                        mkIteratedFunTy g (List.map (mkRefTupledTy g) curriedArgTys) returnTy
                    else tyR

                let memberInfoOpt =
                    match memberContainerInfo with
                    | Some tcref ->
                        let isExtrinsic = (declKind = ExtrinsicExtensionBinding)
                        let memberInfoTransient = MakeMemberDataAndMangledNameForMemberVal(g, tcref, isExtrinsic, attrs, [], memberFlags, valSynInfo, id, false)
                        Some memberInfoTransient
                    | None ->
                        None

                ValSpecResult(altActualParent, memberInfoOpt, id, enclosingDeclaredTypars, declaredTypars, tyR, prelimValReprInfo, declKind)

            [ yield reallyGenerateOneMember(id, valSynInfo, tyR, memberFlags)
              if CompileAsEvent g attrs then
                    let valSynInfo = EventDeclarationNormalization.ConvertSynInfo id.idRange valSynInfo
                    let memberFlags = EventDeclarationNormalization.ConvertMemberFlags memberFlags
                    let delTy = FindDelegateTypeOfPropertyEvent g cenv.amap id.idText id.idRange declaredTy
                    let ty =
                       if memberFlags.IsInstance then
                           mkFunTy g thisTy (mkFunTy g delTy g.unit_ty)
                       else
                           mkFunTy g delTy g.unit_ty
                    yield reallyGenerateOneMember(ident("add_" + id.idText, id.idRange), valSynInfo, ty, memberFlags)
                    yield reallyGenerateOneMember(ident("remove_" + id.idText, id.idRange), valSynInfo, ty, memberFlags) ]

        match memberFlags.MemberKind with
        | SynMemberKind.ClassConstructor
        | SynMemberKind.Constructor
        | SynMemberKind.Member
        | SynMemberKind.PropertyGet
        | SynMemberKind.PropertySet ->
            generateOneMember memberFlags, tpenv
        | SynMemberKind.PropertyGetSet ->
            [ yield! generateOneMember({memberFlags with MemberKind=SynMemberKind.PropertyGet})
              yield! generateOneMember({memberFlags with MemberKind=SynMemberKind.PropertySet}) ], tpenv
    | _ ->
        let valSynInfo = AdjustValSynInfoInSignature g declaredTy valSynInfo
        let prelimValReprInfo = TranslateSynValInfo cenv id.idRange (TcAttributes cenv env) valSynInfo
        [ ValSpecResult(altActualParent, None, id, enclosingDeclaredTypars, declaredTypars, declaredTy, prelimValReprInfo, declKind) ], tpenv

//-------------------------------------------------------------------------
// Bind types
//-------------------------------------------------------------------------

/// Check and elaborate a type or measure parameter occurrence
/// If kindOpt=Some kind, then this is the kind we're expecting (we're in *analysis* mode)
/// If kindOpt=None, we need to determine the kind (we're in *synthesis* mode)
///
and TcTypeOrMeasureParameter kindOpt cenv (env: TcEnv) newOk tpenv (SynTypar(id, _, _) as tp) =
    let checkRes (res: Typar) =
        match kindOpt, res.Kind with
        | Some TyparKind.Measure, TyparKind.Type -> error (Error(FSComp.SR.tcExpectedUnitOfMeasureMarkWithAttribute(), id.idRange)); res, tpenv
        | Some TyparKind.Type, TyparKind.Measure -> error (Error(FSComp.SR.tcExpectedTypeParameter(), id.idRange)); res, tpenv
        | _, _ ->
            let item = Item.TypeVar(id.idText, res)
            CallNameResolutionSink cenv.tcSink (id.idRange, env.NameEnv, item, emptyTyparInst, ItemOccurrence.UseInType, env.AccessRights)
            res, tpenv
    let key = id.idText

    // Check if it has been declared
    match env.eNameResEnv.eTypars.TryGetValue key with
    | true, res -> checkRes res
    | _ ->

    // Check if it is already in the implicitly scoped environment
    match TryFindUnscopedTypar key tpenv with
    | Some res -> checkRes res
    | None ->

        // Otherwise, it is a new implicitly scoped type variable. Check if these
        // are allowed.
        if newOk = NoNewTypars then
            let suggestTypeParameters (addToBuffer: string -> unit) =
                for p in env.eNameResEnv.eTypars do
                    addToBuffer ("'" + p.Key)

                match tpenv with
                | UnscopedTyparEnv elements ->
                    for p in elements do
                        addToBuffer ("'" + p.Key)

            let reportedId = Ident("'" + id.idText, id.idRange)
            error (UndefinedName(0, FSComp.SR.undefinedNameTypeParameter, reportedId, suggestTypeParameters))

        // OK, this is an implicit declaration of a type parameter
        // The kind defaults to Type
        let kind = match kindOpt with None -> TyparKind.Type | Some kind -> kind
        let tpR = Construct.NewTypar (kind, TyparRigidity.WarnIfNotRigid, tp, false, TyparDynamicReq.Yes, [], false, false)
        let item = Item.TypeVar(id.idText, tpR)

        CallNameResolutionSink cenv.tcSink (id.idRange, env.NameEnv, item, emptyTyparInst, ItemOccurrence.UseInType, env.AccessRights)

        tpR, AddUnscopedTypar key tpR tpenv

and TcTypar (cenv: cenv) env newOk tpenv tp : Typar * UnscopedTyparEnv =
    TcTypeOrMeasureParameter (Some TyparKind.Type) cenv env newOk tpenv tp

and TcTyparDecl (cenv: cenv) env synTyparDecl =
    let g = cenv.g
    let (SynTyparDecl (attributes = Attributes synAttrs; typar = synTypar)) = synTyparDecl
    let (SynTypar (ident = id)) = synTypar

    let attrs = TcAttributes cenv env AttributeTargets.GenericParameter synAttrs
    let hasMeasureAttr = HasFSharpAttribute g g.attrib_MeasureAttribute attrs
    let hasEqDepAttr = HasFSharpAttribute g g.attrib_EqualityConditionalOnAttribute attrs
    let hasCompDepAttr = HasFSharpAttribute g g.attrib_ComparisonConditionalOnAttribute attrs
    let attrs = attrs |> filterOutWellKnownAttribs g WellKnownEntityAttributes.MeasureAttribute WellKnownValAttributes.None
    let kind = if hasMeasureAttr then TyparKind.Measure else TyparKind.Type
    let tp = Construct.NewTypar (kind, TyparRigidity.WarnIfNotRigid, synTypar, false, TyparDynamicReq.Yes, attrs, hasEqDepAttr, hasCompDepAttr)

    match attrs with
    | ValAttribString g WellKnownValAttributes.CompiledNameAttribute compiledName ->
        tp.SetILName (Some compiledName)
    | _ ->
        ()
    let item = Item.TypeVar(id.idText, tp)

    CallNameResolutionSink cenv.tcSink (id.idRange, env.NameEnv, item, emptyTyparInst, ItemOccurrence.UseInType, env.eAccessRights)

    tp

and TcTyparDecls (cenv: cenv) env synTypars =
    List.map (TcTyparDecl cenv env) synTypars

/// Check and elaborate a syntactic type or unit-of-measure
///
/// If kindOpt=Some kind, then this is the kind we're expecting (we're doing kind checking)
/// If kindOpt=None, we need to determine the kind (we're doing kind inference)
///
and TcTypeOrMeasure kindOpt (cenv: cenv) newOk checkConstraints occ (iwsam: WarnOnIWSAM) env (tpenv: UnscopedTyparEnv) synTy =
    let g = cenv.g

    match synTy with
    | SynType.LongIdent(SynLongIdent([], _, _)) ->
        // special case when type name is absent - i.e. empty inherit part in type declaration
        g.obj_ty_ambivalent, tpenv

    | SynType.LongIdent synLongId ->
        TcLongIdentType kindOpt cenv newOk checkConstraints occ iwsam env tpenv synLongId

    | MultiDimensionArrayType (rank, elemTy, m) ->
        TcArrayType cenv newOk checkConstraints occ env tpenv rank elemTy m

    | SynType.App (StripParenTypes (SynType.LongIdent longId), _, args, _, _, postfix, m) ->
        TcLongIdentAppType kindOpt cenv newOk checkConstraints occ iwsam env tpenv longId postfix args m

    | SynType.LongIdentApp (synLeftTy, synLongId, _, args, _commas, _, m) ->
        TcNestedAppType cenv newOk checkConstraints occ iwsam env tpenv synLeftTy synLongId args m

    | SynType.Tuple(isStruct, segments, m) ->
        TcTupleType kindOpt cenv newOk checkConstraints occ env tpenv isStruct segments m

    | SynType.AnonRecd(fields = []) ->
        // The parser takes care of error messages
        NewErrorType(), tpenv

    | SynType.AnonRecd(isStruct, args, m) ->
        TcAnonRecdType cenv newOk checkConstraints occ env tpenv isStruct args m

    | SynType.Fun(argType = domainTy; returnType = resultTy) ->
        TcFunctionType cenv newOk checkConstraints occ env tpenv domainTy resultTy

    | SynType.Array (rank , elemTy, m) ->
        TcArrayType cenv newOk checkConstraints occ env tpenv rank elemTy m

    | SynType.Var (tp, _) ->
        TcTypeParameter kindOpt cenv env newOk tpenv tp

    | SynType.Anon m ->
        TcAnonType kindOpt cenv newOk tpenv m

    | SynType.WithGlobalConstraints(synInnerTy, synConstraints, _) ->
        TcTypeWithConstraints cenv env newOk checkConstraints occ tpenv synInnerTy synConstraints

    | SynType.HashConstraint(synInnerTy, m) ->
        TcTypeHashConstraint cenv env newOk checkConstraints occ tpenv synInnerTy m

    | SynType.Intersection (tp, tys, m, _) ->
        TcIntersectionConstraint cenv env newOk checkConstraints occ tpenv tp tys m

    | SynType.StaticConstant (synConst, m) ->
        TcTypeStaticConstant kindOpt tpenv synConst m

    | SynType.StaticConstantNull m
    | SynType.StaticConstantNamed (_, _, m)
    | SynType.StaticConstantExpr (_, m) ->
        errorR(Error(FSComp.SR.parsInvalidLiteralInType(), m))
        NewErrorType (), tpenv

    | SynType.WithNull(innerTy, ambivalent, m, _) ->
        let innerTyC, tpenv = TcTypeAndRecover cenv newOk checkConstraints occ WarnOnIWSAM.Yes env tpenv innerTy
        let nullness = if ambivalent then KnownAmbivalentToNull else KnownWithNull
        let tyWithNull = TcAddNullnessToType false cenv env nullness innerTyC m
        tyWithNull, tpenv

    | SynType.MeasurePower(ty, exponent, m) ->
        TcTypeMeasurePower kindOpt cenv newOk checkConstraints occ env tpenv ty exponent m

    | SynType.App(arg1, _, args, _, _, postfix, m) ->
        TcTypeMeasureApp kindOpt cenv newOk checkConstraints occ env tpenv arg1 args postfix m

    | SynType.Paren(innerType, _)
    | SynType.SignatureParameter(usedType = innerType) ->
        TcTypeOrMeasure kindOpt cenv newOk checkConstraints occ iwsam env tpenv innerType

    | SynType.Or(range = m) ->
        // The inner types are expected to be collected by (|TypesForTypar|) at this point.
        error(Error(FSComp.SR.tcSynTypeOrInvalidInDeclaration(), m))

    | SynType.FromParseError _ ->
        NewErrorType (), tpenv

and CheckIWSAM (cenv: cenv) (env: TcEnv) checkConstraints iwsam m tcref =
    let g = cenv.g
    let ty = generalizedTyconRef g tcref

    if iwsam = WarnOnIWSAM.Yes && isInterfaceTy g ty && checkConstraints = CheckCxs then
        let meths = AllMethInfosOfTypeInScope ResultCollectionSettings.AllResults cenv.infoReader env.NameEnv None env.eAccessRights IgnoreOverrides m ty

        if meths |> List.exists (fun meth -> not meth.IsInstance && meth.IsDispatchSlot && not meth.IsExtensionMember) then
            let tcref = tcrefOfAppTy g ty
            warning(Error(FSComp.SR.tcUsingInterfaceWithStaticAbstractMethodAsType(tcref.DisplayNameWithStaticParametersAndUnderscoreTypars), m))

and TcLongIdentType kindOpt (cenv: cenv) newOk checkConstraints occ iwsam env tpenv synLongId =
    let (SynLongIdent(tc, _, _)) = synLongId
    let m = synLongId.Range
    let ad = env.eAccessRights

    let tinstEnclosing, tcref, inst = ForceRaise(ResolveTypeLongIdent cenv.tcSink cenv.nameResolver occ OpenQualified env.NameEnv ad tc TypeNameResolutionStaticArgsInfo.DefiniteEmpty PermitDirectReferenceToGeneratedType.No)

    CheckIWSAM cenv env checkConstraints iwsam m tcref

    match kindOpt, tcref.TypeOrMeasureKind with
    | Some TyparKind.Type, TyparKind.Measure ->
        error(Error(FSComp.SR.tcExpectedTypeNotUnitOfMeasure(), m))
        NewErrorType (), tpenv
    | Some TyparKind.Measure, TyparKind.Type ->
        error(Error(FSComp.SR.tcExpectedUnitOfMeasureNotType(), m))
        TType_measure (NewErrorMeasure ()), tpenv
    | _, TyparKind.Measure ->
        TType_measure (Measure.Const(tcref, m)), tpenv
    | _, TyparKind.Type ->
        TcTypeApp cenv newOk checkConstraints occ env tpenv m tcref tinstEnclosing [] inst

/// Some.Long.TypeName<ty1, ty2>
/// ty1 SomeLongTypeName
and TcLongIdentAppType kindOpt (cenv: cenv) newOk checkConstraints occ iwsam env tpenv longId postfix args m =
    let (SynLongIdent(tc, _, _)) = longId
    let ad = env.eAccessRights

    let tinstEnclosing, tcref, inst =
        let tyResInfo = TypeNameResolutionStaticArgsInfo.FromTyArgs args.Length
        ResolveTypeLongIdent cenv.tcSink cenv.nameResolver ItemOccurrence.UseInType OpenQualified env.eNameResEnv ad tc tyResInfo PermitDirectReferenceToGeneratedType.No
        |> ForceRaise

    CheckIWSAM cenv env checkConstraints iwsam m tcref

    match kindOpt, tcref.TypeOrMeasureKind with
    | Some TyparKind.Type, TyparKind.Measure ->
        error(Error(FSComp.SR.tcExpectedTypeNotUnitOfMeasure(), m))
        NewErrorType (), tpenv

    | Some TyparKind.Measure, TyparKind.Type ->
        error(Error(FSComp.SR.tcExpectedUnitOfMeasureNotType(), m))
        TType_measure (NewErrorMeasure ()), tpenv

    | _, TyparKind.Type ->
        if postfix && tcref.Typars m |> List.exists (fun tp -> match tp.Kind with TyparKind.Measure -> true | _ -> false) then
            error(Error(FSComp.SR.tcInvalidUnitsOfMeasurePrefix(), m))
        TcTypeApp cenv newOk checkConstraints occ env tpenv m tcref tinstEnclosing args inst

    | _, TyparKind.Measure ->
        match args, postfix with
        | [arg], true ->
            let ms, tpenv = TcMeasure cenv newOk checkConstraints occ env tpenv arg m
            TType_measure (Measure.Prod(Measure.Const(tcref, tcref.Range), ms, ms.Range)), tpenv

        | _, _ ->
            errorR(Error(FSComp.SR.tcUnitsOfMeasureInvalidInTypeConstructor(), m))
            NewErrorType (), tpenv

and TcNestedAppType (cenv: cenv) newOk checkConstraints occ iwsam env tpenv synLeftTy synLongId args m =
    let g = cenv.g
    let ad = env.eAccessRights
    let (SynLongIdent(longId, _, _)) = synLongId
    let leftTy, tpenv = TcType cenv newOk checkConstraints occ iwsam env tpenv synLeftTy
    match leftTy with
    | AppTy g (tcref, tinst) ->
        let tcref, inst = ResolveTypeLongIdentInTyconRef cenv.tcSink cenv.nameResolver env.eNameResEnv (TypeNameResolutionInfo.ResolveToTypeRefs (TypeNameResolutionStaticArgsInfo.FromTyArgs args.Length)) ad m tcref longId
        TcTypeApp cenv newOk checkConstraints occ env tpenv m tcref tinst args inst
    | _ ->
        error(Error(FSComp.SR.tcTypeHasNoNestedTypes(), m))

and TcTupleType kindOpt (cenv: cenv) newOk checkConstraints occ env tpenv isStruct (args: SynTupleTypeSegment list) m =
    let tupInfo = mkTupInfo isStruct
    if isStruct then
        let argsR,tpenv = TcTypesAsTuple cenv newOk checkConstraints occ env tpenv args m
        TType_tuple(tupInfo, argsR), tpenv
    else
        let isMeasure =
            match kindOpt with
            | Some TyparKind.Measure -> true
            | None -> args |> List.exists(function | SynTupleTypeSegment.Slash _ -> true | _ -> false)
            | Some _ -> false

        if isMeasure then
            let ms,tpenv = TcMeasuresAsTuple cenv newOk checkConstraints occ env tpenv args m
            TType_measure ms,tpenv
        else
            let argsR,tpenv = TcTypesAsTuple cenv newOk checkConstraints occ env tpenv args m
            TType_tuple(tupInfo, argsR), tpenv

and CheckAnonRecdTypeDuplicateFields (elems: Ident array) =
    elems |> Array.iteri (fun i (uc1: Ident) ->
        elems |> Array.iteri (fun j (uc2: Ident) ->
            if j > i && uc1.idText = uc2.idText then
               errorR(Error(FSComp.SR.tcAnonRecdTypeDuplicateFieldId(uc1.idText), uc1.idRange))))

and TcAnonRecdType (cenv: cenv) newOk checkConstraints occ env tpenv isStruct args m =
    let tupInfo = mkTupInfo isStruct
    let unsortedFieldIds = args |> List.map fst |> List.toArray
    if unsortedFieldIds.Length > 1 then
        CheckAnonRecdTypeDuplicateFields unsortedFieldIds
    let tup = args |> List.map (fun (_, t) -> SynTupleTypeSegment.Type t)
    let argsR,tpenv = TcTypesAsTuple cenv newOk checkConstraints occ env tpenv tup m
    let anonInfo = AnonRecdTypeInfo.Create(cenv.thisCcu, tupInfo, unsortedFieldIds)

    // Sort into canonical order
    let sortedFieldTys, sortedCheckedArgTys = List.zip args argsR |> List.indexed |> List.sortBy (fun (i,_) -> unsortedFieldIds[i].idText) |> List.map snd |> List.unzip

    sortedFieldTys |> List.iteri (fun i (x,_) ->
        let item = Item.AnonRecdField(anonInfo, sortedCheckedArgTys, i, x.idRange)
        CallNameResolutionSink cenv.tcSink (x.idRange,env.NameEnv,item,emptyTyparInst,ItemOccurrence.UseInType,env.eAccessRights))

    TType_anon(anonInfo, sortedCheckedArgTys),tpenv

and TcFunctionType (cenv: cenv) newOk checkConstraints occ env tpenv domainTy resultTy =
    let g = cenv.g
    let domainTyR, tpenv = TcTypeAndRecover cenv newOk checkConstraints occ WarnOnIWSAM.Yes env tpenv domainTy
    let resultTyR, tpenv = TcTypeAndRecover cenv newOk checkConstraints occ WarnOnIWSAM.Yes env tpenv resultTy
    let tyR = mkFunTy g domainTyR resultTyR
    tyR, tpenv

and TcArrayType (cenv: cenv) newOk checkConstraints occ env tpenv rank elemTy m =
    let g = cenv.g
    let elemTy, tpenv = TcTypeAndRecover cenv newOk checkConstraints occ WarnOnIWSAM.Yes env tpenv elemTy
    let tyR = mkArrayTy g rank g.knownWithoutNull elemTy m
    tyR, tpenv

and TcTypeParameter kindOpt (cenv: cenv) env newOk tpenv tp =
    let tpR, tpenv = TcTypeOrMeasureParameter kindOpt cenv env newOk tpenv tp
    match tpR.Kind with
    | TyparKind.Measure -> TType_measure (Measure.Var tpR), tpenv
    | TyparKind.Type -> mkTyparTy tpR, tpenv

// _ types
and TcAnonType kindOpt (cenv: cenv) newOk tpenv m =
    let tp: Typar = TcAnonTypeOrMeasure kindOpt cenv TyparRigidity.Anon TyparDynamicReq.No newOk m
    match tp.Kind with
    | TyparKind.Measure -> TType_measure (Measure.Var tp), tpenv
    | TyparKind.Type -> mkTyparTy tp, tpenv

and TcTypeWithConstraints (cenv: cenv) env newOk checkConstraints occ tpenv synTy synConstraints =
    let ty, tpenv = TcTypeAndRecover cenv newOk checkConstraints occ WarnOnIWSAM.Yes env tpenv synTy
    let tpenv = TcTyparConstraints cenv newOk checkConstraints occ env tpenv synConstraints
    ty, tpenv

// #typ
and TcTypeHashConstraint (cenv: cenv) env newOk checkConstraints occ tpenv synTy m =
    let tp = TcAnonTypeOrMeasure (Some TyparKind.Type) cenv TyparRigidity.WarnIfNotRigid TyparDynamicReq.Yes newOk m
    let ty, tpenv = TcTypeAndRecover cenv newOk checkConstraints occ WarnOnIWSAM.No env tpenv synTy
    let tpTy = mkTyparTy tp
    AddCxTypeMustSubsumeType ContextInfo.NoContext env.DisplayEnv cenv.css m NoTrace ty tpTy
    tpTy, tpenv

// (x: 't & #I1 & #I2)
// (x: #I1 & #I2)
and TcIntersectionConstraint (cenv: cenv) env newOk checkConstraints occ tpenv synTypar synTys m =
    let tp, tpenv =
        match synTypar with
        | Some synTypar -> TcTypeOrMeasureParameter (Some TyparKind.Type) cenv env newOk tpenv synTypar
        | _ -> TcAnonTypeOrMeasure (Some TyparKind.Type) cenv TyparRigidity.WarnIfNotRigid TyparDynamicReq.Yes newOk m, tpenv

    let typarTy = mkTyparTy tp

    let tpenv =
        synTys
        |> List.fold (fun tpenv ty ->
            match ty with
            | SynType.HashConstraint (ty, m) ->
                let ty, tpenv = TcTypeAndRecover cenv newOk checkConstraints occ WarnOnIWSAM.No env tpenv ty
                AddCxTypeMustSubsumeType ContextInfo.NoContext env.DisplayEnv cenv.css m NoTrace ty typarTy
                tpenv
            | _ -> tpenv
        ) tpenv

    let tpTy = tp.AsType KnownAmbivalentToNull // TODO: NULLNESS
    tpTy, tpenv

and TcTypeStaticConstant kindOpt tpenv c m =
    match c, kindOpt with
    | _, Some TyparKind.Type ->
        errorR(Error(FSComp.SR.parsInvalidLiteralInType(), m))
        NewErrorType (), tpenv
    | SynConst.Int32 1, _ ->
        TType_measure (Measure.One m), tpenv
    | _ ->
        errorR(Error(FSComp.SR.parsInvalidLiteralInType(), m))
        NewErrorType (), tpenv

and TcTypeMeasurePower kindOpt (cenv: cenv) newOk checkConstraints occ env tpenv ty exponent m =
    match kindOpt with
    | Some TyparKind.Type ->
        errorR(Error(FSComp.SR.tcUnexpectedSymbolInTypeExpression("^"), m))
        NewErrorType (), tpenv
    | _ ->
        let ms, tpenv = TcMeasure cenv newOk checkConstraints occ env tpenv ty m
        TType_measure (Measure.RationalPower (ms, TcSynRationalConst exponent)), tpenv

and TcTypeMeasureApp kindOpt (cenv: cenv) newOk checkConstraints occ env tpenv arg1 args postfix m =
    match arg1 with
    | StripParenTypes (SynType.Var(_, m1) | SynType.MeasurePower(_, _, m1)) ->
        match kindOpt, args, postfix with
        | (None | Some TyparKind.Measure), [arg2], true ->
            let ms1, tpenv = TcMeasure cenv newOk checkConstraints occ env tpenv arg1 m1
            let ms2, tpenv = TcMeasure cenv newOk checkConstraints occ env tpenv arg2 m
            TType_measure (Measure.Prod(ms1, ms2, unionRanges ms1.Range ms2.Range)), tpenv

        | _ ->
            errorR(Error(FSComp.SR.tcTypeParameterInvalidAsTypeConstructor(), m))
            NewErrorType (), tpenv

    | StripParenTypes(SynType.FromParseError _) ->
        NewErrorType (), tpenv

    | _ ->
        errorR(Error(FSComp.SR.tcIllegalSyntaxInTypeExpression(), m))
        NewErrorType (), tpenv

and TcType (cenv: cenv) newOk checkConstraints occ iwsam env (tpenv: UnscopedTyparEnv) ty =
    TcTypeOrMeasure (Some TyparKind.Type) cenv newOk checkConstraints occ iwsam env tpenv ty

and TcMeasure (cenv: cenv) newOk checkConstraints occ env (tpenv: UnscopedTyparEnv) (StripParenTypes ty) m =
    match ty with
    | SynType.Anon m ->
        error(Error(FSComp.SR.tcAnonymousUnitsOfMeasureCannotBeNested(), m))
        NewErrorMeasure (), tpenv
    | _ ->
        match TcTypeOrMeasure (Some TyparKind.Measure) cenv newOk checkConstraints occ WarnOnIWSAM.Yes env tpenv ty with
        | TType_measure ms, tpenv -> ms, tpenv
        | _ ->
            error(Error(FSComp.SR.tcExpectedUnitOfMeasureNotType(), m))
            NewErrorMeasure (), tpenv

and TcAnonTypeOrMeasure kindOpt _cenv rigid dyn newOk m =
    if newOk = NoNewTypars then errorR (Error(FSComp.SR.tcAnonymousTypeInvalidInDeclaration(), m))

    let rigid =
        if rigid = TyparRigidity.Anon && newOk = NewTyparsOKButWarnIfNotRigid then
            TyparRigidity.WarnIfNotRigid
        else
            rigid

    let kind =
        match kindOpt with
        | Some TyparKind.Measure -> TyparKind.Measure
        | _ -> TyparKind.Type

    NewAnonTypar (kind, m, rigid, TyparStaticReq.None, dyn)

and TcTypes (cenv: cenv) newOk checkConstraints occ iwsam env tpenv args =
    List.mapFold (TcTypeAndRecover cenv newOk checkConstraints occ iwsam env) tpenv args

and TcTypesAsTuple (cenv: cenv) newOk checkConstraints occ env tpenv (args: SynTupleTypeSegment list) m =
    let hasASlash =
        args
        |> List.exists(function | SynTupleTypeSegment.Slash _ -> true | _ -> false)

    if hasASlash then errorR(Error(FSComp.SR.tcUnexpectedSlashInType(), m))

    let args : SynType list = getTypeFromTuplePath args
    match args with
    | [] -> error(InternalError("empty tuple type", m))
    | [ty] -> let ty, tpenv = TcTypeAndRecover cenv newOk checkConstraints occ WarnOnIWSAM.Yes env tpenv ty in [ty], tpenv
    | ty :: args ->
        let ty, tpenv = TcTypeAndRecover cenv newOk checkConstraints occ WarnOnIWSAM.Yes env tpenv ty
        let args = List.map SynTupleTypeSegment.Type args
        let tys, tpenv = TcTypesAsTuple cenv newOk checkConstraints occ env tpenv args m
        ty :: tys, tpenv

// Type-check a list of measures separated by juxtaposition, * or /
and TcMeasuresAsTuple (cenv: cenv) newOk checkConstraints occ env (tpenv: UnscopedTyparEnv) (args: SynTupleTypeSegment list) m =
    let rec gather (args: SynTupleTypeSegment list) tpenv acc =
        match args with
        | [] -> acc, tpenv
        | SynTupleTypeSegment.Type ty :: args ->
            let ms1, tpenv = TcMeasure cenv newOk checkConstraints occ env tpenv ty m
            gather args tpenv ms1
        | SynTupleTypeSegment.Star _ :: SynTupleTypeSegment.Type ty :: args ->
            let ms1, tpenv = TcMeasure cenv newOk checkConstraints occ env tpenv ty m
            gather args tpenv (Measure.Prod(acc, ms1, unionRanges acc.Range ms1.Range))
        | SynTupleTypeSegment.Slash _ :: SynTupleTypeSegment.Type ty :: args ->
            let ms1, tpenv = TcMeasure cenv newOk checkConstraints occ env tpenv ty m
            let ms2 = Measure.Inv ms1
            gather args tpenv (Measure.Prod(acc, ms2, unionRanges acc.Range ms2.Range))
        | _ -> failwith "impossible"
    gather args tpenv (Measure.One m)

and TcTypesOrMeasures optKinds (cenv: cenv) newOk checkConstraints occ env tpenv args m =
    match optKinds with
    | None ->
        List.mapFold (TcTypeOrMeasure None cenv newOk checkConstraints occ WarnOnIWSAM.Yes env) tpenv args
    | Some kinds ->
        if List.length kinds = List.length args then
            let ttypes, tpenv = List.mapFold (fun tpenv (arg, kind) -> TcTypeOrMeasure (Some kind) cenv newOk checkConstraints occ WarnOnIWSAM.Yes env tpenv arg) tpenv (List.zip args kinds)

            for ttype in ttypes do
                match stripTyEqns cenv.g ttype with
                | TType_measure tm -> CheckUnitOfMeasureAttributes cenv.g tm
                | _ -> ()
                                
            ttypes, tpenv
            
        elif isNil kinds then error(Error(FSComp.SR.tcUnexpectedTypeArguments(), m))
        else error(Error(FSComp.SR.tcTypeParameterArityMismatch((List.length kinds), (List.length args)), m))

and TcTyparConstraints (cenv: cenv) newOk checkConstraints occ env tpenv synConstraints =
    // Mark up default constraints with a priority in reverse order: last gets 0, second
    // last gets 1 etc. See comment on TyparConstraint.DefaultsTo
    let _, tpenv = List.fold (fun (ridx, tpenv) tc -> ridx - 1, TcTyparConstraint ridx cenv newOk checkConstraints occ env tpenv tc) (List.length synConstraints - 1, tpenv) synConstraints
    tpenv

#if !NO_TYPEPROVIDERS
and TcStaticConstantParameter (cenv: cenv) (env: TcEnv) tpenv kind (StripParenTypes v) idOpt container =
    let g = cenv.g
    let fail() = error(Error(FSComp.SR.etInvalidStaticArgument(NicePrint.minimalStringOfType env.DisplayEnv kind), v.Range))
    let record ttype =
        match idOpt with
        | Some id ->
            let item = Item.OtherName (Some id, ttype, None, Some container, id.idRange)
            CallNameResolutionSink cenv.tcSink (id.idRange, env.NameEnv, item, emptyTyparInst, ItemOccurrence.Use, env.AccessRights)
        | _ -> ()

    match v with
    | SynType.StaticConstant(sc, _) ->
        let v =
            match sc with
            | SynConst.Byte n when typeEquiv g g.byte_ty kind -> record(g.byte_ty); box (n: byte)
            | SynConst.Int16 n when typeEquiv g g.int16_ty kind -> record(g.int16_ty); box (n: int16)
            | SynConst.Int32 n when typeEquiv g g.int32_ty kind -> record(g.int32_ty); box (n: int)
            | SynConst.Int64 n when typeEquiv g g.int64_ty kind -> record(g.int64_ty); box (n: int64)
            | SynConst.SByte n when typeEquiv g g.sbyte_ty kind -> record(g.sbyte_ty); box (n: sbyte)
            | SynConst.UInt16 n when typeEquiv g g.uint16_ty kind -> record(g.uint16_ty); box (n: uint16)
            | SynConst.UInt32 n when typeEquiv g g.uint32_ty kind -> record(g.uint32_ty); box (n: uint32)
            | SynConst.UInt64 n when typeEquiv g g.uint64_ty kind -> record(g.uint64_ty); box (n: uint64)
            | SynConst.Decimal n when typeEquiv g g.decimal_ty kind -> record(g.decimal_ty); box (n: decimal)
            | SynConst.Single n when typeEquiv g g.float32_ty kind -> record(g.float32_ty); box (n: single)
            | SynConst.Double n when typeEquiv g g.float_ty kind -> record(g.float_ty); box (n: double)
            | SynConst.Char n when typeEquiv g g.char_ty kind -> record(g.char_ty); box (n: char)
            | SynConst.String (s, _, _) when typeEquiv g g.string_ty kind -> record(g.string_ty); box (s: string)
            | SynConst.SourceIdentifier (i, s, m) when typeEquiv g g.string_ty kind ->
                let s = applyLineDirectivesToSourceIdentifier i s m
                record(g.string_ty); box (s: string)
            | SynConst.Bool b when typeEquiv g g.bool_ty kind -> record(g.bool_ty); box (b: bool)
            | _ -> fail()
        v, tpenv

    | SynType.StaticConstantExpr(e, _ ) ->

        // If an error occurs, don't try to recover, since the constant expression will be nothing like what we need
        let te, tpenv' = TcExprNoRecover cenv (MustEqual kind) env tpenv e

        // Evaluate the constant expression using static attribute argument rules
        let te = EvalLiteralExprOrAttribArg g te
        let v =
            match stripDebugPoints (stripExpr te) with
            // Check we have a residue constant. We know the type was correct because we checked the expression with this type.
            | Expr.Const (c, _, _) ->
                match c with
                | Const.Byte n -> record(g.byte_ty); box (n: byte)
                | Const.Int16 n -> record(g.int16_ty); box (n: int16)
                | Const.Int32 n -> record(g.int32_ty); box (n: int)
                | Const.Int64 n -> record(g.int64_ty); box (n: int64)
                | Const.SByte n -> record(g.sbyte_ty); box (n: sbyte)
                | Const.UInt16 n -> record(g.uint16_ty); box (n: uint16)
                | Const.UInt32 n -> record(g.uint32_ty); box (n: uint32)
                | Const.UInt64 n -> record(g.uint64_ty); box (n: uint64)
                | Const.Decimal n -> record(g.decimal_ty); box (n: decimal)
                | Const.Single n -> record(g.float32_ty); box (n: single)
                | Const.Double n -> record(g.float_ty); box (n: double)
                | Const.Char n -> record(g.char_ty); box (n: char)
                | Const.String s -> record(g.string_ty); box (s: string)
                | Const.Bool b -> record(g.bool_ty); box (b: bool)
                | _ -> fail()
            | _ -> error(Error(FSComp.SR.tcInvalidConstantExpression(), v.Range))
        v, tpenv'

    | SynType.LongIdent synLongId ->
        let m = synLongId.Range
        TcStaticConstantParameter cenv env tpenv kind (SynType.StaticConstantExpr(SynExpr.LongIdent (false, synLongId, None, m), m)) idOpt container

    | _ ->
        fail()

and CrackStaticConstantArgs (cenv: cenv) env tpenv (staticParameters: Tainted<ProvidedParameterInfo>[], args: SynType list, container, containerName, m) =
    let args =
        args |> List.map (function
            | StripParenTypes (SynType.StaticConstantNamed(StripParenTypes (SynType.LongIdent(SynLongIdent([id], _, _))), v, _)) -> Some id, v
            | v -> None, v)

    let unnamedArgs = args |> Seq.takeWhile (fst >> Option.isNone) |> Seq.toArray |> Array.map snd
    let otherArgs = args |> List.skipWhile (fst >> Option.isNone)
    let namedArgs = otherArgs |> List.takeWhile (fst >> Option.isSome) |> List.map (map1Of2 Option.get)
    let otherArgs = otherArgs |> List.skipWhile (fst >> Option.isSome)
    if not otherArgs.IsEmpty then
        error (Error(FSComp.SR.etBadUnnamedStaticArgs(), m))

    let indexedStaticParameters = staticParameters |> Array.toList |> List.indexed
    for n, _ in namedArgs do
         match indexedStaticParameters |> List.filter (fun (j, sp) -> j >= unnamedArgs.Length && n.idText = sp.PUntaint((fun sp -> sp.Name), m)) with
         | [] ->
             if staticParameters |> Array.exists (fun sp -> n.idText = sp.PUntaint((fun sp -> sp.Name), n.idRange)) then
                 error (Error(FSComp.SR.etStaticParameterAlreadyHasValue n.idText, n.idRange))
             else
                 error (Error(FSComp.SR.etNoStaticParameterWithName n.idText, n.idRange))
         | [_] -> ()
         | _ -> error (Error(FSComp.SR.etMultipleStaticParameterWithName n.idText, n.idRange))

    if staticParameters.Length < namedArgs.Length + unnamedArgs.Length then
        error (Error(FSComp.SR.etTooManyStaticParameters(staticParameters.Length, unnamedArgs.Length, namedArgs.Length), m))

    let argsInStaticParameterOrderIncludingDefaults =
        staticParameters |> Array.mapi (fun i sp ->
            let spKind = ImportProvidedType cenv.amap m (sp.PApply((fun x -> x.ParameterType), m))
            let spName = sp.PUntaint((fun sp -> sp.Name), m)
            if i < unnamedArgs.Length then
                let v = unnamedArgs[i]
                let v, _tpenv = TcStaticConstantParameter cenv env tpenv spKind v None container
                v
            else
                match namedArgs |> List.filter (fun (n, _) -> n.idText = spName) with
                | [(n, v)] ->
                    let v, _tpenv = TcStaticConstantParameter cenv env tpenv spKind v (Some n) container
                    v
                | [] ->
                    if sp.PUntaint((fun sp -> sp.IsOptional), m) then
                         match sp.PUntaint((fun sp -> sp.RawDefaultValue), m) with
                         | null -> error (Error(FSComp.SR.etStaticParameterRequiresAValue (spName, containerName, containerName, spName), m))
                         | v -> v
                    else
                      error (Error(FSComp.SR.etStaticParameterRequiresAValue (spName, containerName, containerName, spName), m))
                 | ps ->
                      error (Error(FSComp.SR.etMultipleStaticParameterWithName spName, (fst (List.last ps)).idRange)))

    argsInStaticParameterOrderIncludingDefaults

and TcProvidedTypeAppToStaticConstantArgs (cenv: cenv) env generatedTypePathOpt tpenv (tcref: TyconRef) (args: SynType list) m =
    // Static argument expressions should not get debug points
    let env = { env with eIsControlFlow = false }

    let typeBeforeArguments =
        match tcref.TypeReprInfo with
        | TProvidedTypeRepr info -> info.ProvidedType
        | _ -> failwith "unreachable"

    let staticParameters = typeBeforeArguments.PApplyWithProvider((fun (typeBeforeArguments, provider) -> typeBeforeArguments.GetStaticParameters provider), range=m)
    let staticParameters = staticParameters.PApplyArray(id, "GetStaticParameters", m)

    let argsInStaticParameterOrderIncludingDefaults = CrackStaticConstantArgs cenv env tpenv (staticParameters, args, ArgumentContainer.Type tcref, tcref.DisplayName, m)

    // Take the static arguments (as SynType's) and convert them to objects of the appropriate type, based on the expected kind.
    let providedTypeAfterStaticArguments, checkTypeName =
        match TryApplyProvidedType(typeBeforeArguments, generatedTypePathOpt, argsInStaticParameterOrderIncludingDefaults, m) with
        | None -> error(Error(FSComp.SR.etErrorApplyingStaticArgumentsToType(), m))
        | Some (ty, checkTypeName) -> (ty, checkTypeName)

    let hasNoArgs = (argsInStaticParameterOrderIncludingDefaults.Length = 0)
    hasNoArgs, providedTypeAfterStaticArguments, checkTypeName

and TryTcMethodAppToStaticConstantArgs (cenv: cenv) env tpenv (minfos: MethInfo list, argsOpt, mExprAndArg, mItem) =
    match minfos, argsOpt with
    | [minfo], Some (args, _) ->
        match minfo.ProvidedStaticParameterInfo with
        | Some (methBeforeArguments, staticParams) ->
            let providedMethAfterStaticArguments = TcProvidedMethodAppToStaticConstantArgs cenv env tpenv (minfo, methBeforeArguments, staticParams, args, mExprAndArg)
            let minfoAfterStaticArguments = ProvidedMeth(cenv.amap, providedMethAfterStaticArguments, minfo.ExtensionMemberPriorityOption, mItem)
            Some minfoAfterStaticArguments
        | _ -> None
    | _ -> None

and TcProvidedMethodAppToStaticConstantArgs (cenv: cenv) env tpenv (minfo, methBeforeArguments, staticParams, args, m) =

    let argsInStaticParameterOrderIncludingDefaults = CrackStaticConstantArgs cenv env tpenv (staticParams, args, ArgumentContainer.Method minfo, minfo.DisplayName, m)

    let providedMethAfterStaticArguments =
        match TryApplyProvidedMethod(methBeforeArguments, argsInStaticParameterOrderIncludingDefaults, m) with
        | None -> error(Error(FSComp.SR.etErrorApplyingStaticArgumentsToMethod(), m))
        | Some meth -> meth

    providedMethAfterStaticArguments

and TcProvidedTypeApp (cenv: cenv) env tpenv tcref args m =
    let hasNoArgs, providedTypeAfterStaticArguments, checkTypeName = TcProvidedTypeAppToStaticConstantArgs cenv env None tpenv tcref args m

    let isGenerated = providedTypeAfterStaticArguments.PUntaint((fun st -> not st.IsErased), m)

    //printfn "adding entity for provided type '%s', isDirectReferenceToGenerated = %b, isGenerated = %b" (st.PUntaint((fun st -> st.Name), m)) isDirectReferenceToGenerated isGenerated
    let isDirectReferenceToGenerated = isGenerated && IsGeneratedTypeDirectReference (providedTypeAfterStaticArguments, m)
    if isDirectReferenceToGenerated then
        error(Error(FSComp.SR.etDirectReferenceToGeneratedTypeNotAllowed(tcref.DisplayName), m))

    // We put the type name check after the 'isDirectReferenceToGenerated' check because we need the 'isDirectReferenceToGenerated' error to be shown for generated types
    checkTypeName()
    if hasNoArgs then
        mkWoNullAppTy tcref [], tpenv
    else
        let ty = ImportProvidedType cenv.amap m providedTypeAfterStaticArguments
        ty, tpenv
#endif

/// Typecheck an application of a generic type to type arguments.
///
/// Note that the generic type may be a nested generic type List<T>.ListEnumerator<U>.
/// In this case, 'argsR is only the instantiation of the suffix type arguments, and pathTypeArgs gives
/// the prefix of type arguments.
and TcTypeApp (cenv: cenv) newOk checkConstraints occ env tpenv m tcref pathTypeArgs (synArgTys: SynType list) (tinst: TypeInst) =
    let g = cenv.g
    CheckTyconAccessible cenv.amap m env.AccessRights tcref |> ignore
    CheckEntityAttributes g tcref m |> CommitOperationResult

#if !NO_TYPEPROVIDERS
    // Provided types are (currently) always non-generic. Their names may include mangled
    // static parameters, which are passed by the provider.
    if tcref.Deref.IsProvided then TcProvidedTypeApp cenv env tpenv tcref synArgTys m else
#endif

    let synArgTysLength = synArgTys.Length
    let pathTypeArgsLength = pathTypeArgs.Length
    if tinst.Length <> pathTypeArgsLength + synArgTysLength then
        error (TyconBadArgs(env.DisplayEnv, tcref, pathTypeArgsLength + synArgTysLength, m))

    let tps = tinst |> List.skip pathTypeArgsLength |> List.map (fun t ->
        match t with
        | TType_var(typar, _)
        | TType_measure(Measure.Var typar) -> typar
        | t -> failwith $"TcTypeApp: {t}"
    )

    // If we're not checking constraints, i.e. when we first assert the super/interfaces of a type definition, then just
    // clear the constraint lists of the freshly generated type variables. A little ugly but fairly localized.
    if checkConstraints = NoCheckCxs then tps |> List.iter (fun tp -> tp.SetConstraints [])

    let argTys, tpenv =
        // Get the suffix of typars
        let tpsForArgs = List.skip (tps.Length - synArgTysLength) tps
        let kindsForArgs = tpsForArgs |> List.map (fun tp -> tp.Kind)
        TcTypesOrMeasures (Some kindsForArgs) cenv newOk checkConstraints occ env tpenv synArgTys m

    // Add the types of the enclosing class for a nested type
    let actualArgTys = pathTypeArgs @ argTys

    if checkConstraints = CheckCxs then
        List.iter2 (UnifyTypes cenv env m) tinst actualArgTys

    // Try to decode System.Tuple --> F# tuple types etc.
    let ty = g.decompileType tcref actualArgTys g.knownWithoutNull

    ty, tpenv

and TcTypeOrMeasureAndRecover kindOpt (cenv: cenv) newOk checkConstraints occ iwsam env tpenv ty =
    let g = cenv.g
    try
        TcTypeOrMeasure kindOpt cenv newOk checkConstraints occ iwsam env tpenv ty
    with RecoverableException e ->
        errorRecovery e ty.Range

        let recoveryTy =
            match kindOpt, newOk with
            | Some TyparKind.Measure, NoNewTypars -> TType_measure(Measure.One ty.Range)
            | Some TyparKind.Measure, _ -> TType_measure (NewErrorMeasure ())
            | _, NoNewTypars -> g.obj_ty_ambivalent
            | _ -> NewErrorType ()

        recoveryTy, tpenv

and TcTypeAndRecover (cenv: cenv) newOk checkConstraints occ iwsam env tpenv ty =
    TcTypeOrMeasureAndRecover (Some TyparKind.Type) cenv newOk checkConstraints occ iwsam env tpenv ty

and TcNestedTypeApplication (cenv: cenv) newOk checkConstraints occ iwsam env tpenv mWholeTypeApp ty pathTypeArgs tyargs =
    let g = cenv.g

    let ty = convertToTypeWithMetadataIfPossible g ty

    if not (isAppTy g ty) then
        error(Error(FSComp.SR.tcTypeHasNoNestedTypes(), mWholeTypeApp))

    match ty with
    | TType_app(tcref, inst, _) ->
        CheckIWSAM cenv env checkConstraints iwsam mWholeTypeApp tcref
        TcTypeApp cenv newOk checkConstraints occ env tpenv mWholeTypeApp tcref pathTypeArgs tyargs inst
    | _ ->
        error(InternalError("TcNestedTypeApplication: expected type application", mWholeTypeApp))

/// The pattern syntax can also represent active pattern arguments. This routine
/// converts from the pattern syntax to the expression syntax.
///
/// Note we parse arguments to parameterized pattern labels as patterns, not expressions.
/// This means the range of syntactic expression forms that can be used here is limited.
and ConvSynPatToSynExpr synPat =
    match synPat with
    | SynPat.FromParseError(innerPat, _) ->
        ConvSynPatToSynExpr innerPat

    | SynPat.Const (c, m) ->
        SynExpr.Const (c, m)

    | SynPat.Named (SynIdent(id,_), _, None, _) ->
        SynExpr.Ident id

    | SynPat.Typed (innerPat, tgtTy, m) ->
        SynExpr.Typed (ConvSynPatToSynExpr innerPat, tgtTy, m)

    | SynPat.LongIdent (longDotId=SynLongIdent(longId, dotms, trivia) as synLongId; argPats=args; accessibility=None; range=m) ->
        let args = match args with SynArgPats.Pats args -> args | _ -> failwith "impossible: active patterns can be used only with SynConstructorArgs.Pats"
        let e =
            if not dotms.IsEmpty && dotms.Length = longId.Length then
                let e = SynExpr.LongIdent (false, SynLongIdent(longId, List.truncate (dotms.Length - 1) dotms, trivia), None, m)
                SynExpr.DiscardAfterMissingQualificationAfterDot (e, List.last dotms, unionRanges e.Range (List.last dotms))
            else SynExpr.LongIdent (false, synLongId, None, m)
        List.fold (fun f x -> mkSynApp1 f (ConvSynPatToSynExpr x) m) e args

    | SynPat.Tuple (isStruct, args, _, m) ->
        SynExpr.Tuple (isStruct, List.map ConvSynPatToSynExpr args, [], m)

    | SynPat.Paren (innerPat, _) ->
        ConvSynPatToSynExpr innerPat

    | SynPat.ArrayOrList (isArray, args, m) ->
        SynExpr.ArrayOrList (isArray,List.map ConvSynPatToSynExpr args, m)

    | SynPat.QuoteExpr (e,_) ->
        e

    | SynPat.Null m ->
        SynExpr.Null m

    | _ ->
        error(Error(FSComp.SR.tcInvalidArgForParameterizedPattern(), synPat.Range))

/// Check a long identifier 'Case' or 'Case argsR' that has been resolved to an active pattern case
and TcPatLongIdentActivePatternCase warnOnUpper (cenv: cenv) (env: TcEnv) vFlags patEnv ty (mLongId, item, apref, args, m) =
    let g = cenv.g
    let (TcPatLinearEnv(tpenv, names, takenNames)) = patEnv
    let (APElemRef (apinfo, vref, idx, isStructRetTy)) = apref

    let cenv =
        if g.checkNullness then
            match tryGetWarnOnWithoutNullMessage g vref.Attribs with
            | Some _ as warnMsg -> { cenv with css.WarnWhenUsingWithoutNullOnAWithNullTarget = warnMsg }
            | None -> cenv
        else
            cenv

    // Report information about the 'active recognizer' occurrence to IDE
    CallNameResolutionSink cenv.tcSink (mLongId, env.NameEnv, item, emptyTyparInst, ItemOccurrence.Pattern, env.eAccessRights)

    // TOTAL/PARTIAL ACTIVE PATTERNS
    let _, vExpr, _, _, tinst, _ = TcVal cenv env tpenv vref None None m
    let vExpr = MakeApplicableExprWithFlex cenv env vExpr
    let vExprTy = vExpr.Type

    let activePatArgsAsSynPats, patArg =
        // only cases which return unit or unresolved type (in AP definition) compatible with unit can omit output arg
        let canOmit retTy =
            let couldResolveToUnit ty =
                tryDestTyparTy g ty
                |> ValueOption.exists (fun typar ->
                    not typar.IsSolved
                    && typar.Constraints |> List.forall (fun c ->
                        let (|Unit|_|) ty = if isUnitTy g ty then Some Unit else None

                        match c with
                        // These apply or could apply to unit.
                        | TyparConstraint.IsReferenceType _
                        | TyparConstraint.SupportsComparison _
                        | TyparConstraint.SupportsEquality _
                        | TyparConstraint.DefaultsTo (ty = Unit)
                        | TyparConstraint.AllowsRefStruct _
                        | TyparConstraint.MayResolveMember _ -> true

                        // Any other kind of constraint is incompatible with unit.
                        | TyparConstraint.CoercesTo _
                        | TyparConstraint.DefaultsTo _
                        | TyparConstraint.IsDelegate _
                        | TyparConstraint.IsEnum _
                        | TyparConstraint.IsNonNullableStruct _
                        | TyparConstraint.NotSupportsNull _
                        | TyparConstraint.IsUnmanaged _
                        | TyparConstraint.RequiresDefaultConstructor _
                        | TyparConstraint.SimpleChoice _
                        | TyparConstraint.NotSupportsNull _
                        | TyparConstraint.SupportsNull _ -> false))

            let caseRetTy =
                if isOptionTy g retTy then destOptionTy g retTy
                elif isValueOptionTy g retTy then destValueOptionTy g retTy
                elif isChoiceTy g retTy then destChoiceTy g retTy idx
                else retTy

            isUnitTy g caseRetTy || couldResolveToUnit caseRetTy

        // This bit of type-directed analysis ensures that parameterized partial active patterns returning unit do not need to take an argument
        let dtys, retTy = stripFunTy g vExprTy
        let paramCount = if dtys.Length = 0 then 0 else dtys.Length - 1

        let showErrMsg returnCount =
            let fmtExprArgs paramCount =
                let rec loop i (sb: Text.StringBuilder) =
                    let cutoff = 10
                    if i > paramCount then sb.ToString()
                    elif i > cutoff then sb.Append("...").ToString()
                    else loop (i + 1) (sb.Append(" e").Append i)

                loop 1 (Text.StringBuilder())

            let caseName = apinfo.ActiveTags[idx]
            let msg =
                match paramCount, returnCount with
                | 0, 0 -> FSComp.SR.tcActivePatternArgsCountNotMatchNoArgsNoPat(caseName, caseName)
                | 0, _ -> FSComp.SR.tcActivePatternArgsCountNotMatchOnlyPat(caseName)
                | _, 0 -> FSComp.SR.tcActivePatternArgsCountNotMatchArgs(paramCount, caseName, fmtExprArgs paramCount)
                | _, _ -> FSComp.SR.tcActivePatternArgsCountNotMatchArgsAndPat(paramCount, caseName, fmtExprArgs paramCount)
            error(Error(msg, m))

        let isUnsolvedTyparTy g ty = tryDestTyparTy g ty |> ValueOption.exists (fun typar -> not typar.IsSolved)

        // partial active pattern (returning bool) doesn't have output arg
        if (not apinfo.IsTotal && isBoolTy g retTy) then
            checkLanguageFeatureError g.langVersion LanguageFeature.BooleanReturningAndReturnTypeDirectedPartialActivePattern m
            if paramCount = List.length args then
                args, SynPat.Const(SynConst.Unit, m)
            else
                showErrMsg 0

        // for single case active pattern, if not all parameter provided, output will be a function
        // that takes the remaining parameter as input
        elif apinfo.IsTotal && apinfo.ActiveTags.Length = 1 && dtys.Length >= args.Length && not args.IsEmpty then
            List.frontAndBack args

        // active pattern cases returning unit or unknown things (in AP definition) can omit output arg
        elif paramCount = args.Length then
             // only cases which return unit or unresolved type (in AP definition) can omit output arg
             if canOmit retTy then
                args, SynPat.Const(SynConst.Unit, m)
             else
                 showErrMsg 1

        // active pattern in function param (e.g. let f (|P|_|) = ...)
        // or in mutual recursion with a lambda: `and (|P|) x = fun y -> …`
        elif isUnsolvedTyparTy g vExprTy || tryDestFunTy g vExprTy |> ValueOption.exists (fun (_, rangeTy) -> isUnsolvedTyparTy g rangeTy) then
            List.frontAndBack args

        // args count should equal to AP function params count
        elif dtys.Length <> args.Length then
            let returnCount =
                match dtys with
                // val (|P|)   : expr1:_ -> unit
                // val (|P|_|) : expr1:_ -> unit option
                // val (|P|_|) : expr1:_ -> unit voption
                | [_] when canOmit retTy -> 0
                | _ -> 1

            showErrMsg returnCount
        else
            List.frontAndBack args

    if not (isNil activePatArgsAsSynPats) && apinfo.ActiveTags.Length <> 1 then
        errorR (Error (FSComp.SR.tcRequireActivePatternWithOneResult (), m))

    let activePatArgsAsSynExprs = List.map ConvSynPatToSynExpr activePatArgsAsSynPats

    let activePatResTys = NewInferenceTypes g apinfo.ActiveTags
    let activePatType = apinfo.OverallType g m ty activePatResTys isStructRetTy

    let delayed =
        activePatArgsAsSynExprs
        |> List.map (fun arg -> DelayedApp(ExprAtomicFlag.NonAtomic, false, None, arg, unionRanges mLongId arg.Range))

    let activePatExpr, tpenv = PropagateThenTcDelayed cenv (MustEqual activePatType) env tpenv m vExpr vExprTy ExprAtomicFlag.NonAtomic delayed

    let patEnvR = TcPatLinearEnv(tpenv, names, takenNames)

    if idx >= activePatResTys.Length then error(Error(FSComp.SR.tcInvalidIndexIntoActivePatternArray(), m))
    let argTy = List.item idx activePatResTys

    let patArgPhase2, acc = cenv.TcPat warnOnUpper cenv env None vFlags patEnvR argTy patArg

    // The identity of an active pattern consists of its value and the types it is applied to.
    // If there are any expression args then we've lost identity.
    let activePatIdentity = if isNil activePatArgsAsSynExprs then Some (vref, tinst) else None
    let phase2 values = TPat_query((activePatExpr, activePatResTys, isStructRetTy, activePatIdentity, idx, apinfo), patArgPhase2 values, m)
    phase2, acc

and RecordNameAndTypeResolutions (cenv: cenv) env tpenv expr =
    // This function is motivated by cases like
    //    query { for ... join(for x in f(). }
    // where there is incomplete code in a query, and we are current just dropping a piece of the AST on the floor (above, the bit inside the 'join').
    //
    // The problem with dropping the AST on the floor is that we get no captured resolutions, which means no Intellisense/QuickInfo/ParamHelp.
    //
    // The fix is to semi-typecheck this AST-fragment, just to get resolutions captured.
    suppressErrorReporting (fun () ->
        try ignore(TcExprOfUnknownType cenv env tpenv expr)
        with e -> ())

and RecordNameAndTypeResolutionsDelayed (cenv: cenv) env tpenv delayed =

    let rec dummyCheckedDelayed delayed =
        match delayed with
        | DelayedApp (_hpa, _, _, arg, _mExprAndArg) :: otherDelayed ->
            RecordNameAndTypeResolutions cenv env tpenv arg
            dummyCheckedDelayed otherDelayed
        | _ -> ()
    dummyCheckedDelayed delayed

and TcExprOfUnknownType (cenv: cenv) env tpenv synExpr =
    let g = cenv.g
    let exprTy = NewInferenceType g
    let expr, tpenv = TcExpr cenv (MustEqual exprTy) env tpenv synExpr
    expr, exprTy, tpenv

// This is the old way of introducing flexibility via subtype constraints, still active
// for compat reasons.
and TcExprFlex (cenv: cenv) flex compat (desiredTy: TType) (env: TcEnv) tpenv (synExpr: SynExpr) =
    let g = cenv.g

    if flex then
        let argTy = NewInferenceType g
        (destTyparTy g argTy).SetSupportsNullFlex(true)
        if compat then
            (destTyparTy g argTy).SetIsCompatFlex(true)

        AddCxTypeMustSubsumeType (nullnessContextOnly env) env.DisplayEnv cenv.css synExpr.Range NoTrace desiredTy argTy

        let expr2, tpenv = TcExprFlex2 cenv argTy env false tpenv synExpr
        let expr3 = mkCoerceIfNeeded g desiredTy argTy expr2
        expr3, tpenv
    else
        TcExprFlex2 cenv desiredTy env false tpenv synExpr

and TcExprFlex2 (cenv: cenv) desiredTy env isMethodArg tpenv synExpr =
    TcExpr cenv (MustConvertTo (isMethodArg, desiredTy)) env tpenv synExpr

and TcExpr (cenv: cenv) ty (env: TcEnv) tpenv (synExpr: SynExpr) =

    let g = cenv.g

    // Guard the stack for deeply nested expressions
    cenv.stackGuard.Guard <| fun () ->

    // Start an error recovery handler, and check for stack recursion depth, moving to a new stack if necessary.
    // Note the try/with can lead to tail-recursion problems for iterated constructs, e.g. let... in...
    // So be careful!
    try
        TcExprNoRecover cenv ty env tpenv synExpr
    with RecoverableException exn ->
        let m = synExpr.Range
        // Error recovery - return some rubbish expression, but replace/annotate
        // the type of the current expression with a type variable that indicates an error
        errorRecovery exn m
        SolveTypeAsError env.DisplayEnv cenv.css m ty.Commit
        mkThrow m ty.Commit (mkOne g m), tpenv

and TcExprNoRecover (cenv: cenv) (ty: OverallTy) (env: TcEnv) tpenv (synExpr: SynExpr) =

    // Count our way through the expression shape that makes up an object constructor
    // See notes at definition of "ctor" re. object model constructors.
    let env =
        if GetCtorShapeCounter env > 0 then AdjustCtorShapeCounter (fun x -> x - 1) env
        else env

    TcExprThen cenv ty env tpenv false synExpr []

// This recursive entry is only used from one callsite (DiscardAfterMissingQualificationAfterDot)
// and has been added relatively late in F# 4.0 to preserve the structure of previous code. It pushes a 'delayed' parameter
// through TcExprOfUnknownType, TcExpr and TcExprNoRecover
and TcExprOfUnknownTypeThen (cenv: cenv) env tpenv synExpr delayed =
    let g = cenv.g

    let exprTy = NewInferenceType g

    let expr, tpenv =
      try
          TcExprThen cenv (MustEqual exprTy) env tpenv false synExpr delayed
      with RecoverableException exn ->
          let m = synExpr.Range
          errorRecovery exn m
          SolveTypeAsError env.DisplayEnv cenv.css m exprTy
          mkThrow m exprTy (mkOne g m), tpenv

    expr, exprTy, tpenv

/// This is used to typecheck legitimate 'main body of constructor' expressions
and TcExprThatIsCtorBody safeInitInfo (cenv: cenv) overallTy env tpenv synExpr =
    let g = cenv.g
    let env = {env with eCtorInfo = Some (CtorInfo.InitialExplicit safeInitInfo) }
    let expr, tpenv = TcExpr cenv overallTy env tpenv synExpr
    let expr = CheckAndRewriteObjectCtor g env expr
    expr, tpenv

/// This is used to typecheck all ordinary expressions including constituent
/// parts of ctor.
and TcExprThatCanBeCtorBody (cenv: cenv) overallTy env tpenv synExpr =
    let env = if AreWithinCtorShape env then AdjustCtorShapeCounter (fun x -> x + 1) env else env
    TcExpr cenv overallTy env tpenv synExpr

/// This is used to typecheck legitimate 'non-main body of object constructor' expressions
and TcExprThatCantBeCtorBody (cenv: cenv) overallTy env tpenv synExpr =
    let env = if AreWithinCtorShape env then ExitCtorShapeRegion env else env
    TcExpr cenv overallTy env tpenv synExpr

/// This is used to typecheck legitimate 'non-main body of object constructor' expressions
and TcStmtThatCantBeCtorBody (cenv: cenv) env tpenv synExpr =
    let env = if AreWithinCtorShape env then ExitCtorShapeRegion env else env
    TcStmt cenv env tpenv synExpr

and TcStmt (cenv: cenv) env tpenv synExpr =
    let g = cenv.g
    let expr, ty, tpenv = TcExprOfUnknownType cenv env tpenv synExpr
    let m = synExpr.Range
    let wasUnit = UnifyUnitType cenv env m ty expr
    if wasUnit then
        expr, tpenv
    else
        mkCompGenSequential m expr (mkUnit g m), tpenv

and TryTcStmt (cenv: cenv) env tpenv synExpr =
    let expr, ty, tpenv = TcExprOfUnknownType cenv env tpenv synExpr
    let m = synExpr.Range
    let hasTypeUnit = TryUnifyUnitTypeWithoutWarning cenv env m ty
    hasTypeUnit, ty, expr, tpenv

and CheckForAdjacentListExpression (cenv: cenv) synExpr hpa isInfix delayed (arg: SynExpr) =
    let g = cenv.g
    // func (arg)[arg2] gives warning that .[ must be used.
    match delayed with
    | DelayedApp (hpa2, isSugar2, _, arg2, _) :: _ when not isInfix && (hpa = ExprAtomicFlag.NonAtomic) && isAdjacentListExpr isSugar2 hpa2 (Some synExpr) arg2 ->
        let mWarning = unionRanges arg.Range arg2.Range

        match arg with
        | SynExpr.Paren _ ->
            if g.langVersion.SupportsFeature LanguageFeature.IndexerNotationWithoutDot then
                warning(Error(FSComp.SR.tcParenThenAdjacentListArgumentNeedsAdjustment(), mWarning))
            elif not (g.langVersion.IsExplicitlySpecifiedAs50OrBefore()) then
                informationalWarning(Error(FSComp.SR.tcParenThenAdjacentListArgumentReserved(), mWarning))

        | SynExpr.ArrayOrListComputed _
        | SynExpr.ArrayOrList _ ->
            if g.langVersion.SupportsFeature LanguageFeature.IndexerNotationWithoutDot then
                warning(Error(FSComp.SR.tcListThenAdjacentListArgumentNeedsAdjustment(), mWarning))
            elif not (g.langVersion.IsExplicitlySpecifiedAs50OrBefore()) then
                informationalWarning(Error(FSComp.SR.tcListThenAdjacentListArgumentReserved(), mWarning))

        | _ ->
            if g.langVersion.SupportsFeature LanguageFeature.IndexerNotationWithoutDot then
                warning(Error(FSComp.SR.tcOtherThenAdjacentListArgumentNeedsAdjustment(), mWarning))
            elif not (g.langVersion.IsExplicitlySpecifiedAs50OrBefore()) then
                informationalWarning(Error(FSComp.SR.tcOtherThenAdjacentListArgumentReserved(), mWarning))

    | _ -> ()

/// During checking of expressions of the form (x(y)).z(w1, w2)
/// keep a stack of things on the right. This lets us recognize
/// method applications and other item-based syntax.
and TcExprThen (cenv: cenv) overallTy env tpenv isArg synExpr delayed =
    let g = cenv.g

    let cachedExpression =
        env.eCachedImplicitYieldExpressions.FindAll synExpr.Range
        |> List.tryPick (fun (se, ty, e) ->
            if obj.ReferenceEquals(se, synExpr) then Some (ty, e) else None
        )

    match cachedExpression with
    | Some (ty, expr) ->
        UnifyOverallType cenv env synExpr.Range overallTy ty
        expr, tpenv
    | _ ->


        match synExpr with

        // A.
        // A.B.
        | SynExpr.DiscardAfterMissingQualificationAfterDot (expr1, _, m) ->
            let _, _, tpenv = suppressErrorReporting (fun () -> TcExprOfUnknownTypeThen cenv env tpenv expr1 [DelayedDot])
            mkDefault(m, overallTy.Commit), tpenv

        // A
        // A.B.C
        | LongOrSingleIdent (isOpt, longId, altNameRefCellOpt, mLongId) ->
            TcNonControlFlowExpr env <| fun env ->

            if isOpt then errorR(Error(FSComp.SR.tcSyntaxErrorUnexpectedQMark(), mLongId))

            // Check to see if pattern translation decided to use an alternative identifier.
            match altNameRefCellOpt with
            | Some {contents = SynSimplePatAlternativeIdInfo.Decided altId} ->
                TcExprThen cenv overallTy env tpenv isArg (SynExpr.LongIdent (isOpt, SynLongIdent([altId], [], [None]), None, mLongId)) delayed
            | _ ->
                TcLongIdentThen cenv overallTy env tpenv longId delayed

        // f?x<-v
        | SynExpr.Set(SynExpr.Dynamic(e1, _, e2, _) , rhsExpr, m) ->
            TcExprThenSetDynamic cenv overallTy env tpenv isArg e1 e2 rhsExpr m delayed

        // f x
        // f(x)  // hpa=true
        // f[x]  // hpa=true
        | SynExpr.App (hpa, isInfix, func, arg, mFuncAndArg) ->
            match func with
            | SynExpr.DotLambda _ -> errorR(Error(FSComp.SR.tcDotLambdaAtNotSupportedExpression(), func.Range))
            | _ -> ()

            TcNonControlFlowExpr env <| fun env ->

            CheckForAdjacentListExpression cenv synExpr hpa isInfix delayed arg

            TcExprThen cenv overallTy env tpenv false func ((DelayedApp (hpa, isInfix, Some func, arg, mFuncAndArg)) :: delayed)

        // e1?e2
        | SynExpr.Dynamic(e1, mQmark, e2, _) ->
             TcExprThenDynamic cenv overallTy env tpenv isArg e1 mQmark e2 delayed

        // e<tyargs>
        | SynExpr.TypeApp (func, _, typeArgs, _, _, mTypeArgs, mFuncAndTypeArgs) ->
            TcExprThen cenv overallTy env tpenv false func ((DelayedTypeApp (typeArgs, mTypeArgs, mFuncAndTypeArgs)) :: delayed)

        // expr1.id1
        // expr1.id1.id2
        // etc.
        | SynExpr.DotGet (expr1, _, SynLongIdent(longId, _, _), _) ->
            TcNonControlFlowExpr env <| fun env ->
            TcExprThen cenv overallTy env tpenv false expr1 ((DelayedDotLookup (longId, synExpr.Range)) :: delayed)

        // expr1.[expr2]
        // expr1.[e21, ..., e2n]
        // etc.
        | SynExpr.DotIndexedGet (expr1, IndexerArgs indexArgs, mDot, mWholeExpr) ->
            TcNonControlFlowExpr env <| fun env ->
            if not isArg && g.langVersion.SupportsFeature LanguageFeature.IndexerNotationWithoutDot then
                informationalWarning(Error(FSComp.SR.tcIndexNotationDeprecated(), mDot))
            TcIndexerThen cenv env overallTy mWholeExpr mDot tpenv None expr1 indexArgs delayed

        // expr1.[expr2] <- expr3
        // expr1.[e21, ..., e2n] <- expr3
        // etc.
        | SynExpr.DotIndexedSet (expr1, IndexerArgs indexArgs, expr3, mOfLeftOfSet, mDot, mWholeExpr) ->
            TcNonControlFlowExpr env <| fun env ->
            if g.langVersion.SupportsFeature LanguageFeature.IndexerNotationWithoutDot then
                warning(Error(FSComp.SR.tcIndexNotationDeprecated(), mDot))
            // Wrap in extra parens: like MakeDelayedSet,
            // but we don't actually want to delay it here.
            let setInfo = SynExpr.Paren (expr3, range0, None, expr3.Range), mOfLeftOfSet
            TcIndexerThen cenv env overallTy mWholeExpr mDot tpenv (Some setInfo) expr1 indexArgs delayed

        // Part of 'T.Ident
        | SynExpr.Typar (typar, m) ->
            TcTyparExprThen cenv overallTy env tpenv typar m delayed

        //  ^expr
        | SynExpr.IndexFromEnd (rightExpr, m) ->
            errorR(Error(FSComp.SR.tcTraitInvocationShouldUseTick(), m))
            // Incorporate the '^'  into the rightExpr, producing a nested SynExpr.Typar
            let adjustedExpr = ParseHelpers.adjustHatPrefixToTyparLookup m rightExpr
            TcExprThen cenv overallTy env tpenv isArg adjustedExpr delayed

        | _ ->
            match delayed with
            | [] -> TcExprUndelayed cenv overallTy env tpenv synExpr
            | _ ->
                let expr, exprTy, tpenv = TcExprUndelayedNoType cenv env tpenv synExpr
                PropagateThenTcDelayed cenv overallTy env tpenv synExpr.Range (MakeApplicableExprNoFlex cenv expr) exprTy ExprAtomicFlag.NonAtomic delayed

and TcExprThenSetDynamic (cenv: cenv) overallTy env tpenv isArg e1 e2 rhsExpr m delayed =
    let e2 = mkDynamicArgExpr e2
    let appExpr = mkSynQMarkSet m e1 e2 rhsExpr
    TcExprThen cenv overallTy env tpenv isArg appExpr delayed

and TcExprThenDynamic (cenv: cenv) overallTy env tpenv isArg e1 mQmark e2 delayed =
   let appExpr =
       let argExpr = mkDynamicArgExpr e2
       mkSynInfix mQmark e1 "?" argExpr

   TcExprThen cenv overallTy env tpenv isArg appExpr delayed

and TcExprsWithFlexes (cenv: cenv) env m tpenv flexes (argTys: TType list) (args: SynExpr list) =
    if args.Length <> argTys.Length then error(Error(FSComp.SR.tcExpressionCountMisMatch(argTys.Length, args.Length), m))
    (tpenv, List.zip3 flexes argTys args) ||> List.mapFold (fun tpenv (flex, ty, e) ->
         TcExprFlex cenv flex false ty env tpenv e)

and TcExprsNoFlexes (cenv: cenv) env m tpenv (argTys: TType list) (args: SynExpr list) =
    if args.Length <> argTys.Length then error(Error(FSComp.SR.tcExpressionCountMisMatch(argTys.Length, args.Length), m))
    (tpenv, List.zip argTys args) ||> List.mapFold (fun tpenv (ty, e) ->
         TcExprFlex2 cenv ty env false tpenv e)

and CheckSuperInit (cenv: cenv) objTy m =
    let g = cenv.g

    // Check the type is not abstract
    match tryTcrefOfAppTy g objTy with
    | ValueSome tcref when isAbstractTycon tcref.Deref ->
        errorR(Error(FSComp.SR.tcAbstractTypeCannotBeInstantiated(), m))
    | _ -> ()

and TcExprUndelayedNoType (cenv: cenv) env tpenv synExpr =
    let g = cenv.g
    let overallTy = NewInferenceType g
    let expr, tpenv = TcExprUndelayed cenv (MustEqual overallTy) env tpenv synExpr
    expr, overallTy, tpenv

/// Process a leaf construct where the actual type (or an approximation of it such as '_ list'
/// or '_ array') is already sufficiently pre-known, and the information in the overall type
/// can be eagerly propagated into the actual type (UnifyOverallType), including pre-calculating
/// any type-directed conversion. This must mean that types extracted when processing the expression are not
/// considered in determining any type-directed conversion.
///
/// Used for:
///   - Array or List expressions (both computed and fixed-size), to propagate from the overall type into the array/list type
///     e.g. to infer element types, which may be relevant to processing each individual expression and the 'yield'
///     returns.
///
///   - 'new ABC<_>(args)' expressions, to propagate from the overall type into the 'ABC<_>' type, e.g. to infer type parameters,
///     which may be relevant to checking the arguments.
///
///   - object expressions '{ new ABC<_>(args) with ... }', to propagate from the overall type into the
///     object type, e.g. to infer type parameters, which may be relevant to checking the arguments and
///     methods of the object expression.
///
///   - string literal expressions (though the propagation is not essential in this case)
///
and TcPropagatingExprLeafThenConvert (cenv: cenv) overallTy actualTy (env: TcEnv) (* canAdhoc *) m (f: unit -> Expr * UnscopedTyparEnv) =
    let g = cenv.g

    match overallTy with
    | MustConvertTo _ when g.langVersion.SupportsFeature LanguageFeature.AdditionalTypeDirectedConversions ->
        assert (g.langVersion.SupportsFeature LanguageFeature.AdditionalTypeDirectedConversions)

        // Compute the conversion _before_ processing the construct. We know enough to process this conversion eagerly.
        UnifyOverallType cenv env m overallTy actualTy

        // Process the construct
        let expr, tpenv = f ()

        // Build the conversion
        let expr2 = TcAdjustExprForTypeDirectedConversions cenv overallTy actualTy env (* canAdhoc *) m expr
        expr2, tpenv
    | _ ->
        UnifyTypes cenv env m overallTy.Commit actualTy
        f ()

/// Process a leaf construct, for cases where we propagate the overall type eagerly in
/// some cases. Then apply additional type-directed conversions.
///
/// However in some cases favour propagating characteristics of the overall type.
///
/// 'isPropagating' indicates if propagation occurs
/// 'processExpr' does the actual processing of the construct.
///
/// Used for
///  - tuple       (except if overallTy is a tuple type or a variable type that can become one)
///  - anon record (except if overallTy is an anon record type or a variable type that can become one)
///  - record      (except if overallTy is requiresCtor || haveCtor or a record type or a variable type that can become one))
and TcPossiblyPropagatingExprLeafThenConvert isPropagating (cenv: cenv) (overallTy: OverallTy) (env: TcEnv) m processExpr =

    let g = cenv.g

    match overallTy with
    | MustConvertTo(_, reqdTy) when g.langVersion.SupportsFeature LanguageFeature.AdditionalTypeDirectedConversions && not (isPropagating reqdTy) ->
        TcNonPropagatingExprLeafThenConvert cenv overallTy env m (fun () ->
            let exprTy = NewInferenceType g

            // Here 'processExpr' will eventually do the unification with exprTy.
            let expr, tpenv = processExpr exprTy
            expr, exprTy, tpenv)
    | _ ->
        // Here 'processExpr' will do the unification with the overall type.
        processExpr overallTy.Commit

/// Process a leaf construct where the processing of the construct is initially independent
/// of the overall type. Determine and apply additional type-directed conversions after the processing
/// is complete, as the inferred type of the expression may enable a type-directed conversion.
///
/// Used for:
///   - trait call
///   - LibraryOnlyUnionCaseFieldGet
///   - constants
and TcNonPropagatingExprLeafThenConvert (cenv: cenv) (overallTy: OverallTy) (env: TcEnv) m processExpr =

    // Process the construct
    let expr, exprTy, tpenv = processExpr ()

    // Now compute the conversion, based on the post-processing type
    UnifyOverallType cenv env m overallTy exprTy

    let expr2 = TcAdjustExprForTypeDirectedConversions cenv overallTy exprTy env m expr
    expr2, tpenv

and TcAdjustExprForTypeDirectedConversions (cenv: cenv) (overallTy: OverallTy) actualTy (env: TcEnv) (* canAdhoc *) m expr =
    let g = cenv.g

    match overallTy with
    | MustConvertTo (isMethodArg, reqdTy) when g.langVersion.SupportsFeature LanguageFeature.AdditionalTypeDirectedConversions || (g.langVersion.SupportsFeature LanguageFeature.NullableOptionalInterop && isMethodArg) ->
        let tcVal = LightweightTcValForUsingInBuildMethodCall g
        AdjustExprForTypeDirectedConversions tcVal g cenv.amap cenv.infoReader env.AccessRights reqdTy actualTy m expr
    | _ ->
        expr

and TcNonControlFlowExpr (env: TcEnv) f =
    if env.eIsControlFlow then
        let envinner = { env with eIsControlFlow = false }
        let res, tpenv = f envinner
        let m = res.Range

        // If the range is associated with calls like `async.For` for computation expression syntax control-flow
        // desugaring then don't emit a debug point - the debug points are placed separately in CheckComputationExpressions.fs
        match m.NotedSourceConstruct with
        | NotedSourceConstruct.Binding
        | NotedSourceConstruct.Finally
        | NotedSourceConstruct.Try
        | NotedSourceConstruct.For
        | NotedSourceConstruct.InOrTo
        | NotedSourceConstruct.Combine
        | NotedSourceConstruct.With
        | NotedSourceConstruct.While
        | NotedSourceConstruct.DelayOrQuoteOrRun ->
            res, tpenv
        | NotedSourceConstruct.None ->
            // Skip outer debug point for "expr1 && expr2" and "expr1 || expr2"
            let res2 =
                match res with
                | IfThenElseExpr _ -> res
                | _ -> mkDebugPoint res.Range res
            res2, tpenv
    else
        f env

and TcExprUndelayed (cenv: cenv) (overallTy: OverallTy) env tpenv (synExpr: SynExpr) =

    let g = cenv.g

    match synExpr with
    // ( * )
    | SynExpr.Paren (SynExpr.IndexRange (None, mOperator, None, _m1, _m2, _), _, _, _) ->
        let replacementExpr = SynExpr.Ident(ident(CompileOpName "*", mOperator))
        TcExpr cenv overallTy env tpenv replacementExpr

    | SynExpr.Paren (expr2, _, _, mWholeExprIncludingParentheses) ->
        // We invoke CallExprHasTypeSink for every construct which is atomic in the syntax, i.e. where a '.' immediately following the
        // construct is a dot-lookup for the result of the construct.
        CallExprHasTypeSink cenv.tcSink (mWholeExprIncludingParentheses, env.NameEnv, overallTy.Commit, env.AccessRights)
        let env = ShrinkContext env mWholeExprIncludingParentheses expr2.Range
        TcExpr cenv overallTy env tpenv expr2

    | SynExpr.DotIndexedGet _
    | SynExpr.DotIndexedSet _
    | SynExpr.Typar _
    | SynExpr.TypeApp _
    | SynExpr.Ident _
    | SynExpr.LongIdent _
    | SynExpr.App _
    | SynExpr.Dynamic _
    | SynExpr.DotGet _
    | SynExpr.DiscardAfterMissingQualificationAfterDot _ ->
        error(Error(FSComp.SR.tcExprUndelayed(), synExpr.Range))

    | SynExpr.Const (SynConst.String (s, _, m), _) ->
        TcNonControlFlowExpr env <| fun env ->
        CallExprHasTypeSink cenv.tcSink (m, env.NameEnv, overallTy.Commit, env.AccessRights)
        TcConstStringExpr cenv overallTy env m tpenv s LiteralArgumentType.Inline

    | SynExpr.InterpolatedString (parts, _, m) ->
        TcNonControlFlowExpr env <| fun env ->
        checkLanguageFeatureError g.langVersion LanguageFeature.StringInterpolation m
        CallExprHasTypeSink cenv.tcSink (m, env.NameEnv, overallTy.Commit, env.AccessRights)
        TcInterpolatedStringExpr cenv overallTy env m tpenv parts

    | SynExpr.Const (synConst, m) ->
        TcNonControlFlowExpr env <| fun env ->
        CallExprHasTypeSink cenv.tcSink (m, env.NameEnv, overallTy.Commit, env.AccessRights)
        TcConstExpr cenv overallTy env m tpenv synConst

    | SynExpr.DotLambda (synExpr, m, trivia) ->
        match env.NameEnv.eUnqualifiedItems |> Map.tryFind "_arg1" with
        // Compiler-generated _arg items can have more forms, the real underscore will be 1-character wide
        | Some (Item.Value(valRef)) when valRef.Range.StartColumn+1 = valRef.Range.EndColumn ->
            warning(Error(FSComp.SR.tcAmbiguousDiscardDotLambda(), trivia.UnderscoreRange))
        | _ -> ()

        let unaryArg = mkSynId trivia.UnderscoreRange (cenv.synArgNameGenerator.New())
        let svar = mkSynCompGenSimplePatVar unaryArg
        let pushedExpr = pushUnaryArg synExpr unaryArg
        let lambda = SynExpr.Lambda(false, false, SynSimplePats.SimplePats([ svar ],[], svar.Range), pushedExpr, None, m, SynExprLambdaTrivia.Zero)
        TcIteratedLambdas cenv true env overallTy Set.empty tpenv lambda
    | SynExpr.Lambda _ ->
        TcIteratedLambdas cenv true env overallTy Set.empty tpenv synExpr

    | SynExpr.Match (spMatch, synInputExpr, synClauses, _m, _trivia) ->
        TcExprMatch cenv overallTy env tpenv synInputExpr spMatch synClauses

    | SynExpr.MatchLambda (isExnMatch, mFunction, clauses, spMatch, m) ->
        TcExprMatchLambda cenv overallTy env tpenv (isExnMatch, mFunction, clauses, spMatch, m)

    | SynExpr.Assert (x, m) ->
        TcNonControlFlowExpr env <| fun env ->
        TcAssertExpr cenv overallTy env m tpenv x

    | SynExpr.DebugPoint (dp, isControlFlow, innerExpr) ->
        let env = { env with eIsControlFlow = isControlFlow }
        let innerExprR, tpenv = TcExpr cenv overallTy env tpenv innerExpr
        Expr.DebugPoint (dp, innerExprR), tpenv

    | SynExpr.Fixed (_, m) ->
        error(Error(FSComp.SR.tcFixedNotAllowed(), m))

    // e: ty
    | SynExpr.Typed (synBodyExpr, synType, m) ->
        TcExprTypeAnnotated cenv overallTy env tpenv (synBodyExpr, synType, m)

    // e :? ty
    | SynExpr.TypeTest (synInnerExpr, tgtTy, m) ->
        TcNonControlFlowExpr env <| fun env ->
        TcExprTypeTest cenv overallTy env tpenv (synInnerExpr, tgtTy, m)

    // SynExpr.AddressOf is noted in the syntax ast in order to recognize it as concrete type information
    // during type checking, in particular prior to resolving overloads. This helps distinguish
    // its use at method calls from the use of the conflicting 'ref' mechanism for passing byref parameters
    | SynExpr.AddressOf (byref, synInnerExpr, mOperator, m) ->
        TcNonControlFlowExpr env <| fun env ->
        TcExpr cenv overallTy env tpenv (mkSynPrefixPrim mOperator m (if byref then "~&" else "~&&") synInnerExpr)

    | SynExpr.Upcast (synInnerExpr, _, m) | SynExpr.InferredUpcast (synInnerExpr, m) ->
        TcNonControlFlowExpr env <| fun env ->
        TcExprUpcast cenv overallTy env tpenv (synExpr, synInnerExpr, m)

    | SynExpr.Downcast (synInnerExpr, _, m) | SynExpr.InferredDowncast (synInnerExpr, m) ->
        TcNonControlFlowExpr env <| fun env ->
        TcExprDowncast cenv overallTy env tpenv (synExpr, synInnerExpr, m)

    | SynExpr.Null m ->
        TcNonControlFlowExpr env <| fun env ->
        AddCxTypeUseSupportsNull env.DisplayEnv cenv.css m NoTrace overallTy.Commit
        let tyWithNull = addNullnessToTy KnownWithNull overallTy.Commit
        mkNull m tyWithNull, tpenv

    | SynExpr.Lazy (synInnerExpr, m) ->
        TcNonControlFlowExpr env <| fun env ->
        TcExprLazy cenv overallTy env tpenv (synInnerExpr, m)

    | SynExpr.Tuple (isExplicitStruct, args, _, m) ->
        TcNonControlFlowExpr env <| fun env ->
        TcExprTuple cenv overallTy env tpenv (isExplicitStruct, args, m)

    | SynExpr.AnonRecd (isStruct, withExprOpt, unsortedFieldExprs, mWholeExpr, trivia) ->
        match withExprOpt with 
        | None | IsSimpleOrBoundExpr ->
            TcNonControlFlowExpr env <| fun env ->
            TcPossiblyPropagatingExprLeafThenConvert (fun ty -> isAnonRecdTy g ty || isTyparTy g ty) cenv overallTy env mWholeExpr (fun overallTy ->
                TcAnonRecdExpr cenv overallTy env tpenv (isStruct, withExprOpt, unsortedFieldExprs, mWholeExpr)
            )
        | Some withExpr ->
            BindOriginalRecdExpr withExpr (fun withExpr -> SynExpr.AnonRecd (isStruct, withExpr, unsortedFieldExprs, mWholeExpr, trivia))
            |> TcExpr cenv overallTy env tpenv

    | SynExpr.ArrayOrList (isArray, args, m) ->
        TcNonControlFlowExpr env <| fun env ->
        TcExprArrayOrList cenv overallTy env tpenv (isArray, args, m)

    | SynExpr.New (superInit, synObjTy, arg, mNewExpr) ->
        let g = cenv.g
        let objTy, tpenv = TcType cenv NewTyparsOK CheckCxs ItemOccurrence.Use WarnOnIWSAM.Yes env tpenv synObjTy

        // Stamp constructor result as KnownFromConstructor so the constraint solver
        // knows this is provably non-null (even for AllowNullLiteral types).
        let objTy = if g.checkNullness then replaceNullnessOfTy Nullness.KnownFromConstructor objTy else objTy

        TcNonControlFlowExpr env <| fun env ->
        TcPropagatingExprLeafThenConvert cenv overallTy objTy env (* true *) mNewExpr (fun () ->
          TcNewExpr cenv env tpenv objTy (Some synObjTy.Range) superInit arg mNewExpr
        )

    | SynExpr.ObjExpr (synObjTy, argopt, _mWith, binds, members, extraImpls, mNewExpr, m) ->
        let members = desugarGetSetMembers members
        let extraImpls =
            extraImpls
            |> List.map (fun (SynInterfaceImpl(interfaceTy, withKeyword, bindings, members, m)) ->
                SynInterfaceImpl(interfaceTy, withKeyword, bindings, desugarGetSetMembers members, m)
            )
        TcNonControlFlowExpr env <| fun env ->
        let binds = unionBindingAndMembers binds members
        TcExprObjectExpr cenv overallTy env tpenv (synObjTy, argopt, binds, extraImpls, mNewExpr, m)

    | SynExpr.Record (inherits, withExprOpt, synRecdFields, mWholeExpr) ->        
        match withExprOpt with
        | None | IsSimpleOrBoundExpr ->
            TcNonControlFlowExpr env <| fun env ->
            TcExprRecord cenv overallTy env tpenv (inherits, withExprOpt, synRecdFields, mWholeExpr)
        | Some withExpr ->
            BindOriginalRecdExpr withExpr (fun withExpr -> SynExpr.Record (inherits, withExpr, synRecdFields, mWholeExpr))
            |> TcExpr cenv overallTy env tpenv

    | SynExpr.While (spWhile, synGuardExpr, synBodyExpr, m) ->
        TcExprWhileLoop cenv overallTy env tpenv (spWhile, synGuardExpr, synBodyExpr, m)

    | SynExpr.For (spFor, spTo, id, _, start, dir, finish, body, m) ->
        TcExprIntegerForLoop cenv overallTy env tpenv (spFor, spTo, id, start, dir, finish, body, m)

    | SynExpr.ForEach (spFor, spIn, SeqExprOnly seqExprOnly, isFromSource, pat, synEnumExpr, synBodyExpr, m) ->
        TcForEachExpr cenv overallTy env tpenv (seqExprOnly, isFromSource, pat, synEnumExpr, synBodyExpr, m, spFor, spIn, m)

    | SynExpr.ComputationExpr (hasSeqBuilder, comp, m) ->
        let isIndexRange = match comp with | SynExpr.IndexRange _ -> true | _ -> false
        let deprecatedPlacesWhereSeqCanBeOmitted =
            cenv.g.langVersion.SupportsFeature LanguageFeature.DeprecatePlacesWhereSeqCanBeOmitted
        if
            deprecatedPlacesWhereSeqCanBeOmitted
            && isIndexRange
            && not hasSeqBuilder
            && not cenv.g.compilingFSharpCore
        then
            warning (Error(FSComp.SR.chkDeprecatePlacesWhereSeqCanBeOmitted (), m))

        let env = ExitFamilyRegion env
        cenv.TcSequenceExpressionEntry cenv env overallTy tpenv (hasSeqBuilder, comp) m

    | SynExpr.ArrayOrListComputed (isArray, comp, m) ->
        TcNonControlFlowExpr env <| fun env ->
        let env = ExitFamilyRegion env
        CallExprHasTypeSink cenv.tcSink (m, env.NameEnv, overallTy.Commit, env.eAccessRights)
        cenv.TcArrayOrListComputedExpression cenv env overallTy tpenv (isArray, comp)  m

    | SynExpr.LetOrUse letOrUse ->
        match letOrUse with
        | { Bindings = SynBinding(trivia = { LeadingKeyword = leadingKeyword }) :: _ } 
            when letOrUse.IsBang ->
            errorR(Error(FSComp.SR.tcConstructRequiresComputationExpression(), leadingKeyword.Range))
        | _ -> ()

        TcLinearExprs (TcExprThatCanBeCtorBody cenv) cenv env overallTy tpenv false synExpr id

    | SynExpr.TryWith (synBodyExpr, synWithClauses, mTryToLast, spTry, spWith, trivia) ->
        TcExprTryWith cenv overallTy env tpenv (synBodyExpr, synWithClauses, trivia.WithToEndRange, mTryToLast, spTry, spWith)

    | SynExpr.TryFinally (synBodyExpr, synFinallyExpr, mTryToLast, spTry, spFinally, _trivia) ->
        TcExprTryFinally cenv overallTy env tpenv (synBodyExpr, synFinallyExpr, mTryToLast, spTry, spFinally)

    | SynExpr.JoinIn (expr1, mInToken, expr2, mAll) ->
        TcExprJoinIn cenv overallTy env tpenv (expr1, mInToken, expr2, mAll)

    | SynExpr.ArbitraryAfterError (_debugStr, m) ->
        //SolveTypeAsError cenv env.DisplayEnv m overallTy
        mkDefault(m, overallTy.Commit), tpenv

    | SynExpr.FromParseError (expr1, m) ->
        //SolveTypeAsError cenv env.DisplayEnv m overallTy
        let _, tpenv = TcExpr cenv overallTy env tpenv expr1
        mkDefault(m, overallTy.Commit), tpenv

    | SynExpr.Sequential (sp, dir, synExpr1, synExpr2, m, _) ->
        TcExprSequential cenv overallTy env tpenv (synExpr, sp, dir, synExpr1, synExpr2, m)

    // Used to implement the type-directed 'implicit yield' rule for computation expressions
    | SynExpr.SequentialOrImplicitYield (sp, synExpr1, synExpr2, otherExpr, m) ->
        TcExprSequentialOrImplicitYield cenv overallTy env tpenv (sp, synExpr1, synExpr2, otherExpr, m)

    | SynExpr.Do (synInnerExpr, m) ->
        UnifyTypes cenv env m overallTy.Commit g.unit_ty
        TcStmtThatCantBeCtorBody cenv env tpenv synInnerExpr

    | SynExpr.IfThenElse _ ->
        TcLinearExprs (TcExprThatCanBeCtorBody cenv) cenv env overallTy tpenv false synExpr id

    // This is for internal use in the libraries only
    | SynExpr.LibraryOnlyStaticOptimization (constraints, expr2, expr3, m) ->
        TcNonControlFlowExpr env <| fun env ->
        TcExprStaticOptimization cenv overallTy env tpenv (constraints, expr2, expr3, m)

    // synExpr1.longId <- expr2
    | SynExpr.DotSet (synExpr1, synLongId, synExpr2, mStmt) ->
        TcNonControlFlowExpr env <| fun env ->
        TcExprDotSet cenv overallTy env tpenv (synExpr1, synLongId, synExpr2, mStmt)

    // synExpr1 <- synExpr2
    | SynExpr.Set (synExpr1, synExpr2, mStmt) ->
        TcNonControlFlowExpr env <| fun env ->
        TcExprThen cenv overallTy env tpenv false synExpr1 [MakeDelayedSet(synExpr2, mStmt)]

    // synExpr1.longId(synExpr2) <- expr3, very rarely used named property setters
    | SynExpr.DotNamedIndexedPropertySet (synExpr1, synLongId, synExpr2, expr3, mStmt) ->
        TcNonControlFlowExpr env <| fun env ->
        // Wrap in extra parens: like MakeDelayedSet,
        // but we don't actually want to delay it here.
        let setInfo = SynExpr.Paren (expr3, range0, None, expr3.Range)
        TcExprDotNamedIndexedPropertySet cenv overallTy env tpenv (synExpr1, synLongId, synExpr2, setInfo, mStmt)

    | SynExpr.LongIdentSet (synLongId, synExpr2, m) ->
        TcNonControlFlowExpr env <| fun env ->
        TcExprLongIdentSet cenv overallTy env tpenv (synLongId, synExpr2, m)

    // Type.Items(synExpr1) <- synExpr2
    | SynExpr.NamedIndexedPropertySet (synLongId, synExpr1, synExpr2, mStmt) ->
        TcNonControlFlowExpr env <| fun env ->
        // Wrap in extra parens: like MakeDelayedSet,
        // but we don't actually want to delay it here.
        let setInfo = SynExpr.Paren (synExpr2, range0, None, synExpr2.Range)
        TcExprNamedIndexPropertySet cenv overallTy env tpenv (synLongId, synExpr1, setInfo, mStmt)

    | SynExpr.TraitCall (TypesForTypar tps, synMemberSig, arg, m) ->
        TcNonControlFlowExpr env <| fun env ->
        TcExprTraitCall cenv overallTy env tpenv (tps, synMemberSig, arg, m)

    | SynExpr.LibraryOnlyUnionCaseFieldGet (synExpr1, longId, fieldNum, m) ->
        TcNonControlFlowExpr env <| fun env ->
        TcExprUnionCaseFieldGet cenv overallTy env tpenv (synExpr1, longId, fieldNum, m)

    | SynExpr.LibraryOnlyUnionCaseFieldSet (synExpr1, longId, fieldNum, synExpr2, m) ->
        TcNonControlFlowExpr env <| fun env ->
        TcExprUnionCaseFieldSet cenv overallTy env tpenv (synExpr1, longId, fieldNum, synExpr2, m)

    | SynExpr.LibraryOnlyILAssembly (s, tyargs, args, rtys, m) ->
        TcNonControlFlowExpr env <| fun env ->
        TcExprILAssembly cenv overallTy env tpenv (s, tyargs, args, rtys, m)

    | SynExpr.Quote (oper, raw, ast, isFromQueryExpression, m) ->
        TcNonControlFlowExpr env <| fun env ->
        CallExprHasTypeSink cenv.tcSink (m, env.NameEnv, overallTy.Commit, env.AccessRights)
        TcQuotationExpr cenv overallTy env tpenv (oper, raw, ast, isFromQueryExpression, m)

    | SynExpr.YieldOrReturn ((isTrueYield, _), _, _m, { YieldOrReturnKeyword = m })
    | SynExpr.YieldOrReturnFrom ((isTrueYield, _), _, _m, { YieldOrReturnFromKeyword = m }) when isTrueYield ->
        error(Error(FSComp.SR.tcConstructRequiresListArrayOrSequence(), m))

    | SynExpr.YieldOrReturn ((_, isTrueReturn), _, _m, { YieldOrReturnKeyword = m })
    | SynExpr.YieldOrReturnFrom ((_, isTrueReturn), _, _m, { YieldOrReturnFromKeyword = m }) when isTrueReturn ->
        error(Error(FSComp.SR.tcConstructRequiresComputationExpressions(), m))

    | SynExpr.YieldOrReturn (trivia = { YieldOrReturnKeyword = m })
    | SynExpr.YieldOrReturnFrom (trivia = { YieldOrReturnFromKeyword = m })
    | SynExpr.ImplicitZero m ->
        error(Error(FSComp.SR.tcConstructRequiresSequenceOrComputations(), m))

    | SynExpr.DoBang (trivia = { DoBangKeyword = m })
    | SynExpr.MatchBang (trivia = { MatchBangKeyword = m })
    | SynExpr.WhileBang (range = m) ->
        error(Error(FSComp.SR.tcConstructRequiresComputationExpression(), m))
    | SynExpr.IndexFromEnd (rightExpr, m) ->
        errorR(Error(FSComp.SR.tcTraitInvocationShouldUseTick(), m))
        let adjustedExpr = ParseHelpers.adjustHatPrefixToTyparLookup m rightExpr
        TcExprUndelayed cenv overallTy env tpenv adjustedExpr

    | SynExpr.IndexRange (range=m) ->
        error(Error(FSComp.SR.tcInvalidIndexerExpression(), m))

and TcExprMatch (cenv: cenv) overallTy env tpenv synInputExpr spMatch synClauses =
    let inputExpr, inputTy, tpenv =
        let env = { env with eIsControlFlow = false }
        TcExprOfUnknownType cenv env tpenv synInputExpr
    let mInputExpr = synInputExpr.Range
    let env = { env with eIsControlFlow = true }
    let matchVal, matchExpr, tpenv = TcAndPatternCompileMatchClauses mInputExpr mInputExpr ThrowIncompleteMatchException cenv (Some inputExpr) inputTy overallTy env tpenv synClauses
    let overallExpr = mkLet spMatch mInputExpr matchVal inputExpr matchExpr
    overallExpr, tpenv

// (function[spMatch] pat1 -> expr1 ... | patN -> exprN)
//
//  -->
//      (fun anonArg -> let[spMatch] anonVal = anonArg in pat1 -> expr1 ... | patN -> exprN)
//
// Note the presence of the "let" is visible in quotations regardless of the presence of sequence points, so
//     <@ function x -> (x: int) @>
// is
//     Lambda (_arg2, Let (x, _arg2, x))
and TcExprMatchLambda (cenv: cenv) overallTy env tpenv (isExnMatch, mFunction, clauses, spMatch, m) =
    let domainTy, resultTy = UnifyFunctionType None cenv env.DisplayEnv m overallTy.Commit
    let idv1, idve1 = mkCompGenLocal mFunction (cenv.synArgNameGenerator.New()) domainTy
    CallExprHasTypeSink cenv.tcSink (mFunction.StartRange, env.NameEnv, domainTy, env.AccessRights)
    CallExprHasTypeSink cenv.tcSink (m, env.NameEnv, overallTy.Commit, env.AccessRights)
    let envinner = ExitFamilyRegion env
    let envinner = { envinner with eIsControlFlow = true }
    let idv2, matchExpr, tpenv = TcAndPatternCompileMatchClauses m mFunction (if isExnMatch then Throw else ThrowIncompleteMatchException) cenv None domainTy (MustConvertTo (false, resultTy)) envinner tpenv clauses
    let overallExpr = mkMultiLambda m [idv1] ((mkLet spMatch m idv2 idve1 matchExpr), resultTy)
    overallExpr, tpenv

and TcExprTypeAnnotated (cenv: cenv) overallTy env tpenv (synBodyExpr, synType, m) =
    let tgtTy, tpenv = TcTypeAndRecover cenv NewTyparsOK CheckCxs ItemOccurrence.UseInType WarnOnIWSAM.Yes env tpenv synType
    UnifyOverallType cenv env m overallTy tgtTy
    let bodyExpr, tpenv = TcExpr cenv (MustConvertTo (false, tgtTy)) env tpenv synBodyExpr
    let bodyExpr2 = TcAdjustExprForTypeDirectedConversions cenv overallTy tgtTy env m bodyExpr
    bodyExpr2, tpenv

and TcExprTypeTest (cenv: cenv) overallTy env tpenv (synInnerExpr, tgtTy, m) =
    let g = cenv.g
    let innerExpr, srcTy, tpenv = TcExprOfUnknownType cenv env tpenv synInnerExpr
    UnifyTypes cenv env m overallTy.Commit g.bool_ty
    let tgtTy, tpenv = TcType cenv NewTyparsOK CheckCxs ItemOccurrence.UseInType WarnOnIWSAM.Yes env tpenv tgtTy
    TcRuntimeTypeTest false true cenv env.DisplayEnv m tgtTy srcTy
    let expr = mkCallTypeTest g m tgtTy innerExpr
    expr, tpenv

and TcExprUpcast (cenv: cenv) overallTy env tpenv (synExpr, synInnerExpr, m) =
    let innerExpr, srcTy, tpenv = TcExprOfUnknownType cenv env tpenv synInnerExpr
    let tgtTy, tpenv =
        match synExpr with
        | SynExpr.Upcast (_, tgtTy, m) ->
            let tgtTy, tpenv = TcType cenv NewTyparsOK CheckCxs ItemOccurrence.UseInType WarnOnIWSAM.Yes env tpenv tgtTy
            UnifyTypes cenv env m tgtTy overallTy.Commit
            tgtTy, tpenv
        | SynExpr.InferredUpcast _ ->
            overallTy.Commit, tpenv
        | _ -> failwith "upcast"
    TcStaticUpcast cenv env.DisplayEnv synInnerExpr.Range m tgtTy srcTy
    let expr = mkCoerceExpr(innerExpr, tgtTy, m, srcTy)
    expr, tpenv

and TcExprDowncast (cenv: cenv) overallTy env tpenv (synExpr, synInnerExpr, m) =
    let g = cenv.g

    let innerExpr, srcTy, tpenv = TcExprOfUnknownType cenv env tpenv synInnerExpr

    let tgtTy, tpenv, isOperator =
        match synExpr with
        | SynExpr.Downcast (_, tgtTy, m) ->
            let tgtTy, tpenv = TcType cenv NewTyparsOK CheckCxs ItemOccurrence.UseInType WarnOnIWSAM.Yes env tpenv tgtTy
            UnifyTypes cenv env m tgtTy overallTy.Commit
            tgtTy, tpenv, true
        | SynExpr.InferredDowncast _ -> overallTy.Commit, tpenv, false
        | _ -> failwith "downcast"

    TcRuntimeTypeTest true isOperator cenv env.DisplayEnv m tgtTy srcTy

    // TcRuntimeTypeTest ensures tgtTy is a nominal type. Hence we can insert a check here
    // based on the nullness semantics of the nominal type.
    let expr = 
        match (tgtTy,g) with
        | NullTrueValue | NullableRefType | NullableTypar when g.checkNullness -> mkCallUnboxFast g m tgtTy innerExpr   
        | _ ->  mkCallUnbox g m tgtTy innerExpr
    expr, tpenv

and TcExprLazy (cenv: cenv) overallTy env tpenv (synInnerExpr, m) =
    let g = cenv.g
    let innerTy = NewInferenceType g
    UnifyTypes cenv env m overallTy.Commit (mkLazyTy g innerTy)
    let envinner = ExitFamilyRegion env
    let envinner = { envinner with eIsControlFlow = true }
    let innerExpr, tpenv = TcExpr cenv (MustEqual innerTy) envinner tpenv synInnerExpr
    let expr = mkLazyDelayed g m innerTy (mkUnitDelayLambda g m innerExpr)
    expr, tpenv

and CheckTupleIsCorrectLength g (env: TcEnv) m tupleTy (args: 'a list) tcArgs =
    if isAnyTupleTy g tupleTy then
        let tupInfo, ptys = destAnyTupleTy g tupleTy

        if args.Length <> ptys.Length then
            let argTys = NewInferenceTypes g args
            suppressErrorReporting (fun () -> tcArgs argTys)
            let actualTy = TType_tuple (tupInfo, argTys)

            // We let error recovery handle this exception
            error (ErrorFromAddingTypeEquation(g, env.DisplayEnv, tupleTy, actualTy,
                   ConstraintSolverTupleDiffLengths(env.DisplayEnv, env.eContextInfo, ptys, argTys, m, m), m))

and TcExprTuple (cenv: cenv) overallTy env tpenv (isExplicitStruct, args, m) =
    let g = cenv.g
    TcPossiblyPropagatingExprLeafThenConvert (fun ty -> isAnyTupleTy g ty || isTyparTy g ty) cenv overallTy env m (fun overallTy ->

        CheckTupleIsCorrectLength g env m overallTy args (fun argTys -> TcExprsNoFlexes cenv env m tpenv argTys args |> ignore)

        let tupInfo, argTys = UnifyTupleTypeAndInferCharacteristics env.eContextInfo cenv env.DisplayEnv m overallTy isExplicitStruct args
        let argsR, tpenv = TcExprsNoFlexes cenv env m tpenv argTys args
        let expr = mkAnyTupled g m tupInfo argsR argTys
        CallExprHasTypeSink cenv.tcSink (m, env.NameEnv, mkAnyTupledTy g tupInfo argTys, env.eAccessRights)
        expr, tpenv
    )

and TcExprArrayOrList (cenv: cenv) overallTy env tpenv (isArray, args, m) =
    let g = cenv.g

    CallExprHasTypeSink cenv.tcSink (m, env.NameEnv, overallTy.Commit, env.AccessRights)
    let argTy = NewInferenceType g
    let actualTy = if isArray then mkArrayType g argTy else mkListTy g argTy

    // Propagating type directed conversion, e.g. for
    //     let x : seq<int64>  = [ 1; 2 ]
    // Consider also the case where there is no relation but an op_Implicit is enabled from List<_> to C
    //    let x : C = [ B(); B() ]

    TcPropagatingExprLeafThenConvert cenv overallTy actualTy env m (fun () ->

        // Always allow subsumption if a nominal type is known prior to type checking any arguments
        let flex = not (isTyparTy g argTy)
        let mutable first = true
        let getInitEnv m =
            if first then
                first <- false
                env
            else
                { env with eContextInfo = ContextInfo.CollectionElement (isArray, m) }

        let argsR, tpenv = List.mapFold (fun tpenv (x: SynExpr) -> TcExprFlex cenv flex false argTy (getInitEnv x.Range) tpenv x) tpenv args

        let expr =
            if isArray then Expr.Op (TOp.Array, [argTy], argsR, m)
            else List.foldBack (mkCons g argTy) argsR (mkNil g m argTy)
        expr, tpenv
    )

// Note could be combined with TcObjectExpr
and TcExprObjectExpr (cenv: cenv) overallTy env tpenv (synObjTy, argopt, binds, extraImpls, mNewExpr, m) =
    let g = cenv.g

    CallExprHasTypeSink cenv.tcSink (m, env.NameEnv, overallTy.Commit, env.eAccessRights)

    // Note, allowing canAdhoc = true would disable subtype-based propagation from overallTy into checking of structure
    //
    // For example
    //    let x : A seq = { new Collection<_> with ... the element type should be known in here! }
    //
    // So op_Implicit is effectively disabled for direct uses of object expressions
    //let canAdhoc = false

    let mObjTy = synObjTy.Range

    let objTy, tpenv = TcType cenv NewTyparsOK CheckCxs ItemOccurrence.UseInType WarnOnIWSAM.Yes env tpenv synObjTy

    // Work out the type of any interfaces to implement
    let extraImpls, tpenv =
        (tpenv, extraImpls) ||> List.mapFold (fun tpenv (SynInterfaceImpl(synIntfTy, _mWith, bindings, members, m)) ->
            let overrides = unionBindingAndMembers bindings members
            let intfTy, tpenv = TcType cenv NewTyparsOK CheckCxs ItemOccurrence.UseInType WarnOnIWSAM.Yes env tpenv synIntfTy
            if not (isInterfaceTy g intfTy) then
                error(Error(FSComp.SR.tcExpectedInterfaceType(), m))
            if isErasedType g intfTy then
                errorR(Error(FSComp.SR.tcCannotInheritFromErasedType(), m))
            (m, intfTy, overrides), tpenv)

    let realObjTy = if isObjTyAnyNullness g objTy && not (isNil extraImpls) then (p23 (List.head extraImpls)) else objTy

    TcPropagatingExprLeafThenConvert cenv overallTy realObjTy env (* canAdhoc *) m (fun () ->
        TcObjectExpr cenv env tpenv (objTy, realObjTy, argopt, binds, extraImpls, mObjTy, mNewExpr, m)
    )

and TcExprRecord (cenv: cenv) overallTy env tpenv (inherits, withExprOpt, synRecdFields, mWholeExpr) =
    let g = cenv.g
    CallExprHasTypeSink cenv.tcSink (mWholeExpr, env.NameEnv, overallTy.Commit, env.AccessRights)
    let requiresCtor = (GetCtorShapeCounter env = 1) // Get special expression forms for constructors
    let haveCtor = Option.isSome inherits
    TcPossiblyPropagatingExprLeafThenConvert (fun ty -> requiresCtor || haveCtor || isRecdTy g ty || isTyparTy g ty) cenv overallTy env mWholeExpr (fun overallTy ->
        TcRecdExpr cenv overallTy env tpenv (inherits, withExprOpt, synRecdFields, mWholeExpr)
    )

and TcExprWhileLoop (cenv: cenv) overallTy env tpenv (spWhile, synGuardExpr, synBodyExpr, m) =
    let g = cenv.g
    UnifyTypes cenv env m overallTy.Commit g.unit_ty

    let guardExpr, tpenv =
        let env = { env with eIsControlFlow = false }
        TcExpr cenv (MustEqual g.bool_ty) env tpenv synGuardExpr

    let bodyExpr, tpenv =
        let env = { env with eIsControlFlow = true }
        TcStmt cenv env tpenv synBodyExpr

    mkWhile g (spWhile, NoSpecialWhileLoopMarker, guardExpr, bodyExpr, m), tpenv

and TcExprIntegerForLoop (cenv: cenv) overallTy env tpenv (spFor, spTo, id, start, dir, finish, body, m) =
    let g = cenv.g
    UnifyTypes cenv env m overallTy.Commit g.unit_ty

    let startExpr, tpenv =
        let env = { env with eIsControlFlow = false }
        TcExpr cenv (MustEqual g.int_ty) env tpenv start

    let finishExpr, tpenv =
        let env = { env with eIsControlFlow = false }
        TcExpr cenv (MustEqual g.int_ty) env tpenv finish

    let idv, _ = mkLocal id.idRange id.idText g.int_ty
    let envinner = AddLocalVal g cenv.tcSink m idv env
    let envinner = { envinner with eIsControlFlow = true }

    // notify name resolution sink about loop variable
    let item = Item.Value(mkLocalValRef idv)
    CallNameResolutionSink cenv.tcSink (idv.Range, env.NameEnv, item, emptyTyparInst, ItemOccurrence.Binding, env.AccessRights)

    let bodyExpr, tpenv = TcStmt cenv envinner tpenv body
    mkFastForLoop g (spFor, spTo, m, idv, startExpr, dir, finishExpr, bodyExpr), tpenv

and TcExprTryWith (cenv: cenv) overallTy env tpenv (synBodyExpr, synWithClauses, mWithToLast, mTryToLast, spTry, spWith) =
    let g = cenv.g

    let env = { env with eIsControlFlow = true }
    let bodyExpr, tpenv = TcExpr cenv overallTy env tpenv synBodyExpr

    // Compile the pattern twice, once as a List.filter with all succeeding targets returning "1", and once as a proper catch block.
    let filterClauses =
        synWithClauses |> List.map (fun clause ->
            let (SynMatchClause(pat, synWhenExprOpt, _, m, _, trivia)) = clause
            let oneExpr =  SynExpr.Const (SynConst.Int32 1, m)
            SynMatchClause(pat, synWhenExprOpt, oneExpr, m, DebugPointAtTarget.No, trivia))

    let checkedFilterClauses, tpenv = TcMatchClauses cenv g.exn_ty (MustEqual g.int_ty) env tpenv filterClauses
    let checkedHandlerClauses, tpenv = TcMatchClauses cenv g.exn_ty overallTy env tpenv synWithClauses
    let v1, filterExpr = CompilePatternForMatchClauses cenv env mWithToLast mWithToLast true FailFilter None g.exn_ty g.int_ty checkedFilterClauses
    let v2, handlerExpr = CompilePatternForMatchClauses cenv env mWithToLast mWithToLast true Rethrow None g.exn_ty overallTy.Commit checkedHandlerClauses
    mkTryWith g (bodyExpr, v1, filterExpr, v2, handlerExpr, mTryToLast, overallTy.Commit, spTry, spWith), tpenv

and TcExprTryFinally (cenv: cenv) overallTy env tpenv (synBodyExpr, synFinallyExpr, mTryToLast, spTry, spFinally) =
    let g = cenv.g
    let env = { env with eIsControlFlow = true }
    let bodyExpr, tpenv = TcExpr cenv overallTy env tpenv synBodyExpr
    let finallyExpr, tpenv = TcStmt cenv env tpenv synFinallyExpr
    mkTryFinally g (bodyExpr, finallyExpr, mTryToLast, overallTy.Commit, spTry, spFinally), tpenv

and TcExprJoinIn (cenv: cenv) overallTy env tpenv (synExpr1, mInToken, synExpr2, mAll) =
    errorR(Error(FSComp.SR.parsUnfinishedExpression("in"), mInToken))
    let _, _, tpenv = suppressErrorReporting (fun () -> TcExprOfUnknownType cenv env tpenv synExpr1)
    let _, _, tpenv = suppressErrorReporting (fun () -> TcExprOfUnknownType cenv env tpenv synExpr2)
    mkDefault(mAll, overallTy.Commit), tpenv

and TcExprSequential (cenv: cenv) overallTy env tpenv (synExpr, _sp, dir, synExpr1, synExpr2, m) =
    if dir then
        TcLinearExprs (TcExprThatCanBeCtorBody cenv) cenv env overallTy tpenv false synExpr id
    else
        // Constructors using "new (...) = <ctor-expr> then <expr>"
        let env = { env with eIsControlFlow = true }
        let expr1, tpenv = TcExprThatCanBeCtorBody cenv overallTy env tpenv synExpr1
        if (GetCtorShapeCounter env) <> 1 then
            errorR(Error(FSComp.SR.tcExpressionFormRequiresObjectConstructor(), m))
        let expr2, tpenv = TcStmtThatCantBeCtorBody cenv env tpenv synExpr2
        Expr.Sequential (expr1, expr2, ThenDoSeq, m), tpenv

and TcExprSequentialOrImplicitYield (cenv: cenv) overallTy env tpenv (sp, synExpr1, synExpr2, otherExpr, m) =

    let isStmt, expr1Ty, expr1, tpenv =
        let env1 = { env with eIsControlFlow = (match sp with DebugPointAtSequential.SuppressNeither | DebugPointAtSequential.SuppressExpr -> true | _ -> false) }
        TryTcStmt cenv env1 tpenv synExpr1

    if isStmt then
        let env2 = { env with eIsControlFlow = (match sp with DebugPointAtSequential.SuppressNeither | DebugPointAtSequential.SuppressStmt -> true | _ -> false) }
        let env2 = ShrinkContext env2 m synExpr2.Range
        let expr2, tpenv = TcExprThatCanBeCtorBody cenv overallTy env2 tpenv synExpr2
        Expr.Sequential(expr1, expr2, NormalSeq, m), tpenv
    else
        // The first expression wasn't unit-typed, so proceed to the alternative interpretation
        // Note a copy of the first expression is embedded in 'otherExpr' and thus
        // this will type-check the first expression over again.
        let cachedExpr =
            match expr1 with
            | Expr.DebugPoint(_,e) -> e
            | _ -> expr1

        env.eCachedImplicitYieldExpressions.Add(synExpr1.Range, (synExpr1, expr1Ty, cachedExpr))
        try TcExpr cenv overallTy env tpenv otherExpr
        finally env.eCachedImplicitYieldExpressions.Remove synExpr1.Range

and TcExprStaticOptimization (cenv: cenv) overallTy env tpenv (constraints, synExpr2, expr3, m) =
    let constraintsR, tpenv = List.mapFold (TcStaticOptimizationConstraint cenv env) tpenv constraints
    // Do not force the types of the two expressions to be equal
    // This means uses of this construct have to be very carefully written
    let expr2, _, tpenv = TcExprOfUnknownType cenv env tpenv synExpr2
    let expr3, tpenv = TcExpr cenv overallTy env tpenv expr3
    Expr.StaticOptimization (constraintsR, expr2, expr3, m), tpenv

/// synExpr1.longId <- synExpr2
and TcExprDotSet (cenv: cenv) overallTy env tpenv (synExpr1, synLongId, synExpr2, mStmt) =
    let (SynLongIdent(longId, _, _)) = synLongId
    let mExprAndDotLookup = unionRanges synExpr1.Range (rangeOfLid longId)
    TcExprThen cenv overallTy env tpenv false synExpr1 [DelayedDotLookup(longId, mExprAndDotLookup); MakeDelayedSet(synExpr2, mStmt)]

/// synExpr1.longId(synExpr2) <- expr3, very rarely used named property setters
and TcExprDotNamedIndexedPropertySet (cenv: cenv) overallTy env tpenv (synExpr1, synLongId, synExpr2, expr3, mStmt) =
    let (SynLongIdent(longId, _, _)) = synLongId
    let mExprAndDotLookup = unionRanges synExpr1.Range (rangeOfLid longId)
    TcExprThen cenv overallTy env tpenv false synExpr1
        [ DelayedDotLookup(longId, mExprAndDotLookup);
          DelayedApp(ExprAtomicFlag.Atomic, false, None, synExpr2, mStmt)
          MakeDelayedSet(expr3, mStmt)]

and TcExprLongIdentSet (cenv: cenv) overallTy env tpenv (synLongId, synExpr2, m) =
    TcLongIdentThen cenv overallTy env tpenv synLongId [ MakeDelayedSet(synExpr2, m) ]

// Type.Items(synExpr1) <- synExpr2
and TcExprNamedIndexPropertySet (cenv: cenv) overallTy env tpenv (synLongId, synExpr1, synExpr2, mStmt) =
    TcLongIdentThen cenv overallTy env tpenv synLongId
        [ DelayedApp(ExprAtomicFlag.Atomic, false, None, synExpr1, mStmt)
          MakeDelayedSet(synExpr2, mStmt) ]

and TcExprTraitCall (cenv: cenv) overallTy env tpenv (synTypes, synMemberSig, arg, m) =
    let g = cenv.g
    TcNonPropagatingExprLeafThenConvert cenv overallTy env m (fun () ->
        let traitInfo, tpenv = TcPseudoMemberSpec cenv NewTyparsOK env synTypes tpenv synMemberSig m
        if BakedInTraitConstraintNames.Contains traitInfo.MemberLogicalName then
            warning(BakedInMemberConstraintName(traitInfo.MemberLogicalName, m))

        let argTys = traitInfo.CompiledObjectAndArgumentTypes
        let returnTy = traitInfo.GetReturnType g
        let args, namedCallerArgs = GetMethodArgs arg
        if not (isNil namedCallerArgs) then errorR(Error(FSComp.SR.tcNamedArgumentsCannotBeUsedInMemberTraits(), m))
        // Subsumption at trait calls if arguments have nominal type prior to unification of any arguments or return type
        let flexes = argTys |> List.map (isTyparTy g >> not)
        let argsR, tpenv = TcExprsWithFlexes cenv env m tpenv flexes argTys args
        AddCxMethodConstraint env.DisplayEnv cenv.css m NoTrace traitInfo
        Expr.Op (TOp.TraitCall traitInfo, [], argsR, m), returnTy, tpenv
    )

and TcExprUnionCaseFieldGet (cenv: cenv) overallTy env tpenv (synExpr1, longId, fieldNum, m) =
    let g = cenv.g
    TcNonPropagatingExprLeafThenConvert cenv overallTy env m (fun () ->
        let expr1, ty1, tpenv = TcExprOfUnknownType cenv env tpenv synExpr1
        let mkf, ty2 =
            TcUnionCaseOrExnField cenv env ty1 m longId fieldNum
                ((fun (a, b) n -> mkUnionCaseFieldGetUnproven g (expr1, a, b, n, m)),
                 (fun a n -> mkExnCaseFieldGet(expr1, a, n, m)))
        mkf fieldNum, ty2, tpenv
    )

and TcExprUnionCaseFieldSet (cenv: cenv) overallTy env tpenv (synExpr1, longId, fieldNum, synExpr2, m) =
    let g = cenv.g
    UnifyTypes cenv env m overallTy.Commit g.unit_ty
    let expr1, ty1, tpenv = TcExprOfUnknownType cenv env tpenv synExpr1
    let mkf, ty2 =
        TcUnionCaseOrExnField cenv env ty1 m longId fieldNum
            ((fun (a, b) n expr2R ->
                if not (isUnionCaseFieldMutable g a n) then errorR(Error(FSComp.SR.tcFieldIsNotMutable(), m))
                mkUnionCaseFieldSet(expr1, a, b, n, expr2R, m)),
             (fun a n expr2R ->
                if not (isExnFieldMutable a n) then errorR(Error(FSComp.SR.tcFieldIsNotMutable(), m))
                mkExnCaseFieldSet(expr1, a, n, expr2R, m)))
    let expr2, tpenv = TcExpr cenv (MustEqual ty2) env tpenv synExpr2
    mkf fieldNum expr2, tpenv

and TcExprILAssembly (cenv: cenv) overallTy env tpenv (ilInstrs, synTyArgs, synArgs, synRetTys, m) =
    let g = cenv.g
    let ilInstrs = (ilInstrs :?> ILInstr[])
    let argTys = NewInferenceTypes g synArgs
    let tyargs, tpenv = TcTypes cenv NewTyparsOK CheckCxs ItemOccurrence.UseInType WarnOnIWSAM.Yes env tpenv synTyArgs
    // No subsumption at uses of IL assembly code
    let args, tpenv = TcExprsNoFlexes cenv env m tpenv argTys synArgs
    let retTys, tpenv = TcTypes cenv NewTyparsOK CheckCxs ItemOccurrence.UseInType WarnOnIWSAM.Yes env tpenv synRetTys
    let returnTy =
        match retTys with
        | [] -> g.unit_ty
        | [ returnTy ] -> returnTy
        | _ -> error(InternalError("Only zero or one pushed items are permitted in IL assembly code", m))
    UnifyTypes cenv env m overallTy.Commit returnTy
    mkAsmExpr (Array.toList ilInstrs, tyargs, args, retTys, m), tpenv

/// Check lambdas as a group, to catch duplicate names in patterns
and TcIteratedLambdas (cenv: cenv) isFirst (env: TcEnv) overallTy takenNames tpenv e =
    let g = cenv.g
    match e with
    | SynExpr.Lambda (isMember, isSubsequent, synSimplePats, bodyExpr, parsedData, m, _trivia) when isMember || isFirst || isSubsequent ->
        let domainTy, resultTy = UnifyFunctionType None cenv env.DisplayEnv m overallTy.Commit
        let parsedPatterns =
            parsedData
            |> Option.map fst
            |> Option.defaultValue []
            
        let vs, TcPatLinearEnv (tpenv, names, takenNames) =
            cenv.TcSimplePats cenv isMember CheckCxs domainTy env (TcPatLinearEnv (tpenv, Map.empty, takenNames)) synSimplePats (parsedPatterns, isFirst)

        let envinner, _, vspecMap = MakeAndPublishSimpleValsForMergedScope cenv env m names
        let byrefs = vspecMap |> Map.map (fun _ v -> isByrefTy g v.Type, v)
        let envinner = if isMember then envinner else ExitFamilyRegion envinner
        let vspecs = vs |> List.map (fun nm -> NameMap.find nm vspecMap)

        // Match up the arginfos with the generated arguments and apply any information extracted from the attributes
        let envinner =
            match envinner.eLambdaArgInfos with
            | infos :: rest ->
                 if infos.Length = vspecs.Length then
                    (vspecs, infos) ||> List.iter2 (fun v argInfo ->
                        v.SetArgReprInfoForDisplay (Some argInfo)
                        let inlineIfLambda = ArgReprInfoHasWellKnownAttribute g WellKnownValAttributes.InlineIfLambdaAttribute argInfo
                        if inlineIfLambda then
                            v.SetInlineIfLambda())
                 { envinner with eLambdaArgInfos = rest }
            | [] -> envinner

        let bodyExpr, tpenv = TcIteratedLambdas cenv false envinner (MustConvertTo (false, resultTy)) takenNames tpenv bodyExpr
        CallExprHasTypeSink cenv.tcSink (m, env.NameEnv, overallTy.Commit, env.AccessRights)

        // See bug 5758: Non-monotonicity in inference: need to ensure that parameters are never inferred to have byref type, instead it is always declared
        byrefs |> Map.iter (fun _ (orig, v) ->
            if not orig && isByrefTy g v.Type then errorR(Error(FSComp.SR.tcParameterInferredByref v.DisplayName, v.Range)))

        mkMultiLambda m vspecs (bodyExpr, resultTy), tpenv

    | e ->
        let env = { env with eIsControlFlow = true }
        TcExpr cenv overallTy env tpenv e

and TcTyparExprThen (cenv: cenv) overallTy env tpenv synTypar m delayed =
    match delayed with
    //'T     .Ident
    //^T     .Ident   (args) ..
    | DelayedDotLookup (ident :: rest, m2) :: delayed2 ->
        let ad = env.eAccessRights
        let tp, tpenv = TcTypar cenv env NoNewTypars tpenv synTypar
        let mExprAndLongId = unionRanges synTypar.Range ident.idRange
        let ty = mkTyparTy tp
        let lookupKind = LookupKind.Expr LookupIsInstance.Ambivalent
        let item, _rest = ResolveLongIdentInType cenv.tcSink cenv.nameResolver env.NameEnv lookupKind ident.idRange ad ident IgnoreOverrides TypeNameResolutionInfo.Default ty
        let delayed3 =
            match rest with
            | [] -> delayed2
            | _ -> DelayedDotLookup (rest, m2) :: delayed2
        CallNameResolutionSink cenv.tcSink (ident.idRange, env.NameEnv, item, emptyTyparInst, ItemOccurrence.Use, env.AccessRights)
        TcItemThen cenv overallTy env tpenv ([], item, mExprAndLongId, [], AfterResolution.DoNothing) (Some ty) delayed3
        //TcLookupItemThen cenv overallTy env tpenv mObjExpr objExpr objExprTy delayed item mItem rest afterResolution
    | _ ->
        let (SynTypar(_, q, _)) = synTypar
        let msg =
            match q with
            | TyparStaticReq.None -> FSComp.SR.parsIncompleteTyparExpr1()
            | TyparStaticReq.HeadType -> FSComp.SR.parsIncompleteTyparExpr2()
        error (Error(msg, m))

and (|IndexArgOptionalFromEnd|) (cenv: cenv) indexArg =
    match indexArg with
    | SynExpr.IndexFromEnd (a, m) ->
        if not (cenv.g.langVersion.SupportsFeature LanguageFeature.FromEndSlicing) then
            errorR (Error(FSComp.SR.fromEndSlicingRequiresVFive(), m))
        (a, true, m)
    | _ -> (indexArg, false, indexArg.Range)

and DecodeIndexArg (cenv: cenv) indexArg =
    match indexArg with
    | SynExpr.IndexRange (info1, _opm, info2, m1, m2, _) ->
        let info1 =
            match info1 with
            | Some (IndexArgOptionalFromEnd cenv (expr1, isFromEnd1, _)) -> Some (expr1, isFromEnd1)
            | None -> None
        let info2 =
            match info2 with
            | Some (IndexArgOptionalFromEnd cenv (synExpr2, isFromEnd2, _)) -> Some (synExpr2, isFromEnd2)
            | None -> None
        IndexArgRange (info1, info2, m1, m2)
    | IndexArgOptionalFromEnd cenv (expr, isFromEnd, m) ->
        IndexArgItem(expr, isFromEnd, m)

and DecodeIndexArgs (cenv: cenv) indexArgs =
    indexArgs |> List.map (DecodeIndexArg cenv)

and (|IndexerArgs|) expr =
    match expr with
    | SynExpr.Tuple (false, argExprs, _, _) -> argExprs
    | _ -> [expr]

and TcIndexerThen (cenv: cenv) env overallTy mWholeExpr mDot tpenv (setInfo: _ option) synLeftExpr indexArgs delayed =
    let leftExpr, leftExprTy, tpenv = TcExprOfUnknownType cenv env tpenv synLeftExpr
    let expandedIndexArgs = ExpandIndexArgs cenv (Some synLeftExpr) indexArgs
    TcIndexingThen cenv env overallTy mWholeExpr mDot tpenv setInfo (Some synLeftExpr) leftExpr leftExprTy expandedIndexArgs indexArgs delayed

// Eliminate GetReverseIndex from index args
and ExpandIndexArgs (cenv: cenv) (synLeftExprOpt: SynExpr option) indexArgs =

    // xs.GetReverseIndex rank offset - 1
    let rewriteReverseExpr (rank: int) (offset: SynExpr) (range: range) =
        let rankExpr = SynExpr.Const(SynConst.Int32 rank, range)
        let sliceArgs = SynExpr.Paren(SynExpr.Tuple(false, [rankExpr; offset], [], range), range, Some range, range)
        match synLeftExprOpt with
        | None -> error(Error(FSComp.SR.tcInvalidUseOfReverseIndex(), range))
        | Some xsId ->
            mkSynApp1
                (mkSynDot range range xsId (SynIdent((mkSynId (range.MakeSynthetic()) "GetReverseIndex"), None)))
                sliceArgs
                range

    let mkSynSomeExpr (m: range) x =
        let m = m.MakeSynthetic()
        SynExpr.App (ExprAtomicFlag.NonAtomic, false, mkSynLidGet m CorePath "Some", x, m)

    let mkSynNoneExpr (m: range) =
        let m = m.MakeSynthetic()
        mkSynLidGet m CorePath "None"

    let expandedIndexArgs =
        indexArgs
        |> List.mapi ( fun pos indexerArg ->
            match DecodeIndexArg cenv indexerArg with
            | IndexArgItem(expr, fromEnd, range) ->
                [ if fromEnd then rewriteReverseExpr pos expr range else expr ]
            | IndexArgRange(info1, info2, range1, range2) ->
                [
                   match info1 with
                   | Some (a1, isFromEnd1) ->
                       yield mkSynSomeExpr range1 (if isFromEnd1 then rewriteReverseExpr pos a1 range1 else a1)
                   | None ->
                       yield mkSynNoneExpr range1
                   match info2 with
                   | Some (a2, isFromEnd2) ->
                       yield mkSynSomeExpr range2 (if isFromEnd2 then rewriteReverseExpr pos a2 range2 else a2)
                   | None ->
                       yield mkSynNoneExpr range1
                ]
        )
        |> List.collect id

    expandedIndexArgs

// Check expr.[idx]
// This is a little over complicated for my liking. Basically we want to interpret expr1.[idx] as expr1.Item(idx).
// However it's not so simple as all that. First "Item" can have a different name according to an attribute in
// .NET metadata. This means we manually typecheck 'expr and look to see if it has a nominal type. We then
// do the right thing in each case.
and TcIndexingThen cenv env overallTy mWholeExpr mDot tpenv setInfo synLeftExprOpt expr exprTy expandedIndexArgs indexArgs delayed =
    let g = cenv.g
    let ad = env.AccessRights

    // Find the first type in the effective hierarchy that either has a DefaultMember attribute OR
    // has a member called 'Item'
    let isIndex = indexArgs |> List.forall (fun indexArg -> match DecodeIndexArg cenv indexArg with IndexArgItem _ -> true | _ -> false)
    let propName =
        if isIndex then
            FoldPrimaryHierarchyOfType (fun ty acc ->
                match acc with
                | None ->
                    match tryTcrefOfAppTy g ty with
                    | ValueSome tcref ->
                        TryFindTyconRefStringAttributeFast g mWholeExpr WellKnownILAttributes.DefaultMemberAttribute g.attrib_DefaultMemberAttribute tcref
                    | _ ->
                        let item = Some "Item"
                        match AllPropInfosOfTypeInScope ResultCollectionSettings.AtMostOneResult cenv.infoReader env.NameEnv item ad IgnoreOverrides mWholeExpr ty with
                        | [] -> None
                        | _ -> item
                 | _ -> acc)
              g
              cenv.amap
              mWholeExpr
              AllowMultiIntfInstantiations.Yes
              exprTy
              None
        else Some "GetSlice"

    let isNominal = isAppTy g exprTy

    let isArray = isArrayTy g exprTy
    let isString = typeEquiv g g.string_ty exprTy

    let idxRange = indexArgs |> List.map (fun e -> e.Range) |> List.reduce unionRanges

    let MakeIndexParam setSliceArrayOption =
       match DecodeIndexArgs cenv indexArgs with
       | [] -> failwith "unexpected empty index list"
       | [IndexArgItem _] -> SynExpr.Paren (expandedIndexArgs.Head, range0, None, idxRange)
       | _ -> SynExpr.Paren (SynExpr.Tuple (false, expandedIndexArgs @ Option.toList setSliceArrayOption, [], idxRange), range0, None, idxRange)

    let attemptArrayString =
        let indexOpPath = ["Microsoft";"FSharp";"Core";"LanguagePrimitives";"IntrinsicFunctions"]
        let sliceOpPath = ["Microsoft";"FSharp";"Core";"Operators";"OperatorIntrinsics"]

        let info =
            if isArray then
                let fixedIndex3d4dEnabled = g.langVersion.SupportsFeature LanguageFeature.FixedIndexSlice3d4d
                let indexArgs = List.map (DecodeIndexArg cenv) indexArgs
                match indexArgs, setInfo with
                | [IndexArgItem _; IndexArgItem _], None                                        -> Some (indexOpPath, "GetArray2D", expandedIndexArgs)
                | [IndexArgItem _; IndexArgItem _; IndexArgItem _;], None                        -> Some (indexOpPath, "GetArray3D", expandedIndexArgs)
                | [IndexArgItem _; IndexArgItem _; IndexArgItem _; IndexArgItem _], None          -> Some (indexOpPath, "GetArray4D", expandedIndexArgs)
                | [IndexArgItem _], None                                                       -> Some (indexOpPath, "GetArray", expandedIndexArgs)
                | [IndexArgItem _; IndexArgItem _], Some (expr3, _)                                -> Some (indexOpPath, "SetArray2D", (expandedIndexArgs @ [expr3]))
                | [IndexArgItem _; IndexArgItem _; IndexArgItem _;], Some (expr3, _)                -> Some (indexOpPath, "SetArray3D", (expandedIndexArgs @ [expr3]))
                | [IndexArgItem _; IndexArgItem _; IndexArgItem _; IndexArgItem _], Some (expr3, _)  -> Some (indexOpPath, "SetArray4D", (expandedIndexArgs @ [expr3]))
                | [IndexArgItem _], Some (expr3, _)                                               -> Some (indexOpPath, "SetArray", (expandedIndexArgs @ [expr3]))
                | [IndexArgRange _], None                                                       -> Some (sliceOpPath, "GetArraySlice", expandedIndexArgs)
                | [IndexArgItem _;IndexArgRange _], None                                         -> Some (sliceOpPath, "GetArraySlice2DFixed1", expandedIndexArgs)
                | [IndexArgRange _;IndexArgItem _], None                                         -> Some (sliceOpPath, "GetArraySlice2DFixed2", expandedIndexArgs)
                | [IndexArgRange _;IndexArgRange _], None                                         -> Some (sliceOpPath, "GetArraySlice2D", expandedIndexArgs)
                | [IndexArgRange _;IndexArgRange _;IndexArgRange _], None                           -> Some (sliceOpPath, "GetArraySlice3D", expandedIndexArgs)
                | [IndexArgRange _;IndexArgRange _;IndexArgRange _;IndexArgRange _], None             -> Some (sliceOpPath, "GetArraySlice4D", expandedIndexArgs)
                | [IndexArgRange _], Some (expr3, _)                                               -> Some (sliceOpPath, "SetArraySlice", (expandedIndexArgs @ [expr3]))
                | [IndexArgRange _;IndexArgRange _], Some (expr3, _)                                 -> Some (sliceOpPath, "SetArraySlice2D", (expandedIndexArgs @ [expr3]))
                | [IndexArgItem _;IndexArgRange _], Some (expr3, _)                                 -> Some (sliceOpPath, "SetArraySlice2DFixed1", (expandedIndexArgs @ [expr3]))
                | [IndexArgRange _;IndexArgItem _], Some (expr3, _)                                 -> Some (sliceOpPath, "SetArraySlice2DFixed2", (expandedIndexArgs @ [expr3]))
                | [IndexArgRange _;IndexArgRange _;IndexArgRange _], Some (expr3, _)                   -> Some (sliceOpPath, "SetArraySlice3D", (expandedIndexArgs @ [expr3]))
                | [IndexArgRange _;IndexArgRange _;IndexArgRange _;IndexArgRange _], Some (expr3, _)     -> Some (sliceOpPath, "SetArraySlice4D", (expandedIndexArgs @ [expr3]))
                | _ when fixedIndex3d4dEnabled ->
                    match indexArgs, setInfo with
                    | [IndexArgItem _;IndexArgRange _;IndexArgRange _], None                      -> Some (sliceOpPath, "GetArraySlice3DFixedSingle1", expandedIndexArgs)
                    | [IndexArgRange _;IndexArgItem _;IndexArgRange _], None                      -> Some (sliceOpPath, "GetArraySlice3DFixedSingle2", expandedIndexArgs)
                    | [IndexArgRange _;IndexArgRange _;IndexArgItem _], None                      -> Some (sliceOpPath, "GetArraySlice3DFixedSingle3", expandedIndexArgs)
                    | [IndexArgItem _;IndexArgItem _;IndexArgRange _], None                      -> Some (sliceOpPath, "GetArraySlice3DFixedDouble1", expandedIndexArgs)
                    | [IndexArgItem _;IndexArgRange _;IndexArgItem _], None                      -> Some (sliceOpPath, "GetArraySlice3DFixedDouble2", expandedIndexArgs)
                    | [IndexArgRange _;IndexArgItem _;IndexArgItem _], None                      -> Some (sliceOpPath, "GetArraySlice3DFixedDouble3", expandedIndexArgs)
                    | [IndexArgItem _;IndexArgRange _;IndexArgRange _;IndexArgRange _], None        -> Some (sliceOpPath, "GetArraySlice4DFixedSingle1", expandedIndexArgs)
                    | [IndexArgRange _;IndexArgItem _;IndexArgRange _;IndexArgRange _], None        -> Some (sliceOpPath, "GetArraySlice4DFixedSingle2", expandedIndexArgs)
                    | [IndexArgRange _;IndexArgRange _;IndexArgItem _;IndexArgRange _], None        -> Some (sliceOpPath, "GetArraySlice4DFixedSingle3", expandedIndexArgs)
                    | [IndexArgRange _;IndexArgRange _;IndexArgRange _;IndexArgItem _], None        -> Some (sliceOpPath, "GetArraySlice4DFixedSingle4", expandedIndexArgs)
                    | [IndexArgItem _;IndexArgItem _;IndexArgRange _;IndexArgRange _], None        -> Some (sliceOpPath, "GetArraySlice4DFixedDouble1", expandedIndexArgs)
                    | [IndexArgItem _;IndexArgRange _;IndexArgItem _;IndexArgRange _], None        -> Some (sliceOpPath, "GetArraySlice4DFixedDouble2", expandedIndexArgs)
                    | [IndexArgItem _;IndexArgRange _;IndexArgRange _;IndexArgItem _], None        -> Some (sliceOpPath, "GetArraySlice4DFixedDouble3", expandedIndexArgs)
                    | [IndexArgRange _;IndexArgItem _;IndexArgItem _;IndexArgRange _], None        -> Some (sliceOpPath, "GetArraySlice4DFixedDouble4", expandedIndexArgs)
                    | [IndexArgRange _;IndexArgItem _;IndexArgRange _;IndexArgItem _], None        -> Some (sliceOpPath, "GetArraySlice4DFixedDouble5", expandedIndexArgs)
                    | [IndexArgRange _;IndexArgRange _;IndexArgItem _;IndexArgItem _], None        -> Some (sliceOpPath, "GetArraySlice4DFixedDouble6", expandedIndexArgs)
                    | [IndexArgRange _;IndexArgItem _;IndexArgItem _;IndexArgItem _], None        -> Some (sliceOpPath, "GetArraySlice4DFixedTriple1", expandedIndexArgs)
                    | [IndexArgItem _;IndexArgRange _;IndexArgItem _;IndexArgItem _], None        -> Some (sliceOpPath, "GetArraySlice4DFixedTriple2", expandedIndexArgs)
                    | [IndexArgItem _;IndexArgItem _;IndexArgRange _;IndexArgItem _], None        -> Some (sliceOpPath, "GetArraySlice4DFixedTriple3", expandedIndexArgs)
                    | [IndexArgItem _;IndexArgItem _;IndexArgItem _;IndexArgRange _], None        -> Some (sliceOpPath, "GetArraySlice4DFixedTriple4", expandedIndexArgs)
                    | [IndexArgItem _;IndexArgRange _;IndexArgRange _], Some (expr3, _)               -> Some (sliceOpPath, "SetArraySlice3DFixedSingle1", (expandedIndexArgs @ [expr3]))
                    | [IndexArgRange _;IndexArgItem _;IndexArgRange _], Some (expr3, _)               -> Some (sliceOpPath, "SetArraySlice3DFixedSingle2", (expandedIndexArgs @ [expr3]))
                    | [IndexArgRange _;IndexArgRange _;IndexArgItem _], Some (expr3, _)               -> Some (sliceOpPath, "SetArraySlice3DFixedSingle3", (expandedIndexArgs @ [expr3]))
                    | [IndexArgItem _;IndexArgItem _;IndexArgRange _], Some (expr3, _)               -> Some (sliceOpPath, "SetArraySlice3DFixedDouble1", (expandedIndexArgs @ [expr3]))
                    | [IndexArgItem _;IndexArgRange _;IndexArgItem _], Some (expr3, _)               -> Some (sliceOpPath, "SetArraySlice3DFixedDouble2", (expandedIndexArgs @ [expr3]))
                    | [IndexArgRange _;IndexArgItem _;IndexArgItem _], Some (expr3, _)               -> Some (sliceOpPath, "SetArraySlice3DFixedDouble3", (expandedIndexArgs @ [expr3]))
                    | [IndexArgItem _;IndexArgRange _;IndexArgRange _;IndexArgRange _], Some (expr3, _) -> Some (sliceOpPath, "SetArraySlice4DFixedSingle1", expandedIndexArgs @ [expr3])
                    | [IndexArgRange _;IndexArgItem _;IndexArgRange _;IndexArgRange _], Some (expr3, _) -> Some (sliceOpPath, "SetArraySlice4DFixedSingle2", expandedIndexArgs @ [expr3])
                    | [IndexArgRange _;IndexArgRange _;IndexArgItem _;IndexArgRange _], Some (expr3, _) -> Some (sliceOpPath, "SetArraySlice4DFixedSingle3", expandedIndexArgs @ [expr3])
                    | [IndexArgRange _;IndexArgRange _;IndexArgRange _;IndexArgItem _], Some (expr3, _) -> Some (sliceOpPath, "SetArraySlice4DFixedSingle4", expandedIndexArgs @ [expr3])
                    | [IndexArgItem _;IndexArgItem _;IndexArgRange _;IndexArgRange _], Some (expr3, _) -> Some (sliceOpPath, "SetArraySlice4DFixedDouble1", expandedIndexArgs @ [expr3])
                    | [IndexArgItem _;IndexArgRange _;IndexArgItem _;IndexArgRange _], Some (expr3, _) -> Some (sliceOpPath, "SetArraySlice4DFixedDouble2", expandedIndexArgs @ [expr3])
                    | [IndexArgItem _;IndexArgRange _;IndexArgRange _;IndexArgItem _], Some (expr3, _) -> Some (sliceOpPath, "SetArraySlice4DFixedDouble3", expandedIndexArgs @ [expr3])
                    | [IndexArgRange _;IndexArgItem _;IndexArgItem _;IndexArgRange _], Some (expr3, _) -> Some (sliceOpPath, "SetArraySlice4DFixedDouble4", expandedIndexArgs @ [expr3])
                    | [IndexArgRange _;IndexArgItem _;IndexArgRange _;IndexArgItem _], Some (expr3, _) -> Some (sliceOpPath, "SetArraySlice4DFixedDouble5", expandedIndexArgs @ [expr3])
                    | [IndexArgRange _;IndexArgRange _;IndexArgItem _;IndexArgItem _], Some (expr3, _) -> Some (sliceOpPath, "SetArraySlice4DFixedDouble6", expandedIndexArgs @ [expr3])
                    | [IndexArgRange _;IndexArgItem _;IndexArgItem _;IndexArgItem _], Some (expr3, _) -> Some (sliceOpPath, "SetArraySlice4DFixedTriple1", expandedIndexArgs @ [expr3])
                    | [IndexArgItem _;IndexArgRange _;IndexArgItem _;IndexArgItem _], Some (expr3, _) -> Some (sliceOpPath, "SetArraySlice4DFixedTriple2", expandedIndexArgs @ [expr3])
                    | [IndexArgItem _;IndexArgItem _;IndexArgRange _;IndexArgItem _], Some (expr3, _) -> Some (sliceOpPath, "SetArraySlice4DFixedTriple3", expandedIndexArgs @ [expr3])
                    | [IndexArgItem _;IndexArgItem _;IndexArgItem _;IndexArgRange _], Some (expr3, _) -> Some (sliceOpPath, "SetArraySlice4DFixedTriple4", expandedIndexArgs @ [expr3])
                    | _ -> None
                | _ -> None

            elif isString then
                match DecodeIndexArgs cenv indexArgs, setInfo with
                | [IndexArgRange _], None -> Some (sliceOpPath, "GetStringSlice", expandedIndexArgs)
                | [IndexArgItem _], None -> Some (indexOpPath, "GetString", expandedIndexArgs)
                | _ -> None

            else None

        match info with
        | None -> None
        | Some (path, functionName, indexArgs) ->
            let operPath = mkSynLidGet (mDot.MakeSynthetic()) path functionName
            let f, fty, tpenv = TcExprOfUnknownType cenv env tpenv operPath
            let domainTy, resultTy = UnifyFunctionType (Some mWholeExpr) cenv env.DisplayEnv mWholeExpr fty
            UnifyTypes cenv env mWholeExpr domainTy exprTy
            let f', resultTy = buildApp cenv (MakeApplicableExprNoFlex cenv f) resultTy expr mWholeExpr
            let delayed = List.foldBack (fun idx acc -> DelayedApp(ExprAtomicFlag.Atomic, true, None, idx, mWholeExpr) :: acc) indexArgs delayed // atomic, otherwise no ar.[1] <- xyz
            Some (PropagateThenTcDelayed cenv overallTy env tpenv mWholeExpr f' resultTy ExprAtomicFlag.Atomic delayed )

    match attemptArrayString with
    | Some res -> res
    | None when isNominal || Option.isSome propName ->
        let nm =
            match propName with
            | None -> "Item"
            | Some nm -> nm
        let delayed =
            match setInfo with
            // expr1.[expr2]
            | None  ->
                [ DelayedDotLookup([ ident(nm, mWholeExpr)], mWholeExpr)
                  DelayedApp(ExprAtomicFlag.Atomic, true, synLeftExprOpt, MakeIndexParam None, mWholeExpr)
                  yield! delayed ]

            // expr1.[expr2] <- expr3   --> expr1.Item(expr2) <- expr3
            | Some (expr3, mOfLeftOfSet) ->
                if isIndex then
                    [ DelayedDotLookup([ident(nm, mOfLeftOfSet)], mOfLeftOfSet)
                      DelayedApp(ExprAtomicFlag.Atomic, true, synLeftExprOpt, MakeIndexParam None, mOfLeftOfSet)
                      MakeDelayedSet(expr3, mWholeExpr)
                      yield! delayed ]
                else
                    [ DelayedDotLookup([ident("SetSlice", mOfLeftOfSet)], mOfLeftOfSet)
                      DelayedApp(ExprAtomicFlag.Atomic, true, synLeftExprOpt, MakeIndexParam (Some expr3), mWholeExpr)
                      yield! delayed ]

        PropagateThenTcDelayed cenv overallTy env tpenv mDot (MakeApplicableExprNoFlex cenv expr) exprTy ExprAtomicFlag.Atomic delayed

    | _ ->
        // deprecated constrained lookup
        error(Error(FSComp.SR.tcObjectOfIndeterminateTypeUsedRequireTypeConstraint(), mWholeExpr))

/// Check a 'new Type(args)' expression, also an 'inheritedTys declaration in an implicit or explicit class
/// For 'new Type(args)', mWholeExprOrObjTy is the whole expression
/// For 'inherit Type(args)', mWholeExprOrObjTy is the whole expression
/// For an implicit inherit from System.Object or a default constructor, mWholeExprOrObjTy is the type name of the type being defined
and TcNewExpr cenv env tpenv objTy mObjTyOpt superInit arg mWholeExprOrObjTy =
    let g = cenv.g
    let ad = env.AccessRights

    // Handle the case 'new 'a()'
    if (isTyparTy g objTy) then
        if superInit then error(Error(FSComp.SR.tcCannotInheritFromVariableType(), mWholeExprOrObjTy))
        AddCxTypeMustSupportDefaultCtor env.DisplayEnv cenv.css mWholeExprOrObjTy NoTrace objTy

        match arg with
        | SynExpr.Const (SynConst.Unit, _) -> ()
        | _ -> errorR(Error(FSComp.SR.tcObjectConstructorsOnTypeParametersCannotTakeArguments(), mWholeExprOrObjTy))

        mkCallCreateInstance g mWholeExprOrObjTy objTy, tpenv
    else
        if not (isAppTy g objTy) && not (isAnyTupleTy g objTy) then error(Error(FSComp.SR.tcNamedTypeRequired(if superInit then "inherit" else "new"), mWholeExprOrObjTy))
        let item = ForceRaise (ResolveObjectConstructor cenv.nameResolver env.DisplayEnv mWholeExprOrObjTy ad objTy)

        TcCtorCall false cenv env tpenv (MustEqual objTy) objTy mObjTyOpt item superInit [arg] mWholeExprOrObjTy [] None

/// Check an 'inheritedTys declaration in an implicit or explicit class
and TcCtorCall isNaked cenv env tpenv (overallTy: OverallTy) objTy mObjTyOpt item superInit args mWholeCall delayed afterTcOverloadResolutionOpt =
    let g = cenv.g
    let ad = env.AccessRights

    let isSuperInit = (if superInit then CtorValUsedAsSuperInit else NormalValUse)
    let mItem = match mObjTyOpt with Some m -> m | None -> mWholeCall

    if isInterfaceTy g objTy then
        error(Error((if superInit then FSComp.SR.tcInheritCannotBeUsedOnInterfaceType() else FSComp.SR.tcNewCannotBeUsedOnInterfaceType()), mWholeCall))

    match item, args with
    | Item.CtorGroup(methodName, minfos), _ ->
        let meths = List.map (fun minfo -> minfo, None) minfos
        if isNaked && TypeFeasiblySubsumesType 0 g cenv.amap mWholeCall g.system_IDisposableNull_ty NoCoerce objTy then
            warning(Error(FSComp.SR.tcIDisposableTypeShouldUseNew(), mWholeCall))

        // Check the type is not abstract
        // skip this check if this ctor call is either 'inherit(...)' or call is located within constructor shape
        if not (superInit || AreWithinCtorShape env)
            then CheckSuperInit cenv objTy mWholeCall

        // Pre-unify expected type with KnownFromConstructor nullness so the constraint solver
        // sees constructor results as provably non-null (issue #18021).
        // Skip when args is empty: the constructor is used as a first-class function (e.g. |> ClassName)
        // and overallTy is a function type, not the return type.
        if g.checkNullness && not args.IsEmpty && TypeNullIsExtraValueNew g mWholeCall objTy then
            UnifyTypes cenv env mWholeCall overallTy.Commit (replaceNullnessOfTy Nullness.KnownFromConstructor objTy)

        let afterResolution =
            match mObjTyOpt, afterTcOverloadResolutionOpt with
            | _, Some action -> action
            | Some mObjTy, None -> ForNewConstructors cenv.tcSink env mObjTy methodName minfos
            | None, _ -> AfterResolution.DoNothing

        TcMethodApplicationThen cenv env overallTy (Some objTy) tpenv None [] mWholeCall mItem methodName ad PossiblyMutates false meths afterResolution isSuperInit args ExprAtomicFlag.NonAtomic None delayed

    | Item.DelegateCtor ty, [arg] ->
        // Re-record the name resolution since we now know it's a constructor call
        match mObjTyOpt with
        | Some mObjTy -> CallNameResolutionSink cenv.tcSink (mObjTy, env.NameEnv, item, emptyTyparInst, ItemOccurrence.Use, env.AccessRights)
        | None -> ()
        TcNewDelegateThen cenv (MustEqual objTy) env tpenv mItem mWholeCall ty arg ExprAtomicFlag.NonAtomic delayed

    | _ ->
        error(Error(FSComp.SR.tcSyntaxCanOnlyBeUsedToCreateObjectTypes(if superInit then "inherit" else "new"), mWholeCall))

// Check a record construction expression
and TcRecordConstruction (cenv: cenv) (overallTy: TType) isObjExpr env tpenv withExprInfoOpt objTy fldsList m =
    let g = cenv.g

    let tcref, tinst = destAppTy g objTy
    let tycon = tcref.Deref
    UnifyTypes cenv env m overallTy objTy

    // Types with implicit constructors can't use record or object syntax: all constructions must go through the implicit constructor
    let supportsObjectExpressionWithoutOverrides = isObjExpr && g.langVersion.SupportsFeature(LanguageFeature.AllowObjectExpressionWithoutOverrides)
    if not supportsObjectExpressionWithoutOverrides && tycon.MembersOfFSharpTyconByName |> NameMultiMap.existsInRange (fun v -> v.IsIncrClassConstructor) then
        errorR(Error(FSComp.SR.tcConstructorRequiresCall(tycon.DisplayName), m))

    let fspecs = tycon.TrueInstanceFieldsAsList
    // Freshen types and work out their subtype flexibility
    let fldsList =
        [ for fname, fexpr in fldsList do
              let fspec =
                  try
                      fspecs |> List.find (fun fspec -> fspec.LogicalName = fname)
                  with :? KeyNotFoundException ->
                      error (Error(FSComp.SR.tcUndefinedField(fname, NicePrint.minimalStringOfType env.DisplayEnv objTy), m))
              let fty = actualTyOfRecdFieldForTycon tycon tinst fspec
              let flex = not (isTyparTy g fty)
              yield (fname, fexpr, fty, flex) ]

    // Type check and generalize the supplied bindings
    let fldsList, tpenv =
        let env = { env with eContextInfo = ContextInfo.RecordFields }
        (tpenv, fldsList) ||> List.mapFold (fun tpenv (fname, fexpr, fty, flex) ->
              let fieldExpr, tpenv = TcExprFlex cenv flex false fty env tpenv fexpr
              (fname, fieldExpr), tpenv)

    // Add rebindings for unbound field when an "old value" is available
    // Effect order: mutable fields may get modified by other bindings...
    let oldFldsList =
        match withExprInfoOpt with
        | None -> []
        | Some (_, _, withExprAddrValExpr) ->
            let fieldNameUnbound name2 = fldsList |> List.forall (fun (name, _) -> name <> name2)
            let flds =
                fspecs |> List.choose (fun rfld ->
                    if fieldNameUnbound rfld.LogicalName && not rfld.IsZeroInit then
                        Some(rfld.LogicalName, mkRecdFieldGetViaExprAddr (withExprAddrValExpr, tcref.MakeNestedRecdFieldRef rfld, tinst, m))
                    else
                        None)
            flds

    let fldsList = fldsList @ oldFldsList

    // From now on only interested in fspecs that truly need values.
    let fspecs = fspecs |> List.filter (fun f -> not f.IsZeroInit)

    // Check all fields are bound
    fspecs |> List.iter (fun fspec ->
      if not (fldsList |> List.exists (fun (fname, _) -> fname = fspec.LogicalName)) then
        error(Error(FSComp.SR.tcFieldRequiresAssignment(fspec.rfield_id.idText, fullDisplayTextOfTyconRef tcref), m)))

    // Other checks (overlap with above check now clear)
    let ns1 = NameSet.ofList (List.map fst fldsList)
    let ns2 = NameSet.ofList (List.map (fun x -> x.rfield_id.idText) fspecs)

    match withExprInfoOpt with
    | None ->
        if not (Zset.subset ns2 ns1) then
            error(MissingFields(Zset.elements (Zset.diff ns2 ns1), m))
    | _ ->
        // `TransformAstForNestedUpdates` creates record constructions with synthetic ranges.
        // Don't emit the warning for nested field updates, because it does not really make sense.
        if oldFldsList.IsEmpty && not m.IsSynthetic then
            let enabledByLangFeature = g.langVersion.SupportsFeature LanguageFeature.WarningWhenCopyAndUpdateRecordChangesAllFields
            warning(ErrorEnabledWithLanguageFeature(FSComp.SR.tcCopyAndUpdateRecordChangesAllFields(fullDisplayTextOfTyconRef tcref), m, enabledByLangFeature))

    if not (Zset.subset ns1 ns2) then
        error (Error(FSComp.SR.tcExtraneousFieldsGivenValues(), m))

    // Build record
    let rfrefs = List.map (fst >> mkRecdFieldRef tcref) fldsList

    // Check accessibility: this is also done in BuildFieldMap, but also need to check
    // for fields in { new R with a=1 and b=2 } constructions and { r with a=1 } copy-and-update expressions
    for rfref in rfrefs do
        CheckRecdFieldAccessible cenv.amap m env.eAccessRights rfref |> ignore
        if isObjExpr then
            CheckFSharpAttributes g rfref.PropertyAttribs m |> CommitOperationResult

    let args = List.map snd fldsList

    let expr = mkRecordExpr g (GetRecdInfo env, tcref, tinst, rfrefs, args, m)

    let expr =
      match withExprInfoOpt with
      | None ->
          // '{ recd fields }'. //
          expr

      | Some (withExpr, withExprAddrVal, _) ->
          // '{ recd with fields }'.
          // Assign the first object to a tmp and then construct
          let wrap, oldaddr, _readonly, _writeonly = mkExprAddrOfExpr g tycon.IsStructOrEnumTycon false NeverMutates withExpr None m
          wrap (mkCompGenLet m withExprAddrVal oldaddr expr)

    expr, tpenv

//-------------------------------------------------------------------------
// TcObjectExpr
//-------------------------------------------------------------------------

and GetNameAndSynValInfoOfObjExprBinding _cenv _env b =
    let (NormalizedBinding (_, _, _, _, _, _, _, valSynData, pat, rhsExpr, mBinding, _)) = b
    let (SynValData(memberFlags = memberFlagsOpt; valInfo = valSynInfo)) = valSynData
    match pat, memberFlagsOpt with

    // This is the normal case for F# 'with member x.M(...) = ...'
    | SynPat.InstanceMember(_thisId, memberId, _, None, _), Some memberFlags ->
         let logicalMethId = ident (ComputeLogicalName memberId memberFlags, memberId.idRange)
         logicalMethId.idText, valSynInfo

    | _ ->
        // This is for the deprecated form 'with M(...) = ...'
        let rec lookPat pat =
            match pat with
            | SynPat.Typed(pat, _, _) -> lookPat pat
            | SynPat.FromParseError(pat, _) -> lookPat pat
            | SynPat.Named (SynIdent(id,_), _, None, _) ->
                let (NormalizedBindingRhs(pushedPats, _, _)) = rhsExpr
                let infosForExplicitArgs = pushedPats |> List.map SynInfo.InferSynArgInfoFromSimplePats
                let infosForExplicitArgs = SynInfo.AdjustMemberArgs SynMemberKind.Member infosForExplicitArgs
                let infosForExplicitArgs = SynInfo.AdjustArgsForUnitElimination infosForExplicitArgs
                let argInfos = [SynInfo.selfMetadata] @ infosForExplicitArgs
                let retInfo = SynInfo.unnamedRetVal //SynInfo.InferSynReturnData pushedRetInfoOpt
                let valSynData = SynValInfo(argInfos, retInfo)
                (id.idText, valSynData)
            | _ -> error(Error(FSComp.SR.tcObjectExpressionsCanOnlyOverrideAbstractOrVirtual(), mBinding))

        lookPat pat


and FreshenObjExprAbstractSlot (cenv: cenv) (env: TcEnv) (implTy: TType) virtNameAndArityPairs (bind, bindAttribs, bindName, absSlots:(_ * MethInfo) list) =

    let g = cenv.g

    let (NormalizedBinding (typars=synTyparDecls; mBinding=mBinding)) = bind

    match absSlots with
    | [] when not (CompileAsEvent g bindAttribs) ->
        let absSlotsByName = List.filter (fst >> fst >> (=) bindName) virtNameAndArityPairs
        let getSignature absSlot = (NicePrint.stringOfMethInfo cenv.infoReader mBinding env.DisplayEnv absSlot).Replace("abstract ", "")
        let getDetails (absSlot: MethInfo) =
            if absSlot.GetParamTypes(cenv.amap, mBinding, []) |> List.existsSquared (isAnyTupleTy g) then
                FSComp.SR.tupleRequiredInAbstractMethod()
            else ""

        // Compute the argument counts of the member arguments
        let _, synValInfo = GetNameAndSynValInfoOfObjExprBinding cenv env bind
        let arity =
            match SynInfo.AritiesOfArgs synValInfo with
            | _ :: x :: _ -> x
            | _ -> 0

        match absSlotsByName with
        | [] ->
            let tcref = tcrefOfAppTy g implTy
            let containsNonAbstractMemberWithSameName =
                tcref.MembersOfFSharpTyconByName
                |> Seq.exists (fun kv -> kv.Value |> List.exists (fun valRef -> valRef.DisplayName = bindName))

            let suggestVirtualMembers (addToBuffer: string -> unit) =
                for (x, _), _ in virtNameAndArityPairs do
                    addToBuffer x

            if containsNonAbstractMemberWithSameName then
                errorR(ErrorWithSuggestions(FSComp.SR.tcMemberFoundIsNotAbstractOrVirtual(tcref.DisplayName, bindName), mBinding, bindName, suggestVirtualMembers))
            else
                errorR(ErrorWithSuggestions(FSComp.SR.tcNoAbstractOrVirtualMemberFound bindName, mBinding, bindName, suggestVirtualMembers))

        | [ (_, absSlot: MethInfo) ] ->
            errorR(Error(FSComp.SR.tcArgumentArityMismatch(bindName, List.sum absSlot.NumArgs, arity, getSignature absSlot, getDetails absSlot), mBinding))

        | (_, absSlot) :: _ ->
            errorR(Error(FSComp.SR.tcArgumentArityMismatchOneOverload(bindName, List.sum absSlot.NumArgs, arity, getSignature absSlot, getDetails absSlot), mBinding))

        None

    | [ (_, absSlot) ] ->

        let typarsFromAbsSlotAreRigid, typarsFromAbsSlot, argTysFromAbsSlot, retTyFromAbsSlot =
            FreshenAbstractSlot g cenv.amap mBinding synTyparDecls absSlot

        // Work out the required type of the member
        let bindingTy = mkFunTy cenv.g implTy (mkMethodTy cenv.g argTysFromAbsSlot retTyFromAbsSlot)

        Some(typarsFromAbsSlotAreRigid, typarsFromAbsSlot, bindingTy)

    | _ ->
        None

and TcObjectExprBinding (cenv: cenv) (env: TcEnv) implTy tpenv (absSlotInfo, bind) =

    let g = cenv.g

    let (NormalizedBinding(vis, kind, isInline, isMutable, attrs, xmlDoc, synTyparDecls, valSynData, headPat, bindingRhs, mBinding, debugPoint)) = bind
    let (SynValData(memberFlags = memberFlagsOpt)) = valSynData

    // 4a2. adjust the binding, especially in the "member" case, a subset of the logic of AnalyzeAndMakeAndPublishRecursiveValue
    let bindingRhs, logicalMethId, memberFlags =
        let rec lookPat p =
            match p, memberFlagsOpt with
            | SynPat.FromParseError(pat, _), _ -> lookPat pat
            | SynPat.Named (SynIdent(id,_), _, _, _), None ->
                let bindingRhs = PushOnePatternToRhs cenv true (mkSynThisPatVar (ident (CompilerGeneratedName "this", id.idRange))) bindingRhs
                let logicalMethId = id
                let memberFlags = OverrideMemberFlags SynMemberKind.Member
                bindingRhs, logicalMethId, memberFlags

            | SynPat.Named (SynIdent(id,_), _, _, _), Some memberFlags ->
                CheckMemberFlags None NewSlotsOK OverridesOK memberFlags mBinding
                let bindingRhs = PushOnePatternToRhs cenv true (mkSynThisPatVar (ident (CompilerGeneratedName "this", id.idRange))) bindingRhs
                let logicalMethId = id
                bindingRhs, logicalMethId, memberFlags

            | SynPat.InstanceMember(thisId, memberId, _, _, _), Some memberFlags ->
                CheckMemberFlags None NewSlotsOK OverridesOK memberFlags mBinding
                let bindingRhs = PushOnePatternToRhs cenv true (mkSynThisPatVar thisId) bindingRhs
                let logicalMethId = ident (ComputeLogicalName memberId memberFlags, memberId.idRange)
                bindingRhs, logicalMethId, memberFlags
            | _ ->
                error(InternalError("unexpected member binding", mBinding))
        lookPat headPat
    let bind = NormalizedBinding (vis, kind, isInline, isMutable, attrs, xmlDoc, synTyparDecls, valSynData, mkSynPatVar vis logicalMethId, bindingRhs, mBinding, debugPoint)

    // 4b. typecheck the binding
    let bindingTy =
        match absSlotInfo with
        | Some(_, _, memberTyFromAbsSlot) ->
            memberTyFromAbsSlot
        | _ ->
            mkFunTy cenv.g implTy (NewInferenceType cenv.g)

    let CheckedBindingInfo(inlineFlag, bindingAttribs, _, _, ExplicitTyparInfo(_, declaredTypars, _), nameToPrelimValSchemeMap, rhsExpr, _, _, m, _, _, _, _), tpenv =
        let explicitTyparInfo, tpenv = TcNonrecBindingTyparDecls cenv env tpenv bind
        TcNormalizedBinding ObjectExpressionOverrideBinding cenv env tpenv bindingTy None NoSafeInitInfo ([], explicitTyparInfo) bind

    // 4c. generalize the binding - only relevant when implementing a generic virtual method

    match NameMap.range nameToPrelimValSchemeMap with
    | [ PrelimVal1(id=id) ] ->
        let denv = env.DisplayEnv

        let declaredTypars =
            match absSlotInfo with
            | Some(typarsFromAbsSlotAreRigid, typarsFromAbsSlot, _) ->
                if typarsFromAbsSlotAreRigid then typarsFromAbsSlot else declaredTypars
            | _ ->
                declaredTypars
        // Canonicalize constraints prior to generalization
        CanonicalizePartialInferenceProblem cenv.css denv m declaredTypars

        let freeInEnv = GeneralizationHelpers.ComputeUngeneralizableTypars env

        let generalizedTypars = GeneralizationHelpers.ComputeAndGeneralizeGenericTypars(cenv, denv, m, freeInEnv, false, CanGeneralizeConstrainedTypars, inlineFlag, Some rhsExpr, declaredTypars, [], bindingTy, false)
        let declaredTypars = ChooseCanonicalDeclaredTyparsAfterInference g env.DisplayEnv declaredTypars m

        let generalizedTypars = PlaceTyparsInDeclarationOrder declaredTypars generalizedTypars

        (id, memberFlags, (generalizedTypars +-> bindingTy), bindingAttribs, rhsExpr), tpenv
    | _ ->
        error(Error(FSComp.SR.tcSimpleMethodNameRequired(), m))

and ComputeObjectExprOverrides (cenv: cenv) (env: TcEnv) tpenv impls =

    let g = cenv.g

    // Compute the method sets each implemented type needs to implement
    let slotImplSets = DispatchSlotChecking.GetSlotImplSets cenv.infoReader env.DisplayEnv env.AccessRights true (impls |> List.map (fun (m, ty, _) -> ty, m))

    let allImpls =
        (impls, slotImplSets) ||> List.map2 (fun (m, ty, binds) implTySet ->
            let binds = binds |> List.map (BindingNormalization.NormalizeBinding ObjExprBinding cenv env)
            m, ty, binds, implTySet)

    let overridesAndVirts, tpenv =
        (tpenv, allImpls) ||> List.mapFold (fun tpenv (m, implTy, binds, SlotImplSet(reqdSlots, dispatchSlotsKeyed, availPriorOverrides, _) ) ->

            // Generate extra bindings fo object expressions with bindings using the CLIEvent attribute
            let binds, bindsAttributes =
               [ for binding in binds do
                     let (NormalizedBinding(_, _, _, _, bindingSynAttribs, _, _, valSynData, _, _, _, _)) = binding
                     let (SynValData(memberFlags = memberFlagsOpt)) = valSynData
                     let attrTgt = ObjectExpressionOverrideBinding.AllowedAttribTargets memberFlagsOpt
                     let bindingAttribs = TcAttributes cenv env attrTgt bindingSynAttribs
                     yield binding, bindingAttribs
                     for extraBinding in EventDeclarationNormalization.GenerateExtraBindings cenv (bindingAttribs, binding) do
                         yield extraBinding, [] ]
               |> List.unzip

            // 2. collect all name/arity of all overrides
            let dispatchSlots = reqdSlots |> List.map (fun reqdSlot -> reqdSlot.MethodInfo)

            let virtNameAndArityPairs = dispatchSlots |> List.map (fun virt ->
                let vkey = (virt.LogicalName, virt.NumArgs)
                //dprintfn "vkey = %A" vkey
                (vkey, virt))

            let bindNameAndSynInfoPairs = binds |> List.map (GetNameAndSynValInfoOfObjExprBinding cenv env)
            let bindNames = bindNameAndSynInfoPairs |> List.map fst
            let bindKeys =
                bindNameAndSynInfoPairs |> List.map (fun (name, valSynData) ->
                    // Compute the argument counts of the member arguments
                    let argCounts = (SynInfo.AritiesOfArgs valSynData).Tail
                    //dprintfn "name = %A, argCounts = %A" name argCounts
                    (name, argCounts))

            // 3. infer must-have types by name/arity
            let preAssignedVirtsPerBinding =
                bindKeys |> List.map (fun bkey -> List.filter (fst >> (=) bkey) virtNameAndArityPairs)

            let absSlotInfo =
               (List.zip4 binds bindsAttributes bindNames preAssignedVirtsPerBinding)
               |> List.map (FreshenObjExprAbstractSlot cenv env implTy virtNameAndArityPairs)

            // 4. typecheck/typeinfer/generalizer overrides using this information
            let overrides, tpenv = (tpenv, List.zip absSlotInfo binds) ||> List.mapFold (TcObjectExprBinding cenv env implTy)

            // Convert the syntactic info to actual info
            let overrides =
                (overrides, bindNameAndSynInfoPairs) ||> List.map2 (fun (id: Ident, memberFlags, ty, bindingAttribs, bindingBody) (_, valSynData) ->
                    let partialValInfo = TranslateSynValInfo cenv id.idRange (TcAttributes cenv env) valSynData
                    let tps, _ = tryDestForallTy g ty
                    let valInfo = TranslatePartialValReprInfo tps partialValInfo
                    DispatchSlotChecking.GetObjectExprOverrideInfo g cenv.amap (implTy, id, memberFlags, ty, valInfo, bindingAttribs, bindingBody))

            (m, implTy, reqdSlots, dispatchSlotsKeyed, availPriorOverrides, overrides), tpenv)

    overridesAndVirts, tpenv

and CheckSuperType (cenv: cenv) ty m =
    let g = cenv.g

    if typeEquiv g ty g.system_Value_ty ||
       typeEquiv g ty g.system_Enum_ty ||
       typeEquiv g ty g.system_Array_ty ||
       typeEquiv g ty g.system_MulticastDelegate_ty ||
       typeEquiv g ty g.system_Delegate_ty then
         errorR(Error(FSComp.SR.tcPredefinedTypeCannotBeUsedAsSuperType(), m))

    if isErasedType g ty then
        errorR(Error(FSComp.SR.tcCannotInheritFromErasedType(), m))

and TcObjectExpr (cenv: cenv) env tpenv (objTy, realObjTy, argopt, binds, extraImpls, mObjTy, mNewExpr, mWholeExpr) =

    let g = cenv.g
    match tryTcrefOfAppTy g objTy with
    | ValueNone -> error(Error(FSComp.SR.tcNewMustBeUsedWithNamedType(), mNewExpr))
    | ValueSome tcref ->
    let isRecordTy = tcref.IsRecordTycon
    let isInterfaceTy = isInterfaceTy g objTy
    let isFSharpObjModelTy = isFSharpObjModelTy g objTy
    let isOverallTyAbstract = EntityHasWellKnownAttribute g WellKnownEntityAttributes.AbstractClassAttribute tcref.Deref || isAbstractTycon tcref.Deref

    if not isRecordTy && not isInterfaceTy && isSealedTy g objTy then errorR(Error(FSComp.SR.tcCannotCreateExtensionOfSealedType(), mNewExpr))

    CheckSuperType cenv objTy mObjTy

    // Add the object type to the ungeneralizable items
    let env = {env with eUngeneralizableItems = addFreeItemOfTy objTy env.eUngeneralizableItems }

    // Save the enclosing struct context BEFORE EnterFamilyRegion overwrites env.eFamilyType.
    // This is used later to detect struct instance captures that would generate illegal byref fields.
    let enclosingStructTyconRefOpt =
        match env.eFamilyType with
        | Some tcref when tcref.IsStructOrEnumTycon -> Some tcref
        | _ -> None

    // Object expression members can access protected members of the implemented type
    let env = EnterFamilyRegion tcref env
    let ad = env.AccessRights

    if // record construction ? e.g { A = 1; B = 2 }
       isRecordTy ||
       // object construction?  e.g. new A() { ... }
       (isFSharpObjModelTy && not isInterfaceTy && argopt.IsNone) then

        if argopt.IsSome then error(Error(FSComp.SR.tcNoArgumentsForRecordValue(), mWholeExpr))
        if not (isNil extraImpls) then error(Error(FSComp.SR.tcNoInterfaceImplementationForConstructionExpression(), mNewExpr))
        if isFSharpObjModelTy && GetCtorShapeCounter env <> 1 then
            error(Error(FSComp.SR.tcObjectConstructionCanOnlyBeUsedInClassTypes(), mNewExpr))
        let fldsList =
            binds |> List.map (fun b ->
                match BindingNormalization.NormalizeBinding ObjExprBinding cenv env b with
                | NormalizedBinding (_, _, _, _, [], _, _, _, SynPat.Named(SynIdent(id,_), _, _, _), NormalizedBindingRhs(_, _, rhsExpr), _, _) -> id.idText, rhsExpr
                | _ -> error(Error(FSComp.SR.tcOnlySimpleBindingsCanBeUsedInConstructionExpressions(), b.RangeOfBindingWithoutRhs)))

        TcRecordConstruction cenv objTy true env tpenv None objTy fldsList mWholeExpr
    else
        // object expression construction e.g. { new A() with ... } or { new IA with ... }
        let ctorCall, baseIdOpt, tpenv =
            if isInterfaceTy then
                match argopt with
                | None ->
                    BuildObjCtorCall g mWholeExpr, None, tpenv
                | Some _ ->
                    error(Error(FSComp.SR.tcConstructorForInterfacesDoNotTakeArguments(), mNewExpr))
            else
                let item = ForceRaise (ResolveObjectConstructor cenv.nameResolver env.DisplayEnv mObjTy ad objTy)

                if isFSharpObjModelTy && GetCtorShapeCounter env = 1 then
                    error(Error(FSComp.SR.tcObjectsMustBeInitializedWithObjectExpression(), mNewExpr))

                match item, argopt with
                | Item.CtorGroup(methodName, minfos), Some (arg, baseIdOpt) ->
                    let meths = minfos |> List.map (fun minfo -> minfo, None)
                    let afterResolution = ForNewConstructors cenv.tcSink env mObjTy methodName minfos
                    let ad = env.AccessRights

                    let expr, tpenv = TcMethodApplicationThen cenv env (MustEqual objTy) None tpenv None [] mWholeExpr mObjTy methodName ad PossiblyMutates false meths afterResolution CtorValUsedAsSuperInit [arg] ExprAtomicFlag.Atomic None []
                    // The 'base' value is always bound
                    let baseIdOpt = (match baseIdOpt with None -> Some(ident("base", mObjTy)) | Some id -> Some id)
                    expr, baseIdOpt, tpenv

                | Item.CtorGroup _, None ->
                    error(Error(FSComp.SR.tcConstructorRequiresArguments(), mNewExpr))

                | _ -> error(Error(FSComp.SR.tcNewRequiresObjectConstructor(), mNewExpr))

        let baseValOpt = MakeAndPublishBaseVal cenv env baseIdOpt objTy
        let env = Option.foldBack (AddLocalVal g cenv.tcSink mNewExpr) baseValOpt env
        let impls = (mWholeExpr, objTy, binds) :: extraImpls

        // 1. collect all the relevant abstract slots for each type we have to implement

        let overridesAndVirts, tpenv = ComputeObjectExprOverrides cenv env tpenv impls

        // 2. check usage conditions 
        for ovd in overridesAndVirts do
            let m, implTy, dispatchSlots, dispatchSlotsKeyed, availPriorOverrides, overrides = ovd
            let overrideSpecs = overrides |> List.map fst
            let hasStaticMembers = dispatchSlots |> List.exists (fun reqdSlot -> not reqdSlot.MethodInfo.IsInstance)
            if hasStaticMembers then
                errorR(Error(FSComp.SR.chkStaticMembersOnObjectExpressions(), mObjTy))

            DispatchSlotChecking.CheckOverridesAreAllUsedOnce (env.DisplayEnv, g, cenv.infoReader, true, implTy, dispatchSlotsKeyed, availPriorOverrides, overrideSpecs)

            if not hasStaticMembers then
                DispatchSlotChecking.CheckDispatchSlotsAreImplemented (env.DisplayEnv, cenv.infoReader, m, env.NameEnv, cenv.tcSink, isOverallTyAbstract, true, false, implTy, dispatchSlots, availPriorOverrides, overrideSpecs) |> ignore

        // 3. create the specs of overrides
        let allTypeImpls =
          overridesAndVirts |> List.map (fun (m, implTy, _, dispatchSlotsKeyed, _, overrides) ->
              let overrides' =
                  [ for overrideMeth in overrides do
                        let overrideInfo, (_, thisVal, methodVars, bindingAttribs, bindingBody) = overrideMeth
                        let (Override(_, _, id, mtps, _, _, _, isFakeEventProperty, _, isInstance)) = overrideInfo

                        if not isFakeEventProperty && isInstance then
                            let searchForOverride =
                                dispatchSlotsKeyed
                                |> NameMultiMap.find id.idText
                                |> List.tryPick (fun reqdSlot ->
                                     let virt = reqdSlot.MethodInfo
                                     if DispatchSlotChecking.IsExactMatch g cenv.amap m virt overrideInfo then
                                         Some virt
                                     else
                                         None)

                            let overridden =
                                match searchForOverride with
                                | Some x -> x
                                | None -> error(Error(FSComp.SR.tcAtLeastOneOverrideIsInvalid(), mObjTy))

                            yield TObjExprMethod(overridden.GetSlotSig(cenv.amap, m), bindingAttribs, mtps, [thisVal] :: methodVars, bindingBody, id.idRange) ]
              (implTy, overrides'))

        let objtyR, overrides' = allTypeImpls.Head
        assert (typeEquiv g objTy objtyR)
        let extraImpls = allTypeImpls.Tail
        let supportsObjectExpressionWithoutOverrides = g.langVersion.SupportsFeature(LanguageFeature.AllowObjectExpressionWithoutOverrides)

        if not supportsObjectExpressionWithoutOverrides && not isInterfaceTy && overrides'.IsEmpty && extraImpls.IsEmpty then
           errorR (Error(FSComp.SR.tcInvalidObjectExpressionSyntaxForm (), mWholeExpr))

        // 4. Build the implementation
        // Check for struct instance captures that would generate illegal byref fields.
        // See AnalyzeObjExprStructCaptures and TransformObjExprForStructByrefCaptures for details.
        let shouldTransform, structCaptures, _ = 
            AnalyzeObjExprStructCaptures enclosingStructTyconRefOpt ctorCall overrides' extraImpls

        let expr =
            if not shouldTransform then
                // No transformation needed - build the object expression directly
                let expr = mkObjExpr(objtyR, baseValOpt, ctorCall, overrides', extraImpls, mWholeExpr)
                mkCoerceIfNeeded g realObjTy objtyR expr
            else
                // Transform to avoid byref captures
                TransformObjExprForStructByrefCaptures g mWholeExpr structCaptures objtyR baseValOpt ctorCall overrides' extraImpls realObjTy

        expr, tpenv

//-------------------------------------------------------------------------
// TcConstStringExpr
//-------------------------------------------------------------------------

/// Check a constant string expression. It might be a 'printf' format string
and TcConstStringExpr cenv (overallTy: OverallTy) env m tpenv (s: string) literalType =
    let rec isFormat g ty =
        match stripTyEqns g ty with
        | TType_app (tcref, _, _) -> tyconRefEq g tcref g.format4_tcr || tyconRefEq g tcref g.format_tcr
        | TType_var (typar, _) ->
            typar.Constraints
            |> List.exists (fun c ->
                match c with
                | TyparConstraint.CoercesTo (ty, _) -> isFormat g ty
                | _ -> false)
        | _ -> false

    let g = cenv.g


    match isFormat g overallTy.Commit, literalType with
    | true, LiteralArgumentType.StaticField ->
        checkLanguageFeatureAndRecover g.langVersion LanguageFeature.NonInlineLiteralsAsPrintfFormat m
        TcFormatStringExpr cenv overallTy env m tpenv s literalType

    | true, LiteralArgumentType.Inline ->
        TcFormatStringExpr cenv overallTy env m tpenv s literalType

    | false, LiteralArgumentType.StaticField ->
        Expr.Const (TcFieldInit m (ILFieldInit.String s), m, g.string_ty), tpenv

    | false, LiteralArgumentType.Inline ->
        TcPropagatingExprLeafThenConvert cenv overallTy g.string_ty env (* true *) m (fun () ->
                mkString g m s, tpenv)

and TcFormatStringExpr cenv (overallTy: OverallTy) env m tpenv (fmtString: string) formatStringLiteralType =
    let g = cenv.g
    let aty = NewInferenceType g
    let bty = NewInferenceType g
    let cty = NewInferenceType g
    let dty = NewInferenceType g
    let ety = NewInferenceType g
    let formatTy = mkPrintfFormatTy g aty bty cty dty ety

    // This might qualify as a format string - check via a type directed rule
    let ok = not (isObjTyAnyNullness g overallTy.Commit) && AddCxTypeMustSubsumeTypeUndoIfFailed env.DisplayEnv cenv.css m overallTy.Commit formatTy

    if ok then
        // Parse the format string to work out the phantom types
        let formatStringCheckContext =
            match cenv.tcSink.CurrentSink, formatStringLiteralType with
            | Some sink, LiteralArgumentType.Inline -> sink.FormatStringCheckContext
            | _ -> None

        let normalizedString = fmtString.Replace("\r\n", "\n").Replace("\r", "\n")

        let _argTys, atyRequired, etyRequired, _percentATys, specifierLocations, _dotnetFormatString =
            try CheckFormatStrings.ParseFormatString m [m] g false false formatStringCheckContext normalizedString bty cty dty
            with Failure errString -> error (Error(FSComp.SR.tcUnableToParseFormatString errString, m))

        match cenv.tcSink.CurrentSink with
        | None -> ()
        | Some sink ->
            for specifierLocation, numArgs in specifierLocations do
                sink.NotifyFormatSpecifierLocation(specifierLocation, numArgs)

        UnifyTypes cenv env m aty atyRequired
        UnifyTypes cenv env m ety etyRequired
        let fmtExpr = mkCallNewFormat g m aty bty cty dty ety (mkString g m fmtString)
        fmtExpr, tpenv

    else
        TcPropagatingExprLeafThenConvert cenv overallTy g.string_ty env (* true *) m (fun () ->
            mkString g m fmtString, tpenv
        )

/// Check an interpolated string expression
and [<TailCall>] warnForFunctionValuesInFillExprs (g: TcGlobals) argTys synFillExprs =
    match argTys, synFillExprs with
    | argTy :: restTys, (synFillExpr: SynExpr) :: restExprs ->
        if isFunTy g argTy || isDelegateTy g argTy then
            warning (Error(FSComp.SR.tcFunctionValueUsedAsInterpolatedStringArg (), synFillExpr.Range))

        warnForFunctionValuesInFillExprs g restTys restExprs
    | _ -> ()

and TcInterpolatedStringExpr cenv (overallTy: OverallTy) env m tpenv (parts: SynInterpolatedStringPart list) =
    let g = cenv.g

    let synFillExprs =
        parts
        |> List.choose (function
            | SynInterpolatedStringPart.String _ -> None
            | SynInterpolatedStringPart.FillExpr (fillExpr, _)  ->
                match fillExpr with
                // Detect "x" part of "...{x,3}..."
                | SynExpr.Tuple (false, [e; SynExpr.Const (SynConst.Int32 _align, _)], _, _) -> Some e
                | e -> Some e)

    let stringFragmentRanges =
        parts
        |> List.choose (function
            | SynInterpolatedStringPart.String (_,m) -> Some m
            | SynInterpolatedStringPart.FillExpr _  -> None)

    let printerTy = NewInferenceType g
    let printerArgTy = NewInferenceType g
    let printerResidueTy = NewInferenceType g
    let printerResultTy = NewInferenceType g
    let printerTupleTy = NewInferenceType g
    let formatTy = mkPrintfFormatTy g printerTy printerArgTy printerResidueTy printerResultTy printerTupleTy

    // Check the library support is available in the referenced FSharp.Core
    let newFormatMethod =
        match GetIntrinsicConstructorInfosOfType cenv.infoReader m formatTy |> List.filter (fun minfo -> minfo.NumArgs = [3]) with
        | [ctorInfo] -> ctorInfo
        | _ -> languageFeatureNotSupportedInLibraryError LanguageFeature.StringInterpolation m

    let stringKind =
        // If this is an interpolated string then try to force the result to be a string
        if (AddCxTypeEqualsTypeUndoIfFailed env.DisplayEnv cenv.css m overallTy.Commit g.string_ty) then

            // And if that succeeds, the result of printing is a string
            UnifyTypes cenv env m printerArgTy g.unit_ty
            UnifyTypes cenv env m printerResidueTy g.string_ty
            UnifyTypes cenv env m printerResultTy overallTy.Commit

            // And if that succeeds, the printerTy and printerResultTy must be the same (there are no curried arguments)
            UnifyTypes cenv env m printerTy printerResultTy

            Choice1Of2 (true, newFormatMethod)

        // ... or if that fails then may be a FormattableString by a type-directed rule....
        elif (not (isObjTyAnyNullness g overallTy.Commit) &&
              ((g.system_FormattableString_tcref.CanDeref && AddCxTypeMustSubsumeTypeUndoIfFailed env.DisplayEnv cenv.css m overallTy.Commit g.system_FormattableString_ty)
               || (g.system_IFormattable_tcref.CanDeref && AddCxTypeMustSubsumeTypeUndoIfFailed env.DisplayEnv cenv.css m overallTy.Commit g.system_IFormattable_ty))) then

            // And if that succeeds, the result of printing is a string
            UnifyTypes cenv env m printerArgTy g.unit_ty
            UnifyTypes cenv env m printerResidueTy g.string_ty
            UnifyTypes cenv env m printerResultTy overallTy.Commit

            // Find the FormattableStringFactor.Create method in the .NET libraries
            let ad = env.eAccessRights
            let createMethodOpt =
                match TryFindIntrinsicOrExtensionMethInfo ResultCollectionSettings.AllResults cenv env m ad "Create" g.system_FormattableStringFactory_ty with
                | [x] -> Some x
                | _ -> None

            match createMethodOpt with
            | Some createMethod -> Choice2Of2 createMethod
            | None -> languageFeatureNotSupportedInLibraryError LanguageFeature.StringInterpolation m

        // ... or if that fails then may be a PrintfFormat by a type-directed rule....
        elif not (isObjTyAnyNullness g overallTy.Commit) && AddCxTypeMustSubsumeTypeUndoIfFailed env.DisplayEnv cenv.css m overallTy.Commit formatTy then

            // And if that succeeds, the printerTy and printerResultTy must be the same (there are no curried arguments)
            UnifyTypes cenv env m printerTy printerResultTy
            Choice1Of2 (false, newFormatMethod)

        else
            Choice1Of2 (true, newFormatMethod)

    let isFormattableString = (match stringKind with Choice2Of2 _ -> true | _ -> false)

    // The format string used for checking in CheckFormatStrings. This replaces interpolation holes with %P
    let printfFormatString =
        parts
        |> List.map (function
            | SynInterpolatedStringPart.String (s, _) -> s
            | SynInterpolatedStringPart.FillExpr (fillExpr, format) ->
                let alignText =
                    match fillExpr with
                    // Validate and detect ",3" part of "...{x,3}..."
                    | SynExpr.Tuple (false, args, _, _) ->
                        match args with
                        | [_; SynExpr.Const (SynConst.Int32 align, _)] -> string align
                        | _ -> errorR(Error(FSComp.SR.tcInvalidAlignmentInInterpolatedString(), m)); ""
                    | _ -> ""
                let formatText = match format with None -> "()" | Some n -> "(" + n.idText + ")"
                "%" + alignText + "P" + formatText )
        |> String.concat ""

    // Parse the format string to work out the phantom types and check for absence of '%' specifiers in FormattableString
    //
    // If FormatStringCheckContext is set (i.e. we are doing foreground checking in the IDE)
    // then we check the string twice, once to collect % positions and once to get errors.
    // The process of getting % positions doesn't process the string in a semantically accurate way
    // (but is enough to report % locations correctly), as it fetched the pieces from the
    // original source and this may include some additional characters,
    // and also doesn't raise all necessary errors
    match cenv.tcSink.CurrentSink with
    | Some sink when sink.FormatStringCheckContext.IsSome ->
        try
            let _argTys, _printerTy, _printerTupleTyRequired, _percentATys, specifierLocations, _dotnetFormatString =
                CheckFormatStrings.ParseFormatString m stringFragmentRanges g true isFormattableString sink.FormatStringCheckContext printfFormatString printerArgTy printerResidueTy printerResultTy
            for specifierLocation, numArgs in specifierLocations do
                sink.NotifyFormatSpecifierLocation(specifierLocation, numArgs)
        with _err->
            ()
    | _ -> ()

    let argTys, _printerTy, printerTupleTyRequired, percentATys, _specifierLocations, dotnetFormatString =
        try
            CheckFormatStrings.ParseFormatString m stringFragmentRanges g true isFormattableString None printfFormatString printerArgTy printerResidueTy printerResultTy
        with Failure errString ->
            error (Error(FSComp.SR.tcUnableToParseInterpolatedString errString, m))

    // Check the expressions filling the holes
    if argTys.Length <> synFillExprs.Length then
        error (Error(FSComp.SR.tcInterpolationMixedWithPercent(), m))

    match stringKind with

    // The case for $"..." used as type string and $"...%d{x}..." used as type PrintfFormat - create a PrintfFormat that captures
    // is arguments
    | Choice1Of2 (isString, newFormatMethod) ->

        UnifyTypes cenv env m printerTupleTy printerTupleTyRequired

        // Type check the expressions filling the holes

        if List.isEmpty synFillExprs then
            if isString then
                let str = mkString g m (printfFormatString.Replace("%%", "%"))
                TcPropagatingExprLeafThenConvert cenv overallTy g.string_ty env (* true *) m (fun () ->
                    str, tpenv
                )
            else
                let str = mkString g m printfFormatString
                mkCallNewFormat g m printerTy printerArgTy printerResidueTy printerResultTy printerTupleTy str, tpenv
        else
            // Type check the expressions filling the holes
            let fillExprs, tpenv = TcExprsNoFlexes cenv env m tpenv argTys synFillExprs

            if g.langVersion.SupportsFeature LanguageFeature.WarnWhenFunctionValueUsedAsInterpolatedStringArg then
                warnForFunctionValuesInFillExprs g argTys synFillExprs

            // Take all interpolated string parts and typed fill expressions
            // and convert them to typed expressions that can be used as args to System.String.Concat
            // return an empty list if there are some format specifiers that make lowering to not applicable
            let rec concatenable acc fillExprs parts =
                match fillExprs, parts with
                | [], [] ->
                    List.rev acc
                | [], SynInterpolatedStringPart.FillExpr _ :: _
                | _, [] ->
                    // This should never happen, there will always be as many typed fill expressions
                    // as there are FillExprs in the interpolated string parts
                    error(InternalError("Mismatch in interpolation expression count", m))
                | _, SynInterpolatedStringPart.String (WithTrailingStringSpecifierRemoved "", _) :: parts ->
                    // If the string is empty (after trimming %s of the end), we skip it
                    concatenable acc fillExprs parts

                | _, SynInterpolatedStringPart.String (WithTrailingStringSpecifierRemoved HasFormatSpecifier, _) :: _
                | _, SynInterpolatedStringPart.FillExpr (_, Some _) :: _
                | _, SynInterpolatedStringPart.FillExpr (SynExpr.Tuple (isStruct = false; exprs = [_; SynExpr.Const (SynConst.Int32 _, _)]), _) :: _ ->
                    // There was a format specifier like %20s{..} or {..,20} or {x:hh}, which means we cannot simply concat
                    []

                | _, SynInterpolatedStringPart.String (s & WithTrailingStringSpecifierRemoved trimmed, m) :: parts ->
                    let finalStr = trimmed.Replace("%%", "%")
                    concatenable (mkString g (shiftEnd 0 (finalStr.Length - s.Length) m) finalStr :: acc) fillExprs parts

                | fillExpr :: fillExprs, SynInterpolatedStringPart.FillExpr _ :: parts ->
                    concatenable (fillExpr :: acc) fillExprs parts

            let canLower =
                g.langVersion.SupportsFeature LanguageFeature.LowerInterpolatedStringToConcat
                && isString
                && argTys |> List.forall (isStringTy g)

            let concatenableExprs = if canLower then concatenable [] fillExprs parts else []

            match concatenableExprs with
            | [p1; p2; p3; p4] -> TcPropagatingExprLeafThenConvert cenv overallTy g.string_ty env m (fun () -> mkStaticCall_String_Concat4 g m p1 p2 p3 p4, tpenv)
            | [p1; p2; p3] -> TcPropagatingExprLeafThenConvert cenv overallTy g.string_ty env m (fun () -> mkStaticCall_String_Concat3 g m p1 p2 p3, tpenv)
            | [p1; p2] -> TcPropagatingExprLeafThenConvert cenv overallTy g.string_ty env m (fun () -> mkStaticCall_String_Concat2 g m p1 p2, tpenv)
            | [p1] -> p1, tpenv
            | _ ->

                let fillExprsBoxed = (argTys, fillExprs) ||> List.map2 (mkCallBox g m)

                let argsExpr = mkArray (g.obj_ty_withNulls, fillExprsBoxed, m)
                let percentATysExpr =
                    if percentATys.Length = 0 then
                        mkNull m (mkArrayType g g.system_Type_ty)
                    else
                        let tyExprs = percentATys |> Array.map (mkCallTypeOf g m) |> Array.toList
                        mkArray (g.system_Type_ty, tyExprs, m)

                let fmtExpr = MakeMethInfoCall cenv.amap m newFormatMethod [] [mkString g m printfFormatString; argsExpr; percentATysExpr] None

                if isString then
                    TcPropagatingExprLeafThenConvert cenv overallTy g.string_ty env (* true *) m (fun () ->
                        // Make the call to sprintf
                        mkCall_sprintf g m printerTy fmtExpr [], tpenv
                    )
                else
                    fmtExpr, tpenv

    // The case for $"..." used as type FormattableString or IFormattable
    | Choice2Of2 createFormattableStringMethod ->

        // Type check the expressions filling the holes
        let fillExprs, tpenv = TcExprsNoFlexes cenv env m tpenv argTys synFillExprs

        if g.langVersion.SupportsFeature LanguageFeature.WarnWhenFunctionValueUsedAsInterpolatedStringArg then
            warnForFunctionValuesInFillExprs g argTys synFillExprs

        let fillExprsBoxed = (argTys, fillExprs) ||> List.map2 (mkCallBox g m)

        let dotnetFormatStringExpr = mkString g m dotnetFormatString
        let argsExpr = mkArray (g.obj_ty_withNulls, fillExprsBoxed, m)

        // FormattableString are *always* turned into FormattableStringFactory.Create calls, boxing each argument
        let createExpr, _ = BuildPossiblyConditionalMethodCall cenv env NeverMutates m false createFormattableStringMethod NormalValUse [] [dotnetFormatStringExpr; argsExpr] [] None

        let resultExpr =
            if typeEquiv g overallTy.Commit g.system_IFormattable_ty then
                mkCoerceIfNeeded g g.system_IFormattable_ty g.system_FormattableString_ty createExpr
            else
                createExpr
        resultExpr, tpenv

//-------------------------------------------------------------------------
// TcConstExpr
//-------------------------------------------------------------------------

/// Check a constant expression.
and TcConstExpr cenv (overallTy: OverallTy) env m tpenv c =

    let g = cenv.g

    match c with
    | SynConst.Bytes (bytes, _, m) ->
      let actualTy = mkByteArrayTy g
      TcPropagatingExprLeafThenConvert cenv overallTy actualTy env (* true *) m <| fun ()->
       Expr.Op (TOp.Bytes bytes, [], [], m), tpenv

    | SynConst.UInt16s arr ->
      let actualTy = mkArrayType g g.uint16_ty
      TcPropagatingExprLeafThenConvert cenv overallTy actualTy env (* true *) m <| fun () ->
       Expr.Op (TOp.UInt16s arr, [], [], m), tpenv

    | SynConst.UserNum (s, suffix) ->
        let expr =
            let modName = "NumericLiteral" + suffix
            let ad = env.eAccessRights
            match ResolveLongIdentAsModuleOrNamespace cenv.tcSink cenv.amap m true OpenQualified env.eNameResEnv ad (ident (modName, m)) [] false ShouldNotifySink.Yes with
            | Result []
            | Exception _ -> error(Error(FSComp.SR.tcNumericLiteralRequiresModule modName, m))
            | Result ((_, mref, _) :: _) ->
                let expr =
                    try
                        match int32 s with
                        | 0 -> SynExpr.App (ExprAtomicFlag.Atomic, false, mkSynLidGet m [modName] "FromZero", SynExpr.Const (SynConst.Unit, m), m)
                        | 1 -> SynExpr.App (ExprAtomicFlag.Atomic, false, mkSynLidGet m [modName] "FromOne", SynExpr.Const (SynConst.Unit, m), m)
                        | i32 -> SynExpr.App (ExprAtomicFlag.Atomic, false, mkSynLidGet m [modName] "FromInt32", SynExpr.Const (SynConst.Int32 i32, m), m)
                    with _ ->
                        try
                            let i64 = int64 s
                            SynExpr.App (ExprAtomicFlag.Atomic, false, mkSynLidGet m [modName] "FromInt64", SynExpr.Const (SynConst.Int64 i64, m), m)
                        with _ ->
                            SynExpr.App (ExprAtomicFlag.Atomic, false, mkSynLidGet m [modName] "FromString", SynExpr.Const (SynConst.String (s, SynStringKind.Regular, m), m), m)

                if suffix <> "I" then
                    expr
                else
                    match ccuOfTyconRef mref with
                    | Some ccu when ccuEq ccu g.fslibCcu ->
                        SynExpr.Typed (expr, SynType.LongIdent(SynLongIdent(pathToSynLid m ["System";"Numerics";"BigInteger"], [], [None;None;None])), m)
                    | _ ->
                        expr

        TcExpr cenv overallTy env tpenv expr

    | _ ->
      TcNonPropagatingExprLeafThenConvert cenv overallTy env m (fun () ->
        let cTy = NewInferenceType g
        let c' = TcConst cenv cTy m env c
        let rec checkAttributeInMeasure ty =
            match stripTyEqns g ty with
            | TType_app(typeInstantiation= ttypes) -> ttypes |> List.iter checkAttributeInMeasure
            | TType_fun(rangeType= rangeType) -> checkAttributeInMeasure rangeType
            | TType_measure tm -> CheckUnitOfMeasureAttributes g tm
            | _ -> ()
    
        checkAttributeInMeasure cTy
        Expr.Const (c', m, cTy), cTy, tpenv)

//-------------------------------------------------------------------------
// TcAssertExpr
//-------------------------------------------------------------------------

// Check an 'assert x' expression.
and TcAssertExpr cenv overallTy env (m: range) tpenv x =
    let synm = m.MakeSynthetic() // Mark as synthetic so the language service won't pick it up.
    let callDiagnosticsExpr = SynExpr.App (ExprAtomicFlag.Atomic, false, mkSynLidGet synm ["System";"Diagnostics";"Debug"] "Assert",
                                           // wrap an extra parentheses so 'assert(x=1) isn't considered a named argument to a method call
                                           SynExpr.Paren (x, range0, None, synm), synm)

    TcExpr cenv overallTy env tpenv callDiagnosticsExpr

and TcRecdExpr cenv overallTy env tpenv (inherits, withExprOpt, synRecdFields, mWholeExpr) =
    CallExprHasTypeSink cenv.tcSink (mWholeExpr, env.NameEnv, overallTy, env.eAccessRights)
    let g = cenv.g

    let requiresCtor = (GetCtorShapeCounter env = 1) // Get special expression forms for constructors
    let haveCtor = Option.isSome inherits

    let withExprOptChecked, tpenv =
        match withExprOpt with
        | None -> None, tpenv
        | Some (origExpr, _) ->
            match inherits with
            | Some (_, _, mInherits, _, _) -> error(Error(FSComp.SR.tcInvalidRecordConstruction(), mInherits))
            | None ->
                let withExpr, tpenv = TcExpr cenv (MustEqual overallTy) env tpenv origExpr
                Some withExpr, tpenv

    let hasOrigExpr = withExprOptChecked.IsSome

    let fldsList =
        let flds =
            synRecdFields
            |> List.map (fun (SynExprRecordField (fieldName = (synLongId, isOk); expr = exprBeingAssigned)) ->
                // if we met at least one field that is not syntactically correct - raise ReportedError to transfer control to the recovery routine
                if not isOk then
                    // raising ReportedError None transfers control to the closest errorRecovery point but do not make any records into log
                    // we assume that parse errors were already reported
                    raise (ReportedError None)

                match withExprOpt, synLongId.LongIdent, exprBeingAssigned with
                | _, [ id ], _ -> ([], id), exprBeingAssigned
                | Some withExpr, lid, Some exprBeingAssigned -> TransformAstForNestedUpdates cenv env overallTy lid exprBeingAssigned withExpr
                | _ -> List.frontAndBack synLongId.LongIdent, exprBeingAssigned)

        let flds = if hasOrigExpr then GroupUpdatesToNestedFields flds else flds
        // Check if the overall type is an anon record type and if so raise an copy-update syntax error
        // let f (r: {| A: int; C: int |}) = { r with A = 1; B = 2; C = 3 }
        if isAnonRecdTy cenv.g overallTy || isStructAnonRecdTy cenv.g overallTy then
            for fld, _ in flds do
                let _, fldId = fld
                match TryFindAnonRecdFieldOfType g overallTy fldId.idText with
                | Some item ->
                    CallNameResolutionSink cenv.tcSink (fldId.idRange, env.eNameResEnv, item, emptyTyparInst, ItemOccurrence.UseInType, env.eAccessRights)
                | None -> ()
            let firstPartRange = withStartEnd mWholeExpr.Start (mkPos mWholeExpr.StartLine (mWholeExpr.StartColumn + 1)) mWholeExpr
            // Use the  left { in the expression
            errorR(Error(FSComp.SR.chkCopyUpdateSyntaxInAnonRecords(), firstPartRange))
            // Use the  right } in the expression
            let lastPartRange = withStartEnd (mkPos mWholeExpr.StartLine (mWholeExpr.EndColumn - 1)) (mkPos mWholeExpr.StartLine mWholeExpr.EndColumn) mWholeExpr
            errorR(Error(FSComp.SR.chkCopyUpdateSyntaxInAnonRecords(), lastPartRange))
            []
        else
            // If the overall type is a record type build a map of the fields
            match flds with
            | [] -> []
            | _ ->
                match BuildFieldMap cenv env hasOrigExpr overallTy flds mWholeExpr with
                | None -> []
                | Some(tinst, tcref, _, fldsList) ->

                let gtyp = mkWoNullAppTy tcref tinst
                UnifyTypes cenv env mWholeExpr overallTy gtyp

                // (#15290) For copy-and-update expressions, register the record type as a related symbol
                // so that "Find All References" on the record type includes copy-and-update usages.
                // Reported via CallRelatedSymbolSink to avoid affecting colorization or symbol info.
                if hasOrigExpr then
                    let item = Item.Types(tcref.DisplayName, [gtyp])
                    CallRelatedSymbolSink cenv.tcSink (mWholeExpr, item, RelatedSymbolUseKind.CopyAndUpdateRecord)

                [ for n, v in fldsList do
                    match v with
                    | Some v -> yield n, v
                    | None -> () ]

    let withExprInfoOpt =
        match withExprOptChecked with
        | None -> None
        | Some withExpr ->
            let withExprAddrVal, withExprAddrValExpr = mkCompGenLocal mWholeExpr "inputRecord" (if isStructTy g overallTy then mkByrefTy g overallTy else overallTy)
            Some(withExpr, withExprAddrVal, withExprAddrValExpr)

    if hasOrigExpr && not (isRecdTy g overallTy || isAnonRecdTy g overallTy) then
        errorR(Error(FSComp.SR.tcExpressionFormRequiresRecordTypes(), mWholeExpr))

    if requiresCtor || haveCtor then
        if not (isFSharpObjModelTy g overallTy) then
            // Deliberate no-recovery failure here to prevent cascading internal errors
            error(Error(FSComp.SR.tcInheritedTypeIsNotObjectModelType(), mWholeExpr))
        if not requiresCtor then
            errorR(Error(FSComp.SR.tcObjectConstructionExpressionCanOnlyImplementConstructorsInObjectModelTypes(), mWholeExpr))
    else
        if isNil synRecdFields then
            let errorInfo = if hasOrigExpr then FSComp.SR.tcEmptyCopyAndUpdateRecordInvalid() else FSComp.SR.tcEmptyRecordInvalid()
            error(Error(errorInfo, mWholeExpr))

        if isFSharpObjModelTy g overallTy then errorR(Error(FSComp.SR.tcTypeIsNotARecordTypeNeedConstructor(), mWholeExpr))
        elif not (isRecdTy g overallTy || fldsList.IsEmpty) then errorR(Error(FSComp.SR.tcTypeIsNotARecordType(), mWholeExpr))

    let superInitExprOpt , tpenv =
        match inherits, GetSuperTypeOfType g cenv.amap mWholeExpr overallTy with
        | Some (superTy, arg, m, _, _), Some realSuperTy ->
            // Constructor expression, with an explicit 'inheritedTys clause. Check the inherits clause.
            let e, tpenv = TcExpr cenv (MustEqual realSuperTy) env tpenv (SynExpr.New (true, superTy, arg, m))
            Some e, tpenv
        | None, Some realSuperTy when requiresCtor ->
            // Constructor expression, No 'inherited' clause, hence look for a default constructor
            let e, tpenv = TcNewExpr cenv env tpenv realSuperTy None true (SynExpr.Const (SynConst.Unit, mWholeExpr)) mWholeExpr
            Some e, tpenv
        | None, _ ->
            None, tpenv
        | _, None ->
            errorR(InternalError("Unexpected failure in getting super type", mWholeExpr))
            None, tpenv

    if fldsList.IsEmpty && isTyparTy g overallTy || isAnonRecdTy g overallTy then
        SolveTypeAsError env.DisplayEnv cenv.css mWholeExpr overallTy
        mkDefault (mWholeExpr, overallTy), tpenv
    else
        let expr, tpenv = TcRecordConstruction cenv overallTy false env tpenv withExprInfoOpt overallTy fldsList mWholeExpr

        let expr =
            match superInitExprOpt  with
            | _ when isStructTy g overallTy -> expr
            | Some superInitExpr  -> mkCompGenSequential mWholeExpr superInitExpr  expr
            | None -> expr
        expr, tpenv

and CheckAnonRecdExprDuplicateFields (elems: Ident array) =
    elems |> Array.iteri (fun i (uc1: Ident) ->
        elems |> Array.iteri (fun j (uc2: Ident) ->
            if j > i && uc1.idText = uc2.idText then
               errorR(Error (FSComp.SR.tcAnonRecdDuplicateFieldId(uc1.idText), uc1.idRange))))

// Check '{| .... |}'
and TcAnonRecdExpr cenv (overallTy: TType) env tpenv (isStruct, optOrigSynExpr, unsortedFieldIdsAndSynExprsGiven, mWholeExpr) =
    match optOrigSynExpr with
    | None ->
        TcNewAnonRecdExpr cenv overallTy env tpenv (isStruct, unsortedFieldIdsAndSynExprsGiven, mWholeExpr)

    | Some orig ->
        // Ideally we should also check for duplicate field IDs in the TcCopyAndUpdateAnonRecdExpr case, but currently the logic is too complex to guarantee a proper error reporting
        // So here we error instead errorR to avoid cascading  internal errors
        unsortedFieldIdsAndSynExprsGiven
        |> List.countBy (fun (fId, _, _) -> textOfLid fId.LongIdent)
        |> List.iter (fun (label, count) ->
            if count > 1 then error (Error (FSComp.SR.tcAnonRecdDuplicateFieldId(label), mWholeExpr)))

        TcCopyAndUpdateAnonRecdExpr cenv overallTy env tpenv (isStruct, orig, unsortedFieldIdsAndSynExprsGiven, mWholeExpr)

and TcNewAnonRecdExpr cenv (overallTy: TType) env tpenv (isStruct, unsortedFieldIdsAndSynExprsGiven, mWholeExpr) =

    let g = cenv.g
    let unsortedFieldSynExprsGiven = unsortedFieldIdsAndSynExprsGiven |> List.map (fun (_, _, fieldExpr) -> fieldExpr)
    let unsortedFieldIds = unsortedFieldIdsAndSynExprsGiven |> List.map (fun (synLongIdent, _, _) -> synLongIdent.LongIdent[0]) |> List.toArray
    let anonInfo, sortedFieldTys = UnifyAnonRecdTypeAndInferCharacteristics env.eContextInfo cenv env.DisplayEnv mWholeExpr overallTy isStruct unsortedFieldIds

    if unsortedFieldIds.Length > 1 then
        CheckAnonRecdExprDuplicateFields unsortedFieldIds

    // Sort into canonical order
    let sortedIndexedArgs =
        unsortedFieldIdsAndSynExprsGiven
        |> List.indexed
        |> List.sortBy (fun (i,_) -> unsortedFieldIds[i].idText)

    // Map from sorted indexes to unsorted indexes
    let sigma = sortedIndexedArgs |> List.map fst |> List.toArray
    let sortedFieldExprs = sortedIndexedArgs |> List.map snd

    sortedFieldExprs |> List.iteri (fun j (synLongIdent, _, _) ->
        let m = rangeOfLid synLongIdent.LongIdent
        let item = Item.AnonRecdField(anonInfo, sortedFieldTys, j, m)
        CallNameResolutionSink cenv.tcSink (m, env.NameEnv, item, emptyTyparInst, ItemOccurrence.Use, env.eAccessRights))

    let unsortedFieldTys =
        sortedFieldTys
        |> List.indexed
        |> List.sortBy (fun (sortedIdx, _) -> sigma[sortedIdx])
        |> List.map snd

    let flexes = unsortedFieldTys |> List.map (fun _ -> true)

    let unsortedCheckedArgs, tpenv = TcExprsWithFlexes cenv env mWholeExpr tpenv flexes unsortedFieldTys unsortedFieldSynExprsGiven

    mkAnonRecd g mWholeExpr anonInfo unsortedFieldIds unsortedCheckedArgs unsortedFieldTys, tpenv

and TcCopyAndUpdateAnonRecdExpr cenv (overallTy: TType) env tpenv (isStruct, (origExpr, blockSeparator), unsortedFieldIdsAndSynExprsGiven, mWholeExpr) =
    // The fairly complex case '{| origExpr with X = 1; Y = 2 |}'
    // The origExpr may be either a record or anonymous record.
    // The origExpr may be either a struct or not.
    // All the properties of origExpr are copied across except where they are overridden.
    // The result is a field-sorted anonymous record.
    //
    // Unlike in the case of record type copy-and-update we do _not_ assume that the origExpr has the same type as the overall expression.
    // Unlike in the case of record type copy-and-update {| a with X = 1 |} does not force a.X to exist or have had type 'int'

    let g = cenv.g
    let origExprTy = NewInferenceType g
    let origExprChecked, tpenv = TcExpr cenv (MustEqual origExprTy) env tpenv origExpr
    let oldv, oldve = mkCompGenLocal mWholeExpr "inputRecord" origExprTy
    let mOrigExpr = origExpr.Range

    if not (isAppTy g origExprTy || isAnonRecdTy g origExprTy) then
        error (Error (FSComp.SR.tcCopyAndUpdateNeedsRecordType(), mOrigExpr))

    // Expand expressions with respect to potential nesting
    let unsortedFieldIdsAndSynExprsGiven =
        unsortedFieldIdsAndSynExprsGiven
        |> List.map (fun (synLongIdent, _, exprBeingAssigned) ->
            match synLongIdent.LongIdent with
            | [] -> error(Error(FSComp.SR.nrUnexpectedEmptyLongId(), mWholeExpr))
            | [ id ] -> ([], id), Some exprBeingAssigned
            | lid -> TransformAstForNestedUpdates cenv env origExprTy lid exprBeingAssigned (origExpr, blockSeparator))
        |> GroupUpdatesToNestedFields

    let unsortedFieldSynExprsGiven = unsortedFieldIdsAndSynExprsGiven |> List.choose snd

    let origExprIsStruct =
        match tryDestAnonRecdTy g origExprTy with
        | ValueSome (anonInfo, _) -> evalTupInfoIsStruct anonInfo.TupInfo
        | ValueNone ->
            let tcref, _ = destAppTy g origExprTy
            tcref.IsStructOrEnumTycon

    let wrap, oldveaddr, _readonly, _writeonly =
        mkExprAddrOfExpr g origExprIsStruct false NeverMutates oldve None mOrigExpr

    // Put all the expressions in unsorted order. The new bindings come first. The origin of each is tracked using
    ///   - Choice1Of2 for a new binding
    ///   - Choice2Of2 for a binding coming from the original expression
    let unsortedIdAndExprsAll =
        [|
            for (_, id), e in unsortedFieldIdsAndSynExprsGiven do
                yield (id, Choice1Of2 e)
            match tryDestAnonRecdTy g origExprTy with
            | ValueSome (anonInfo, tinst) ->
                for i, id in Array.indexed anonInfo.SortedIds do
                    yield id, Choice2Of2 (mkAnonRecdFieldGetViaExprAddr (anonInfo, oldveaddr, tinst, i, mOrigExpr))
            | ValueNone ->
                match tryAppTy g origExprTy with
                | ValueSome(tcref, tinst) when tcref.IsRecordTycon ->
                    let fspecs = tcref.Deref.TrueInstanceFieldsAsList
                    for fspec in fspecs do
                        yield fspec.Id, Choice2Of2 (mkRecdFieldGetViaExprAddr (oldveaddr, tcref.MakeNestedRecdFieldRef fspec, tinst, mOrigExpr))
                | _ ->
                    error (Error (FSComp.SR.tcCopyAndUpdateNeedsRecordType(), mOrigExpr))
        |]
        |> Array.distinctBy (fst >> textOfId)

    let unsortedFieldIdsAll = Array.map fst unsortedIdAndExprsAll

    let anonInfo, sortedFieldTysAll = UnifyAnonRecdTypeAndInferCharacteristics env.eContextInfo cenv env.DisplayEnv mWholeExpr overallTy isStruct unsortedFieldIdsAll

    let sortedIndexedFieldsAll = unsortedIdAndExprsAll |> Array.indexed |> Array.sortBy (snd >> fst >> textOfId)

    // map from sorted indexes to unsorted indexes
    let sigma = Array.map fst sortedIndexedFieldsAll

    let sortedFieldsAll = Array.map snd sortedIndexedFieldsAll

    // Report _all_ identifiers to name resolution. We should likely just report the ones
    // that are explicit in source code.
    sortedFieldsAll |> Array.iteri (fun j (fieldId, expr) ->
        match expr with
        | Choice1Of2 _ ->
            let item = Item.AnonRecdField(anonInfo, sortedFieldTysAll, j, fieldId.idRange)
            CallNameResolutionSink cenv.tcSink (fieldId.idRange, env.NameEnv, item, emptyTyparInst, ItemOccurrence.Use, env.eAccessRights)
        | Choice2Of2 _ -> ())

    let unsortedFieldTysAll =
        sortedFieldTysAll
        |> List.indexed
        |> List.sortBy (fun (sortedIdx, _) -> sigma[sortedIdx])
        |> List.map snd

    let unsortedFieldTysGiven =
        unsortedFieldTysAll
        |> List.take unsortedFieldIdsAndSynExprsGiven.Length

    let flexes = unsortedFieldTysGiven |> List.map (fun _ -> true)

    // Check the expressions in unsorted order
    let unsortedFieldExprsGiven, tpenv =
        TcExprsWithFlexes cenv env mWholeExpr tpenv flexes unsortedFieldTysGiven unsortedFieldSynExprsGiven

    let unsortedFieldExprsGiven = unsortedFieldExprsGiven |> List.toArray

    let unsortedFieldIds =
        unsortedIdAndExprsAll
        |> Array.map fst

    let unsortedFieldExprs =
        unsortedIdAndExprsAll
        |> Array.mapi (fun unsortedIdx (_, expr) ->
            match expr with
            | Choice1Of2 _ -> unsortedFieldExprsGiven[unsortedIdx]
            | Choice2Of2 subExpr -> UnifyTypes cenv env mOrigExpr (tyOfExpr g subExpr) unsortedFieldTysAll[unsortedIdx]; subExpr)
        |> List.ofArray

    // Permute the expressions to sorted order in the TAST
    let expr = mkAnonRecd g mWholeExpr anonInfo unsortedFieldIds unsortedFieldExprs unsortedFieldTysAll
    let expr = wrap expr

    // Bind the original expression
    let expr = mkCompGenLet mOrigExpr oldv origExprChecked expr
    expr, tpenv

and TcForEachExpr cenv overallTy env tpenv (seqExprOnly, isFromSource, synPat, synEnumExpr, synBodyExpr, mWholeExpr, spFor, spIn, m) =

    let g = cenv.g

    assert isFromSource
    if seqExprOnly then warning (Error(FSComp.SR.tcExpressionRequiresSequence(), m))

    let synEnumExpr =
        match RewriteRangeExpr synEnumExpr with
        | Some e -> e
        | None -> synEnumExpr

    let tryGetOptimizeSpanMethodsAux g m ty isReadOnlySpan =
        match (if isReadOnlySpan then tryDestReadOnlySpanTy g m ty else tryDestSpanTy g m ty) with
        | Some(_, destTy) ->
            match TryFindFSharpSignatureInstanceGetterProperty cenv env m "Item" ty [ g.int32_ty; (if isReadOnlySpan then mkInByrefTy g destTy else mkByrefTy g destTy) ],
                  TryFindFSharpSignatureInstanceGetterProperty cenv env m "Length" ty [ g.int32_ty ] with
            | Some(itemPropInfo), Some(lengthPropInfo) ->
                ValueSome(itemPropInfo.GetterMethod, lengthPropInfo.GetterMethod, isReadOnlySpan)
            | _ ->
                ValueNone
        | _ ->
            ValueNone

    let tryGetOptimizeSpanMethods g m ty =
        let result = tryGetOptimizeSpanMethodsAux g m ty false
        if result.IsSome then
            result
        else
            tryGetOptimizeSpanMethodsAux g m ty true

    UnifyTypes cenv env mWholeExpr overallTy.Commit g.unit_ty

    let mPat = synPat.Range
    let mBodyExpr = synBodyExpr.Range
    let mEnumExpr = synEnumExpr.Range
    let mFor = match spFor with DebugPointAtFor.Yes mStart -> mStart | DebugPointAtFor.No -> mEnumExpr
    let mIn = match spIn with DebugPointAtInOrTo.Yes mStart -> mStart | DebugPointAtInOrTo.No -> mBodyExpr
    let spEnumExpr = DebugPointAtBinding.Yes mEnumExpr
    let spForBind = match spFor with DebugPointAtFor.Yes m -> DebugPointAtBinding.Yes m | DebugPointAtFor.No -> DebugPointAtBinding.NoneAtSticky
    let spInAsWhile = match spIn with DebugPointAtInOrTo.Yes m -> DebugPointAtWhile.Yes m | DebugPointAtInOrTo.No -> DebugPointAtWhile.No

    // Check the expression being enumerated
    let enumExpr, enumExprTy, tpenv =
        let env = { env with eIsControlFlow = false }
        TcExprOfUnknownType cenv env tpenv synEnumExpr

    // Depending on its type we compile it in different ways
    let enumElemTy, bodyExprFixup, overallExprFixup, iterationTechnique =
        match stripDebugPoints enumExpr with

        // optimize 'for i in n .. m do'
        | Expr.App (Expr.Val (vref, _, _), _, [tyarg], [startExpr;finishExpr], _)
             when valRefEq g vref g.range_op_vref && typeEquiv g tyarg g.int_ty ->
               (g.int32_ty, (fun _ x -> x), id, Choice1Of3 (startExpr, finishExpr))

        // optimize 'for i in arr do'
        | _ when isArray1DTy g enumExprTy ->
            let arrVar, arrExpr = mkCompGenLocal mEnumExpr "arr" enumExprTy
            let idxVar, idxExpr = mkCompGenLocal mPat "idx" g.int32_ty
            let elemTy = destArrayTy g enumExprTy

            // Evaluate the array index lookup
            let bodyExprFixup elemVar bodyExpr = mkInvisibleLet mIn elemVar (mkLdelem g mIn elemTy arrExpr idxExpr) bodyExpr

            // Evaluate the array expression once and put it in arrVar
            let overallExprFixup overallExpr = mkLet spForBind mFor arrVar enumExpr overallExpr

            // Ask for a loop over integers for the given range
            (elemTy, bodyExprFixup, overallExprFixup, Choice2Of3 (idxVar, mkZero g mFor, mkDecr g mFor (mkLdlen g mFor arrExpr)))

        | _ ->
            // try optimize 'for i in span do' for span or readonlyspan
            match tryGetOptimizeSpanMethods g mWholeExpr enumExprTy with
            | ValueSome(getItemMethInfo, getLengthMethInfo, isReadOnlySpan) ->
                let tcVal = LightweightTcValForUsingInBuildMethodCall g
                let spanVar, spanExpr = mkCompGenLocal mEnumExpr "span" enumExprTy
                let idxVar, idxExpr = mkCompGenLocal mPat "idx" g.int32_ty
                let _, elemTy = if isReadOnlySpan then destReadOnlySpanTy g mWholeExpr enumExprTy else destSpanTy g mWholeExpr enumExprTy
                let elemAddrTy = if isReadOnlySpan then mkInByrefTy g elemTy else mkByrefTy g elemTy

                // Evaluate the span index lookup
                let bodyExprFixup elemVar bodyExpr =
                    let elemAddrVar, _ = mkCompGenLocal mIn "addr" elemAddrTy
                    let e = mkInvisibleLet mIn elemVar (mkAddrGet mIn (mkLocalValRef elemAddrVar)) bodyExpr
                    let getItemCallExpr, _ = BuildMethodCall tcVal g cenv.amap PossiblyMutates mWholeExpr true getItemMethInfo ValUseFlag.NormalValUse [] [ spanExpr ] [ idxExpr ] None
                    mkInvisibleLet mIn elemAddrVar getItemCallExpr e

                // Evaluate the span expression once and put it in spanVar
                let overallExprFixup overallExpr = mkLet spForBind mFor spanVar enumExpr overallExpr

                let getLengthCallExpr, _ = BuildMethodCall tcVal g cenv.amap PossiblyMutates mWholeExpr true getLengthMethInfo ValUseFlag.NormalValUse [] [ spanExpr ] [] None

                // Ask for a loop over integers for the given range
                (elemTy, bodyExprFixup, overallExprFixup, Choice2Of3 (idxVar, mkZero g mFor, mkDecr g mFor getLengthCallExpr))

            | _ ->
                let enumerableVar, enumerableExprInVar = mkCompGenLocal mEnumExpr "inputSequence" enumExprTy
                let enumeratorVar, enumeratorExpr, _, enumElemTy, getEnumExpr, getEnumTy, guardExpr, _, currentExpr =
                    AnalyzeArbitraryExprAsEnumerable cenv env true mEnumExpr enumExprTy enumerableExprInVar
                (enumElemTy, (fun _ x -> x), id, Choice3Of3(enumerableVar, enumeratorVar, enumeratorExpr, getEnumExpr, getEnumTy, guardExpr, currentExpr))

    let pat, _, vspecs, envinner, tpenv =
        let env = { env with eIsControlFlow = false }
        TcMatchPattern cenv enumElemTy env tpenv synPat None TcTrueMatchClause.No

    let elemVar, pat =
        // nice: don't introduce awful temporary for r.h.s. in the 99% case where we know what we're binding it to
        match pat with
        | TPat_as (pat1, PatternValBinding(v, GeneralizedType([], _)), _) ->
              v, pat1
        | _ ->
              let tmp, _ = mkCompGenLocal pat.Range "forLoopVar" enumElemTy
              tmp, pat

    // Check the body of the loop
    let bodyExpr, tpenv =
        let envinner = { envinner with eIsControlFlow = true }
        TcStmt cenv envinner tpenv synBodyExpr

    // Add the pattern match compilation
    let bodyExpr =
        let valsDefinedByMatching = ListSet.remove valEq elemVar vspecs
        CompilePatternForMatch
            cenv env synEnumExpr.Range pat.Range false IgnoreWithWarning (elemVar, [], None)
            [MatchClause(pat, None, TTarget(valsDefinedByMatching, bodyExpr, None), mIn)]
            enumElemTy
            overallTy.Commit

    // Apply the fixup to bind the elemVar if needed
    let bodyExpr = bodyExprFixup elemVar bodyExpr

    // Build the overall loop
    let overallExpr =

        match iterationTechnique with

        // Build iteration as a for loop
        | Choice1Of3(startExpr, finishExpr) ->
            mkFastForLoop g (spFor, spIn, mWholeExpr, elemVar, startExpr, true, finishExpr, bodyExpr)

        // Build iteration as a for loop with a specific index variable that is not the same as the elemVar
        | Choice2Of3(idxVar, startExpr, finishExpr) ->
            mkFastForLoop g (DebugPointAtFor.No, spIn, mWholeExpr, idxVar, startExpr, true, finishExpr, bodyExpr)

        // Build iteration as a while loop with a try/finally disposal
        | Choice3Of3(enumerableVar, enumeratorVar, _, getEnumExpr, _, guardExpr, currentExpr) ->

            // This compiled for must be matched EXACTLY by CompiledForEachExpr
            mkLet spForBind mFor enumerableVar enumExpr
              (mkLet spEnumExpr mFor enumeratorVar getEnumExpr
                   (mkTryFinally g
                       (mkWhile g
                           (spInAsWhile,
                            WhileLoopForCompiledForEachExprMarker, guardExpr,
                            mkInvisibleLet mIn elemVar currentExpr bodyExpr,
                            mFor),
                        BuildDisposableCleanup cenv env mWholeExpr enumeratorVar,
                        mFor, g.unit_ty, DebugPointAtTry.No, DebugPointAtFinally.No)))

    let overallExpr = overallExprFixup overallExpr
    overallExpr, tpenv

//-------------------------------------------------------------------------
// TcQuotationExpr
//-------------------------------------------------------------------------

and TcQuotationExpr cenv overallTy env tpenv (_oper, raw, ast, isFromQueryExpression, m) =

    let g = cenv.g

    let astTy = NewInferenceType g

    // Assert the overall type for the domain of the quotation template
    UnifyTypes cenv env m overallTy.Commit (if raw then mkRawQuotedExprTy g else mkQuotedExprTy g astTy)

    // Check the expression
    let expr, tpenv = TcExpr cenv (MustEqual astTy) env tpenv ast

    // Wrap the expression
    let expr = Expr.Quote (expr, ref None, isFromQueryExpression, m, overallTy.Commit)

    // Coerce it if needed
    let expr = if raw then mkCoerceExpr(expr, (mkRawQuotedExprTy g), m, (tyOfExpr g expr)) else expr

    // We serialize the quoted expression to bytes in IlxGen after type inference etc. is complete.
    expr, tpenv

/// When checking sequence of function applications,
/// type applications and dot-notation projections, first extract known
/// type information from the applications.
///
/// 'overalltyR is the type expected for the entire chain of expr + lookups.
/// 'exprtyR is the type of the expression on the left of the lookup chain.
///
/// We propagate information from the expected overall type 'overalltyR. The use
/// of function application syntax unambiguously implies that 'overalltyR is a function type.
and Propagate (cenv: cenv) (overallTy: OverallTy) (env: TcEnv) tpenv (expr: ApplicableExpr) exprTy delayed =

    let g = cenv.g

    let rec propagate isAddrOf delayedList mExpr exprTy =
        match delayedList with
        | [] ->

            if not (isNil delayed) then

                // We generate a tag inference parameter to the return type for "&x" and 'NativePtr.toByRef'
                // See RFC FS-1053.md
                let exprTy =
                    if isAddrOf && isByrefTy g exprTy then
                        mkByrefTyWithInference g (destByrefTy g exprTy) (NewByRefKindInferenceType g mExpr)
                    elif isByrefTy g exprTy then
                        // Implicit dereference on byref on return
                        if isByrefTy g overallTy.Commit then
                             errorR(Error(FSComp.SR.tcByrefReturnImplicitlyDereferenced(), mExpr))
                        destByrefTy g exprTy
                    else
                        exprTy

                // at the end of the application chain allow coercion introduction
                UnifyOverallTypeAndRecover cenv env mExpr overallTy exprTy

        | DelayedDot :: _
        | DelayedSet _ :: _
        | DelayedDotLookup _ :: _ -> ()
        | DelayedTypeApp (_, _mTypeArgs, mExprAndTypeArgs) :: delayedList' ->
            // Note this case should not occur: would eventually give an "Unexpected type application" error in TcDelayed
            propagate isAddrOf delayedList' mExprAndTypeArgs exprTy

        | DelayedApp (atomicFlag, isSugar, synLeftExprOpt, synArg, mExprAndArg) :: delayedList' ->
            let denv = env.DisplayEnv
            match UnifyFunctionTypeUndoIfFailed cenv denv mExpr exprTy with
            | ValueSome (_, resultTy) ->

                // We add tag parameter to the return type for "&x" and 'NativePtr.toByRef'
                // See RFC FS-1053.md
                let isAddrOf =
                    match expr with
                    | ApplicableExpr(expr=Expr.App (Expr.Val (vref, _, _), _, _, [], _))
                        when (valRefEq g vref g.addrof_vref ||
                              valRefEq g vref g.nativeptr_tobyref_vref) -> true
                    | _ -> false

                propagate isAddrOf delayedList' mExprAndArg resultTy

            | _ ->
                let mArg = synArg.Range
                match synArg with
                // async { ... }
                // seq { ... }
                | SynExpr.ComputationExpr _ -> ()

                // async { }
                // seq { }
                | SynExpr.Record (None, None, [], _) when g.langVersion.SupportsFeature LanguageFeature.EmptyBodiedComputationExpressions -> ()

                // expr[idx]
                // expr[idx1, idx2]
                // expr[idx1..]
                // expr[..idx1]
                // expr[idx1..idx2]
                | SynExpr.ArrayOrListComputed(false, _, _) ->
                    let isAdjacent = isAdjacentListExpr isSugar atomicFlag synLeftExprOpt synArg
                    if isAdjacent && g.langVersion.SupportsFeature LanguageFeature.IndexerNotationWithoutDot then
                        // This is the non-error path
                        ()
                    else
                        // This is the error path. The error we give depends on what's enabled.
                        //
                        // First, 'delayed' is about to be dropped on the floor, do rudimentary checking to get name resolutions in its body
                        RecordNameAndTypeResolutionsDelayed cenv env tpenv delayed
                        let vName =
                            match expr.Expr with
                            | Expr.Val (d, _, _) -> Some d.DisplayName
                            | _ -> None
                        if isAdjacent then
                            if IsIndexerType g cenv.amap expr.Type then
                                if g.langVersion.IsExplicitlySpecifiedAs50OrBefore() then
                                    error (NotAFunctionButIndexer(denv, overallTy.Commit, vName, mExpr, mArg, false))
                                match vName with
                                | Some nm ->
                                    error(Error(FSComp.SR.tcNotAFunctionButIndexerNamedIndexingNotYetEnabled(nm, nm), mExprAndArg))
                                | _ ->
                                    error(Error(FSComp.SR.tcNotAFunctionButIndexerIndexingNotYetEnabled(), mExprAndArg))
                            else
                                match vName with
                                | Some nm ->
                                    error(Error(FSComp.SR.tcNotAnIndexerNamedIndexingNotYetEnabled(nm), mExprAndArg))
                                | _ ->
                                    error(Error(FSComp.SR.tcNotAnIndexerIndexingNotYetEnabled(), mExprAndArg))
                        else
                            if IsIndexerType g cenv.amap expr.Type then
                                let old = not (g.langVersion.SupportsFeature LanguageFeature.IndexerNotationWithoutDot)
                                error (NotAFunctionButIndexer(denv, overallTy.Commit, vName, mExpr, mArg, old))
                            else
                                error (NotAFunction(denv, overallTy.Commit, mExpr, mArg))

                // f x  (where 'f' is not a function)
                | _ ->
                    // 'delayed' is about to be dropped on the floor, first do rudimentary checking to get name resolutions in its body
                    RecordNameAndTypeResolutionsDelayed cenv env tpenv delayed
                    error (NotAFunction(denv, overallTy.Commit, mExpr, mArg))

    propagate false delayed expr.Range exprTy

and PropagateThenTcDelayed cenv (overallTy: OverallTy) env tpenv mExpr expr exprTy (atomicFlag: ExprAtomicFlag) delayed =
    Propagate cenv overallTy env tpenv expr exprTy delayed
    TcDelayed cenv overallTy env tpenv mExpr expr exprTy atomicFlag delayed

/// Typecheck "expr ... " constructs where "..." is a sequence of applications,
/// type applications and dot-notation projections.
and TcDelayed cenv (overallTy: OverallTy) env tpenv mExpr expr exprTy (atomicFlag: ExprAtomicFlag) delayed =

    let g = cenv.g

    // OK, we've typechecked the thing on the left of the delayed lookup chain.
    // We can now record for posterity the type of this expression and the location of the expression.
    if (atomicFlag = ExprAtomicFlag.Atomic) then
        CallExprHasTypeSink cenv.tcSink (mExpr, env.NameEnv, exprTy, env.eAccessRights)
    else
        CallExprHasTypeSinkSynthetic cenv.tcSink (mExpr, env.NameEnv, exprTy, env.eAccessRights)

    match delayed with
    | []
    | DelayedDot :: _ ->
        // at the end of the application chain allow coercion introduction
        UnifyOverallType cenv env mExpr overallTy exprTy
        let expr2 = TcAdjustExprForTypeDirectedConversions cenv overallTy exprTy env (* true  *) mExpr expr.Expr
        expr2, tpenv

    // Expr.M (args) where x.M is a .NET method or index property
    // expr.M<tyargs>(args) where x.M is a .NET method or index property
    // expr.M where x.M is a .NET method or index property
    | DelayedDotLookup (longId, mDotLookup) :: otherDelayed ->
        TcLookupThen cenv overallTy env tpenv mExpr expr.Expr exprTy longId otherDelayed mDotLookup

    // f x
    | DelayedApp (atomicFlag, isSugar, synLeftExpr, synArg, mExprAndArg) :: otherDelayed ->
        TcApplicationThen cenv overallTy env tpenv mExprAndArg synLeftExpr expr exprTy synArg atomicFlag isSugar otherDelayed

    // f<tyargs>
    | DelayedTypeApp (_, mTypeArgs, _mExprAndTypeArgs) :: _ ->
        error(Error(FSComp.SR.tcUnexpectedTypeArguments(), mTypeArgs))

    | DelayedSet (synExpr2, mStmt) :: otherDelayed ->
        if not (isNil otherDelayed) then error(Error(FSComp.SR.tcInvalidAssignment(), mExpr))
        UnifyTypes cenv env mExpr overallTy.Commit g.unit_ty
        let expr = expr.Expr
        let _wrap, exprAddress, _readonly, _writeonly = mkExprAddrOfExpr g true false DefinitelyMutates expr None mExpr
        let vTy = tyOfExpr g expr
        // Always allow subsumption on assignment to fields
        let expr2, tpenv = TcExprFlex cenv true false vTy env tpenv synExpr2
        let v, _ve = mkCompGenLocal mExpr "addr" (mkByrefTy g vTy)
        mkCompGenLet mStmt v exprAddress (mkAddrSet mStmt (mkLocalValRef v) expr2), tpenv

/// Convert the delayed identifiers to a dot-lookup.
///
/// TcItemThen: For StaticItem [.Lookup], mPrior is the range of StaticItem
/// TcLookupThen: For expr.InstanceItem [.Lookup], mPrior is the range of expr.InstanceItem
and delayRest rest mPrior delayed =
    match rest with
    | [] -> delayed
    | longId ->
        let mPriorAndLongId = unionRanges mPrior (rangeOfLid longId)
        DelayedDotLookup (rest, mPriorAndLongId) :: delayed

/// Typecheck "nameof" expressions
and TcNameOfExpr (cenv: cenv) env tpenv (synArg: SynExpr) =

    let g = cenv.g

    let rec stripParens expr =
        match expr with
        | SynExpr.Paren(expr, _, _, _) -> stripParens expr
        | _ -> expr

    let cleanSynArg = stripParens synArg
    let m = cleanSynArg.Range
    let rec check overallTyOpt resultOpt expr (delayed: DelayedItem list) =
        match expr with
        | LongOrSingleIdent (false, SynLongIdent(longId, _, trivia), _, _) ->

            let ad = env.eAccessRights
            let result = defaultArg resultOpt (List.last longId)

            // Demangle back to source operator name if the lengths in the ranges indicate the
            // original source range matches exactly
            let result =
                match List.tryLast trivia |> Option.bind id with
                | Some (IdentTrivia.OriginalNotation(text = text))
                | Some (IdentTrivia.OriginalNotationWithParen(text = text)) -> ident(text, result.idRange)
                | _ ->
                    if IsLogicalOpName result.idText then
                        let demangled = ConvertValLogicalNameToDisplayNameCore result.idText
                        if demangled.Length = result.idRange.EndColumn - result.idRange.StartColumn then
                            ident(demangled, result.idRange)
                        else result
                    else result

            // Nameof resolution resolves to a symbol and in general we make that the same symbol as
            // would resolve if the long ident was used as an expression at the given location.
            //
            // So we first check if the first identifier resolves as an expression, if so commit and resolve.
            //
            // However we don't commit for a type names - nameof allows 'naked' type names and thus all type name
            // resolutions are checked separately in the next step.
            let typeNameResInfo = GetLongIdentTypeNameInfo delayed
            let nameResolutionResult = ResolveLongIdentAsExprAndComputeRange cenv.tcSink cenv.nameResolver (rangeOfLid longId) ad env.eNameResEnv typeNameResInfo longId None
            let resolvesAsExpr =
                match nameResolutionResult with
                | Result (_, item, _, _, _ as res)
                    when
                         (match item with
                          | Item.DelegateCtor _
                          | Item.CtorGroup _ -> false
                          | Item.Types _ when delayed.IsEmpty ->
                              match delayed with
                              | [] | [DelayedTypeApp _] -> false
                              | _ -> true
                          | _ -> true) ->
                    let overallTy = match overallTyOpt with None -> MustEqual (NewInferenceType g) | Some t -> t
                    let _, _ = TcItemThen cenv overallTy env tpenv res None delayed
                    true
                | _ ->
                    false
            if resolvesAsExpr then result else

            // If it's not an expression then try to resolve it as a type name
            let resolvedToTypeName =
                if (match delayed with [DelayedTypeApp _] | [] -> true | _ -> false) then
                    let (TypeNameResolutionInfo(_, staticArgsInfo)) = GetLongIdentTypeNameInfo delayed
                    match ResolveTypeLongIdent cenv.tcSink cenv.nameResolver ItemOccurrence.UseInAttribute OpenQualified env.eNameResEnv ad longId staticArgsInfo PermitDirectReferenceToGeneratedType.No with
                    | Result (tinstEnclosing, tcref, inst) when IsEntityAccessible cenv.amap m ad tcref ->
                        match delayed with
                        | [DelayedTypeApp (tyargs, _, mExprAndTypeArgs)] ->
                            TcTypeApp cenv NewTyparsOK CheckCxs ItemOccurrence.UseInType env tpenv mExprAndTypeArgs tcref tinstEnclosing tyargs inst |> ignore
                        | _ -> ()
                        true // resolved to a type name, done with checks
                    | _ ->
                        false
                else
                    false
            if resolvedToTypeName then result else

            // If it's not an expression or type name then resolve it as a module
            let resolvedToModuleOrNamespaceName =
                if delayed.IsEmpty then
                    let id,rest = List.headAndTail longId
                    match ResolveLongIdentAsModuleOrNamespace cenv.tcSink cenv.amap m true OpenQualified env.eNameResEnv ad id rest true ShouldNotifySink.Yes with
                    | Result modref when delayed.IsEmpty && modref |> List.exists (p23 >> IsEntityAccessible cenv.amap m ad) ->
                        true // resolved to a module or namespace, done with checks
                    | _ ->
                        false
                else
                    false
            if resolvedToModuleOrNamespaceName then result else

            ForceRaise nameResolutionResult |> ignore
            // If that didn't give an exception then raise a generic error
            error (Error(FSComp.SR.expressionHasNoName(), m))

        // expr<tyargs> allowed, even with qualifications
        | SynExpr.TypeApp (hd, _, types, _, _, _, m) ->
            check overallTyOpt resultOpt hd (DelayedTypeApp(types, m, m) :: delayed)

        // expr.ID allowed
        | SynExpr.DotGet (hd, _, SynLongIdent(longId, _, _), _) ->
            let result = defaultArg resultOpt (List.last longId)
            check overallTyOpt (Some result) hd ((DelayedDotLookup (longId, expr.Range)) :: delayed)

        // "(expr)" allowed with no subsequent qualifications
        | SynExpr.Paren(expr, _, _, _) when delayed.IsEmpty && overallTyOpt.IsNone ->
            check overallTyOpt resultOpt expr delayed

        // expr : type" allowed with no subsequent qualifications
        | SynExpr.Typed (synBodyExpr, synType, _) when delayed.IsEmpty && overallTyOpt.IsNone ->
            let tgtTy, _tpenv = TcTypeAndRecover cenv NewTyparsOK CheckCxs ItemOccurrence.UseInType WarnOnIWSAM.Yes env tpenv synType
            check (Some (MustEqual tgtTy)) resultOpt synBodyExpr delayed

        | _ ->
            error (Error(FSComp.SR.expressionHasNoName(), m))

    let lastIdent = check None None cleanSynArg []
    TcNameOfExprResult cenv lastIdent m

and TcNameOfExprResult (cenv: cenv) (lastIdent: Ident) m =
    let g = cenv.g
    let constRange = withEnd (mkPos m.StartLine (m.StartColumn + lastIdent.idText.Length + 2)) m // `2` are for quotes
    Expr.Const(Const.String(lastIdent.idText), constRange, g.string_ty)

//-------------------------------------------------------------------------
// TcApplicationThen: Typecheck "expr x" + projections
//-------------------------------------------------------------------------

// leftExpr[idx] gives a warning
and isAdjacentListExpr isSugar atomicFlag (synLeftExprOpt: SynExpr option) (synArg: SynExpr) =
    not isSugar  &&
    if atomicFlag = ExprAtomicFlag.Atomic then
        match synArg with
        | SynExpr.ArrayOrList (false, _, _)
        | SynExpr.ArrayOrListComputed (false, _, _) -> true
        | _ -> false
    else
        match synLeftExprOpt with
        | Some synLeftExpr ->
            match synArg with
            | SynExpr.ArrayOrList (false, _, _)
            | SynExpr.ArrayOrListComputed (false, _, _) ->
                synLeftExpr.Range.IsAdjacentTo synArg.Range
            | _ -> false
        | _ -> false

// Check f x
// Check f[x]
// Check seq { expr }
// Check async { expr }
and TcApplicationThen (cenv: cenv) (overallTy: OverallTy) env tpenv mExprAndArg synLeftExprOpt leftExpr exprTy (synArg: SynExpr) atomicFlag isSugar delayed =
    let g = cenv.g
    let denv = env.DisplayEnv
    let mArg = synArg.Range
    let mLeftExpr = leftExpr.Range

    /// Treat an application of a value to an empty record expression
    /// as a computation expression with a single unit expression.
    /// Insert a (), i.e., such that builder { } ≡ builder { () }.
    /// This transformation is only valid for language
    /// versions that support this feature.
    let (|EmptyFieldListAsUnit|_|) recordFields =
        match recordFields with
        | [] when g.langVersion.SupportsFeature LanguageFeature.EmptyBodiedComputationExpressions -> Some (EmptyFieldListAsUnit (SynExpr.Const (SynConst.Unit, range0)))
        | _ -> None

    // If the type of 'synArg' unifies as a function type, then this is a function application, otherwise
    // it is an error or a computation expression or indexer or delegate invoke
    match UnifyFunctionTypeUndoIfFailed cenv denv mLeftExpr exprTy with
    | ValueSome (domainTy, resultTy) ->

        // atomicLeftExpr[idx] unifying as application gives a warning
        if not isSugar then
            checkHighPrecedenceFunctionApplicationToList g [synArg] atomicFlag mExprAndArg

        match leftExpr with
        | ApplicableExpr(expr=NameOfExpr g _) when g.langVersion.SupportsFeature LanguageFeature.NameOf ->
            let replacementExpr = TcNameOfExpr cenv env tpenv synArg
            TcDelayed cenv overallTy env tpenv mExprAndArg (ApplicableExpr(cenv, replacementExpr, true, None)) g.string_ty ExprAtomicFlag.Atomic delayed
        | _ ->
            // Notice the special case 'seq { ... }'. In this case 'seq' is actually a function in the F# library.
            // Set a flag in the syntax tree to say we noticed a leading 'seq'
            //
            // Note that 'seq' predated computation expressions and is not actually a computation expression builder
            // though users don't realise that.
            let synArg =
                match synArg with
                // seq { comp }
                // seq { }
                | SynExpr.ComputationExpr (false, comp, m)
                | SynExpr.Record (None, None, EmptyFieldListAsUnit comp, m) when
                        (match leftExpr with
                         | ApplicableExpr(expr=Expr.Op(TOp.Coerce, _, [SeqExpr g], _)) -> true
                         | _ -> false) ->
                    SynExpr.ComputationExpr (true, comp, m)

                | _ -> synArg

            let arg, tpenv =
                // treat left and right of '||' and '&&' as control flow, so for example
                //     f expr1 && g expr2
                // will have debug points on "f expr1" and "g expr2"
                let env =
                    match leftExpr with
                    | ApplicableExpr(expr=Expr.Val (vref, _, _))
                    | ApplicableExpr(expr=Expr.App (Expr.Val (vref, _, _), _, _, [_], _))
                         when valRefEq g vref g.and2_vref
                           || valRefEq g vref g.or2_vref -> { env with eIsControlFlow = true }
                    | _ -> env

                // Propagate captured argument range so nullness warnings point to the original nullable value.
                let env =
                    if g.checkNullness && isFunTy g domainTy then
                        match leftExpr with
                        | ApplicableExpr(expr=Expr.App (_, _, _, capturedArgs, _)) when not capturedArgs.IsEmpty ->
                            let lastCapturedArg = List.last capturedArgs
                            if not (isFunTy g (tyOfExpr g lastCapturedArg)) then
                                { env with eContextInfo = ContextInfo.NullnessCheckOfCapturedArg lastCapturedArg.Range }
                            else
                                env
                        | _ -> env
                    else
                        env

                TcExprFlex2 cenv domainTy env false tpenv synArg

            let exprAndArg, resultTy = buildApp cenv leftExpr resultTy arg mExprAndArg
            TcDelayed cenv overallTy env tpenv mExprAndArg exprAndArg resultTy atomicFlag delayed

    | ValueNone ->
        // Type-directed invocables

        match synArg with
        // leftExpr[idx]
        // leftExpr[idx] <- expr2
        | SynExpr.ArrayOrListComputed(false, IndexerArgs indexArgs, m)
              when
                isAdjacentListExpr isSugar atomicFlag synLeftExprOpt synArg &&
                g.langVersion.SupportsFeature LanguageFeature.IndexerNotationWithoutDot ->

            let expandedIndexArgs = ExpandIndexArgs cenv synLeftExprOpt indexArgs
            let setInfo, delayed =
                match delayed with
                | DelayedSet(expr3, _) :: rest -> Some (expr3, unionRanges leftExpr.Range synArg.Range), rest
                | _ -> None, delayed
            TcIndexingThen cenv env overallTy mExprAndArg m tpenv setInfo synLeftExprOpt leftExpr.Expr exprTy expandedIndexArgs indexArgs delayed

        // Perhaps 'leftExpr' is a computation expression builder, and 'arg' is '{ ... }' or '{ }':
        // leftExpr { comp }
        // leftExpr { }
        | SynExpr.ComputationExpr (false, comp, _m)
        | SynExpr.Record (None, None, EmptyFieldListAsUnit comp, _m) ->
            let bodyOfCompExpr, tpenv = cenv.TcComputationExpression cenv env overallTy tpenv (mLeftExpr, leftExpr.Expr, exprTy, comp)
            TcDelayed cenv overallTy env tpenv mExprAndArg (MakeApplicableExprNoFlex cenv bodyOfCompExpr) (tyOfExpr g bodyOfCompExpr) ExprAtomicFlag.NonAtomic delayed

        | _ ->
            error (NotAFunction(denv, overallTy.Commit, mLeftExpr, mArg))

//-------------------------------------------------------------------------
// TcLongIdentThen: Typecheck "A.B.C<D>.E.F ... " constructs
//-------------------------------------------------------------------------

and GetLongIdentTypeNameInfo delayed =
    // Given 'MyOverloadedType<int>.MySubType...' use the number of given type arguments to help
    // resolve type name lookup of 'MyOverloadedType'
    // Also determine if type names should resolve to Item.Types or Item.CtorGroup
    match delayed with
    | DelayedTypeApp (tyargs, _, _) :: (DelayedDot | DelayedDotLookup _) :: _ ->
        // cases like 'MyType<int>.Sth'
        TypeNameResolutionInfo(ResolveTypeNamesToTypeRefs, TypeNameResolutionStaticArgsInfo.FromTyArgs tyargs.Length)

    | DelayedTypeApp (tyargs, _, _) :: _ ->
        // Note, this also covers the case 'MyType<int>.' (without LValue_get), which is needed for VS (when typing)
        TypeNameResolutionInfo(ResolveTypeNamesToCtors, TypeNameResolutionStaticArgsInfo.FromTyArgs tyargs.Length)

    | _ ->
        TypeNameResolutionInfo.Default

and TcLongIdentThen (cenv: cenv) (overallTy: OverallTy) env tpenv (SynLongIdent(longId, _, _)) delayed =

    let ad = env.eAccessRights
    let typeNameResInfo = GetLongIdentTypeNameInfo delayed
    let nameResolutionResult =
        let maybeAppliedArgExpr = DelayedItem.maybeAppliedArgForPreferExtensionOverProperty delayed
        ResolveLongIdentAsExprAndComputeRange cenv.tcSink cenv.nameResolver (rangeOfLid longId) ad env.eNameResEnv typeNameResInfo longId maybeAppliedArgExpr
        |> ForceRaise
    TcItemThen cenv overallTy env tpenv nameResolutionResult None delayed

//-------------------------------------------------------------------------
// Typecheck "item+projections"
//------------------------------------------------------------------------- *)

// mItem is the textual range covered by the long identifiers that make up the item
and TcItemThen (cenv: cenv) (overallTy: OverallTy) env tpenv (tinstEnclosing, item, mItem, rest, afterResolution) staticTyOpt delayed =
    let delayed = delayRest rest mItem delayed
    match item with
    // x where x is a union case or active pattern result tag.
    | Item.UnionCase _ | Item.ExnCase _ | Item.ActivePatternResult _ as item ->
        TcUnionCaseOrExnCaseOrActivePatternResultItemThen cenv overallTy env item tpenv mItem delayed

    | Item.Types(nm, ty :: _) ->
        TcTypeItemThen cenv overallTy env nm ty tpenv mItem tinstEnclosing delayed

    | Item.MethodGroup (methodName, minfos, _) ->
        TcMethodItemThen cenv overallTy env item methodName minfos tpenv mItem afterResolution staticTyOpt delayed

    | Item.Trait traitInfo ->
        TcTraitItemThen cenv overallTy env None traitInfo tpenv mItem delayed

    | Item.CtorGroup(nm, minfos) ->
        TcCtorItemThen cenv overallTy env item nm minfos tinstEnclosing tpenv mItem afterResolution delayed

    | Item.ImplicitOp(id, sln) ->
        TcImplicitOpItemThen cenv overallTy env id sln tpenv mItem delayed

    | Item.DelegateCtor ty ->
        TcDelegateCtorItemThen cenv overallTy env ty tinstEnclosing tpenv mItem delayed

    | Item.Value vref ->
        TcValueItemThen cenv overallTy env vref tpenv mItem afterResolution delayed

    | Item.Property (nm, pinfos, _) ->
        TcPropertyItemThen cenv overallTy env nm pinfos tpenv mItem afterResolution staticTyOpt delayed

    | Item.ILField finfo ->
        TcILFieldItemThen cenv overallTy env finfo tpenv mItem delayed

    | Item.RecdField rfinfo ->
        TcRecdFieldItemThen cenv overallTy env rfinfo tpenv mItem delayed

    | Item.Event einfo ->
        TcEventItemThen cenv overallTy env tpenv mItem mItem None einfo delayed

    | Item.CustomOperation (nm, usageTextOpt, _) ->
        // 'delayed' is about to be dropped on the floor, first do rudimentary checking to get name resolutions in its body
        RecordNameAndTypeResolutionsDelayed cenv env tpenv delayed
        match usageTextOpt() with
        | None -> error(Error(FSComp.SR.tcCustomOperationNotUsedCorrectly nm, mItem))
        | Some usageText -> error(Error(FSComp.SR.tcCustomOperationNotUsedCorrectly2(nm, usageText), mItem))

    // These items are not expected here - they are only used for reporting symbols from name resolution to language service
    | Item.ActivePatternCase _
    | Item.AnonRecdField _
    | Item.OtherName _
    | Item.CustomBuilder _
    | Item.ModuleOrNamespaces _
    | Item.NewDef _
    | Item.SetterArg _
    | Item.TypeVar _
    | Item.UnionCaseField _
    | Item.UnqualifiedType _
    | Item.Types(_, []) ->
        error(Error(FSComp.SR.tcLookupMayNotBeUsedHere(), mItem))

/// Type check the application of a union case. Also used to cover constructions of F# exception values, and
/// applications of active pattern result labels.
//
// NOTE: the code for this is all a bit convoluted and should really be simplified/regularized.
and TcUnionCaseOrExnCaseOrActivePatternResultItemThen (cenv: cenv) overallTy env item tpenv mItem delayed =
    let g = cenv.g
    let ad = env.eAccessRights
    // ucaseAppTy is the type of the union constructor applied to its (optional) argument
    let ucaseAppTy = NewInferenceType g
    let mkConstrApp, argTys, argNames =
        match item with
        | Item.ActivePatternResult(apinfo, _apOverallTy, n, m) ->
            let aparity = apinfo.ActiveTags.Length
            match aparity with
            | 0 | 1 ->
                let mkConstrApp _mArgs = function [arg] -> arg | _ -> error(InternalError("ApplyUnionCaseOrExn", mItem))
                mkConstrApp, [ucaseAppTy], [ for s, m in apinfo.ActiveTagsWithRanges -> mkSynId m s ]
            | _ ->
                let ucref = mkChoiceCaseRef g m aparity n
                let _, _, tinst, _ = FreshenTyconRef2 g mItem ucref.TyconRef
                let ucinfo = UnionCaseInfo (tinst, ucref)
                ApplyUnionCaseOrExnTypes mItem cenv env ucaseAppTy (Item.UnionCase(ucinfo, false))
        | _ ->
            ApplyUnionCaseOrExnTypes mItem cenv env ucaseAppTy item
    let numArgTys = List.length argTys

    // Subsumption at data constructions if argument type is nominal prior to equations for any arguments or return types
    let flexes = argTys |> List.map (isTyparTy g >> not)

    let (|FittedArgs|_|) arg =
        match arg with
        | SynExprParen(SynExpr.Tuple (false, args, _, _), _, _, _)
        | SynExpr.Tuple (false, args, _, _) when numArgTys > 1 -> Some args
        | SynExprParen(arg, _, _, _)
        | arg when numArgTys = 1 -> Some [arg]
        | _ -> None

    match delayed with
    // This is where the constructor is applied to an argument
    | DelayedApp (atomicFlag, _, _, (FittedArgs args as origArg), mExprAndArg) :: otherDelayed ->
        // assert the overall result type if possible
        if isNil otherDelayed then
            UnifyOverallType cenv env mExprAndArg overallTy ucaseAppTy

        let numArgs = List.length args
        UnionCaseOrExnCheck env numArgTys numArgs mExprAndArg

        // if we manage to get here - number of formal arguments = number of actual arguments
        // apply named parameters
        let args =
            // GetMethodArgs checks that no named parameters are located before positional
            let unnamedArgs, namedCallerArgs = GetMethodArgs origArg
            match namedCallerArgs with
            | [] ->
                args
            | _ ->
                let fittedArgs = Array.zeroCreate numArgTys

                // first: put all positional arguments
                let mutable currentIndex = 0
                for arg in unnamedArgs do
                    if currentIndex < fittedArgs.Length then
                        fittedArgs[currentIndex] <- arg
                        currentIndex <- currentIndex + 1

                let SEEN_NAMED_ARGUMENT = -1

                // Dealing with named arguments is a bit tricky since prior to these changes we have an ambiguous situation:
                // regular notation for named parameters Some(Value = 5) can mean either
                //   1) create "bool option" with value - result of equality operation or
                //   2) create "int option" using named arg syntax.
                // So far we've used 1) so we cannot immediately switch to 2) since it will be a definite breaking change.

                for _, id, arg in namedCallerArgs do
                    match argNames |> List.tryFindIndex (fun id2 -> id.idText = id2.idText) with
                    | Some i ->
                        if isNull(box fittedArgs[i]) then
                            fittedArgs[i] <- arg
                            let argItem =
                                match item with
                                | Item.UnionCase (uci, _) -> Item.UnionCaseField (uci, i)
                                | Item.ExnCase tref -> Item.RecdField (RecdFieldInfo ([], RecdFieldRef (tref, id.idText)))
                                | _ -> failwithf "Expecting union case or exception item, got: %O" item
                            CallNameResolutionSink cenv.tcSink (id.idRange, env.NameEnv, argItem, emptyTyparInst, ItemOccurrence.Use, ad)
                        else error(Error(FSComp.SR.tcUnionCaseFieldCannotBeUsedMoreThanOnce(id.idText), id.idRange))
                        currentIndex <- SEEN_NAMED_ARGUMENT
                    | None ->
                        // ambiguity may appear only when if argument is boolean\generic.
                        // if
                        // - we didn't find argument with specified name AND
                        // - we have not seen any named arguments so far AND
                        // - type of current argument is bool\generic
                        // then we'll favor old behavior and treat current argument as positional.
                        let isSpecialCaseForBackwardCompatibility =
                            (currentIndex <> SEEN_NAMED_ARGUMENT) &&
                            (currentIndex < numArgTys) &&
                            match stripTyEqns g argTys[currentIndex] with
                            | TType_app(tcref, _, _) -> tyconRefEq g g.bool_tcr tcref || tyconRefEq g g.system_Bool_tcref tcref
                            | TType_var _ -> true
                            | _ -> false

                        if isSpecialCaseForBackwardCompatibility then
                            assert isNull(box fittedArgs[currentIndex])
                            fittedArgs[currentIndex] <- List.item currentIndex args // grab original argument, not item from the list of named parameters
                            currentIndex <- currentIndex + 1
                        else
                            match item with
                            | Item.UnionCase(uci, _) ->
                                error(Error(FSComp.SR.tcUnionCaseConstructorDoesNotHaveFieldWithGivenName(uci.DisplayName, id.idText), id.idRange))
                            | Item.ExnCase tcref ->
                                error(Error(FSComp.SR.tcExceptionConstructorDoesNotHaveFieldWithGivenName(tcref.DisplayName, id.idText), id.idRange))
                            | Item.ActivePatternResult _ ->
                                error(Error(FSComp.SR.tcActivePatternsDoNotHaveFields(), id.idRange))
                            | _ ->
                                error(Error(FSComp.SR.tcConstructorDoesNotHaveFieldWithGivenName(id.idText), id.idRange))

                assert (Seq.forall (box >> ((<>) null) ) fittedArgs)
                List.ofArray fittedArgs

        let argsR, tpenv = TcExprsWithFlexes cenv env mExprAndArg tpenv flexes argTys args
        PropagateThenTcDelayed cenv overallTy env tpenv mExprAndArg (MakeApplicableExprNoFlex cenv (mkConstrApp mExprAndArg argsR)) ucaseAppTy atomicFlag otherDelayed

    | DelayedTypeApp (_x, mTypeArgs, _mExprAndTypeArgs) :: _delayed' ->
        error(Error(FSComp.SR.tcUnexpectedTypeArguments(), mTypeArgs))
    | _ ->
        // Work out how many syntactic arguments we really expect. Also return a function that builds the overall
        // expression, but don't apply this function until after we've checked that the number of arguments is OK
        // (or else we would be building an invalid expression)

        // Unit-taking active pattern result can be applied to no args
        let numArgs, mkExpr =
            // This is where the constructor is an active pattern result applied to no argument
            // Unit-taking active pattern result can be applied to no args
            if (numArgTys = 1 && match item with Item.ActivePatternResult _ -> true | _ -> false) then
                UnifyTypes cenv env mItem (List.head argTys) g.unit_ty
                1, (fun () -> mkConstrApp mItem [mkUnit g mItem])

            // This is where the constructor expects no arguments and is applied to no argument
            elif numArgTys = 0 then
                0, (fun () -> mkConstrApp mItem [])
            else
                // This is where the constructor expects arguments but is not applied to arguments, hence build a lambda
                numArgTys,
                (fun () ->
                    let argNamesIfFeatureEnabled =
                        if g.langVersion.SupportsFeature LanguageFeature.ImprovedImpliedArgumentNames then
                            argNames
                        else
                            []

                    let vs, args =
                        argTys
                        |> List.mapi (fun i ty ->
                            let argName = argNamesIfFeatureEnabled |> List.tryItem i |> Option.map (fun x -> x.idText) |> Option.defaultWith (fun () -> "arg" + string i)
                            mkCompGenLocal mItem argName ty)
                        |> List.unzip

                    let constrApp = mkConstrApp mItem args
                    let lam = mkMultiLambda mItem vs (constrApp, tyOfExpr g constrApp)
                    lam)
        UnionCaseOrExnCheck env numArgTys numArgs mItem
        let expr = mkExpr()
        let exprTy = tyOfExpr g expr
        PropagateThenTcDelayed cenv overallTy env tpenv mItem (MakeApplicableExprNoFlex cenv expr) exprTy ExprAtomicFlag.Atomic delayed

and TcTypeItemThen (cenv: cenv) overallTy env nm ty tpenv mItem tinstEnclosing delayed =
    let g = cenv.g
    let ad = env.eAccessRights
    match delayed with
    | DelayedTypeApp(tyargs, _mTypeArgs, mExprAndTypeArgs) :: DelayedDotLookup (longId, mLongId) :: otherDelayed ->
        // If Item.Types is returned then the ty will be of the form TType_app(tcref, genericTyargs) where tyargs
        // is a fresh instantiation for tcref. TcNestedTypeApplication will chop off precisely #genericTyargs args
        // and replace them by 'tyargs'
        let ty, tpenv = TcNestedTypeApplication cenv NewTyparsOK CheckCxs ItemOccurrence.UseInType WarnOnIWSAM.Yes env tpenv mExprAndTypeArgs ty tinstEnclosing tyargs

        // Report information about the whole expression including type arguments to VS
        let item = Item.Types(nm, [ty])
        CallNameResolutionSink cenv.tcSink (mExprAndTypeArgs, env.NameEnv, item, emptyTyparInst, ItemOccurrence.Use, env.eAccessRights)
        let typeNameResInfo = GetLongIdentTypeNameInfo otherDelayed
        let item, mItem, rest, afterResolution = ResolveExprDotLongIdentAndComputeRange cenv.tcSink cenv.nameResolver (unionRanges mExprAndTypeArgs mLongId) ad env.eNameResEnv ty longId typeNameResInfo IgnoreOverrides true None
        TcItemThen cenv overallTy env tpenv ((argsOfAppTy g ty), item, mItem, rest, afterResolution) None otherDelayed

    | DelayedTypeApp(tyargs, _mTypeArgs, mExprAndTypeArgs) :: _delayed' ->
        // A case where we have an incomplete name e.g. 'Foo<int>.' - we still want to report it to VS!
        let ty, _ = TcNestedTypeApplication cenv NewTyparsOK CheckCxs ItemOccurrence.UseInType WarnOnIWSAM.Yes env tpenv mExprAndTypeArgs ty tinstEnclosing tyargs
        let item = Item.Types(nm, [ty])
        CallNameResolutionSink cenv.tcSink (mExprAndTypeArgs, env.NameEnv, item, emptyTyparInst, ItemOccurrence.Use, env.eAccessRights)

        // Same error as in the following case
        error(Error(FSComp.SR.tcInvalidUseOfTypeName(), mItem))

    | _ ->
        // In this case the type is not generic, and indeed we should never have returned Item.Types.
        // That's because ResolveTypeNamesToCtors should have been set at the original
        // call to ResolveLongIdentAsExprAndComputeRange
        if isInterfaceTy g ty then
            error(Error(FSComp.SR.tcInvalidUseOfInterfaceType(), mItem))
        else
            error(Error(FSComp.SR.tcInvalidUseOfTypeName(), mItem))

and TcMethodItemThen (cenv: cenv) overallTy env item methodName minfos tpenv mItem afterResolution staticTyOpt delayed =
    let ad = env.eAccessRights
    // Static method calls Type.Foo(arg1, ..., argn)
    let meths = List.map (fun minfo -> minfo, None) minfos
    match delayed with
    | DelayedApp (atomicFlag, _, _, arg, mExprAndArg) :: otherDelayed ->
        TcMethodApplicationThen cenv env overallTy None tpenv None [] mExprAndArg mItem methodName ad NeverMutates false meths afterResolution NormalValUse [arg] atomicFlag staticTyOpt otherDelayed

    | DelayedTypeApp(tys, mTypeArgs, mExprAndTypeArgs) :: otherDelayed ->

#if !NO_TYPEPROVIDERS
        match TryTcMethodAppToStaticConstantArgs cenv env tpenv (minfos, Some (tys, mTypeArgs), mExprAndTypeArgs, mItem) with
        | Some minfoAfterStaticArguments ->

            // Replace the resolution including the static parameters, plus the extra information about the original method info
            let item = Item.MethodGroup(methodName, [minfoAfterStaticArguments], Some minfos[0])
            CallNameResolutionSinkReplacing cenv.tcSink (mItem, env.NameEnv, item, [], ItemOccurrence.Use, env.eAccessRights)

            match otherDelayed with
            | DelayedApp(atomicFlag, _, _, arg, mExprAndArg) :: otherDelayed ->
                TcMethodApplicationThen cenv env overallTy None tpenv None [] mExprAndArg mItem methodName ad NeverMutates false [(minfoAfterStaticArguments, None)] afterResolution NormalValUse [arg] atomicFlag staticTyOpt otherDelayed
            | _ ->
                TcMethodApplicationThen cenv env overallTy None tpenv None [] mExprAndTypeArgs mItem methodName ad NeverMutates false [(minfoAfterStaticArguments, None)] afterResolution NormalValUse [] ExprAtomicFlag.Atomic staticTyOpt otherDelayed

        | None ->
#endif

        let tyargs, tpenv = TcTypesOrMeasures None cenv NewTyparsOK CheckCxs ItemOccurrence.UseInType env tpenv tys mTypeArgs

        // FUTURE: can we do better than emptyTyparInst here, in order to display instantiations
        // of type variables in the quick info provided in the IDE? But note we haven't yet even checked if the
        // number of type arguments is correct...
        CallNameResolutionSink cenv.tcSink (mExprAndTypeArgs, env.NameEnv, item, emptyTyparInst, ItemOccurrence.Use, env.eAccessRights)

        match otherDelayed with
        | DelayedApp(atomicFlag, _, _, arg, mExprAndArg) :: otherDelayed ->
            TcMethodApplicationThen cenv env overallTy None tpenv (Some tyargs) [] mExprAndArg mItem methodName ad NeverMutates false meths afterResolution NormalValUse [arg] atomicFlag staticTyOpt otherDelayed
        | _ ->
            TcMethodApplicationThen cenv env overallTy None tpenv (Some tyargs) [] mExprAndTypeArgs mItem methodName ad NeverMutates false meths afterResolution NormalValUse [] ExprAtomicFlag.Atomic staticTyOpt otherDelayed

    | _ ->
#if !NO_TYPEPROVIDERS
        if not minfos.IsEmpty && minfos[0].ProvidedStaticParameterInfo.IsSome then
            error(Error(FSComp.SR.etMissingStaticArgumentsToMethod(), mItem))
#endif
        TcMethodApplicationThen cenv env overallTy None tpenv None [] mItem mItem methodName ad NeverMutates false meths afterResolution NormalValUse [] ExprAtomicFlag.Atomic staticTyOpt delayed

and TcCtorItemThen (cenv: cenv) overallTy env item nm minfos tinstEnclosing tpenv mItem afterResolution delayed =
#if !NO_TYPEPROVIDERS
    let g = cenv.g
    let ad = env.eAccessRights
#endif
    let objTy =
        match minfos with
        | minfo :: _ -> minfo.ApparentEnclosingType
        | [] -> error(Error(FSComp.SR.tcTypeHasNoAccessibleConstructor(), mItem))

    match delayed with
    | DelayedApp(_, _, _, arg, mExprAndArg) :: otherDelayed ->

        CallExprHasTypeSink cenv.tcSink (mExprAndArg, env.NameEnv, objTy, env.eAccessRights)
        TcCtorCall true cenv env tpenv overallTy objTy (Some mItem) item false [arg] mExprAndArg otherDelayed (Some afterResolution)

    | DelayedTypeApp(tyargs, _mTypeArgs, mExprAndTypeArgs) :: DelayedApp(_, _, _, arg, mExprAndArg) :: otherDelayed ->

        let objTyAfterTyArgs, tpenv = TcNestedTypeApplication cenv NewTyparsOK CheckCxs ItemOccurrence.UseInType WarnOnIWSAM.Yes env tpenv mExprAndTypeArgs objTy tinstEnclosing tyargs
        CallExprHasTypeSink cenv.tcSink (mExprAndArg, env.NameEnv, objTyAfterTyArgs, env.eAccessRights)
        let itemAfterTyArgs, minfosAfterTyArgs =
#if !NO_TYPEPROVIDERS
            // If the type is provided and took static arguments then the constructor will have changed
            // to a provided constructor on the statically instantiated type. Re-resolve that constructor.
            match objTyAfterTyArgs with
            | AppTy g (tcref, _) when tcref.Deref.IsProvided ->
                let newItem = ForceRaise (ResolveObjectConstructor cenv.nameResolver env.DisplayEnv mExprAndArg ad objTyAfterTyArgs)
                match newItem with
                | Item.CtorGroup(_, newMinfos) -> newItem, newMinfos
                | _ -> item, minfos
            | _ ->
#endif
                item, minfos

        minfosAfterTyArgs |> List.iter (fun minfo -> UnifyTypes cenv env mExprAndTypeArgs minfo.ApparentEnclosingType objTyAfterTyArgs)
        TcCtorCall true cenv env tpenv overallTy objTyAfterTyArgs (Some mExprAndTypeArgs) itemAfterTyArgs false [arg] mExprAndArg otherDelayed (Some afterResolution)

    | DelayedTypeApp(tyargs, _mTypeArgs, mExprAndTypeArgs) :: otherDelayed ->

        let objTy, tpenv = TcNestedTypeApplication cenv NewTyparsOK CheckCxs ItemOccurrence.UseInType WarnOnIWSAM.Yes env tpenv mExprAndTypeArgs objTy tinstEnclosing tyargs

        // A case where we have an incomplete name e.g. 'Foo<int>.' - we still want to report it to VS!
        let resolvedItem = Item.Types(nm, [objTy])
        CallNameResolutionSink cenv.tcSink (mExprAndTypeArgs, env.NameEnv, resolvedItem, emptyTyparInst, ItemOccurrence.Use, env.eAccessRights)

        minfos |> List.iter (fun minfo -> UnifyTypes cenv env mExprAndTypeArgs minfo.ApparentEnclosingType objTy)
        TcCtorCall true cenv env tpenv overallTy objTy (Some mExprAndTypeArgs) item false [] mExprAndTypeArgs otherDelayed (Some afterResolution)

    | _ ->

        TcCtorCall true cenv env tpenv overallTy objTy (Some mItem) item false [] mItem delayed (Some afterResolution)

and TcTraitItemThen (cenv: cenv) overallTy env objOpt traitInfo tpenv mItem delayed =
    let g = cenv.g

    let argTys = traitInfo.GetLogicalArgumentTypes(g)
    let retTy = traitInfo.GetReturnType(g)

    match traitInfo.SupportTypes with
    | tys when tys.Length > 1 ->
        error(Error (FSComp.SR.tcTraitHasMultipleSupportTypes(traitInfo.MemberDisplayNameCore), mItem))
    | _ -> ()

    match objOpt, traitInfo.MemberFlags.IsInstance with
    | Some _, false -> error (Error (FSComp.SR.tcTraitIsStatic traitInfo.MemberDisplayNameCore, mItem))
    | None, true -> error (Error (FSComp.SR.tcTraitIsNotStatic traitInfo.MemberDisplayNameCore, mItem))
    | _ -> ()

    // If this is an instance trait the object must be evaluated, just in case this is a first-class use of the trait, e.g.
    //     (Compute()).SomeMethod  -->
    //       let obj = Compute() in (fun arg -> SomeMethod(arg))
    //     (Compute()).SomeMethod(3)  -->
    //       let obj = Compute() in (fun arg -> SomeMethod(arg)) 3
    let wrapper, objArgs =
        match argTys with
        | [] ->
            id, Option.toList objOpt
        | _ ->
            match objOpt with
            | None ->
                id, []
            | Some objExpr ->
                // Evaluate the object first
                let objVal, objValExpr = mkCompGenLocal mItem "obj" (tyOfExpr g objExpr)
                mkCompGenLet mItem objVal objExpr, [objValExpr]

    // Build a lambda for the trait call
    let applicableExpr, exprTy =
        // Empty arguments indicates a non-indexer property constraint
        match argTys with
        | [] ->
            let expr = Expr.Op (TOp.TraitCall traitInfo, [], objArgs, mItem)
            let exprTy = tyOfExpr g expr
            let applicableExpr = MakeApplicableExprNoFlex cenv expr
            applicableExpr, exprTy
        | _ ->
            let vs, ves = argTys |> List.mapi (fun i ty -> mkCompGenLocal mItem ("arg" + string i) ty) |> List.unzip
            // Account for a unit mismatch in logical v. compiled arguments
            let compiledArgExprs =
                match argTys, traitInfo.GetCompiledArgumentTypes() with
                | [_], [] -> []
                | _ -> ves
            let traitCall = Expr.Op (TOp.TraitCall traitInfo, [], objArgs@compiledArgExprs, mItem)
            let v, body = MultiLambdaToTupledLambda g vs traitCall
            let expr = mkLambda mItem v (body, retTy)
            let exprTy = tyOfExpr g expr
            let applicableExpr = MakeApplicableExprForTraitCall cenv expr (vs, traitCall)
            applicableExpr, exprTy

    // Propagate the types from the known application structure

    Propagate cenv overallTy env tpenv applicableExpr exprTy delayed

    // Check and apply the arguments
    let resExpr, tpenv = TcDelayed cenv overallTy env tpenv mItem applicableExpr exprTy ExprAtomicFlag.NonAtomic delayed

    // Apply the wrapper to pre-evaluate the object if any
    wrapper resExpr, tpenv

and TcImplicitOpItemThen (cenv: cenv) overallTy env id sln tpenv mItem delayed =
    let g = cenv.g
    let isPrefix = IsLogicalPrefixOperator id.idText
    let isTernary = IsLogicalTernaryOperator id.idText

    let argData =
        if isPrefix then
            [ SynTypar(mkSynId mItem (cenv.synArgNameGenerator.New()), TyparStaticReq.None, true) ]
        elif isTernary then
            [ SynTypar(mkSynId mItem (cenv.synArgNameGenerator.New()), TyparStaticReq.None, true)
              SynTypar(mkSynId mItem (cenv.synArgNameGenerator.New()), TyparStaticReq.None, true)
              SynTypar(mkSynId mItem (cenv.synArgNameGenerator.New()), TyparStaticReq.None, true) ]
        else
            [ SynTypar(mkSynId mItem (cenv.synArgNameGenerator.New()), TyparStaticReq.None, true)
              SynTypar(mkSynId mItem (cenv.synArgNameGenerator.New()), TyparStaticReq.None, true) ]

    let retTyData = SynTypar(mkSynId mItem (cenv.synArgNameGenerator.New()), TyparStaticReq.None, true)
    let argTypars = argData |> List.map (fun d -> Construct.NewTypar (TyparKind.Type, TyparRigidity.Flexible, d, false, TyparDynamicReq.Yes, [], false, false))
    let retTypar = Construct.NewTypar (TyparKind.Type, TyparRigidity.Flexible, retTyData, false, TyparDynamicReq.Yes, [], false, false)
    let argTys = argTypars |> List.map mkTyparTy
    let retTy = mkTyparTy retTypar

    let vs, ves = argTys |> List.mapi (fun i ty -> mkCompGenLocal mItem ("arg" + string i) ty) |> List.unzip

    let memberFlags = StaticMemberFlags SynMemberKind.Member
    let logicalCompiledName = ComputeLogicalName id memberFlags
    let traitInfo = TTrait(argTys, logicalCompiledName, memberFlags, argTys, Some retTy, ref None, sln)

    let expr = Expr.Op (TOp.TraitCall traitInfo, [], ves, mItem)
    let expr = mkLambdas g mItem [] vs (expr, retTy)

    let rec isSimpleArgument e =
        match e with
        | SynExpr.New (_, _, synExpr, _)
        | SynExpr.Paren (synExpr, _, _, _)
        | SynExpr.Typed (synExpr, _, _)
        | SynExpr.TypeApp (synExpr, _, _, _, _, _, _)
        | SynExpr.TypeTest (synExpr, _, _)
        | SynExpr.Upcast (synExpr, _, _)
        | SynExpr.DotGet (synExpr, _, _, _)
        | SynExpr.Downcast (synExpr, _, _)
        | SynExpr.InferredUpcast (synExpr, _)
        | SynExpr.InferredDowncast (synExpr, _)
        | SynExpr.AddressOf (_, synExpr, _, _)
        | SynExpr.DebugPoint (_, _, synExpr)
        | SynExpr.Quote (_, _, synExpr, _, _) -> isSimpleArgument synExpr

        | SynExpr.InterpolatedString _
        | SynExpr.Null _
        | SynExpr.Ident _
        | SynExpr.Const _
        | SynExpr.Typar _
        | SynExpr.LongIdent _
        | SynExpr.DotLambda _
        | SynExpr.Dynamic _ -> true

        | SynExpr.Tuple (_, synExprs, _, _)
        | SynExpr.ArrayOrList (_, synExprs, _) -> synExprs |> List.forall isSimpleArgument
        | SynExpr.Record (copyInfo=copyOpt; recordFields=fields) -> copyOpt |> Option.forall (fst >> isSimpleArgument) && fields |> List.forall ((fun (SynExprRecordField(expr=e)) -> e) >> Option.forall isSimpleArgument)
        | SynExpr.App (_, _, synExpr, synExpr2, _) -> isSimpleArgument synExpr && isSimpleArgument synExpr2
        | SynExpr.IfThenElse (ifExpr=synExpr; thenExpr=synExpr2; elseExpr=synExprOpt) -> isSimpleArgument synExpr && isSimpleArgument synExpr2 && Option.forall isSimpleArgument synExprOpt
        | SynExpr.DotIndexedGet (synExpr, _, _, _) -> isSimpleArgument synExpr
        | SynExpr.ObjExpr _
        | SynExpr.AnonRecd _
        | SynExpr.While _
        | SynExpr.For _
        | SynExpr.ForEach _
        | SynExpr.ArrayOrListComputed _
        | SynExpr.ComputationExpr _
        | SynExpr.Lambda _
        | SynExpr.MatchLambda _
        | SynExpr.Match _
        | SynExpr.Do _
        | SynExpr.Assert _
        | SynExpr.Fixed _
        | SynExpr.TryWith _
        | SynExpr.TryFinally _
        | SynExpr.Lazy _
        | SynExpr.Sequential _
        | SynExpr.SequentialOrImplicitYield _
        | SynExpr.LetOrUse _
        | SynExpr.DotSet _
        | SynExpr.DotIndexedSet _
        | SynExpr.LongIdentSet _
        | SynExpr.Set _
        | SynExpr.JoinIn _
        | SynExpr.NamedIndexedPropertySet _
        | SynExpr.DotNamedIndexedPropertySet _
        | SynExpr.LibraryOnlyILAssembly _
        | SynExpr.LibraryOnlyStaticOptimization _
        | SynExpr.LibraryOnlyUnionCaseFieldGet _
        | SynExpr.LibraryOnlyUnionCaseFieldSet _
        | SynExpr.ArbitraryAfterError _
        | SynExpr.FromParseError _
        | SynExpr.DiscardAfterMissingQualificationAfterDot _
        | SynExpr.ImplicitZero _
        | SynExpr.YieldOrReturn _
        | SynExpr.YieldOrReturnFrom _
        | SynExpr.MatchBang _
        | LetOrUse(_, true, _)
        | SynExpr.DoBang _
        | SynExpr.WhileBang _
        | SynExpr.TraitCall _
        | SynExpr.IndexFromEnd _
        | SynExpr.IndexRange _
            -> false

    // Propagate the known application structure into function types
    Propagate cenv overallTy env tpenv (MakeApplicableExprNoFlex cenv expr) (tyOfExpr g expr) delayed

    // Take all simple arguments and process them before applying the constraint.
    let delayed1, delayed2 =
        let pred = (function DelayedApp (_, _, _, arg, _) -> isSimpleArgument arg | _ -> false)
        List.takeWhile pred delayed, List.skipWhile pred delayed

    let intermediateTy = if isNil delayed2 then overallTy.Commit else NewInferenceType g

    let resultExpr, tpenv = TcDelayed cenv (MustEqual intermediateTy) env tpenv mItem (MakeApplicableExprNoFlex cenv expr) (tyOfExpr g expr) ExprAtomicFlag.NonAtomic delayed1

    // Add the constraint after the application arguments have been checked to allow annotations to kick in on rigid type parameters
    AddCxMethodConstraint env.DisplayEnv cenv.css mItem NoTrace traitInfo

    // Process all remaining arguments after the constraint is asserted
    let resultExpr2, tpenv2 = TcDelayed cenv overallTy env tpenv mItem (MakeApplicableExprNoFlex cenv resultExpr) intermediateTy ExprAtomicFlag.NonAtomic delayed2
    resultExpr2, tpenv2

and TcDelegateCtorItemThen cenv overallTy env ty tinstEnclosing tpenv mItem delayed =
    match delayed with
    | DelayedApp (atomicFlag, _, _, arg, mItemAndArg) :: otherDelayed ->
        TcNewDelegateThen cenv overallTy env tpenv mItem mItemAndArg ty arg atomicFlag otherDelayed
    | DelayedTypeApp(tyargs, _mTypeArgs, mItemAndTypeArgs) :: DelayedApp (atomicFlag, _, _, arg, mItemAndArg) :: otherDelayed ->
        let ty, tpenv = TcNestedTypeApplication cenv NewTyparsOK CheckCxs ItemOccurrence.UseInType WarnOnIWSAM.Yes env tpenv mItemAndTypeArgs ty tinstEnclosing tyargs

        // Report information about the whole expression including type arguments to VS
        let item = Item.DelegateCtor ty
        CallNameResolutionSink cenv.tcSink (mItemAndTypeArgs, env.NameEnv, item, emptyTyparInst, ItemOccurrence.Use, env.eAccessRights)
        TcNewDelegateThen cenv overallTy env tpenv mItem mItemAndArg ty arg atomicFlag otherDelayed
    | _ ->
        error(Error(FSComp.SR.tcInvalidUseOfDelegate(), mItem))

and TcValueItemThen cenv overallTy env vref tpenv mItem afterResolution delayed =
    let g = cenv.g
    match delayed with
    // Mutable value set: 'v <- e'
    | DelayedSet(expr2, mStmt) :: otherDelayed ->
        if not (isNil otherDelayed) then error(Error(FSComp.SR.tcInvalidAssignment(), mStmt))
        UnifyTypes cenv env mStmt overallTy.Commit g.unit_ty
        vref.Deref.SetHasBeenReferenced()
        CheckValAccessible mItem env.AccessRights vref
        CheckValAttributes g vref mItem |> CommitOperationResult
        let vTy = vref.Type
        let vty2 =
            if isByrefTy g vTy then
                destByrefTy g vTy
            else
                if not vref.IsMutable then
                    errorR (ValNotMutable (env.DisplayEnv, vref, mStmt))
                vTy
        // Always allow subsumption on assignment to fields
        let expr2R, tpenv = TcExprFlex cenv true false vty2 env tpenv expr2
        // After assignment, strip KnownFromConstructor from the val's type so subsequent
        // reads no longer bypass AllowNullLiteral warnings for 'not null' constraints.
        if g.checkNullness && not (isByrefTy g vTy) then
            match stripTyparEqns vTy with
            | TType_app(_, _, Nullness.KnownFromConstructor)
            | TType_var(_, Nullness.KnownFromConstructor) ->
                vref.Deref.SetType(replaceNullnessOfTy (Nullness.Known NullnessInfo.WithoutNull) vTy)
            | _ -> ()

        let vExpr =
            if isInByrefTy g vTy then
                errorR(Error(FSComp.SR.writeToReadOnlyByref(), mStmt))
                mkAddrSet mStmt vref expr2R
            elif isByrefTy g vTy then
                mkAddrSet mStmt vref expr2R
            else
                mkValSet mStmt vref expr2R

        PropagateThenTcDelayed cenv overallTy env tpenv mStmt (MakeApplicableExprNoFlex cenv vExpr) (tyOfExpr g vExpr) ExprAtomicFlag.NonAtomic otherDelayed

    // Value instantiation: v<tyargs> ...
    | DelayedTypeApp(tys, _mTypeArgs, mExprAndTypeArgs) :: otherDelayed ->
        // Note: we know this is a NormalValUse or PossibleConstrainedCall because:
        //   - it isn't a CtorValUsedAsSuperInit
        //   - it isn't a CtorValUsedAsSelfInit
        //   - it isn't a VSlotDirectCall (uses of base values do not take type arguments
        // Allow `nameof<'T>` for a generic parameter
        match vref with
        | _ when isNameOfValRef g vref && g.langVersion.SupportsFeature LanguageFeature.NameOf ->
            // Record the resolution of the `nameof` usage so that we can classify it correctly later.
            do
                match afterResolution with
                | AfterResolution.RecordResolution (_, callSink, _, _) -> callSink emptyTyparInst
                | AfterResolution.DoNothing -> ()

            match tys with
            | [SynType.Var(SynTypar(id, _, false) as tp, _m)] ->
                let _tpR, tpenv = TcTypeOrMeasureParameter None cenv env ImplicitlyBoundTyparsAllowed.NoNewTypars tpenv tp
                let vExpr = TcNameOfExprResult cenv id mExprAndTypeArgs
                let vexpFlex = MakeApplicableExprNoFlex cenv vExpr
                PropagateThenTcDelayed cenv overallTy env tpenv mExprAndTypeArgs vexpFlex g.string_ty ExprAtomicFlag.Atomic otherDelayed
            | _ ->
                error (Error(FSComp.SR.expressionHasNoName(), mExprAndTypeArgs))
        | _ ->
        let checkTys tpenv kinds = TcTypesOrMeasures (Some kinds) cenv NewTyparsOK CheckCxs ItemOccurrence.UseInType env tpenv tys mItem
        let _, vExpr, isSpecial, _, _, tpenv = TcVal cenv env tpenv vref (Some (NormalValUse, checkTys)) (Some afterResolution) mItem

        let vexpFlex = (if isSpecial then MakeApplicableExprNoFlex cenv vExpr else MakeApplicableExprWithFlex cenv env vExpr)
        // We need to eventually record the type resolution for an expression, but this is done
        // inside PropagateThenTcDelayed, so we don't have to explicitly call 'CallExprHasTypeSink' here
        PropagateThenTcDelayed cenv overallTy env tpenv mExprAndTypeArgs vexpFlex vexpFlex.Type ExprAtomicFlag.Atomic otherDelayed

    // Value get
    
    | _ ->
        let _, vExpr, isSpecial, _, _, tpenv = TcVal cenv env tpenv vref None (Some afterResolution) mItem

        let vExpr, tpenv =
            match vExpr with
            | Expr.Const (Const.String value, _, _) -> TcConstStringExpr cenv overallTy env mItem tpenv value LiteralArgumentType.StaticField
            | _ -> vExpr, tpenv

        let getCenvForVref cenv (vref:ValRef) = 
            match tryGetWarnOnWithoutNullMessage g vref.Attribs with
            | Some _ as msg -> { cenv with css.WarnWhenUsingWithoutNullOnAWithNullTarget = msg }
            | None when cenv.css.WarnWhenUsingWithoutNullOnAWithNullTarget <> None ->
                { cenv with css.WarnWhenUsingWithoutNullOnAWithNullTarget = None }
            | None -> cenv

        let cenv =
            match vExpr with
            | Expr.App (funcExpr=Expr.Val (valRef=vref)) -> getCenvForVref cenv vref
            | _ -> cenv

        let vexpFlex = if isSpecial then MakeApplicableExprNoFlex cenv vExpr else MakeApplicableExprWithFlex cenv env vExpr

        PropagateThenTcDelayed cenv overallTy env tpenv mItem vexpFlex vexpFlex.Type ExprAtomicFlag.Atomic delayed

and TcPropertyItemThen cenv overallTy env nm pinfos tpenv mItem afterResolution staticTyOpt delayed =
    let g = cenv.g
    let ad = env.eAccessRights

    if isNil pinfos then
        error (InternalError ("Unexpected error: empty property list", mItem))

    // If there are both intrinsics and extensions in pinfos, intrinsics will be listed first.
    // by looking at List.Head we are letting the intrinsics determine indexed/non-indexed
    let pinfo = List.head pinfos

    let _, tyArgsOpt, args, delayed, tpenv =
        if pinfo.IsIndexer then
            GetMemberApplicationArgs delayed cenv env tpenv
        else
            ExprAtomicFlag.Atomic, None, [mkSynUnit mItem], delayed, tpenv

    if not pinfo.IsStatic then
        error (Error (FSComp.SR.tcPropertyIsNotStatic nm, mItem))

    match delayed with
    | DelayedSet(expr2, mStmt) :: otherDelayed ->
        if not (isNil otherDelayed) then error(Error(FSComp.SR.tcInvalidAssignment(), mStmt))

        // Static Property Set (possibly indexer)
        UnifyTypes cenv env mStmt overallTy.Commit g.unit_ty

        let meths = pinfos |> SettersOfPropInfos

        if meths.IsEmpty then
            let meths = pinfos |> GettersOfPropInfos
            let isByrefMethReturnSetter = meths |> List.exists (function _,Some pinfo -> isByrefTy g (pinfo.GetPropertyType(cenv.amap,mItem)) | _ -> false)

            if not isByrefMethReturnSetter then
                errorR (Error (FSComp.SR.tcPropertyCannotBeSet1 nm, mItem))

            // x.P <- ... byref setter
            if isNil meths then error (Error (FSComp.SR.tcPropertyIsNotReadable nm, mItem))
            TcMethodApplicationThen cenv env overallTy None tpenv tyArgsOpt [] mItem mItem nm ad NeverMutates true meths afterResolution NormalValUse args ExprAtomicFlag.Atomic staticTyOpt delayed
        else
            let args = if pinfo.IsIndexer then args else []
            if isNil meths then
                errorR (Error (FSComp.SR.tcPropertyCannotBeSet1 nm, mItem))
            // Note: static calls never mutate a struct object argument
            TcMethodApplicationThen cenv env overallTy None tpenv tyArgsOpt [] mStmt mItem nm ad NeverMutates true meths afterResolution NormalValUse (args@[expr2]) ExprAtomicFlag.NonAtomic staticTyOpt otherDelayed
    | _ ->
        // Static Property Get (possibly indexer)
        let meths = pinfos |> GettersOfPropInfos
        if isNil meths then error (Error (FSComp.SR.tcPropertyIsNotReadable nm, mItem))
        // Note: static calls never mutate a struct object argument
        TcMethodApplicationThen cenv env overallTy None tpenv tyArgsOpt [] mItem mItem nm ad NeverMutates true meths afterResolution NormalValUse args ExprAtomicFlag.Atomic staticTyOpt delayed

and TcILFieldItemThen cenv overallTy env finfo tpenv mItem delayed =
    let g = cenv.g
    let ad = env.eAccessRights
    ILFieldStaticChecks g cenv.amap cenv.infoReader ad mItem finfo
    let fref = finfo.ILFieldRef
    let exprTy = finfo.FieldType(cenv.amap, mItem)
    match delayed with
    | DelayedSet(expr2, mStmt) :: _delayed' ->
        UnifyTypes cenv env mStmt overallTy.Commit g.unit_ty
        // Always allow subsumption on assignment to fields
        let expr2R, tpenv = TcExprFlex cenv true false exprTy env tpenv expr2
        let expr = BuildILStaticFieldSet mStmt finfo expr2R
        expr, tpenv

    | _ ->
        // Get static IL field
        let (expr, tpenv), isSpecial =
            match finfo.LiteralValue with
            | Some (ILFieldInit.String value) when typeEquiv g exprTy g.string_ty ->
                TcConstStringExpr cenv overallTy env mItem tpenv value LiteralArgumentType.StaticField, true
            | Some lit ->
                (Expr.Const (TcFieldInit mItem lit, mItem, exprTy), tpenv), false
            | None ->
                let isStruct = finfo.IsValueType
                let boxity = if isStruct then AsValue else AsObject

                // The empty instantiation on the fspec is OK, since we make the correct fspec in IlxGen.GenAsm
                // This ensures we always get the type instantiation right when doing this from
                // polymorphic code, after inlining etc.
                let fspec = mkILFieldSpec(fref, mkILNamedTy boxity fref.DeclaringTypeRef [])

                let ilInstrs =
                    [ mkNormalLdsfld fspec
                      // Add an I_nop if this is an initonly field to make sure we never recognize it as an lvalue. See mkExprAddrOfExpr.
                      if finfo.IsInitOnly then AI_nop ]

                (mkAsmExpr (ilInstrs, finfo.TypeInst, [], [exprTy], mItem), tpenv), false

        let exprTy, exprFlex =
            if isSpecial then
                let exprFlex = MakeApplicableExprNoFlex cenv expr
                exprFlex.Type, exprFlex
            else
                exprTy, MakeApplicableExprWithFlex cenv env expr

        PropagateThenTcDelayed cenv overallTy env tpenv mItem exprFlex exprTy ExprAtomicFlag.Atomic delayed

and TcRecdFieldItemThen cenv overallTy env rfinfo tpenv mItem delayed =
    let g = cenv.g
    let ad = env.eAccessRights
    // Get static F# field or literal
    CheckRecdFieldInfoAccessible cenv.amap mItem ad rfinfo
    if not rfinfo.IsStatic then error (Error (FSComp.SR.tcFieldIsNotStatic(rfinfo.DisplayName), mItem))
    CheckRecdFieldInfoAttributes g rfinfo mItem |> CommitOperationResult
    let fref = rfinfo.RecdFieldRef
    let fieldTy = rfinfo.FieldType
    match delayed with
    | DelayedSet(expr2, mStmt) :: otherDelayed ->
        if not (isNil otherDelayed) then error(Error(FSComp.SR.tcInvalidAssignment(), mStmt))

        // Set static F# field
        CheckRecdFieldMutation mItem env.DisplayEnv rfinfo
        UnifyTypes cenv env mStmt overallTy.Commit g.unit_ty
        let fieldTy = rfinfo.FieldType
        // Always allow subsumption on assignment to fields
        let expr2R, tpenv = TcExprFlex cenv true false fieldTy env tpenv expr2
        let expr = mkStaticRecdFieldSet (rfinfo.RecdFieldRef, rfinfo.TypeInst, expr2R, mStmt)
        expr, tpenv
    | _ ->
        let exprTy = fieldTy
        let expr =
            match rfinfo.LiteralValue with
            // Get literal F# field
            | Some lit -> Expr.Const (lit, mItem, exprTy)
            // Get static F# field
            | None -> mkStaticRecdFieldGet (fref, rfinfo.TypeInst, mItem)
        PropagateThenTcDelayed cenv overallTy env tpenv mItem (MakeApplicableExprWithFlex cenv env expr) exprTy ExprAtomicFlag.Atomic delayed

//-------------------------------------------------------------------------
// Typecheck "expr.A.B.C ... " constructs
//-------------------------------------------------------------------------

and GetSynMemberApplicationArgs delayed tpenv =
    match delayed with
    | DelayedApp (atomicFlag, _, _, arg, _) :: otherDelayed ->
        atomicFlag, None, [arg], otherDelayed, tpenv
    | DelayedTypeApp(tyargs, mTypeArgs, _) :: DelayedApp (atomicFlag, _, _, arg, _mExprAndArg) :: otherDelayed ->
        (atomicFlag, Some (tyargs, mTypeArgs), [arg], otherDelayed, tpenv)
    | DelayedTypeApp(tyargs, mTypeArgs, _) :: otherDelayed ->
        (ExprAtomicFlag.Atomic, Some (tyargs, mTypeArgs), [], otherDelayed, tpenv)
    | otherDelayed ->
        (ExprAtomicFlag.NonAtomic, None, [], otherDelayed, tpenv)

and TcMemberTyArgsOpt cenv env tpenv tyArgsOpt =
    match tyArgsOpt with
    | None -> None, tpenv
    | Some (tyargs, mTypeArgs) ->
        let tyargsChecked, tpenv = TcTypesOrMeasures None cenv NewTyparsOK CheckCxs ItemOccurrence.UseInType env tpenv tyargs mTypeArgs
        Some tyargsChecked, tpenv

and GetMemberApplicationArgs delayed cenv env tpenv =
    let atomicFlag, tyArgsOpt, args, delayed, tpenv = GetSynMemberApplicationArgs delayed tpenv
    let tyArgsOptChecked, tpenv = TcMemberTyArgsOpt cenv env tpenv tyArgsOpt
    atomicFlag, tyArgsOptChecked, args, delayed, tpenv

and TcLookupThen cenv overallTy env tpenv mObjExpr objExpr objExprTy longId delayed mExprAndLongId =
    let g = cenv.g
    let ad = env.eAccessRights

    let objArgs = [objExpr]

    let findFlag =
        // 'base' calls use a different resolution strategy when finding methods
        // nullness checks need the overrides, since those can change nullable semantics (e.g. ToString from BCL)
        if (g.checkNullness && g.langFeatureNullness) || IsBaseCall objArgs then
            PreferOverrides
        else
            IgnoreOverrides

    // Canonicalize inference problem prior to '.' lookup on variable types
    if isTyparTy g objExprTy then
        CanonicalizePartialInferenceProblem cenv.css env.DisplayEnv mExprAndLongId (freeInTypeLeftToRight g false objExprTy)

    let maybeAppliedArgExpr = DelayedItem.maybeAppliedArgForPreferExtensionOverProperty delayed
    let item, mItem, rest, afterResolution = ResolveExprDotLongIdentAndComputeRange cenv.tcSink cenv.nameResolver mExprAndLongId ad env.NameEnv objExprTy longId TypeNameResolutionInfo.Default findFlag false maybeAppliedArgExpr
    TcLookupItemThen cenv overallTy env tpenv mObjExpr objExpr objExprTy delayed item mItem rest afterResolution

and TcLookupItemThen cenv overallTy env tpenv mObjExpr objExpr objExprTy delayed item mItem rest afterResolution =
    let g = cenv.g
    let ad = env.eAccessRights
    let objArgs = [objExpr]
    let mExprAndItem = unionRanges mObjExpr mItem
    let delayed = delayRest rest mExprAndItem delayed
    match item with
    | Item.MethodGroup (methodName, minfos, _) ->
        let atomicFlag, tyArgsOpt, args, delayed, tpenv = GetSynMemberApplicationArgs delayed tpenv
        // We pass PossiblyMutates here because these may actually mutate a value type object
        // To get better warnings we special case some of the few known mutate-a-struct method names
        let mutates = (if methodName = "MoveNext" || methodName = "GetNextArg" then DefinitelyMutates else PossiblyMutates)

        match minfos with
        | minfo :: _ ->
            // Check if we have properties with "init-only" setters, which we try to call after init is done.
            CheckInitProperties g minfo methodName mItem
        | _ -> ()

#if !NO_TYPEPROVIDERS
        match TryTcMethodAppToStaticConstantArgs cenv env tpenv (minfos, tyArgsOpt, mExprAndItem, mItem) with
        | Some minfoAfterStaticArguments ->
            // Replace the resolution including the static parameters, plus the extra information about the original method info
            let item = Item.MethodGroup(methodName, [minfoAfterStaticArguments], Some minfos[0])
            CallNameResolutionSinkReplacing cenv.tcSink (mExprAndItem, env.NameEnv, item, [], ItemOccurrence.Use, env.eAccessRights)

            TcMethodApplicationThen cenv env overallTy None tpenv None objArgs mExprAndItem mItem methodName ad mutates false [(minfoAfterStaticArguments, None)] afterResolution NormalValUse args atomicFlag None delayed
        | None ->
        if not minfos.IsEmpty && minfos[0].ProvidedStaticParameterInfo.IsSome then
            error(Error(FSComp.SR.etMissingStaticArgumentsToMethod(), mItem))
#endif

        let tyArgsOpt, tpenv = TcMemberTyArgsOpt cenv env tpenv tyArgsOpt
        let meths = minfos |> List.map (fun minfo -> minfo, None)

        TcMethodApplicationThen cenv env overallTy None tpenv tyArgsOpt objArgs mExprAndItem mItem methodName ad mutates false meths afterResolution NormalValUse args atomicFlag None delayed

    | Item.Property (nm, pinfos, _) ->
        // Instance property
        if isNil pinfos then error (InternalError ("Unexpected error: empty property list", mItem))
        // if there are both intrinsics and extensions in pinfos, intrinsics will be listed first.
        // by looking at List.Head we are letting the intrinsics determine indexed/non-indexed
        let pinfo = List.head pinfos
        let atomicFlag, tyArgsOpt, args, delayed, tpenv =
            if pinfo.IsIndexer
            then GetMemberApplicationArgs delayed cenv env tpenv
            else ExprAtomicFlag.Atomic, None, [mkSynUnit mItem], delayed, tpenv
        if pinfo.IsStatic then error (Error (FSComp.SR.tcPropertyIsStatic nm, mItem))


        match delayed with
        | DelayedSet(expr2, mStmt) :: otherDelayed ->
            if not (isNil otherDelayed) then error(Error(FSComp.SR.tcInvalidAssignment(), mStmt))
            // Instance property setter
            UnifyTypes cenv env mStmt overallTy.Commit g.unit_ty
            let meths = SettersOfPropInfos pinfos
            if meths.IsEmpty then
                let meths = pinfos |> GettersOfPropInfos
                let isByrefMethReturnSetter = meths |> List.exists (function _,Some pinfo -> isByrefTy g (pinfo.GetPropertyType(cenv.amap,mItem)) | _ -> false)
                if not isByrefMethReturnSetter then
                    errorR (Error (FSComp.SR.tcPropertyCannotBeSet1 nm, mItem))
                // x.P <- ... byref setter
                if isNil meths then error (Error (FSComp.SR.tcPropertyIsNotReadable nm, mItem))
                TcMethodApplicationThen cenv env overallTy None tpenv tyArgsOpt objArgs mExprAndItem mItem nm ad PossiblyMutates true meths afterResolution NormalValUse args atomicFlag None delayed
            else

                if g.langVersion.SupportsFeature(LanguageFeature.RequiredPropertiesSupport) && pinfo.IsSetterInitOnly then
                    errorR (Error (FSComp.SR.tcInitOnlyPropertyCannotBeSet1 nm, mItem))

                let args = if pinfo.IsIndexer then args else []
                let mut = (if isStructTy g (tyOfExpr g objExpr) then DefinitelyMutates else PossiblyMutates)
                TcMethodApplicationThen cenv env overallTy None tpenv tyArgsOpt objArgs mStmt mItem nm ad mut true meths afterResolution NormalValUse (args @ [expr2]) atomicFlag None []
        | _ ->
            // Instance property getter
            let meths = GettersOfPropInfos pinfos
            if isNil meths then error (Error (FSComp.SR.tcPropertyIsNotReadable nm, mItem))
            TcMethodApplicationThen cenv env overallTy None tpenv tyArgsOpt objArgs mExprAndItem mItem nm ad PossiblyMutates true meths afterResolution NormalValUse args atomicFlag None delayed

    | Item.RecdField rfinfo ->
        // Get or set instance F# field or literal
        RecdFieldInstanceChecks g cenv.amap ad mItem rfinfo
        let tgtTy = rfinfo.DeclaringType
        let boxity = isStructTy g tgtTy
        AddCxTypeMustSubsumeType ContextInfo.NoContext env.DisplayEnv cenv.css mItem NoTrace tgtTy objExprTy
        let objExpr = if boxity then objExpr else mkCoerceExpr(objExpr, tgtTy, mExprAndItem, objExprTy)
        let fieldTy = rfinfo.FieldType
        match delayed with
        | DelayedSet(expr2, mStmt) :: otherDelayed ->
            // Mutable value set: 'v <- e'
            if not (isNil otherDelayed) then error(Error(FSComp.SR.tcInvalidAssignment(), mItem))
            CheckRecdFieldMutation mItem env.DisplayEnv rfinfo
            UnifyTypes cenv env mStmt overallTy.Commit g.unit_ty
            // Always allow subsumption on assignment to fields
            let expr2R, tpenv = TcExprFlex cenv true false fieldTy env tpenv expr2
            BuildRecdFieldSet g mStmt objExpr rfinfo expr2R, tpenv

        | _ ->

            // Instance F# Record or Class field
            let objExpr' = mkRecdFieldGet g (objExpr, rfinfo.RecdFieldRef, rfinfo.TypeInst, mExprAndItem)
            PropagateThenTcDelayed cenv overallTy env tpenv mExprAndItem (MakeApplicableExprWithFlex cenv env objExpr') fieldTy ExprAtomicFlag.Atomic delayed

    | Item.AnonRecdField (anonInfo, tinst, n, _) ->
        let tgtTy = TType_anon (anonInfo, tinst)
        AddCxTypeMustSubsumeType ContextInfo.NoContext env.DisplayEnv cenv.css mItem NoTrace tgtTy objExprTy
        let fieldTy = List.item n tinst
        match delayed with
        | DelayedSet _ :: _otherDelayed ->
            error(Error(FSComp.SR.tcInvalidAssignment(),mItem))
        | _ ->
            // Instance F# Anonymous Record
            let objExpr' = mkAnonRecdFieldGet g (anonInfo,objExpr,tinst,n,mExprAndItem)
            PropagateThenTcDelayed cenv overallTy env tpenv mExprAndItem (MakeApplicableExprWithFlex cenv env objExpr') fieldTy ExprAtomicFlag.Atomic delayed

    | Item.ILField finfo ->
        // Get or set instance IL field
        ILFieldInstanceChecks g cenv.amap ad mItem finfo
        let exprTy = finfo.FieldType(cenv.amap, mItem)

        match delayed with
        // Set instance IL field
        | DelayedSet(expr2, mStmt) :: _delayed' ->
            UnifyTypes cenv env mStmt overallTy.Commit g.unit_ty
            // Always allow subsumption on assignment to fields
            let expr2R, tpenv = TcExprFlex cenv true false exprTy env tpenv expr2
            let expr = BuildILFieldSet g mStmt objExpr finfo expr2R
            expr, tpenv
        | _ ->
            let expr = BuildILFieldGet g cenv.amap mExprAndItem objExpr finfo
            PropagateThenTcDelayed cenv overallTy env tpenv mExprAndItem (MakeApplicableExprWithFlex cenv env expr) exprTy ExprAtomicFlag.Atomic delayed

    | Item.Event einfo ->
        // Instance IL event (fake up event-as-value)
        TcEventItemThen cenv overallTy env tpenv mItem mExprAndItem (Some(objExpr, objExprTy)) einfo delayed

    | Item.Trait traitInfo ->
        TcTraitItemThen cenv overallTy env (Some objExpr) traitInfo tpenv mItem delayed

    | Item.DelegateCtor _ -> error (Error (FSComp.SR.tcConstructorsCannotBeFirstClassValues(), mItem))

    | Item.UnionCase(info, _) ->
        let clashingNames = info.Tycon.MembersOfFSharpTyconSorted |> List.tryFind(fun mem -> mem.DisplayNameCore = info.DisplayNameCore)
        match clashingNames with
        | None -> ()
        | Some value ->
            let kind = if value.IsMember then "member" else "value"
            errorR (NameClash(info.DisplayNameCore, kind, info.DisplayNameCore, value.Range, FSComp.SR.typeInfoUnionCase(), info.DisplayNameCore, value.Range))

        error (Error (FSComp.SR.tcSyntaxFormUsedOnlyWithRecordLabelsPropertiesAndFields(), mItem))
    // These items are not expected here - they can't be the result of a instance member dot-lookup "expr.Ident"
    | Item.ActivePatternResult _
    | Item.CustomOperation _
    | Item.CtorGroup _
    | Item.ExnCase _
    | Item.ImplicitOp _
    | Item.ModuleOrNamespaces _
    | Item.TypeVar _
    | Item.Types _
    | Item.UnionCaseField _
    | Item.UnqualifiedType _
    | Item.Value _
    // These items are not expected here - they are only used for reporting symbols from name resolution to language service
    | Item.NewDef _
    | Item.SetterArg _
    | Item.CustomBuilder _
    | Item.OtherName _
    | Item.ActivePatternCase _ ->
        error (Error (FSComp.SR.tcSyntaxFormUsedOnlyWithRecordLabelsPropertiesAndFields(), mItem))

// Instance IL event (fake up event-as-value)
and TcEventItemThen (cenv: cenv) overallTy env tpenv mItem mExprAndItem objDetails (einfo: EventInfo) delayed =
    let g = cenv.g
    let ad = env.eAccessRights

    let nm = einfo.EventName

    match objDetails, einfo.IsStatic with
    | Some _, true -> error (Error (FSComp.SR.tcEventIsStatic nm, mItem))
    | None, false -> error (Error (FSComp.SR.tcEventIsNotStatic nm, mItem))
    | _ -> ()

    // The F# wrappers around events are null safe (impl is in FSharp.Core). Therefore, from an F# perspective, the type of the delegate can be considered Not Null.
    let delTy = einfo.GetDelegateType(cenv.amap, mItem) |> replaceNullnessOfTy KnownWithoutNull
    let (SigOfFunctionForDelegate(delInvokeMeth, delArgTys, _, _)) = GetSigOfFunctionForDelegate cenv.infoReader delTy mItem ad
    let objArgs = Option.toList (Option.map fst objDetails)
    MethInfoChecks g cenv.amap true None objArgs env.eAccessRights mItem delInvokeMeth

    CheckILEventAttributes g einfo.DeclaringTyconRef (einfo.GetCustomAttrs()) mItem |> CommitOperationResult

    // This checks for and drops the 'object' sender
    let argsTy = ArgsTypeOfEventInfo cenv.infoReader mItem ad einfo
    if not (slotSigHasVoidReturnTy (delInvokeMeth.GetSlotSig(cenv.amap, mItem))) then errorR (nonStandardEventError einfo.EventName mItem)
    let delEventTy = mkIEventType g delTy argsTy

    let bindObjArgs f =
        match objDetails with
        | None -> f []
        | Some (objExpr, objExprTy) -> mkCompGenLetIn mItem "eventTarget" objExprTy objExpr (fun (_, ve) -> f [ve])

    // Bind the object target expression to make sure we only run its side effects once, and to make
    // sure if it's a mutable reference then we dereference it - see FSharp 1.0 bug 942
    let expr =
        bindObjArgs (fun objVars ->
             //     EventHelper ((fun d -> e.add_X(d)), (fun d -> e.remove_X(d)), (fun f -> new 'Delegate(f)))
            mkCallCreateEvent g mItem delTy argsTy
               (let dv, de = mkCompGenLocal mItem "eventDelegate" delTy
                let callExpr, _ = BuildPossiblyConditionalMethodCall cenv env PossiblyMutates mItem false einfo.AddMethod NormalValUse [] objVars [de] None
                mkLambda mItem dv (callExpr, g.unit_ty))
               (let dv, de = mkCompGenLocal mItem "eventDelegate" delTy
                let callExpr, _ = BuildPossiblyConditionalMethodCall cenv env PossiblyMutates mItem false einfo.RemoveMethod NormalValUse [] objVars [de] None
                mkLambda mItem dv (callExpr, g.unit_ty))
               (let fvty = mkFunTy g g.obj_ty_withNulls (mkFunTy g argsTy g.unit_ty)
                let fv, fe = mkCompGenLocal mItem "callback" fvty
                let createExpr = BuildNewDelegateExpr (Some einfo, g, cenv.amap, delTy, delInvokeMeth, delArgTys, fe, fvty, mItem)
                mkLambda mItem fv (createExpr, delTy)))

    let exprTy = delEventTy
    PropagateThenTcDelayed cenv overallTy env tpenv mExprAndItem (MakeApplicableExprNoFlex cenv expr) exprTy ExprAtomicFlag.Atomic delayed


//-------------------------------------------------------------------------
// Method uses can calls
//-------------------------------------------------------------------------

/// Typecheck method/member calls and uses of members as first-class values.
and TcMethodApplicationThen
       cenv
       env
        // The type of the overall expression including "delayed". The method "application" may actually be a use of a member as
        // a first-class function value, when this would be a function type.
       (overallTy: OverallTy)
       objTyOpt   // methodType
       tpenv
       callerTyArgs // The return type of the overall expression including "delayed"
       objArgs      // The 'obj' arguments in obj.M(...) and obj.M, if any
       m           // The range of the object argument or whole application. We immediately union this with the range of the arguments
       mItem       // The range of the item that resolved to the method name
       methodName // string, name of the method
       ad          // accessibility rights of the caller
       mut         // what do we know/assume about whether this method will mutate or not?
       isProp      // is this a property call? Used for better error messages and passed to BuildMethodCall
       meths       // the set of methods we may be calling
       afterResolution // do we need to notify sink after overload resolution
       isSuperInit // is this a special invocation, e.g. a super-class constructor call. Passed through to BuildMethodCall
       args        // the _syntactic_ method arguments, not yet type checked.
       atomicFlag // is the expression atomic or not?
       staticTyOpt // is there a static type that governs the call, different to the nominal type containing the member, e.g. 'T.CallSomeMethod()
       delayed     // further lookups and applications that follow this
     =

    let g = cenv.g

    // Nb. args is always of List.length <= 1 except for indexed setters, when it is 2
    let mWholeExpr = (m, args) ||> List.fold (fun m arg -> unionRanges m arg.Range)

    // c.atomicLeftMethExpr[idx] as application gives a warning
    checkHighPrecedenceFunctionApplicationToList g args atomicFlag mWholeExpr

    // Work out if we know anything about the return type of the overall expression. If there are any delayed
    // lookups then we don't know anything.
    let exprTy = if isNil delayed then overallTy else MustEqual (NewInferenceType g)

    // Call the helper below to do the real checking
    let (expr, attributeAssignedNamedItems, delayed), tpenv =
        TcMethodApplication false cenv env tpenv callerTyArgs objArgs mWholeExpr mItem methodName objTyOpt ad mut isProp meths afterResolution isSuperInit args exprTy staticTyOpt delayed

    // Give errors if some things couldn't be assigned
    if not (isNil attributeAssignedNamedItems) then
        let (CallerNamedArg(id, _)) = List.head attributeAssignedNamedItems
        errorR(Error(FSComp.SR.tcNamedArgumentDidNotMatch(id.idText), id.idRange))

    // Resolve the "delayed" lookups
    let exprTy = (tyOfExpr g expr)

    for problematicTy in GetDisallowedNullness g exprTy do
        let denv = env.DisplayEnv
        warning(Error(FSComp.SR.tcDisallowedNullableApplication(methodName,NicePrint.minimalStringOfType denv problematicTy), m))

    PropagateThenTcDelayed cenv overallTy env tpenv mWholeExpr (MakeApplicableExprNoFlex cenv expr) exprTy atomicFlag delayed

/// Infer initial type information at the callsite from the syntax of an argument, prior to overload resolution.
and GetNewInferenceTypeForMethodArg (cenv: cenv) x =

    let g = cenv.g

    let rec loopExpr expr cont : struct (_ * _) =
        match expr with
        | SynExprParen (a, _, _, _) ->
            loopExpr a cont
        | SynExpr.AddressOf (true, a, _, m) ->
            loopExpr a (cont << fun struct (depth, ty) -> depth + 1, mkByrefTyWithInference g ty (NewByRefKindInferenceType g m))
        | SynExpr.Lambda (body = a)
        | SynExpr.DotLambda (expr = a) ->
            loopExpr a (cont << fun struct (depth, ty) -> depth + 1, mkFunTy g (NewInferenceType g) ty)
        | SynExpr.MatchLambda (matchClauses = SynMatchClause (resultExpr = a) :: clauses) ->
            let loopClause a = loopExpr a (cont << fun struct (depth, ty) -> depth + 1, mkFunTy g (NewInferenceType g) ty)

            // Look at all branches, keeping the one
            // that gives us the most syntactic information.
            (loopClause a, clauses)
            ||> List.fold (fun (maxClauseDepth, _ as acc) (SynMatchClause (resultExpr = a)) ->
                match loopClause a with
                | clauseDepth, ty when clauseDepth > maxClauseDepth -> clauseDepth, ty
                | _ -> acc)
        | SynExpr.Quote (_, raw, a, _, _) ->
            if raw then cont (0, mkRawQuotedExprTy g)
            else loopExpr a (cont << fun struct (depth, ty) -> depth + 1, mkQuotedExprTy g ty)
        | _ -> cont (0, NewInferenceType g)

    let struct (_depth, ty) = loopExpr x id
    ty

and CalledMethHasSingleArgumentGroupOfThisLength n (calledMeth: MethInfo) =
    match calledMeth.NumArgs with
    | [argAttribs] -> argAttribs = n
    | _ -> false

and isSimpleFormalArg info =
    let (ParamAttribs(isParamArrayArg, _isInArg, isOutArg, optArgInfo, callerInfo, _reflArgInfo)) = info
    not isParamArrayArg && not isOutArg && not optArgInfo.IsOptional && callerInfo = NoCallerInfo

and GenerateMatchingSimpleArgumentTypes (cenv: cenv) (calledMeth: MethInfo) mItem =
    let g = cenv.g
    let curriedMethodArgAttribs = calledMeth.GetParamAttribs(cenv.amap, mItem)
    curriedMethodArgAttribs
    |> List.map (List.filter isSimpleFormalArg >> NewInferenceTypes g)

and UnifyMatchingSimpleArgumentTypes (cenv: cenv) (env: TcEnv) exprTy (calledMeth: MethInfo) mMethExpr mItem =
    let g = cenv.g
    let denv = env.DisplayEnv
    let curriedArgTys = GenerateMatchingSimpleArgumentTypes cenv calledMeth mItem
    let returnTy =
        (exprTy, curriedArgTys) ||> List.fold (fun exprTy argTys ->
            let domainTy, resultTy = UnifyFunctionType None cenv denv mMethExpr exprTy
            UnifyTypes cenv env mMethExpr domainTy (mkRefTupledTy g argTys)
            resultTy)
    curriedArgTys, returnTy

/// Split the syntactic arguments (if any) into named and unnamed parameters
///
/// In one case (the second "single named item" rule) we delay the application of a
/// argument until we've produced a lambda that detuples an input tuple
and TcMethodApplication_SplitSynArguments
    (cenv: cenv)
    (env: TcEnv)
    _tpenv
    isProp
    (candidates: MethInfo list)
    (exprTy: OverallTy)
    curriedCallerArgs
    mItem =

    let g = cenv.g
    let denv = env.DisplayEnv

    match curriedCallerArgs with
    | [] ->
        None, None, exprTy
    | _ ->
        let unnamedCurriedCallerArgs, namedCurriedCallerArgs = curriedCallerArgs |> List.map GetMethodArgs |> List.unzip

        // There is an mismatch when _uses_ of indexed property setters in the tc.fs code that calls this function.
        // The arguments are passed as if they are curried with arity [numberOfIndexParameters;1], however in the TAST, indexed property setters
        // are uncurried and have arity [numberOfIndexParameters+1].
        //
        // Here we work around this mismatch by crunching all property argument lists to uncurried form.
        // Ideally the problem needs to be solved at its root cause at the callsites to this function
        let unnamedCurriedCallerArgs, namedCurriedCallerArgs =
            if isProp then
                [List.concat unnamedCurriedCallerArgs], [List.concat namedCurriedCallerArgs]
            else
                unnamedCurriedCallerArgs, namedCurriedCallerArgs

        let MakeUnnamedCallerArgInfo x = (x, GetNewInferenceTypeForMethodArg cenv x, x.Range)

        let singleMethodCurriedArgs =
            match candidates with
            | [calledMeth] when List.forall isNil namedCurriedCallerArgs  ->
                let curriedCalledArgs = calledMeth.GetParamAttribs(cenv.amap, mItem)
                match curriedCalledArgs with
                | [arg :: _] when isSimpleFormalArg arg -> Some(curriedCalledArgs)
                | _ -> None
            | _ -> None

        // "single named item" rule. This is where we have a single accessible method
        //      member x.M(arg1)
        // being used with
        //      x.M (x, y)
        // Without this rule this requires
        //      x.M ((x, y))
        match singleMethodCurriedArgs, unnamedCurriedCallerArgs with
        | Some [[_]], _ ->
            let unnamedCurriedCallerArgs = curriedCallerArgs |> List.map (MakeUnnamedCallerArgInfo >> List.singleton)
            let namedCurriedCallerArgs = namedCurriedCallerArgs |> List.map (fun _ -> [])
            (Some (unnamedCurriedCallerArgs, namedCurriedCallerArgs), None, exprTy)

        // "single named item" rule. This is where we have a single accessible method
        //      member x.M(arg1, arg2)
        // being used with
        //      x.M p
        // We typecheck this as if it has been written "(fun (v1, v2) -> x.M(v1, v2)) p"
        // Without this rule this requires
        //      x.M (fst p, snd p)
        | Some [_ :: args], [[_]] when List.forall isSimpleFormalArg args ->
            // The call lambda has function type
            let exprTy = mkFunTy g (NewInferenceType g) exprTy.Commit

            (None, Some unnamedCurriedCallerArgs.Head.Head, MustEqual exprTy)

        | _ ->
            let unnamedCurriedCallerArgs = unnamedCurriedCallerArgs |> List.mapSquared MakeUnnamedCallerArgInfo
            let namedCurriedCallerArgs = namedCurriedCallerArgs |> List.mapSquared (fun (isOpt, nm, x) ->
                let ty = GetNewInferenceTypeForMethodArg cenv x
                // #435263: compiler crash with .net optional parameters and F# optional syntax
                // named optional arguments should always have option type
                // STRUCT OPTIONS: if we allow struct options as optional arguments then we should relax this and rely
                // on later inference to work out if this is a struct option or ref option
                let ty = if isOpt then mkOptionTy denv.g ty else ty
                nm, isOpt, x, ty, x.Range)

            (Some (unnamedCurriedCallerArgs, namedCurriedCallerArgs), None, exprTy)

// STEP 1. UnifyUniqueOverloading. This happens BEFORE we type check the arguments.
// Extract what we know about the caller arguments, either type-directed if
// no arguments are given or else based on the syntax of the arguments.
and TcMethodApplication_UniqueOverloadInference
    (cenv: cenv)
    (env: TcEnv)
    (exprTy: OverallTy)
    tyArgsOpt
    ad
    objTyOpt
    isCheckingAttributeCall
    callerObjArgTys
    methodName
    curriedCallerArgsOpt
    candidateMethsAndProps
    candidates
    mMethExpr
    mItem
    staticTyOpt =

    let g = cenv.g
    let denv = env.DisplayEnv
    let dummyExpr = mkSynUnit mItem

    // Build the CallerArg values for the caller's arguments.
    // Fake up some arguments if this is the use of a method as a first class function
    let unnamedCurriedCallerArgs, namedCurriedCallerArgs, returnTy =

        match curriedCallerArgsOpt, candidates with
        // "single named item" rule. This is where we have a single accessible method
        //      member x.M(arg1, ..., argN)
        // being used in a first-class way, i.e.
        //      x.M
        // Because there is only one accessible method info available based on the name of the item
        // being accessed we know the number of arguments the first class use of this
        // method will take. Optional and out args are _not_ included, which means they will be resolved
        // to their default values (for optionals) and be part of the return tuple (for out args).
        | None, [calledMeth] ->
            let curriedArgTys, returnTy = UnifyMatchingSimpleArgumentTypes cenv env exprTy.Commit calledMeth mMethExpr mItem
            let unnamedCurriedCallerArgs = curriedArgTys |> List.mapSquared (fun ty -> CallerArg(ty, mMethExpr, false, dummyExpr))
            let namedCurriedCallerArgs = unnamedCurriedCallerArgs |> List.map (fun _ -> [])
            unnamedCurriedCallerArgs, namedCurriedCallerArgs, MustEqual returnTy

        // "type directed" rule for first-class uses of ambiguous methods.
        // By context we know a type for the input argument. If it's a tuple
        // this gives us the potential number of arguments expected. Indeed even if it's a variable
        // type we assume the number of arguments is just "1".
        | None, _ ->

            let domainTy, returnTy = UnifyFunctionTypeAndRecover None cenv denv mMethExpr exprTy.Commit
            let argTys = if isUnitTy g domainTy then [] else tryDestRefTupleTy g domainTy
            // Only apply this rule if a candidate method exists with this number of arguments
            let argTys =
                if candidates |> List.exists (CalledMethHasSingleArgumentGroupOfThisLength argTys.Length) then
                    argTys
                else
                    [domainTy]
            let unnamedCurriedCallerArgs = [argTys |> List.map (fun ty -> CallerArg(ty, mMethExpr, false, dummyExpr)) ]
            let namedCurriedCallerArgs = unnamedCurriedCallerArgs |> List.map (fun _ -> [])
            unnamedCurriedCallerArgs, namedCurriedCallerArgs, MustEqual returnTy

        | Some (unnamedCurriedCallerArgs, namedCurriedCallerArgs), _ ->
            let unnamedCurriedCallerArgs = unnamedCurriedCallerArgs |> List.mapSquared (fun (argExpr, argTy, mArg) -> CallerArg(argTy, mArg, false, argExpr))
            let namedCurriedCallerArgs = namedCurriedCallerArgs |> List.mapSquared (fun (id, isOpt, argExpr, argTy, mArg) -> CallerNamedArg(id, CallerArg(argTy, mArg, isOpt, argExpr)))
            unnamedCurriedCallerArgs, namedCurriedCallerArgs, exprTy

    let callerArgCounts = (List.sumBy List.length unnamedCurriedCallerArgs, List.sumBy List.length namedCurriedCallerArgs)

    let callerArgs = { Unnamed = unnamedCurriedCallerArgs; Named = namedCurriedCallerArgs }

    let arityFilteredCandidates = candidateMethsAndProps

    let makeOneCalledMeth (minfo, pinfoOpt, usesParamArrayConversion) =
        let minst = FreshenMethInfo mItem minfo
        let callerTyArgs =
            match tyArgsOpt with
            | Some tyargs -> minfo.AdjustUserTypeInstForFSharpStyleIndexedExtensionMembers tyargs
            | None -> minst
        CalledMeth<SynExpr>(cenv.infoReader, Some(env.NameEnv), isCheckingAttributeCall, FreshenMethInfo, mMethExpr, ad, minfo, minst, callerTyArgs, pinfoOpt, callerObjArgTys, callerArgs, usesParamArrayConversion, true, objTyOpt, staticTyOpt)

    let preArgumentTypeCheckingCalledMethGroup =
        [ for minfo, pinfoOpt in arityFilteredCandidates do
            let meth = makeOneCalledMeth (minfo, pinfoOpt, true)
            yield meth
            if meth.UsesParamArrayConversion then
                yield makeOneCalledMeth (minfo, pinfoOpt, false) ]

    let uniquelyResolved =
        UnifyUniqueOverloading denv cenv.css mMethExpr callerArgCounts methodName ad preArgumentTypeCheckingCalledMethGroup returnTy

    uniquelyResolved, preArgumentTypeCheckingCalledMethGroup

/// MethodApplication - STEP 2a. First extract what we know about the caller arguments, either type-directed if
/// no arguments are given or else based on the syntax of the arguments.
and TcMethodApplication_CheckArguments
    (cenv: cenv)
    (env: TcEnv)
    (exprTy: OverallTy)
    curriedCallerArgsOpt
    candidates
    (preArgumentTypeCheckingCalledMethGroup: CalledMeth<SynExpr> list)
    callerObjArgTys
    ad
    mMethExpr
    mItem
    tpenv =

    let g = cenv.g
    let denv = env.DisplayEnv
    match curriedCallerArgsOpt with
    | None ->
        let curriedArgTys, curriedArgNamesIfFeatureEnabled, returnTy =
            let paramNamesIfFeatureEnabled (g: TcGlobals) (meth: MethInfo) =
                if g.langVersion.SupportsFeature LanguageFeature.ImprovedImpliedArgumentNames then
                    meth.GetParamNames()
                else
                    []

            match candidates with
            // "single named item" rule. This is where we have a single accessible method
            //      member x.M(arg1, ..., argN)
            // being used in a first-class way, i.e.
            //      x.M
            // Because there is only one accessible method info available based on the name of the item
            // being accessed we know the number of arguments the first class use of this
            // method will take. Optional and out args are _not_ included, which means they will be resolved
            // to their default values (for optionals) and be part of the return tuple (for out args).
            | [calledMeth] ->
                let curriedArgTys, returnTy = UnifyMatchingSimpleArgumentTypes cenv env exprTy.Commit calledMeth mMethExpr mItem
                curriedArgTys, paramNamesIfFeatureEnabled g calledMeth, MustEqual returnTy
            | _ ->
                let domainTy, returnTy = UnifyFunctionTypeAndRecover None cenv denv mMethExpr exprTy.Commit
                let argTys = if isUnitTy g domainTy then [] else tryDestRefTupleTy g domainTy
                // Only apply this rule if a candidate method exists with this number of arguments
                let argTys, argNames =
                    match candidates |> List.tryFind (CalledMethHasSingleArgumentGroupOfThisLength argTys.Length) with
                    | Some meth -> argTys, paramNamesIfFeatureEnabled g meth
                    | None -> [domainTy], [[None]]
                [argTys], argNames, MustEqual returnTy

        let lambdaVarsAndExprs =
            curriedArgTys
            |> List.mapiSquared (fun i j ty ->
                let argName = curriedArgNamesIfFeatureEnabled |> List.tryItem i |> Option.bind (List.tryItem j) |> Option.flatten |> Option.defaultWith (fun () -> "arg" + string i + string j)
                mkCompGenLocal mMethExpr argName ty)

        let unnamedCurriedCallerArgs = lambdaVarsAndExprs |> List.mapSquared (fun (_, e) -> CallerArg(tyOfExpr g e, e.Range, false, e))
        let namedCurriedCallerArgs = lambdaVarsAndExprs |> List.map (fun _ -> [])
        let lambdaVars = List.mapSquared fst lambdaVarsAndExprs
        unnamedCurriedCallerArgs, namedCurriedCallerArgs, Some lambdaVars, returnTy, tpenv

    | Some (unnamedCurriedCallerArgs, namedCurriedCallerArgs) ->
        // This is the case where some explicit arguments have been given.

        let unnamedCurriedCallerArgs = unnamedCurriedCallerArgs |> List.mapSquared (fun (argExpr, argTy, mArg) -> CallerArg(argTy, mArg, false, argExpr))
        let namedCurriedCallerArgs = namedCurriedCallerArgs |> List.mapSquared (fun (id, isOpt, argExpr, argTy, mArg) -> CallerNamedArg(id, CallerArg(argTy, mArg, isOpt, argExpr)))

        // Collect the information for F# 3.1 lambda propagation rule, and apply the caller's object type to the method's object type if the rule is relevant.
        let lambdaPropagationInfo =
            if preArgumentTypeCheckingCalledMethGroup.Length > 1 then
                [| for meth in preArgumentTypeCheckingCalledMethGroup do
                    match ExamineMethodForLambdaPropagation g mMethExpr meth ad with
                    | Some (unnamedInfo, namedInfo) ->
                        let calledObjArgTys = meth.CalledObjArgTys mMethExpr
                        if (calledObjArgTys, callerObjArgTys) ||> Seq.forall2 (fun calledTy callerTy ->
                            let noEagerConstraintApplication =
                                MethInfoHasWellKnownAttributeSpec
                                    g
                                    mMethExpr
                                    { ILFlag = WellKnownILAttributes.NoEagerConstraintApplicationAttribute
                                      ValFlag = WellKnownValAttributes.NoEagerConstraintApplicationAttribute
                                      AttribInfo = g.attrib_NoEagerConstraintApplicationAttribute }
                                    meth.Method

                            // The logic associated with NoEagerConstraintApplicationAttribute is part of the
                            // Tasks and Resumable Code RFC
                            if noEagerConstraintApplication && not (g.langVersion.SupportsFeature LanguageFeature.ResumableStateMachines) then
                                errorR(Error(FSComp.SR.tcNoEagerConstraintApplicationAttribute(), mMethExpr))

                            let extraRigidTps = if noEagerConstraintApplication then Zset.ofList typarOrder (freeInTypeLeftToRight g true callerTy) else emptyFreeTypars

                            AddCxTypeMustSubsumeTypeMatchingOnlyUndoIfFailed denv cenv.css mMethExpr extraRigidTps calledTy callerTy) then

                            yield (List.toArraySquared unnamedInfo, List.toArraySquared namedInfo)
                    | None -> () |]
            else
                [| |]

        // Now typecheck the argument expressions
        let unnamedCurriedCallerArgs, (lambdaPropagationInfo, tpenv) = TcUnnamedMethodArgs cenv env lambdaPropagationInfo tpenv unnamedCurriedCallerArgs
        let namedCurriedCallerArgs, (_, tpenv) = TcMethodNamedArgs cenv env lambdaPropagationInfo tpenv namedCurriedCallerArgs
        unnamedCurriedCallerArgs, namedCurriedCallerArgs, None, exprTy, tpenv

// Adhoc constraints on use of .NET methods
// - Uses of Object.GetHashCode and Object.Equals imply an equality constraint on the object argument
// - Uses of a Dictionary() constructor without an IEqualityComparer argument imply an equality constraint on the first type argument.
and TcAdhocChecksOnLibraryMethods (cenv: cenv) (env: TcEnv) isInstance (finalCalledMeth: CalledMeth<_>) (finalCalledMethInfo: MethInfo) objArgs mMethExpr mItem =
    let g = cenv.g

    if (isInstance &&
        finalCalledMethInfo.IsInstance &&
        typeEquiv g finalCalledMethInfo.ApparentEnclosingType g.obj_ty_ambivalent &&
        (finalCalledMethInfo.LogicalName = "GetHashCode" || finalCalledMethInfo.LogicalName = "Equals")) then

        for objArg in objArgs do
            AddCxTypeMustSupportEquality env.DisplayEnv cenv.css mMethExpr NoTrace (tyOfExpr g objArg)

    if HasHeadType g g.tcref_System_Collections_Generic_Dictionary finalCalledMethInfo.ApparentEnclosingType &&
        finalCalledMethInfo.IsConstructor &&
        not (finalCalledMethInfo.GetParamDatas(cenv.amap, mItem, finalCalledMeth.CalledTyArgs)
            |> List.existsSquared (fun (ParamData(_, _, _, _, _, _, _, ty)) ->
                HasHeadType g g.tcref_System_Collections_Generic_IEqualityComparer ty)) then

        match argsOfAppTy g finalCalledMethInfo.ApparentEnclosingType with
        | [dty; _] -> AddCxTypeMustSupportEquality env.DisplayEnv cenv.css mMethExpr NoTrace dty
        | _ -> ()

/// Method calls, property lookups, attribute constructions etc. get checked through here
and TcMethodApplication
        isCheckingAttributeCall
        (cenv: cenv)
        env
        tpenv
        tyArgsOpt
        objArgs
        mMethExpr // range of the entire method expression
        mItem
        methodName
        (objTyOpt: TType option)
        ad
        mut
        isProp
        calledMethsAndProps
        afterResolution
        isSuperInit
        curriedCallerArgs
        (exprTy: OverallTy)
        staticTyOpt // is there a static type that governs the call, different to the nominal type containing the member, e.g. 'T.CallSomeMethod()
        delayed
    =

    let g = cenv.g
    let denv = env.DisplayEnv
    let callerObjArgTys = objArgs |> List.map (tyOfExpr g)
    let calledMeths = calledMethsAndProps |> List.map fst

    // Uses of curried members are ALWAYS treated as if they are first class uses of members.
    // Curried members may not be overloaded (checked at use-site for curried members brought into scope through extension members)
    let curriedCallerArgs, exprTy, delayed =
        match calledMeths with
        | [calledMeth] when not isProp && calledMeth.NumArgs.Length > 1 ->
            [], MustEqual (NewInferenceType g), [ for x in curriedCallerArgs -> DelayedApp(ExprAtomicFlag.NonAtomic, false, None, x, x.Range) ] @ delayed
        | _ when not isProp && calledMeths |> List.exists (fun calledMeth -> calledMeth.NumArgs.Length > 1) ->
            // This condition should only apply when multiple conflicting curried extension members are brought into scope
            error(Error(FSComp.SR.tcOverloadsCannotHaveCurriedArguments(), mMethExpr))
        | _ ->
            curriedCallerArgs, exprTy, delayed

    let candidateMethsAndProps =
        match calledMethsAndProps |> List.filter (fun (meth, _prop) -> IsMethInfoAccessible cenv.amap mItem ad meth) with
        | [] -> calledMethsAndProps
        | accessibleMeths -> accessibleMeths

    let candidates = candidateMethsAndProps |> List.map fst

    // Step 0. Split the syntactic arguments (if any) into named and unnamed parameters
    let curriedCallerArgsOpt, unnamedDelayedCallerArgExprOpt, exprTy =
        TcMethodApplication_SplitSynArguments cenv env tpenv isProp candidates exprTy curriedCallerArgs mItem

    if isProp && Option.isNone curriedCallerArgsOpt then
        error(Error(FSComp.SR.parsIndexerPropertyRequiresAtLeastOneArgument(), mItem))

    // STEP 1. UnifyUniqueOverloading. This happens BEFORE we type check the arguments.
    // Extract what we know about the caller arguments, either type-directed if
    // no arguments are given or else based on the syntax of the arguments.
    let uniquelyResolved, preArgumentTypeCheckingCalledMethGroup =
        TcMethodApplication_UniqueOverloadInference cenv env exprTy tyArgsOpt ad objTyOpt isCheckingAttributeCall callerObjArgTys methodName curriedCallerArgsOpt candidateMethsAndProps candidates mMethExpr mItem staticTyOpt

    // STEP 2. Check arguments
    let unnamedCurriedCallerArgs, namedCurriedCallerArgs, lambdaVars, returnTy, tpenv =
        TcMethodApplication_CheckArguments cenv env exprTy curriedCallerArgsOpt candidates preArgumentTypeCheckingCalledMethGroup callerObjArgTys ad mMethExpr mItem tpenv

    let preArgumentTypeCheckingCalledMethGroup =
       preArgumentTypeCheckingCalledMethGroup |> List.map (fun cmeth -> (cmeth.Method, cmeth.CalledTyArgs, cmeth.AssociatedPropertyInfo, cmeth.UsesParamArrayConversion))

    let uniquelyResolved =
        match uniquelyResolved with
        | ErrorResult _ ->
            match afterResolution with
            | AfterResolution.DoNothing -> ()
            | AfterResolution.RecordResolution(_, _, _, onFailure) -> onFailure()
        | _ -> ()

        uniquelyResolved |> CommitOperationResult

    // STEP 3. Resolve overloading
    /// Select the called method that's the result of overload resolution
    let finalCalledMeth =

        let callerArgs = { Unnamed = unnamedCurriedCallerArgs ; Named = namedCurriedCallerArgs }

        let postArgumentTypeCheckingCalledMethGroup =
            preArgumentTypeCheckingCalledMethGroup |> List.map (fun (minfo, minst, pinfoOpt, usesParamArrayConversion) ->
                let callerTyArgs =
                    match tyArgsOpt with
                    | Some tyargs -> minfo.AdjustUserTypeInstForFSharpStyleIndexedExtensionMembers tyargs
                    | None -> minst
                CalledMeth<Expr>(cenv.infoReader, Some(env.NameEnv), isCheckingAttributeCall, FreshenMethInfo, mMethExpr, ad, minfo, minst, callerTyArgs, pinfoOpt, callerObjArgTys, callerArgs, usesParamArrayConversion, true, objTyOpt, staticTyOpt))

        // Commit unassociated constraints prior to member overload resolution where there is ambiguity
        // about the possible target of the call.
        if not uniquelyResolved then
            CanonicalizePartialInferenceProblem cenv.css denv mItem
                 (unnamedCurriedCallerArgs |> List.collectSquared (fun callerArg -> freeInTypeLeftToRight g false callerArg.CallerArgumentType))

        let result, errors = ResolveOverloadingForCall denv cenv.css mMethExpr methodName callerArgs ad postArgumentTypeCheckingCalledMethGroup true returnTy

        // Narrow the error range for unresolved overloading from the whole expression (mMethExpr)
        // to just the method name. For instance calls like T.Instance.Method(""), mItem covers
        // the entire "T.Instance.Method" range, so we compute the method-name-only range from
        // the end of mItem and the method name length. See https://github.com/dotnet/fsharp/issues/14284.
        let errors =
            match errors with
            | ErrorResult(warns, UnresolvedOverloading(denvErr, callerArgsErr, failure, _mWide)) ->
                let mMethodName =
                    let itemWidth = mItem.EndColumn - mItem.StartColumn
                    // Only narrow when the range is single-line and the method name fits within it.
                    // Generic constructors may have internal names longer than the source text
                    // (e.g., "ImmutableStack`1" vs source "ImmutableStack").
                    if mItem.StartLine = mItem.EndLine && methodName.Length < itemWidth then
                        let startPos = mkPos mItem.EndLine (mItem.EndColumn - methodName.Length)
                        withStart startPos mItem
                    else
                        mItem
                ErrorResult(warns, UnresolvedOverloading(denvErr, callerArgsErr, failure, mMethodName))
            | other -> other

        match afterResolution, result with
        | AfterResolution.DoNothing, _ -> ()

        // Record the precise override resolution
        | AfterResolution.RecordResolution(Some unrefinedItem, _, callSink, _), Some result
             when result.Method.IsVirtual ->

            let overriding =
                match unrefinedItem with
                | Item.MethodGroup(_, overriddenMeths, _) -> overriddenMeths |> List.map (fun minfo -> minfo, None)
                | Item.Property(info = pinfos) ->
                    if result.Method.LogicalName.StartsWithOrdinal("set_") then
                        SettersOfPropInfos pinfos
                    else
                        GettersOfPropInfos pinfos
                | _ -> []

            let overridingInfo =
                overriding
                |> List.tryFind (fun (minfo, _) -> minfo.IsVirtual && MethInfosEquivByNameAndSig EraseNone true g cenv.amap range0 result.Method minfo)

            match overridingInfo with
            | Some (minfo, pinfoOpt) ->
                let tps = minfo.FormalMethodTypars
                let tyargs = result.CalledTyArgs
                let tpinst = if tps.Length = tyargs.Length then mkTyparInst tps tyargs else []
                (minfo, pinfoOpt, tpinst) |> callSink
            | None ->
                (result.Method, result.AssociatedPropertyInfo, result.CalledTyparInst) |> callSink

        // Record the precise overload resolution and the type instantiation
        | AfterResolution.RecordResolution(_, _, callSink, _), Some result ->
            (result.Method, result.AssociatedPropertyInfo, result.CalledTyparInst) |> callSink

        | AfterResolution.RecordResolution(_, _, _, onFailure), None ->
            onFailure()

        // Raise the errors from the constraint solving
        RaiseOperationResult errors
        match result with
        | None -> error(InternalError("at least one error should be returned by failed method overloading", mItem))
        | Some res -> res

    let finalCalledMethInfo = finalCalledMeth.Method
    let finalCalledMethInst = finalCalledMeth.CalledTyArgs
    let finalAssignedItemSetters = finalCalledMeth.AssignedItemSetters
    let finalAttributeAssignedNamedItems = finalCalledMeth.AttributeAssignedNamedArgs

    // STEP 4. Check the attributes on the method and the corresponding event/property, if any

    finalCalledMeth.AssociatedPropertyInfo |> Option.iter (fun pinfo -> CheckPropInfoAttributes pinfo mItem |> CommitOperationResult)

    let isInstance = not (isNil objArgs)

    MethInfoChecks g cenv.amap isInstance tyArgsOpt objArgs ad mItem finalCalledMethInfo

    TcAdhocChecksOnLibraryMethods cenv env isInstance finalCalledMeth finalCalledMethInfo objArgs mMethExpr mItem

    if not finalCalledMeth.IsIndexParamArraySetter &&
       (finalCalledMeth.ArgSets |> List.existsi (fun i argSet -> argSet.UnnamedCalledArgs |> List.existsi (fun j ca -> ca.Position <> (i, j)))) then
        errorR(Deprecated(FSComp.SR.tcUnnamedArgumentsDoNotFormPrefix(), mMethExpr))

    /// STEP 5. Build the argument list. Adjust for optional arguments, byref arguments and coercions.

    let objArgPreBinder, objArgs, allArgsPreBinders, allArgs, allArgsCoerced, optArgPreBinder, paramArrayPreBinders, outArgExprs, outArgTmpBinds =
        let tcVal = LightweightTcValForUsingInBuildMethodCall g
        AdjustCallerArgs tcVal TcFieldInit env.eCallerMemberName cenv.infoReader ad finalCalledMeth objArgs lambdaVars mItem mMethExpr

    // Record the resolution of the named argument for the Language Service
    allArgs |> List.iter (fun assignedArg ->
        match assignedArg.NamedArgIdOpt with
        | None -> ()
        | Some id ->
            let idOpt = Some (defaultArg assignedArg.CalledArg.NameOpt id)
            let m =
                match assignedArg.CalledArg.NameOpt with
                | Some id -> id.idRange
                | None -> id.idRange
            let container = ArgumentContainer.Method finalCalledMethInfo
            let item = Item.OtherName (idOpt, assignedArg.CalledArg.CalledArgumentType, None, Some container, m)
            CallNameResolutionSink cenv.tcSink (id.idRange, env.NameEnv, item, emptyTyparInst, ItemOccurrence.Use, ad))

    /// STEP 6. Build the call expression, then adjust for byref-returns, out-parameters-as-tuples, post-hoc property assignments, methods-as-first-class-value,

    let callExpr0, exprTy =
        BuildPossiblyConditionalMethodCall cenv env mut mMethExpr isProp finalCalledMethInfo isSuperInit finalCalledMethInst objArgs allArgsCoerced staticTyOpt

    // Handle byref returns
    let callExpr1, exprTy =
        // byref-typed returns get implicitly dereferenced
        let vTy = tyOfExpr g callExpr0
        if isByrefTy g vTy then
            mkDerefAddrExpr mMethExpr callExpr0 mMethExpr vTy, destByrefTy g vTy
        else
            callExpr0, exprTy

    // Bind "out" parameters as part of the result tuple
    let callExpr2, exprTy =
        let expr = callExpr1
        if isNil outArgTmpBinds then
            expr, exprTy
        else
            let outArgTys = outArgExprs |> List.map (tyOfExpr g)
            let expr =
                if isUnitTy g exprTy then
                    mkCompGenSequential mMethExpr expr (mkRefTupled g mMethExpr outArgExprs outArgTys)
                else
                    mkRefTupled g mMethExpr (expr :: outArgExprs) (exprTy :: outArgTys)
            let expr = mkLetsBind mMethExpr outArgTmpBinds expr
            expr, tyOfExpr g expr

    // Handle post-hoc property assignments
    let setterExprPrebinders, callExpr2b =
        let expr = callExpr2
        CheckRequiredProperties g env cenv finalCalledMethInfo finalAssignedItemSetters mMethExpr

        if isCheckingAttributeCall then
            [], expr
        elif isNil finalAssignedItemSetters then
            [], expr
        else
            // This holds the result of the call
            let objv, objExpr = mkMutableCompGenLocal mMethExpr "returnVal" exprTy // mutable in case it's a struct

            // Build the expression that mutates the properties on the result of the call
            let setterExprPrebinders, propSetExpr =
                (mkUnit g mMethExpr, finalAssignedItemSetters) ||> List.mapFold (fun acc assignedItemSetter ->
                        let argExprPrebinder, action, m = TcSetterArgExpr cenv env denv objExpr ad assignedItemSetter finalCalledMethInfo.IsConstructor
                        argExprPrebinder, mkCompGenSequential m acc action)

            // now put them together
            let expr = mkCompGenLet mMethExpr objv expr (mkCompGenSequential mMethExpr propSetExpr objExpr)
            setterExprPrebinders, expr

    // Subsumption or conversion to return type
    let callExpr3 = TcAdjustExprForTypeDirectedConversions cenv returnTy exprTy env mMethExpr callExpr2b

    // Build the lambda expression if any, if the method is used as a first-class value
    let callExpr4 =
        let expr = callExpr3
        match lambdaVars with
        | None -> expr
        | Some curriedLambdaVars ->
            let mkLambda vs expr =
                match vs with
                | [] -> mkUnitDelayLambda g mMethExpr expr
                | _ -> mkMultiLambda mMethExpr vs (expr, tyOfExpr g expr)
            List.foldBack mkLambda curriedLambdaVars expr

    let callExpr5, tpenv =
        let expr = callExpr4
        match unnamedDelayedCallerArgExprOpt with
        | Some synArgExpr ->
            match lambdaVars with
            | Some [lambdaVars] ->
                let argExpr, tpenv = TcExpr cenv (MustEqual (mkRefTupledVarsTy g lambdaVars)) env tpenv synArgExpr
                mkApps g ((expr, tyOfExpr g expr), [], [argExpr], mMethExpr), tpenv
            | _ ->
                error(InternalError("unreachable - expected some lambda vars for a tuple mismatch", mItem))
        | None ->
            expr, tpenv

    // Apply the PreBinders, if any
    let callExpr6 =
        let expr = callExpr5
        let expr = (expr, setterExprPrebinders) ||> List.fold (fun expr argPreBinder -> match argPreBinder with None -> expr | Some f -> f expr)
        let expr = (expr, paramArrayPreBinders) ||> List.fold (fun expr argPreBinder -> match argPreBinder with None -> expr | Some f -> f expr)
        let expr = (expr, allArgsPreBinders) ||> List.fold (fun expr argPreBinder -> match argPreBinder with None -> expr | Some f -> f expr)

        let expr = optArgPreBinder expr
        let expr = objArgPreBinder expr
        expr

    (callExpr6, finalAttributeAssignedNamedItems, delayed), tpenv

/// For Method(X = expr) 'X' can be a property, IL Field or F# record field
and TcSetterArgExpr (cenv: cenv) env denv objExpr ad assignedSetter calledFromConstructor =
    let g = cenv.g
    let (AssignedItemSetter(id, setter, callerArg)) = assignedSetter
    let (CallerArg(callerArgTy, m, isOptCallerArg, argExpr)) = callerArg

    if isOptCallerArg then
        error(Error(FSComp.SR.tcInvalidOptionalAssignmentToPropertyOrField(), m))

    let argExprPrebinder, action, defnItem =
        match setter with
        | AssignedPropSetter (propStaticTyOpt, pinfo, pminfo, pminst) ->

            CheckPropInfoAttributes pinfo id.idRange  |> CommitOperationResult

            if g.langVersion.SupportsFeature(LanguageFeature.RequiredPropertiesSupport) && pinfo.IsSetterInitOnly && not calledFromConstructor then
                errorR (Error (FSComp.SR.tcInitOnlyPropertyCannotBeSet1 pinfo.PropertyName, m))

            MethInfoChecks g cenv.amap true None [objExpr] ad m pminfo
            let calledArgTy = List.head (List.head (pminfo.GetParamTypes(cenv.amap, m, pminst)))
            let tcVal = LightweightTcValForUsingInBuildMethodCall g
            let argExprPrebinder, argExpr = AdjustCallerArgExpr tcVal g cenv.amap cenv.infoReader ad false calledArgTy ReflectedArgInfo.None callerArgTy m argExpr
            let mut = (if isStructTy g (tyOfExpr g objExpr) then DefinitelyMutates else PossiblyMutates)
            let action = BuildPossiblyConditionalMethodCall cenv env mut m true pminfo NormalValUse pminst [objExpr] [argExpr] propStaticTyOpt |> fst
            argExprPrebinder, action, Item.Property (pinfo.PropertyName, [pinfo], None)

        | AssignedILFieldSetter finfo ->
            // Get or set instance IL field
            ILFieldInstanceChecks g cenv.amap ad m finfo
            let calledArgTy = finfo.FieldType (cenv.amap, m)
            let tcVal = LightweightTcValForUsingInBuildMethodCall g
            let argExprPrebinder, argExpr = AdjustCallerArgExpr tcVal g cenv.amap cenv.infoReader ad false calledArgTy ReflectedArgInfo.None callerArgTy m argExpr
            let action = BuildILFieldSet g m objExpr finfo argExpr
            argExprPrebinder, action, Item.ILField finfo

        | AssignedRecdFieldSetter rfinfo ->
            RecdFieldInstanceChecks g cenv.amap ad m rfinfo
            let calledArgTy = rfinfo.FieldType
            CheckRecdFieldMutation m denv rfinfo
            let tcVal = LightweightTcValForUsingInBuildMethodCall g
            let argExprPrebinder, argExpr = AdjustCallerArgExpr tcVal g cenv.amap cenv.infoReader ad false calledArgTy ReflectedArgInfo.None callerArgTy m argExpr
            let action = BuildRecdFieldSet g m objExpr rfinfo argExpr
            argExprPrebinder, action, Item.RecdField rfinfo

    // Record the resolution for the Language Service
    let item = Item.SetterArg (id, defnItem)
    CallNameResolutionSink cenv.tcSink (id.idRange, env.NameEnv, item, emptyTyparInst, ItemOccurrence.Use, ad)

    argExprPrebinder, action, m

and TcUnnamedMethodArgs cenv env lambdaPropagationInfo tpenv args =
    List.mapiFoldSquared (TcUnnamedMethodArg cenv env) (lambdaPropagationInfo, tpenv) args

and TcUnnamedMethodArg cenv env (lambdaPropagationInfo, tpenv) (i, j, CallerArg(argTy, mArg, isOpt, argExpr)) =
    // Try to find the lambda propagation info for the corresponding unnamed argument at this position
    let lambdaPropagationInfoForArg =
        [| for unnamedInfo, _ in lambdaPropagationInfo ->
             if i < unnamedInfo.Length && j < unnamedInfo[i].Length then unnamedInfo[i][j] else NoInfo |]
    TcMethodArg cenv env (lambdaPropagationInfo, tpenv) (lambdaPropagationInfoForArg, CallerArg(argTy, mArg, isOpt, argExpr))

and TcMethodNamedArgs cenv env lambdaPropagationInfo tpenv args =
    List.mapFoldSquared (TcMethodNamedArg cenv env) (lambdaPropagationInfo, tpenv) args

and TcMethodNamedArg cenv env (lambdaPropagationInfo, tpenv) (CallerNamedArg(id, arg)) =
    // Try to find the lambda propagation info for the corresponding named argument
    let lambdaPropagationInfoForArg =
        [| for _, namedInfo in lambdaPropagationInfo ->
             namedInfo |> Array.tryPick (fun namedInfoForArgSet ->
                namedInfoForArgSet |> Array.tryPick (fun (nm, info) ->
                        if nm.idText = id.idText then Some info else None)) |]
        |> Array.map (fun x -> defaultArg x NoInfo)

    let arg', (lambdaPropagationInfo, tpenv) = TcMethodArg cenv env (lambdaPropagationInfo, tpenv) (lambdaPropagationInfoForArg, arg)
    CallerNamedArg(id, arg'), (lambdaPropagationInfo, tpenv)

and TcMethodArg cenv env (lambdaPropagationInfo, tpenv) (lambdaPropagationInfoForArg, CallerArg(callerArgTy, mArg, isOpt, argExpr)) =

    let g = cenv.g

    // Apply the F# 3.1+ rule for extracting information for lambdas
    //
    // Before we check the argument, check to see if we can propagate info from a called lambda expression into the arguments of a received lambda
    if lambdaPropagationInfoForArg.Length > 0 then
        let allOverloadsAreNotCalledArgMatchesForThisArg =
            lambdaPropagationInfoForArg
            |> Array.forall (function ArgDoesNotMatch | CallerLambdaHasArgTypes _ | NoInfo -> true | CalledArgMatchesType _ -> false)

        if allOverloadsAreNotCalledArgMatchesForThisArg then
            let overloadsWhichAreFuncAtThisPosition = lambdaPropagationInfoForArg |> Array.choose (function CallerLambdaHasArgTypes r -> Some (List.toArray r) | _ -> None)
            if overloadsWhichAreFuncAtThisPosition.Length > 0 then
                let minFuncArity = overloadsWhichAreFuncAtThisPosition |> Array.minBy Array.length |> Array.length
                let prefixOfLambdaArgsForEachOverload = overloadsWhichAreFuncAtThisPosition |> Array.map (Array.take minFuncArity)

                if prefixOfLambdaArgsForEachOverload.Length > 0 then
                    let numLambdaVars = prefixOfLambdaArgsForEachOverload[0].Length
                    // Fold across the lambda var positions checking if all method overloads imply the same argument type for a lambda variable.
                    // If so, force the caller to have a function type that looks like the calledLambdaArgTy.
                    // The loop variable callerLambdaTyOpt becomes None if something failed.
                    let rec loop callerLambdaTy lambdaVarNum =
                        if lambdaVarNum < numLambdaVars then
                            let calledLambdaArgTy = prefixOfLambdaArgsForEachOverload[0][lambdaVarNum]
                            let allRowsGiveSameArgumentType =
                                prefixOfLambdaArgsForEachOverload
                                |> Array.forall (fun row -> typeEquiv g calledLambdaArgTy row[lambdaVarNum])

                            if allRowsGiveSameArgumentType then
                                // Force the caller to be a function type.
                                match UnifyFunctionTypeUndoIfFailed cenv env.DisplayEnv mArg callerLambdaTy with
                                | ValueSome (callerLambdaDomainTy, callerLambdaRangeTy) ->
                                    if AddCxTypeEqualsTypeUndoIfFailed env.DisplayEnv cenv.css mArg calledLambdaArgTy callerLambdaDomainTy then
                                        loop callerLambdaRangeTy (lambdaVarNum + 1)
                                | _ -> ()
                    loop callerArgTy 0

    let e', tpenv = TcExprFlex2 cenv callerArgTy env true tpenv argExpr

    // After we have checked, propagate the info from argument into the overloads that receive it.
    //
    // Filter out methods where an argument doesn't match. This just filters them from lambda propagation but not from
    // later method overload resolution.
    let lambdaPropagationInfo =
        [| for info, argInfo in Array.zip lambdaPropagationInfo lambdaPropagationInfoForArg do
              match argInfo with
              | ArgDoesNotMatch -> ()
              | NoInfo | CallerLambdaHasArgTypes _ ->
                  yield info
              | CalledArgMatchesType (adjustedCalledArgTy, noEagerConstraintApplication) ->
                  // If matching, we can solve 'tp1 --> tp2' but we can't transfer extra
                  // constraints from tp1 to tp2.
                  //
                  // The 'task' feature requires this fix to SRTP resolution.
                  let extraRigidTps = if noEagerConstraintApplication then Zset.ofList typarOrder (freeInTypeLeftToRight g true callerArgTy) else emptyFreeTypars
                  if AddCxTypeMustSubsumeTypeMatchingOnlyUndoIfFailed env.DisplayEnv cenv.css mArg extraRigidTps adjustedCalledArgTy callerArgTy then
                     yield info |]

    CallerArg(callerArgTy, mArg, isOpt, e'), (lambdaPropagationInfo, tpenv)

/// Typecheck "Delegate(fun x y z -> ...)" constructs
and TcNewDelegateThen cenv (overallTy: OverallTy) env tpenv mDelTy mExprAndArg delegateTy synArg atomicFlag delayed =
    let g = cenv.g
    let ad = env.eAccessRights

    let intermediateTy = if isNil delayed then overallTy.Commit else NewInferenceType g

    UnifyTypes cenv env mExprAndArg intermediateTy delegateTy

    let (SigOfFunctionForDelegate(delInvokeMeth, delArgTys, _, delFuncTy)) = GetSigOfFunctionForDelegate cenv.infoReader delegateTy mDelTy ad

    // We pass isInstance = true here because we're checking the rights to access the "Invoke" method
    MethInfoChecks g cenv.amap true None [] env.eAccessRights mExprAndArg delInvokeMeth

    let synArgs = GetMethodArgs synArg

    match synArgs with
    | [synFuncArg], [] ->
        let m = synArg.Range
        let callerArg, (_, tpenv) = TcMethodArg cenv env (Array.empty, tpenv) (Array.empty, CallerArg(delFuncTy, m, false, synFuncArg))
        let expr = BuildNewDelegateExpr (None, g, cenv.amap, delegateTy, delInvokeMeth, delArgTys, callerArg.Expr, delFuncTy, m)
        PropagateThenTcDelayed cenv overallTy env tpenv m (MakeApplicableExprNoFlex cenv expr) intermediateTy atomicFlag delayed
    | _ ->
        error(Error(FSComp.SR.tcDelegateConstructorMustBePassed(), mExprAndArg))


and bindLetRec (binds: Bindings) m e =
    if isNil binds then
        e
    else
        Expr.LetRec (binds, e, m, Construct.NewFreeVarsCache())

/// Check for duplicate bindings in simple recursive patterns
and CheckRecursiveBindingIds binds =
    let hashOfBinds = HashSet<string>()

    for SynBinding.SynBinding(headPat=b; range=m) in binds do
        let nm =
            match b with
            | SynPat.Named(SynIdent(id,_), _, _, _)
            | SynPat.As(_, SynPat.Named(SynIdent(id,_), _, _, _), _)
            | SynPat.LongIdent(longDotId=SynLongIdent([id], _, _)) -> id.idText
            | _ -> ""
        if nm <> "" && not (hashOfBinds.Add nm) then
            error(Duplicate("value", nm, m))

/// Process a sequence of sequentials mixed with iterated lets "let ... in let ... in ..." in a tail recursive way
/// This avoids stack overflow on really large "let" and "letrec" lists
and TcLinearExprs bodyChecker cenv env overallTy tpenv isCompExpr synExpr cont =

    let g = cenv.g

    match synExpr with
    | SynExpr.Sequential (sp, true, expr1, expr2, m, _) when not isCompExpr ->
        let expr1R, _ =
            let env1 = { env with eIsControlFlow = (match sp with | DebugPointAtSequential.SuppressNeither | DebugPointAtSequential.SuppressExpr -> true | _ -> false) }
            TcStmtThatCantBeCtorBody cenv env1 tpenv expr1
        let env2 = { env with eIsControlFlow = (match sp with | DebugPointAtSequential.SuppressNeither | DebugPointAtSequential.SuppressStmt -> true | _ -> false) }
        let env2 = ShrinkContext env2 m expr2.Range
        // tailcall
        TcLinearExprs bodyChecker cenv env2 overallTy tpenv isCompExpr expr2 (fun (expr2R, tpenv) ->
            cont (Expr.Sequential (expr1R, expr2R, NormalSeq, m), tpenv))

    | LetOrUse({ IsRecursive = isRec ; Bindings = binds; Body = body; Range = m }, _, isUse) when not (isUse && isCompExpr) ->
        if isRec then
            // TcLinearExprs processes at most one recursive binding, this is not tailcalling
            CheckRecursiveBindingIds binds
            let binds = List.map (fun x -> RecDefnBindingInfo(ExprContainerInfo, NoNewSlots, ExpressionBinding, x)) binds
            if isUse then errorR(Error(FSComp.SR.tcBindingCannotBeUseAndRec(), m))
            let binds, envinner, tpenv = TcLetrecBindings ErrorOnOverrides cenv env tpenv (binds, m, m)
            let envinner = { envinner with eIsControlFlow = true }
            let bodyExpr, tpenv = bodyChecker overallTy envinner tpenv body
            let bodyExpr = bindLetRec binds m bodyExpr
            cont (bodyExpr, tpenv)
        else
            // TcLinearExprs processes multiple 'let' bindings in a tail recursive way
            let mkf, envinner, tpenv = TcLetBinding cenv isUse env ExprContainerInfo ExpressionBinding tpenv (binds, m, body.Range)
            let envinner = ShrinkContext envinner m body.Range
            let envinner = { envinner with eIsControlFlow = true }
            // tailcall
            TcLinearExprs bodyChecker cenv envinner overallTy tpenv isCompExpr body (fun (x, tpenv) ->
                cont (fst (mkf (x, overallTy.Commit)), tpenv))

    | SynExpr.IfThenElse (synBoolExpr, synThenExpr, synElseExprOpt, spIfToThen, isRecovery, m, trivia) when not isCompExpr ->

        let boolExpr, tpenv =
            let env = { env with eIsControlFlow = false }
            TcExprThatCantBeCtorBody cenv (MustEqual g.bool_ty) env tpenv synBoolExpr

        let env = { env with eIsControlFlow = true }
        let thenExpr, tpenv =
            let env =
                match env.eContextInfo with
                | ContextInfo.ElseBranchResult _ -> { env with eContextInfo = ContextInfo.ElseBranchResult synThenExpr.Range }
                | _ ->
                    match synElseExprOpt with
                    | None -> { env with eContextInfo = ContextInfo.OmittedElseBranch synThenExpr.Range }
                    | _ -> { env with eContextInfo = ContextInfo.IfExpression synThenExpr.Range }

            if not isRecovery && Option.isNone synElseExprOpt then
                UnifyTypes cenv env m g.unit_ty overallTy.Commit

            CallExprHasTypeSink cenv.tcSink (m, env.NameEnv, overallTy.Commit, env.eAccessRights)

            TcExprThatCanBeCtorBody cenv overallTy env tpenv synThenExpr

        match synElseExprOpt with
        | None ->
            let elseExpr = mkUnit g trivia.IfToThenRange
            let overallExpr = primMkCond spIfToThen m overallTy.Commit boolExpr thenExpr elseExpr
            cont (overallExpr, tpenv)

        | Some synElseExpr ->
            let env = { env with eContextInfo = ContextInfo.ElseBranchResult synElseExpr.Range }
            TryAllowFlexibleNullnessInControlFlow (*isFirst=*) true g overallTy.Commit
            // tailcall
            TcLinearExprs bodyChecker cenv env overallTy tpenv isCompExpr synElseExpr (fun (elseExpr, tpenv) ->
                let resExpr = primMkCond spIfToThen m overallTy.Commit boolExpr thenExpr elseExpr
                cont (resExpr, tpenv))

    | _ ->
        cont (bodyChecker overallTy env tpenv synExpr)

/// Typecheck and compile pattern-matching constructs
and TcAndPatternCompileMatchClauses mExpr mMatch actionOnFailure cenv inputExprOpt inputTy resultTy env tpenv synClauses =
    let clauses, tpenv = TcMatchClauses cenv inputTy resultTy env tpenv synClauses
    let matchVal, expr = CompilePatternForMatchClauses cenv env mExpr mMatch true actionOnFailure inputExprOpt inputTy resultTy.Commit clauses
    matchVal, expr, tpenv

and TcMatchPattern (cenv: cenv) inputTy env tpenv (synPat: SynPat) (synWhenExprOpt: SynExpr option) (tcTrueMatchClause: TcTrueMatchClause) =
    let g = cenv.g
    let m = synPat.Range
    let warnOnUpperFlag =
        match tcTrueMatchClause with
        | TcTrueMatchClause.Yes -> WarnOnUpperUnionCaseLabel
        | TcTrueMatchClause.No -> WarnOnUpperVariablePatterns

    let patf', TcPatLinearEnv (tpenv, names, _) = cenv.TcPat warnOnUpperFlag cenv env None (TcPatValFlags (ValInline.Optional, permitInferTypars, noArgOrRetAttribs, false, None, false)) (TcPatLinearEnv (tpenv, Map.empty, Set.empty)) inputTy synPat
    let envinner, values, vspecMap = MakeAndPublishSimpleValsForMergedScope cenv env m names

    let whenExprOpt, tpenv =
        match synWhenExprOpt with
        | Some synWhenExpr ->
            let guardEnv = { envinner with eContextInfo = ContextInfo.PatternMatchGuard synWhenExpr.Range }
            let whenExprR, tpenv = TcExpr cenv (MustEqual g.bool_ty) guardEnv tpenv synWhenExpr
            Some whenExprR, tpenv
        | None -> None, tpenv

    patf' (TcPatPhase2Input (values, true)), whenExprOpt, NameMap.range vspecMap, envinner, tpenv

and TcMatchClauses cenv inputTy (resultTy: OverallTy) env tpenv clauses =
    let mutable first = true
    let isFirst() = if first then first <- false; true else false
    let resultList,(tpEnv,_input) =
        List.mapFold (fun (unscopedTyParEnv,inputTy) -> TcMatchClause cenv inputTy resultTy env (isFirst()) unscopedTyParEnv) (tpenv,inputTy) clauses
    resultList,tpEnv

and TcMatchClause cenv inputTy (resultTy: OverallTy) env isFirst tpenv synMatchClause =
    let (SynMatchClause(synPat, synWhenExprOpt, synResultExpr, patm, spTgt, _trivia)) = synMatchClause

    let isTrueMatchClause =
        if synMatchClause.IsTrueMatchClause then
            TcTrueMatchClause.Yes
        else
            TcTrueMatchClause.No
   
    let pat, whenExprOpt, vspecs, envinner, tpenv = TcMatchPattern cenv inputTy env tpenv synPat synWhenExprOpt isTrueMatchClause

    let resultEnv =
        if isFirst then envinner
        else { envinner with eContextInfo = ContextInfo.FollowingPatternMatchClause synResultExpr.Range }

    let resultEnv =
        match spTgt with
        | DebugPointAtTarget.Yes -> { resultEnv with eIsControlFlow = true }
        | DebugPointAtTarget.No -> resultEnv

    let resultExpr, tpenv = TcExprThatCanBeCtorBody cenv resultTy resultEnv tpenv synResultExpr
    TryAllowFlexibleNullnessInControlFlow isFirst cenv.g resultTy.Commit

    let target = TTarget(vspecs, resultExpr, None)

    let inputTypeForNextPatterns=
        let removeNull t =
            // Strip type equations (including abbreviations) and set nullness to non-null.
            // For type abbreviations like `type objnull = obj | null`, we need to expand
            // the abbreviation and apply non-null to the underlying type.
            let stripped = stripTyEqns cenv.g t
            replaceNullnessOfTy KnownWithoutNull stripped
        let rec isWild (p:Pattern) =
            match p with
            | TPat_wild _ -> true
            | TPat_as (p,_,_) -> isWild p
            | TPat_disjs(patterns,_) -> patterns |> List.exists isWild
            | TPat_conjs(patterns,_) -> patterns |> List.forall isWild
            | TPat_tuple (_,pats,_,_) -> pats |> List.forall isWild
            | _ -> false

        let rec eliminateNull (ty:TType) (p:Pattern) =
            match p with
            | TPat_null _ -> removeNull ty
            | TPat_as (p,_,_) -> eliminateNull ty p
            | TPat_disjs(patterns,_) -> (ty,patterns) ||> List.fold eliminateNull
            | TPat_tuple (_,pats,_,_) ->
                match stripTyparEqns ty with
                // In a tuple, if 1 elem is matched for null and the rest are wild => subsequent clauses can strip nullness
                | TType_tuple(ti,tys) when tys.Length = pats.Length && (pats |> List.count (isWild >> not)) = 1 ->
                    TType_tuple(ti, List.map2 eliminateNull tys pats)
                | _ -> ty
            | _ -> ty
        match whenExprOpt with
        | None -> eliminateNull inputTy pat
        | _ -> inputTy

    MatchClause(pat, whenExprOpt, target, patm), (tpenv,inputTypeForNextPatterns)

and TcStaticOptimizationConstraint cenv env tpenv c =
    let g = cenv.g

    match c with
    | SynStaticOptimizationConstraint.WhenTyparTyconEqualsTycon(tp, ty, m) ->
        if not g.compilingFSharpCore then
            errorR(Error(FSComp.SR.tcStaticOptimizationConditionalsOnlyForFSharpLibrary(), m))
        let tyR, tpenv = TcType cenv NewTyparsOK CheckCxs ItemOccurrence.UseInType WarnOnIWSAM.Yes env tpenv ty
        let tpR, tpenv = TcTypar cenv env NewTyparsOK tpenv tp
        TTyconEqualsTycon(mkTyparTy tpR, tyR), tpenv
    | SynStaticOptimizationConstraint.WhenTyparIsStruct(tp, m) ->
        if not g.compilingFSharpCore then
            errorR(Error(FSComp.SR.tcStaticOptimizationConditionalsOnlyForFSharpLibrary(), m))
        let tpR, tpenv = TcTypar cenv env NewTyparsOK tpenv tp
        TTyconIsStruct(mkTyparTy tpR), tpenv

/// Emit a conv.i instruction
and mkConvToNativeInt (g: TcGlobals) e m = Expr.Op (TOp.ILAsm ([ AI_conv ILBasicType.DT_I], [ g.nativeint_ty ]), [], [e], m)

/// Fix up the r.h.s. of a 'use x = fixed expr'
and TcAndBuildFixedExpr (cenv: cenv) env (overallPatTy, fixedExpr, overallExprTy, mBinding) =

    let g = cenv.g

    // Search for GetPinnableReference (like https://learn.microsoft.com/en-us/dotnet/api/system.span-1.getpinnablereference?view=net-7.0)
    // on the target expression, and, if it exists, call it
    let tryBuildGetPinnableReferenceCall () =
        let getPinnableReferenceMInfo =
            TryFindIntrinsicOrExtensionMethInfo ResultCollectionSettings.AllResults cenv env mBinding env.eAccessRights "GetPinnableReference" overallExprTy
            |> List.tryFind (fun mInfo ->
                // GetPinnableReference must be a parameterless method with a byref or inref return value
                match mInfo.GetParamDatas(cenv.amap, mBinding, mInfo.FormalMethodInst), mInfo.GetFSharpReturnType(cenv.amap, mBinding, mInfo.FormalMethodInst) with
                | [[]], retTy when isByrefTy g retTy && mInfo.IsInstance -> true
                | _ -> false
            )

        match getPinnableReferenceMInfo with
        | Some mInfo ->
            checkLanguageFeatureAndRecover g.langVersion LanguageFeature.ExtendedFixedBindings mBinding

            let mInst = FreshenMethInfo mBinding mInfo
            let pinnableReference, actualRetTy = BuildPossiblyConditionalMethodCall cenv env NeverMutates mBinding false mInfo NormalValUse mInst [ fixedExpr ] [] None

            let elemTy = destByrefTy g actualRetTy
            UnifyTypes cenv env mBinding (mkNativePtrTy g elemTy) overallPatTy

            // For value types:
            // let ptr: nativeptr<elem> =
            //   let pinned x = &(expr: 'a).GetPinnableReference()
            //   (nativeint) x

            // For reference types:
            // let ptr: nativeptr<elem> =
            //   if isNull expr then
            //     (nativeint) expr
            //   else
            //     let pinned x = &(expr: 'a).GetPinnableReference()
            //     (nativeint) x

            let pinnedBinding =
                mkCompGenLetIn mBinding "pinnedByref" actualRetTy pinnableReference (fun (v, ve) ->
                    v.SetIsFixed()
                    mkConvToNativeInt g ve mBinding)

            if isStructTy g overallExprTy then
                Some pinnedBinding
            else
                Some (mkNullTest g mBinding fixedExpr pinnedBinding fixedExpr)
        | None ->
            None

    warning(PossibleUnverifiableCode mBinding)

    match overallExprTy with
    | ty when isByrefTy g ty ->
        // Feature ExtendedFixedBindings allows *any* byref to be used with fixed bindings, whereas the old logic only allowed a specific
        // subset. This preserves the old logic when the feature is turned off.
        if not (g.langVersion.SupportsFeature LanguageFeature.ExtendedFixedBindings) then
            let okByRef =
                match stripDebugPoints (stripExpr fixedExpr) with
                | Expr.Op (op, tyargs, args, _) ->
                    match op, tyargs, args with
                    | TOp.ValFieldGetAddr (rfref, _), _, [_] -> not rfref.Tycon.IsStructOrEnumTycon
                    | TOp.ILAsm ([ I_ldflda fspec], _), _, _ -> fspec.DeclaringType.Boxity = ILBoxity.AsObject
                    | TOp.ILAsm ([ I_ldelema _], _), _, _ -> true
                    | TOp.RefAddrGet _, _, _ -> true
                    | _ -> false
                | _ -> false

            if not okByRef then
                errorR (languageFeatureError g.langVersion LanguageFeature.ExtendedFixedBindings mBinding)

        let elemTy = destByrefTy g overallExprTy
        UnifyTypes cenv env mBinding (mkNativePtrTy g elemTy) overallPatTy
        mkCompGenLetIn mBinding "pinnedByref" ty fixedExpr (fun (v, ve) ->
            v.SetIsFixed()
            mkConvToNativeInt g ve mBinding)

    | ty when isStringTy g ty ->
        let getPinnableRefCall =
            if g.langVersion.SupportsFeature LanguageFeature.PreferStringGetPinnableReference then
                tryBuildGetPinnableReferenceCall ()
            else
                None

        match getPinnableRefCall with
        | Some expr -> expr
        | None ->
            let charPtrTy = mkNativePtrTy g g.char_ty
            UnifyTypes cenv env mBinding charPtrTy overallPatTy
            //
            //    let ptr: nativeptr<char> =
            //        let pinned s = str
            //        (nativeptr)s + get_OffsettoStringData()

            mkCompGenLetIn mBinding "pinnedString" g.string_ty fixedExpr (fun (v, ve) ->
                v.SetIsFixed()
                let addrOffset = BuildOffsetToStringData cenv env mBinding
                let stringAsNativeInt = mkConvToNativeInt g ve mBinding
                let plusOffset = Expr.Op (TOp.ILAsm ([ AI_add ], [ g.nativeint_ty ]), [], [stringAsNativeInt; addrOffset], mBinding)
                // check for non-null
                mkNullTest g mBinding ve plusOffset ve)

    | ty when isArray1DTy g ty ->
        let elemTy = destArrayTy g overallExprTy
        let elemPtrTy = mkNativePtrTy g elemTy
        UnifyTypes cenv env mBinding elemPtrTy overallPatTy

        // let ptr: nativeptr<elem> =
        //   let tmpArray: elem[] = arr
        //   if nonNull tmpArray then
        //      if tmpArray.Length <> 0 then
        //         let pinned tmpArrayByref: byref<elem> = &arr.[0]
        //         (nativeint) tmpArrayByref
        //      else
        //         (nativeint) 0
        //   else
        //      (nativeint) 0
        //
        mkCompGenLetIn mBinding "tmpArray" overallExprTy fixedExpr (fun (_, ve) ->
            // This is &arr.[0]
            let elemZeroAddress = mkArrayElemAddress g (false, ILReadonly.NormalAddress, false, ILArrayShape.SingleDimensional, elemTy, [ve; mkInt32 g mBinding 0], mBinding)
            // check for non-null and non-empty
            let zero = mkConvToNativeInt g (mkInt32 g mBinding 0) mBinding
            // This is arr.Length
            let arrayLengthExpr = mkCallArrayLength g mBinding elemTy ve
            mkNullTest g mBinding ve
                (mkNullTest g mBinding arrayLengthExpr
                    (mkCompGenLetIn mBinding "pinnedByref" (mkByrefTy g elemTy) elemZeroAddress (fun (v, ve) ->
                       v.SetIsFixed()
                       (mkConvToNativeInt g ve mBinding)))
                    zero)
                zero)

    | _ ->
        match tryBuildGetPinnableReferenceCall () with
        | Some expr -> expr
        | None -> error(Error(FSComp.SR.tcFixedNotAllowed(), mBinding))


/// Binding checking code, for all bindings including let bindings, let-rec bindings, member bindings and object-expression bindings and
and TcNormalizedBinding declKind (cenv: cenv) env tpenv overallTy safeThisValOpt safeInitInfo (enclosingDeclaredTypars, (ExplicitTyparInfo(_, declaredTypars, _) as explicitTyparInfo)) bind =

    let g = cenv.g

    let envinner = AddDeclaredTypars NoCheckForDuplicateTypars (enclosingDeclaredTypars@declaredTypars) env

    match bind with
    | NormalizedBinding(vis, kind, isInline, isMutable, attrs, xmlDoc, _, valSynData, pat, NormalizedBindingRhs(spatsL, rtyOpt, rhsExpr), _, debugPoint) ->
        let (SynValData(memberFlags = memberFlagsOpt)) = valSynData
        let mBinding = pat.Range

        let isClassLetBinding =
            match declKind, kind with
            | ClassLetBinding _, SynBindingKind.Normal -> true
            | _ -> false

        let callerName =
            match declKind, kind, pat with
            | ExpressionBinding, _, _ -> envinner.eCallerMemberName
            | _, _, (SynPat.Named(SynIdent(name,_), _, _, _) | SynPat.As(_, SynPat.Named(SynIdent(name,_), _, _, _), _)) ->
                match memberFlagsOpt with
                | Some memberFlags ->
                    match memberFlags.MemberKind with
                    | SynMemberKind.PropertyGet | SynMemberKind.PropertySet | SynMemberKind.PropertyGetSet -> Some(name.idText.Substring 4)
                    | SynMemberKind.ClassConstructor -> Some(".ctor")
                    | SynMemberKind.Constructor -> Some(".ctor")
                    | _ -> Some(name.idText)
                | _ -> Some(name.idText)
            | ClassLetBinding false, SynBindingKind.Do, _ -> Some(".ctor")
            | ClassLetBinding true, SynBindingKind.Do, _ -> Some(".cctor")
            | ModuleOrMemberBinding, SynBindingKind.StandaloneExpression, _ -> Some(".cctor")
            | _, _, _ -> envinner.eCallerMemberName

        let envinner = { envinner with eCallerMemberName = callerName }
        let attrTgt = declKind.AllowedAttribTargets memberFlagsOpt

        let isFixed, rhsExpr, overallPatTy, overallExprTy =
            match rhsExpr with
            | SynExpr.Fixed (e, _) -> true, e, NewInferenceType g, overallTy
            // { new Foo()  } is parsed as a SynExpr.ComputationExpr.(See pars.fsy `objExpr` rule).
            // If a SynExpr.ComputationExpr body consists of a single SynExpr.New, and it's not the argument of a computation expression builder type.
            // Then we should treat it as a SynExpr.ObjExpr and make it consistent with the other object expressions. e.g.
            // { new Foo } -> SynExpr.ObjExpr
            // { new Foo() } -> SynExpr.ObjExpr
            // { New Foo with ... } -> SynExpr.ObjExpr
            | SynExpr.ComputationExpr(false, SynExpr.New(_, targetType, expr, m), _) ->        
                false, SynExpr.ObjExpr(targetType, Some(expr, None), None, [], [], [], m, rhsExpr.Range), overallTy, overallTy
            | e -> false, e, overallTy, overallTy

        // Check the attributes of the binding, parameters or return value
        let TcAttrs tgt isRet attrs =
            // For all but attributes positioned at the return value, disallow implicitly
            // targeting the return value.
            let tgtEx = if isRet then enum 0 else AttributeTargets.ReturnValue
            let attrs, _ = TcAttributesMaybeFailEx TcCanFail.ReportAllErrors cenv envinner tgt tgtEx attrs
            let attrs: Attrib list = attrs
            if attrTgt = enum 0 && not (isNil attrs) then
                for attr in attrs do
                    errorR(Error(FSComp.SR.tcAttributesAreNotPermittedOnLetBindings(), attr.Range))
            attrs

        // Rotate [<return:...>] from binding to return value
        // Also patch the syntactic representation
        let retAttribs, valAttribs, valSynData =
            let attribs = TcAttrs attrTgt false attrs
            let rotRetSynAttrs, rotRetAttribs, valAttribs =
                // Do not rotate if some attrs fail to typecheck...
                if attribs.Length <> attrs.Length then [], [], attribs
                else attribs
                     |> List.zip attrs
                     |> List.partition(function | _, Attrib(_, _, _, _, _, Some ts, _) -> ts &&& AttributeTargets.ReturnValue <> enum 0 | _ -> false)
                     |> fun (r, v) -> (List.map fst r, List.map snd r, List.map snd v)
            let retAttribs =
                match rtyOpt with
                | Some (SynBindingReturnInfo(attributes = Attributes retAttrs)) ->
                    rotRetAttribs @ TcAttrs AttributeTargets.ReturnValue true retAttrs
                | None -> rotRetAttribs
            let valSynData =
                match rotRetSynAttrs with
                | [] -> valSynData
                | {Range=mHead} :: _ ->
                let (SynValData(valMf, SynValInfo(args, SynArgInfo(attrs, opt, retId)), valId)) = valSynData
                SynValData(valMf, SynValInfo(args, SynArgInfo({Attributes=rotRetSynAttrs; Range=mHead} :: attrs, opt, retId)), valId)
            retAttribs, valAttribs, valSynData

        let valAttribFlags = computeValWellKnownFlags g valAttribs

        let isVolatile = hasFlag valAttribFlags WellKnownValAttributes.VolatileFieldAttribute
        let inlineFlag = ComputeInlineFlag memberFlagsOpt isInline isMutable g valAttribs mBinding

        let argAttribs =
            spatsL |> List.map (SynInfo.InferSynArgInfoFromSimplePats >> List.map (SynInfo.AttribsOfArgData >> TcAttrs AttributeTargets.Parameter false))

        // Assert the return type of an active pattern. A [<return:Struct>] attribute may be used on a partial active pattern.
        let isStructRetTy = attribsHaveValFlag g WellKnownValAttributes.StructAttribute retAttribs

        let argAndRetAttribs = ArgAndRetAttribs(argAttribs, retAttribs)

        // See RFC FS-1087, the 'Zero' method of a builder may have 'DefaultValueAttribute' indicating it should
        // always be used for empty branches of if/then/else and others
        let isZeroMethod =
            match declKind, pat with
            | ModuleOrMemberBinding, SynPat.Named(SynIdent(id,_), _, _, _) when id.idText = "Zero" ->
                match memberFlagsOpt with
                | Some memberFlags ->
                    match memberFlags.MemberKind with
                    | SynMemberKind.Member -> true
                    | _ -> false
                | _ -> false
            | _ -> false

        let hasDefaultValueAttr = hasFlag valAttribFlags (WellKnownValAttributes.DefaultValueAttribute_True ||| WellKnownValAttributes.DefaultValueAttribute_False)
        if hasDefaultValueAttr && not isZeroMethod then
            errorR(Error(FSComp.SR.tcDefaultValueAttributeRequiresVal(), mBinding))

        let isThreadStatic = hasFlag valAttribFlags (WellKnownValAttributes.ThreadStaticAttribute ||| WellKnownValAttributes.ContextStaticAttribute)
        if isThreadStatic then errorR(DeprecatedThreadStaticBindingWarning mBinding)

        if isVolatile then
            match declKind with
            | ClassLetBinding _ -> ()
            | _ -> errorR(Error(FSComp.SR.tcVolatileOnlyOnClassLetBindings(), mBinding))

            if (not isMutable || isThreadStatic) then
                errorR(Error(FSComp.SR.tcVolatileFieldsMustBeMutable(), mBinding))

        if isFixed && (declKind <> ExpressionBinding || isInline || isMutable) then
            errorR(Error(FSComp.SR.tcFixedNotAllowed(), mBinding))

        if (not declKind.CanBeDllImport || (match memberFlagsOpt with Some memberFlags -> memberFlags.IsInstance | _ -> false)) &&
            hasFlag valAttribFlags WellKnownValAttributes.DllImportAttribute then
            errorR(Error(FSComp.SR.tcDllImportNotAllowed(), mBinding))

        if Option.isNone memberFlagsOpt && hasFlag valAttribFlags WellKnownValAttributes.ConditionalAttribute then
            errorR(Error(FSComp.SR.tcConditionalAttributeRequiresMembers(), mBinding))

        if hasFlag valAttribFlags WellKnownValAttributes.EntryPointAttribute then
            if Option.isSome memberFlagsOpt then
                errorR(Error(FSComp.SR.tcEntryPointAttributeRequiresFunctionInModule(), mBinding))
            else
                let entryPointTy = mkFunTy g (mkArrayType g g.string_ty) g.int_ty
                UnifyTypes cenv env mBinding overallPatTy entryPointTy

        if isMutable && isInline then errorR(Error(FSComp.SR.tcMutableValuesCannotBeInline(), mBinding))

        if isMutable && not (isNil declaredTypars) then errorR(Error(FSComp.SR.tcMutableValuesMayNotHaveGenericParameters(), mBinding))

        let explicitTyparInfo = if isMutable then dontInferTypars else explicitTyparInfo

        if isMutable && not (isNil spatsL) then errorR(Error(FSComp.SR.tcMutableValuesSyntax(), mBinding))

        let isInline =
            if isInline && isNil spatsL && isNil declaredTypars then
                errorR(Error(FSComp.SR.tcOnlyFunctionsCanBeInline(), mBinding))
                false
            else
                isInline

        let isCompGen = false

        // Use the syntactic arity if we're defining a function
        let (SynValData(valInfo = valSynInfo)) = valSynData
        let prelimValReprInfo = TranslateSynValInfo cenv mBinding (TcAttributes cenv env) valSynInfo

        // Check the pattern of the l.h.s. of the binding
        let tcPatPhase2, TcPatLinearEnv (tpenv, nameToPrelimValSchemeMap, _) =
            cenv.TcPat AllIdsOK cenv envinner (Some prelimValReprInfo) (TcPatValFlags (inlineFlag, explicitTyparInfo, argAndRetAttribs, isMutable, vis, isCompGen)) (TcPatLinearEnv (tpenv, NameMap.empty, Set.empty)) overallPatTy pat

        // Add active pattern result names to the environment
        let apinfoOpt =
            match NameMap.range nameToPrelimValSchemeMap with
            | [PrelimVal1(id, _, ty, _, _, _, _, _, _, _, _) ] ->
                match ActivePatternInfoOfValName id.idText id.idRange with
                | Some apinfo -> Some (apinfo, ty, id.idRange)
                | None -> None
            | _ -> None

        // Add active pattern result names to the environment
        let envinner =
            match apinfoOpt with
            | Some (apinfo, apOverallTy, m) ->
                let isMultiCasePartialAP = memberFlagsOpt.IsNone && not apinfo.IsTotal && apinfo.ActiveTags.Length > 1
                if isMultiCasePartialAP then
                    errorR(Error(FSComp.SR.tcPartialActivePattern(), m))
                    
                if Option.isSome memberFlagsOpt && not spatsL.IsEmpty then
                    errorR(Error(FSComp.SR.tcInvalidActivePatternName(apinfo.LogicalName), m))

                apinfo.ActiveTagsWithRanges |> List.iteri (fun i (_tag, tagRange) ->
                    let item = Item.ActivePatternResult(apinfo, apOverallTy, i, tagRange)
                    CallNameResolutionSink cenv.tcSink (tagRange, env.NameEnv, item, emptyTyparInst, ItemOccurrence.Binding, env.AccessRights))

                { envinner with eNameResEnv = AddActivePatternResultTagsToNameEnv apinfo envinner.eNameResEnv apOverallTy m }
            | None ->
                envinner

        // If binding a ctor then set the ugly counter that permits us to write ctor expressions on the r.h.s.
        let isCtor = (match memberFlagsOpt with Some memberFlags -> memberFlags.MemberKind = SynMemberKind.Constructor | _ -> false)

        // Now check the right of the binding.
        //
        // At each module binding, dive into the expression to check for syntax errors and suppress them if they show.
        // Don't do this for lambdas, because we always check for suppression for all lambda bodies in TcIteratedLambdas
        let rhsExprChecked, tpenv =
            // Save the arginfos away to match them up in the lambda
            let (PrelimValReprInfo(argInfos, _)) = prelimValReprInfo

            // The right-hand-side is control flow (has an implicit debug point) in any situation where we
            // haven't extended the debug point to include the 'let', that is, there is a debug point noted
            // at the binding.
            //
            // This includes
            //    let _ = expr
            //    let () = expr
            // which are transformed to sequential expressions in TcLetBinding
            //
            let rhsIsControlFlow =
                match pat with
                | SynPat.Wild _
                | SynPat.Const (SynConst.Unit, _)
                | SynPat.Paren (SynPat.Const (SynConst.Unit, _), _) -> true
                | _ ->

                match debugPoint with
                | DebugPointAtBinding.Yes _ -> false
                | _ -> true

            let envinner = { envinner with eLambdaArgInfos = argInfos; eIsControlFlow = rhsIsControlFlow }

            if isCtor then TcExprThatIsCtorBody (safeThisValOpt, safeInitInfo) cenv (MustEqual overallExprTy) envinner tpenv rhsExpr
            else TcExprThatCantBeCtorBody cenv (MustConvertTo (false, overallExprTy)) envinner tpenv rhsExpr

        if kind = SynBindingKind.StandaloneExpression && not cenv.isScript then
            UnifyUnitType cenv env mBinding overallPatTy rhsExprChecked |> ignore<bool>

        // Fix up the r.h.s. expression for 'fixed'
        let rhsExprChecked =
            if isFixed then TcAndBuildFixedExpr cenv env (overallPatTy, rhsExprChecked, overallExprTy, mBinding)
            else rhsExprChecked

        match apinfoOpt with
        | Some (apinfo, apOverallTy, m) ->
            let activePatResTys = NewInferenceTypes g apinfo.ActiveTags
            let _, apReturnTy = stripFunTy g apOverallTy
            let apRetTy =
                if apinfo.IsTotal then
                    if isStructRetTy then errorR(Error(FSComp.SR.tcInvalidStructReturn(), mBinding))
                    ActivePatternReturnKind.RefTypeWrapper
                else
                    if isStructRetTy || isValueOptionTy cenv.g apReturnTy then ActivePatternReturnKind.StructTypeWrapper
                    elif isBoolTy cenv.g apReturnTy then ActivePatternReturnKind.Boolean
                    else ActivePatternReturnKind.RefTypeWrapper

            match apRetTy with
            | ActivePatternReturnKind.Boolean ->
                checkLanguageFeatureError g.langVersion LanguageFeature.BooleanReturningAndReturnTypeDirectedPartialActivePattern mBinding
            | ActivePatternReturnKind.StructTypeWrapper when not isStructRetTy ->
                checkLanguageFeatureError g.langVersion LanguageFeature.BooleanReturningAndReturnTypeDirectedPartialActivePattern mBinding
            | ActivePatternReturnKind.StructTypeWrapper ->
                checkLanguageFeatureError g.langVersion LanguageFeature.StructActivePattern mBinding
            | ActivePatternReturnKind.RefTypeWrapper -> ()

            UnifyTypes cenv env mBinding (apinfo.ResultType g m activePatResTys apRetTy) apReturnTy

        | None ->
            if isStructRetTy then
                errorR(Error(FSComp.SR.tcInvalidStructReturn(), mBinding))

        // Check other attributes
        let hasLiteralAttr, literalValue = TcLiteral cenv overallExprTy env tpenv (valAttribs, rhsExpr)

        if hasLiteralAttr then
            if isThreadStatic then
                errorR(Error(FSComp.SR.tcIllegalAttributesForLiteral(), mBinding))
            if isMutable then
                errorR(Error(FSComp.SR.tcLiteralCannotBeMutable(), mBinding))
            if isInline then
                errorR(Error(FSComp.SR.tcLiteralCannotBeInline(), mBinding))
            if not (isNil declaredTypars) then
                errorR(Error(FSComp.SR.tcLiteralCannotHaveGenericParameters(), mBinding))

        let supportEnforceAttributeTargets =
            (g.langVersion.SupportsFeature(LanguageFeature.EnforceAttributeTargets) && memberFlagsOpt.IsNone && not attrs.IsEmpty)
            && not isVolatile // VolatileFieldAttribute has a special treatment(specific error FS823)

        if supportEnforceAttributeTargets then
            TcAttributeTargetsOnLetBindings { cenv with tcSink = TcResultsSink.NoSink } env attrs overallPatTy overallExprTy (not declaredTypars.IsEmpty) isClassLetBinding

        CheckedBindingInfo(inlineFlag, valAttribs, xmlDoc, tcPatPhase2, explicitTyparInfo, nameToPrelimValSchemeMap, rhsExprChecked, argAndRetAttribs, overallPatTy, mBinding, debugPoint, isCompGen, literalValue, isFixed), tpenv

// Note:
// - Let bound values can only have attributes that uses AttributeTargets.Field ||| AttributeTargets.Property ||| AttributeTargets.ReturnValue
// - Let function bindings can only have attributes that uses AttributeTargets.Method ||| AttributeTargets.ReturnValue
and TcAttributeTargetsOnLetBindings (cenv: cenv) env attrs overallPatTy overallExprTy areTyparsDeclared isClassLetBinding =
    let attrTgt =
        if
            // It's a type function:
            //     let x<'a> = …
            areTyparsDeclared
            // It's a regular function-valued binding:
            //     let f x = …
            //     let f = fun x -> …
            || isFunTy cenv.g overallPatTy
            || isFunTy cenv.g overallExprTy
        then
            // Class let bindings are a special case, they can have attributes that target fields and properties, since they might be lifted to those and contain lambdas/functions.
            if isClassLetBinding then
                AttributeTargets.ReturnValue ||| AttributeTargets.Method ||| AttributeTargets.Field ||| AttributeTargets.Property
            else
                AttributeTargets.ReturnValue ||| AttributeTargets.Method
        else
            AttributeTargets.ReturnValue ||| AttributeTargets.Field ||| AttributeTargets.Property

    TcAttributesWithPossibleTargets TcCanFail.ReportAllErrors cenv env attrTgt attrs |> ignore

and TcLiteral (cenv: cenv) overallTy env tpenv (attrs, synLiteralValExpr) =

    let g = cenv.g

    let valFlags = computeValWellKnownFlags g attrs

    let hasLiteralAttr =
        hasFlag valFlags WellKnownValAttributes.LiteralAttribute

    if hasLiteralAttr then
        let literalValExpr, _ = TcExpr cenv (MustEqual overallTy) env tpenv synLiteralValExpr
        match EvalLiteralExprOrAttribArg g literalValExpr with
        | Expr.Const (c, _, ty) ->
            if c = Const.Zero && isStructTy g ty then
                warning(Error(FSComp.SR.tcIllegalStructTypeForConstantExpression(), synLiteralValExpr.Range))
                false, None
            else
                true, Some c
        | _ ->
            errorR(Error(FSComp.SR.tcInvalidConstantExpression(), synLiteralValExpr.Range))
            true, Some Const.Unit

    else hasLiteralAttr, None

and TcBindingTyparDecls alwaysRigid cenv env tpenv (ValTyparDecls(synTypars, synTyparConstraints, infer)) =
    let declaredTypars = TcTyparDecls cenv env synTypars
    let envinner = AddDeclaredTypars CheckForDuplicateTypars declaredTypars env
    let tpenv = TcTyparConstraints cenv NoNewTypars CheckCxs ItemOccurrence.UseInType envinner tpenv synTyparConstraints

    let rigidCopyOfDeclaredTypars =
        if alwaysRigid then
            declaredTypars |> List.iter (fun tp -> SetTyparRigid env.DisplayEnv tp.Range tp)
            declaredTypars
        else
            let rigidCopyOfDeclaredTypars = copyTypars false declaredTypars
            // The type parameters used to check rigidity after inference are marked rigid straight away
            rigidCopyOfDeclaredTypars |> List.iter (fun tp -> SetTyparRigid env.DisplayEnv tp.Range tp)
            // The type parameters using during inference will be marked rigid after inference
            declaredTypars |> List.iter (fun tp -> tp.SetRigidity TyparRigidity.WillBeRigid)
            rigidCopyOfDeclaredTypars

    ExplicitTyparInfo(rigidCopyOfDeclaredTypars, declaredTypars, infer), tpenv

and TcNonrecBindingTyparDecls cenv env tpenv bind =
    let (NormalizedBinding(_, _, _, _, _, _, synTyparDecls, _, _, _, _, _)) = bind
    TcBindingTyparDecls true cenv env tpenv synTyparDecls

and TcNonRecursiveBinding declKind cenv env tpenv ty binding =
    // Check for unintended shadowing
    match binding with
    | SynBinding(headPat = SynPat.LongIdent(longDotId = SynLongIdent(id = [ident]); range = headPatRange)) ->
        match env.eNameResEnv.ePatItems.TryFind ident.idText with
        | Some (Item.UnionCase(_, false)) ->
            warning(Error(FSComp.SR.tcInfoIfFunctionShadowsUnionCase(), headPatRange))
        | _ -> ()
    | _ -> ()



    let binding = BindingNormalization.NormalizeBinding ValOrMemberBinding cenv env binding
    let explicitTyparInfo, tpenv = TcNonrecBindingTyparDecls cenv env tpenv binding
    TcNormalizedBinding declKind cenv env tpenv ty None NoSafeInitInfo ([], explicitTyparInfo) binding

and ResolveAttributeType (cenv: cenv) (env: TcEnv) (mAttr: range) (tycon: Ident list) =
    let tpenv = emptyUnscopedTyparEnv
    let ad = env.eAccessRights
    
    let tyPath, tyId = List.frontAndBack tycon
    
    let try1 n =
        let tyid = mkSynId tyId.idRange n
        let tycon = (tyPath @ [tyid])

        match ResolveTypeLongIdent cenv.tcSink cenv.nameResolver ItemOccurrence.UseInAttribute OpenQualified env.eNameResEnv ad tycon TypeNameResolutionStaticArgsInfo.DefiniteEmpty PermitDirectReferenceToGeneratedType.No with
        | Exception err -> raze err
        | Result(tinstEnclosing, tcref, inst) -> success(TcTypeApp cenv NoNewTypars CheckCxs ItemOccurrence.UseInAttribute env tpenv mAttr tcref tinstEnclosing [] inst)

    ForceRaise ((try1 (tyId.idText + "Attribute")) |> otherwise (fun () -> (try1 tyId.idText)))

and CheckAttributeUsage (g: TcGlobals) (mAttr: range) (tcref: TyconRef) (attrTgt: AttributeTargets) (targetIndicator: Ident option) (attrEx: AttributeTargets) =
    // REVIEW: take notice of inherited?
    let validOn, _inherited =
        let validOnDefault = 0x7fff
        let inheritedDefault = true
        if tcref.IsILTycon then
            let tdef = tcref.ILTyconRawMetadata

            match tdef.CustomAttrs with
            | ILAttribDecoded WellKnownILAttributes.AttributeUsageAttribute decoded ->
                match decoded with
                | ([ILAttribElem.Int32 validOn ], named) ->
                    let inherited =
                        match List.tryPick (function "Inherited", _, _, ILAttribElem.Bool res -> Some res | _ -> None) named with
                        | None -> inheritedDefault
                        | Some x -> x
                    (validOn, inherited)
                | ([ILAttribElem.Int32 validOn; ILAttribElem.Bool _allowMultiple; ILAttribElem.Bool inherited ], _) ->
                    (validOn, inherited)
                | _ ->
                    (validOnDefault, inheritedDefault)
            | _ ->
                (validOnDefault, inheritedDefault)
        else
            match tcref.Attribs with
                | EntityAttrib g WellKnownEntityAttributes.AttributeUsageAttribute (Attrib(unnamedArgs = [ AttribInt32Arg validOn ])) ->
                    validOn, inheritedDefault
                | EntityAttrib g WellKnownEntityAttributes.AttributeUsageAttribute (Attrib(unnamedArgs = [ AttribInt32Arg validOn; AttribBoolArg(_allowMultiple); AttribBoolArg inherited])) ->
                    validOn, inherited
                | EntityAttrib g WellKnownEntityAttributes.AttributeUsageAttribute _ ->
                    warning(Error(FSComp.SR.tcUnexpectedConditionInImportedAssembly(), mAttr))
                    validOnDefault, inheritedDefault
                | _ ->
                    validOnDefault, inheritedDefault
    
    // Determine valid attribute targets
    let attributeTargets = enum validOn &&& attrTgt
    let directedTargets =
        match targetIndicator with
        | LongFormAttrTarget attrTarget -> attrTarget
        | UnrecognizedLongAttrTarget attrTarget ->
            errorR(Error(FSComp.SR.tcUnrecognizedAttributeTarget(), attrTarget.idRange))
            attributeTargets
        | ShortFormAttributeTarget -> attributeTargets &&& ~~~ attrEx
  
    let constrainedTargets = attributeTargets &&& directedTargets

    // Check if attribute is valid for the target
    if constrainedTargets = enum 0 then
        if (directedTargets = AttributeTargets.Assembly || directedTargets = AttributeTargets.Module) then
            errorR(Error(FSComp.SR.tcAttributeIsNotValidForLanguageElementUseDo(), mAttr))
        else
            let attributeTargetsToString (targets: int) =
                [|
                    if targets &&& int AttributeTargets.Assembly <> 0 then "assembly"
                    if targets &&& int AttributeTargets.Module <> 0 then "module"
                    if targets &&& int AttributeTargets.Class <> 0 then "class"
                    if targets &&& int AttributeTargets.Struct <> 0 then "struct"
                    if targets &&& int AttributeTargets.Enum <> 0 then "enum"
                    if targets &&& int AttributeTargets.Constructor <> 0 then "constructor"
                    if targets &&& int AttributeTargets.Method <> 0 then "method"
                    if targets &&& int AttributeTargets.Property <> 0 then "property"
                    if targets &&& int AttributeTargets.Field <> 0 then "field"
                    if targets &&& int AttributeTargets.Event <> 0 then "event"
                    if targets &&& int AttributeTargets.Interface <> 0 then "interface"
                    if targets &&& int AttributeTargets.Parameter <> 0 then "parameter"
                    if targets &&& int AttributeTargets.Delegate <> 0 then "delegate"
                    if targets &&& int AttributeTargets.ReturnValue <> 0 then "return value"
                    if targets &&& int AttributeTargets.GenericParameter <> 0 then "type parameter"
                |]

            let elementTargets = attributeTargetsToString (int attrTgt)
            let allowedTargets = attributeTargetsToString validOn

            warning(InvalidAttributeTargetForLanguageElement(elementTargets, allowedTargets, mAttr))
    
    constrainedTargets

//-------------------------------------------------------------------------
// TcAttribute*
// *Ex means the function accepts attribute targets that must be explicit
//------------------------------------------------------------------------

and TcAttributeEx canFail (cenv: cenv) (env: TcEnv) attrTgt attrEx (synAttr: SynAttribute) =

    let g = cenv.g

    let (SynLongIdent(tycon, _, _)) = synAttr.TypeName
    let arg = synAttr.ArgExpr
    let targetIndicator = synAttr.Target
    let isAppliedToGetterOrSetter = synAttr.AppliesToGetterAndSetter
    let mAttr = synAttr.Range
    let _, tyId = List.frontAndBack tycon
    let ad = env.eAccessRights

    // if we're checking an attribute that was applied directly to a getter or a setter, then
    // what we're really checking against is a method, not a property
    let attrTgt = if isAppliedToGetterOrSetter then ((attrTgt ^^^ AttributeTargets.Property) ||| AttributeTargets.Method) else attrTgt
    let ty, tpenv = ResolveAttributeType cenv env mAttr tycon
    if not (IsTypeAccessible g cenv.amap mAttr ad ty) then errorR(Error(FSComp.SR.tcTypeIsInaccessible(), mAttr))

    let tcref = tcrefOfAppTy g ty

    let conditionalCallDefineOpt = TryFindTyconRefStringAttribute g mAttr g.attrib_ConditionalAttribute tcref

    match conditionalCallDefineOpt, cenv.conditionalDefines with
    | Some d, Some defines when not (List.contains d defines) ->
        [], false
    | _ ->
        let constrainedTargets = CheckAttributeUsage g mAttr tcref attrTgt targetIndicator attrEx

        match ResolveObjectConstructor cenv.nameResolver env.DisplayEnv mAttr ad ty with
        | Exception _ when canFail = TcCanFail.IgnoreAllErrors || canFail = TcCanFail.IgnoreMemberResoutionError -> [ ], true
        | res ->

        let item = ForceRaise res

        if not (ExistsHeadTypeInEntireHierarchy g cenv.amap mAttr ty g.tcref_System_Attribute) then
            warning(Error(FSComp.SR.tcTypeDoesNotInheritAttribute(), mAttr))

        let attrib =
            match item with
            | Item.CtorGroup(methodName, minfos) ->
                let meths = minfos |> List.map (fun minfo -> minfo, None)
                let afterResolution = ForNewConstructors cenv.tcSink env tyId.idRange methodName minfos
                let (expr, attributeAssignedNamedItems, _), _ =
                  TcMethodApplication true cenv env tpenv None [] mAttr mAttr methodName None ad PossiblyMutates false meths afterResolution NormalValUse [arg] (MustEqual ty) None []

                UnifyTypes cenv env mAttr ty (tyOfExpr g expr)

                let mkAttribExpr e =
                    AttribExpr(e, EvalLiteralExprOrAttribArg g e)
                    
                let checkPropSetterAttribAccess m (pinfo: PropInfo) =
                    let setterMeth = pinfo.SetterMethod
                    if not <| IsTypeAndMethInfoAccessible cenv.amap m ad ad setterMeth then
                        errorR(Error (FSComp.SR.tcPropertyCannotBeSetPrivateSetter(pinfo.PropertyName), m))                       
                        
                let namedAttribArgMap =
                  attributeAssignedNamedItems |> List.map (fun (CallerNamedArg(id, CallerArg(callerArgTy, m, isOpt, callerArgExpr))) ->
                    if isOpt then error(Error(FSComp.SR.tcOptionalArgumentsCannotBeUsedInCustomAttribute(), m))
                    let m = callerArgExpr.Range
                    let lookupKind = LookupKind.Expr LookupIsInstance.Ambivalent
                    let setterItem, _ = ResolveLongIdentInType cenv.tcSink cenv.nameResolver env.NameEnv lookupKind m ad id IgnoreOverrides TypeNameResolutionInfo.Default ty
                    let nm, isProp, argTy =
                      match setterItem with
                      | Item.Property (info = [pinfo]) ->
                          if not pinfo.HasSetter then
                            errorR(Error(FSComp.SR.tcPropertyCannotBeSet0(), m))
                          checkPropSetterAttribAccess m pinfo
                          id.idText, true, pinfo.GetPropertyType(cenv.amap, m)
                      | Item.ILField finfo ->
                          CheckILFieldInfoAccessible g cenv.amap m ad finfo
                          CheckILFieldAttributes g finfo m
                          id.idText, false, finfo.FieldType(cenv.amap, m)
                      | Item.RecdField rfinfo when not rfinfo.IsStatic ->
                          CheckRecdFieldInfoAttributes g rfinfo m |> CommitOperationResult
                          CheckRecdFieldInfoAccessible cenv.amap m ad rfinfo
                          // This uses the F# backend name mangling of fields....
                          let nm = ComputeFieldName rfinfo.Tycon rfinfo.RecdField
                          nm, false, rfinfo.FieldType
                      | _ ->
                          errorR(Error(FSComp.SR.tcPropertyOrFieldNotFoundInAttribute(), m))
                          id.idText, false, g.unit_ty
                    let propNameItem = Item.SetterArg(id, setterItem)
                    CallNameResolutionSink cenv.tcSink (id.idRange, env.NameEnv, propNameItem, emptyTyparInst, ItemOccurrence.Use, ad)

                    AddCxTypeMustSubsumeType ContextInfo.NoContext env.DisplayEnv cenv.css m NoTrace argTy callerArgTy

                    AttribNamedArg(nm, argTy, isProp, mkAttribExpr callerArgExpr))

                match stripDebugPoints expr with
                | Expr.Op (TOp.ILCall (_, _, isStruct, _, _, _, _, ilMethRef, [], [], _), [], args, m) ->
                    if isStruct then error (Error(FSComp.SR.tcCustomAttributeMustBeReferenceType(), m))
                    if args.Length <> ilMethRef.ArgTypes.Length then error (Error(FSComp.SR.tcCustomAttributeArgumentMismatch(), m))
                    let args = args |> List.map mkAttribExpr
                    Attrib(tcref, ILAttrib ilMethRef, args, namedAttribArgMap, isAppliedToGetterOrSetter, Some constrainedTargets, m)

                | Expr.App (InnerExprPat(ExprValWithPossibleTypeInst(vref, _, _, _)), _, _, args, _) ->
                    let args = args |> List.collect (function Expr.Const (Const.Unit, _, _) -> [] | expr -> tryDestRefTupleExpr expr) |> List.map mkAttribExpr
                    Attrib(tcref, FSAttrib vref, args, namedAttribArgMap, isAppliedToGetterOrSetter, Some constrainedTargets, mAttr)

                | _ ->
                    error (Error(FSComp.SR.tcCustomAttributeMustInvokeConstructor(), mAttr))

            | _ ->
                error(Error(FSComp.SR.tcAttributeExpressionsMustBeConstructorCalls(), mAttr))

        [ (constrainedTargets, attrib) ], false

and TcAttributesWithPossibleTargetsEx canFail (cenv: cenv) env attrTgt attrEx synAttribs =

    let g = cenv.g

    (false, synAttribs) ||> List.collectFold (fun didFail synAttrib ->
        try
            let attribsAndTargets, didFail2 = TcAttributeEx canFail cenv env attrTgt attrEx synAttrib

            // This is where we place any checks that completely exclude the use of some particular
            // attributes from F#.
            let attribs = List.map snd attribsAndTargets
            if HasFSharpAttribute g g.attrib_TypeForwardedToAttribute attribs ||
               HasFSharpAttribute g g.attrib_CompilationArgumentCountsAttribute attribs ||
               HasFSharpAttribute g g.attrib_CompilationMappingAttribute attribs then
                errorR(Error(FSComp.SR.tcUnsupportedAttribute(), synAttrib.Range))

            attribsAndTargets, didFail || didFail2

        with RecoverableException e ->
            errorRecovery e synAttrib.Range
            [], false)

and TcAttributesMaybeFailEx canFail (cenv: cenv) env attrTgt attrEx synAttribs =
    let attribsAndTargets, didFail = TcAttributesWithPossibleTargetsEx canFail cenv env attrTgt attrEx synAttribs
    attribsAndTargets |> List.map snd, didFail

and TcAttributesWithPossibleTargets canFail cenv env attrTgt synAttribs =
    TcAttributesWithPossibleTargetsEx canFail cenv env attrTgt (enum 0) synAttribs

and TcAttributesMaybeFail canFail cenv env attrTgt synAttribs =
    TcAttributesMaybeFailEx canFail cenv env attrTgt (enum 0) synAttribs

and TcAttributesCanFail cenv env attrTgt synAttribs =
    let attrs, didFail = TcAttributesMaybeFail TcCanFail.IgnoreAllErrors cenv env attrTgt synAttribs
    attrs, (fun () -> if didFail then TcAttributes cenv env attrTgt synAttribs else attrs)

and TcAttributes cenv env attrTgt synAttribs =
    TcAttributesMaybeFail TcCanFail.ReportAllErrors cenv env attrTgt synAttribs |> fst

//-------------------------------------------------------------------------
// TcLetBinding
//------------------------------------------------------------------------

and TcLetBinding (cenv: cenv) isUse env containerInfo declKind tpenv (synBinds, synBindsRange, scopem) =

    let g = cenv.g

    // Typecheck all the bindings...
    let checkedBinds, tpenv = List.mapFold (fun tpenv b -> TcNonRecursiveBinding declKind cenv env tpenv (NewInferenceType g) b) tpenv synBinds
    let (ContainerInfo(altActualParent, _)) = containerInfo

    // Canonicalize constraints prior to generalization
    let denv = env.DisplayEnv
    try
        CanonicalizePartialInferenceProblem cenv.css denv synBindsRange
            (checkedBinds |> List.collect (fun tbinfo ->
                let (CheckedBindingInfo(_, _, _, _, explicitTyparInfo, _, _, _, tauTy, _, _, _, _, _)) = tbinfo
                let (ExplicitTyparInfo(_, declaredTypars, _)) = explicitTyparInfo
                let maxInferredTypars = (freeInTypeLeftToRight g false tauTy)
                declaredTypars @ maxInferredTypars))
    with RecoverableException _ -> ()

    let lazyFreeInEnv = lazy (GeneralizationHelpers.ComputeUngeneralizableTypars env)

    // Generalize the bindings...
    ((id, env, tpenv), checkedBinds) ||> List.fold (fun (buildExpr, env, tpenv) tbinfo ->
        let (CheckedBindingInfo(inlineFlag, attrs, xmlDoc, tcPatPhase2, explicitTyparInfo, nameToPrelimValSchemeMap, rhsExpr, _, tauTy, m, debugPoint, _, literalValue, isFixed)) = tbinfo
        let enclosingDeclaredTypars = []
        let (ExplicitTyparInfo(_, declaredTypars, canInferTypars)) = explicitTyparInfo
        let allDeclaredTypars = enclosingDeclaredTypars @ declaredTypars
        let generalizedTypars, prelimValSchemes2 =
            let canInferTypars = GeneralizationHelpers. ComputeCanInferExtraGeneralizableTypars (containerInfo.ParentRef, canInferTypars, None)

            let maxInferredTypars = freeInTypeLeftToRight g false tauTy

            let generalizedTypars =
                if isNil maxInferredTypars && isNil allDeclaredTypars then
                   []
                else
                   let freeInEnv = lazyFreeInEnv.Force()
                   let canConstrain = GeneralizationHelpers.CanGeneralizeConstrainedTyparsForDecl declKind
                   GeneralizationHelpers.ComputeAndGeneralizeGenericTypars
                       (cenv, denv, m, freeInEnv, canInferTypars, canConstrain, inlineFlag, Some rhsExpr, allDeclaredTypars, maxInferredTypars, tauTy, false)

            let prelimValSchemes2 = GeneralizeVals cenv denv enclosingDeclaredTypars generalizedTypars nameToPrelimValSchemeMap

            generalizedTypars, prelimValSchemes2

        // REVIEW: this scopes generalized type variables. Ensure this is handled properly
        // on all other paths.
        let tpenv = HideUnscopedTypars generalizedTypars tpenv
        let valSchemes = NameMap.map (UseCombinedValReprInfo g declKind rhsExpr) prelimValSchemes2
        let values = MakeAndPublishVals cenv env (altActualParent, false, declKind, ValNotInRecScope, valSchemes, attrs, xmlDoc, literalValue)
        let checkedPat = tcPatPhase2 (TcPatPhase2Input (values, true))
        let prelimRecValues = NameMap.map fst values

        // Now bind the r.h.s. to the l.h.s.
        let rhsExpr = mkTypeLambda m generalizedTypars (rhsExpr, tauTy)

        match checkedPat with
        // Don't introduce temporary or 'let' for 'match against wild' or 'match against unit'

        | TPat_wild _ | TPat_const (Const.Unit, _) when not isUse && not isFixed && isNil generalizedTypars ->
            let mkSequentialBind (tm, tmty) = mkSequential m rhsExpr tm, tmty
            (buildExpr >> mkSequentialBind, env, tpenv)
        | _ ->

        let patternInputTmp, checkedPat2 =

            match checkedPat with

            // We don't introduce a temporary for the case
            //   let v = expr
            | TPat_as (pat, PatternValBinding(v, GeneralizedType(generalizedTypars', _)), _)
                when List.lengthsEqAndForall2 typarRefEq generalizedTypars generalizedTypars' ->
                    v, pat

            | _ when inlineFlag.ShouldInline ->
                error(Error(FSComp.SR.tcInvalidInlineSpecification(), m))

            | TPat_query _ when attribsHaveValFlag g WellKnownValAttributes.LiteralAttribute attrs ->
                error(Error(FSComp.SR.tcLiteralAttributeCannotUseActivePattern(), m))

            | _ ->

                let tmp, _ = mkCompGenLocal m "patternInput" (generalizedTypars +-> tauTy)

                if isUse then
                    let isDiscarded = match checkedPat with TPat_wild _ -> true | _ -> false
                    if not isDiscarded then
                        errorR(Error(FSComp.SR.tcInvalidUseBinding(), m))
                    else
                        checkLanguageFeatureError g.langVersion LanguageFeature.UseBindingValueDiscard checkedPat.Range

                elif isFixed then
                    errorR(Error(FSComp.SR.tcInvalidUseBinding(), m))

                // If the overall declaration is declaring statics or a module value, then force the patternInputTmp to also
                // have representation as module value.
                if declKind.MustHaveValReprInfo then
                    AdjustValToHaveValReprInfo tmp altActualParent (InferValReprInfoOfBinding g AllowTypeDirectedDetupling.Yes tmp rhsExpr)

                tmp, checkedPat

        // Add the bind "let patternInputTmp = rhsExpr" to the bodyExpr we get from mkPatBind
        let mkRhsBind (bodyExpr, bodyExprTy) =
            let letExpr = mkLet debugPoint m patternInputTmp rhsExpr bodyExpr
            letExpr, bodyExprTy

        let allValsDefinedByPattern = NameMap.range prelimRecValues

        // Add the compilation of the pattern to the bodyExpr we get from mkCleanup
        let mkPatBind (bodyExpr, bodyExprTy) =
            let valsDefinedByMatching = ListSet.remove valEq patternInputTmp allValsDefinedByPattern
            let clauses = [MatchClause(checkedPat2, None, TTarget(valsDefinedByMatching, bodyExpr, None), m)]
            let matchExpr = CompilePatternForMatch cenv env m m true ThrowIncompleteMatchException (patternInputTmp, generalizedTypars, Some rhsExpr) clauses tauTy bodyExprTy

            let matchExpr =
                if declKind.IsConvertToLinearBindings then
                    LinearizeTopMatch g altActualParent matchExpr
                else
                    matchExpr

            matchExpr, bodyExprTy

        // Add the dispose of any "use x = ..." to bodyExpr
        let mkCleanup (bodyExpr, bodyExprTy) =
            if isUse && not isFixed then
                let isDiscarded = match checkedPat2 with TPat_wild _ -> true | _ -> false
                let allValsDefinedByPattern = if isDiscarded then [patternInputTmp] else allValsDefinedByPattern
                (allValsDefinedByPattern, (bodyExpr, bodyExprTy)) ||> List.foldBack (fun v (bodyExpr, bodyExprTy) ->
                    AddCxTypeMustSubsumeType ContextInfo.NoContext denv cenv.css v.Range NoTrace g.system_IDisposableNull_ty v.Type
                    let cleanupE = BuildDisposableCleanup cenv env m v
                    mkTryFinally g (bodyExpr, cleanupE, m, bodyExprTy, DebugPointAtTry.No, DebugPointAtFinally.No), bodyExprTy)
            else
                (bodyExpr, bodyExprTy)

        let envInner = AddLocalValMap g cenv.tcSink scopem prelimRecValues env

        ((buildExpr >> mkCleanup >> mkPatBind >> mkRhsBind), envInner, tpenv))

/// Return binds corresponding to the linearised let-bindings.
/// This reveals the bound items, e.g. when the lets occur in incremental object defns.
/// RECAP:
///   The LHS of let-bindings are patterns.
///   These patterns could fail, e.g. "let Some x = ...".
///   So let bindings could contain a fork at a match construct, with one branch being the match failure.
///   If bindings are linearised, then this fork is pushed to the RHS.
///   In this case, the let bindings type check to a sequence of bindings.
and TcLetBindings (cenv: cenv) env containerInfo (declKind: DeclKind) tpenv (binds, bindsm, scopem) =
    let g = cenv.g

    assert declKind.IsConvertToLinearBindings
    let mkf, env, tpenv = TcLetBinding cenv false env containerInfo declKind tpenv (binds, bindsm, scopem)
    let unite = mkUnit g bindsm
    let expr, _ = mkf (unite, g.unit_ty)

    let rec stripLets acc expr =
        match stripDebugPoints expr with
        | Expr.Let (bind, body, m, _) -> stripLets (TMDefLet(bind, m) :: acc) body
        | Expr.Sequential (expr1, expr2, NormalSeq, m) -> stripLets (TMDefDo(expr1, m) :: acc) expr2
        | Expr.Const (Const.Unit, _, _) -> List.rev acc
        | _ -> failwith "TcLetBindings: let sequence is non linear. Maybe a LHS pattern was not linearised?"

    let binds = stripLets [] expr
    binds, env, tpenv

and CheckMemberFlags intfSlotTyOpt newslotsOK overridesOK memberFlags m =
    if newslotsOK = NoNewSlots && memberFlags.IsDispatchSlot then
        errorR(Error(FSComp.SR.tcAbstractMembersIllegalInAugmentation(), m))
    if overridesOK = ErrorOnOverrides && memberFlags.MemberKind = SynMemberKind.Constructor then
        errorR(Error(FSComp.SR.tcConstructorsIllegalInAugmentation(), m))
    if overridesOK = WarnOnOverrides && memberFlags.IsOverrideOrExplicitImpl && Option.isNone intfSlotTyOpt then
        warning(OverrideInIntrinsicAugmentation m)
    if overridesOK = ErrorOnOverrides && memberFlags.IsOverrideOrExplicitImpl then
        error(Error(FSComp.SR.tcMethodOverridesIllegalHere(), m))

/// Apply the pre-assumed knowledge available to type inference prior to looking at
/// the _body_ of the binding. For example, in a letrec we may assume this knowledge
/// for each binding in the letrec prior to any type inference. This might, for example,
/// tell us the type of the arguments to a recursive function.
and ApplyTypesFromArgumentPatterns (cenv: cenv, env, optionalArgsOK, ty, m, tpenv, NormalizedBindingRhs (pushedPats, retInfoOpt, e), memberFlagsOpt: SynMemberFlags option) =

    let g = cenv.g

    match pushedPats with
    | [] ->
        match retInfoOpt with
        | None -> ()
        | Some (SynBindingReturnInfo (typeName = retInfoTy; range = m)) ->
            let retInfoTy, _ = TcTypeAndRecover cenv NewTyparsOK CheckCxs ItemOccurrence.UseInType WarnOnIWSAM.Yes env tpenv retInfoTy
            UnifyTypes cenv env m ty retInfoTy
        // Property setters always have "unit" return type
        match memberFlagsOpt with
        | Some memFlags when memFlags.MemberKind = SynMemberKind.PropertySet ->
            UnifyTypes cenv env m ty g.unit_ty
        | _ -> ()

    | pushedPat :: morePushedPats ->
        let domainTy, resultTy = UnifyFunctionType None cenv env.DisplayEnv m ty
        // We apply the type information from the patterns by type checking the
        // "simple" patterns against 'domainTyR'. They get re-typechecked later.
        ignore (cenv.TcSimplePats cenv optionalArgsOK CheckCxs domainTy env (TcPatLinearEnv (tpenv, Map.empty, Set.empty)) pushedPat ([], false))
        ApplyTypesFromArgumentPatterns (cenv, env, optionalArgsOK, resultTy, m, tpenv, NormalizedBindingRhs (morePushedPats, retInfoOpt, e), memberFlagsOpt)

/// Check if the type annotations and inferred type information in a value give a
/// full and complete generic type for a value. If so, enable generic recursion.
and ComputeIsComplete enclosingDeclaredTypars declaredTypars ty =
    Zset.isEmpty (List.fold (fun acc v -> Zset.remove v acc)
                                  (freeInType CollectAllNoCaching ty).FreeTypars
                                  (enclosingDeclaredTypars@declaredTypars))

/// Determine if a uniquely-identified-abstract-slot exists for an override member (or interface member implementation) based on the information available
/// at the syntactic definition of the member (i.e. prior to type inference). If so, we know the expected signature of the override, and the full slotsig
/// it implements. Apply the inferred slotsig.
and ApplyAbstractSlotInference (cenv: cenv) (envinner: TcEnv) (_: Val option) (argsAndRetTy, m, synTyparDecls, declaredTypars, memberId, tcrefObjTy, renaming, intfSlotTyOpt, valSynData, memberFlags: SynMemberFlags, attribs) =

    let g = cenv.g
    let ad = envinner.eAccessRights

    let typToSearchForAbstractMembers =
        match intfSlotTyOpt with
        | Some (ty, abstractSlots) ->
            // The interface type is in terms of the type's type parameters.
            // We need a signature in terms of the values' type parameters.
            ty, Some abstractSlots
        | None ->
            tcrefObjTy, None

    // Determine if a uniquely-identified-override exists based on the information
    // at the member signature. If so, we know the type of this member, and the full slotsig
    // it implements. Apply the inferred slotsig.
    if memberFlags.IsOverrideOrExplicitImpl then

        // for error detection, we want to compare finality when testing for equivalence
        let methInfosEquivByNameAndSig meths =
            match meths with
            | [] -> false
            | head :: tail ->
                tail |> List.forall (MethInfosEquivByNameAndSig EraseNone false g cenv.amap m head)

        match memberFlags.MemberKind with
        | SynMemberKind.Member ->
             let dispatchSlots, dispatchSlotsArityMatch =
                if g.langVersion.SupportsFeature(LanguageFeature.ErrorForNonVirtualMembersOverrides) then
                    GetAbstractMethInfosForSynMethodDecl(cenv.infoReader, ad, memberId, m, typToSearchForAbstractMembers, valSynData, memberFlags, DiscardOnFirstNonOverride)
                else
                    GetAbstractMethInfosForSynMethodDecl(cenv.infoReader, ad, memberId, m, typToSearchForAbstractMembers, valSynData, memberFlags,IgnoreOverrides)

             let uniqueAbstractMethSigs =
                 match dispatchSlots with
                 | [] ->
                     let instanceExpected = memberFlags.IsInstance
                     if instanceExpected then
                        errorR(Error(FSComp.SR.tcNoMemberFoundForOverride(), memberId.idRange))
                     else
                        errorR(Error(FSComp.SR.tcNoStaticMemberFoundForOverride (), memberId.idRange))
                     []

                 | slot :: _ as slots ->
                     match dispatchSlotsArityMatch with
                     | meths when methInfosEquivByNameAndSig meths -> meths
                     | [] ->
                         let raiseGenericArityMismatch() =
                              let details = NicePrint.multiLineStringOfMethInfos cenv.infoReader m envinner.DisplayEnv slots
                              errorR(Error(FSComp.SR.tcOverrideArityMismatch details, memberId.idRange))
                              []

                         match slot with
                         | FSMeth (_, _, valRef, _) ->
                             match valRef.TauType with
                             // https://github.com/dotnet/fsharp/issues/15307
                             // check if abstract method expects tuple, give better error message
                             | TType_fun(_,TType_fun(TType_tuple _,_,_),_) ->
                                 if not slot.NumArgs.IsEmpty && slot.NumArgs.Head = 1 then
                                     errorR(Error(FSComp.SR.tcOverrideUsesMultipleArgumentsInsteadOfTuple(), memberId.idRange))
                                     []
                                 else raiseGenericArityMismatch()
                             | _ -> raiseGenericArityMismatch()
                         | _ -> raiseGenericArityMismatch()
                     | _ -> [] // check that method to override is sealed is located at CheckOverridesAreAllUsedOnce (typrelns.fs)
                      // We hit this case when it is ambiguous which abstract method is being implemented.

             // If we determined a unique member then utilize the type information from the slotsig
             let declaredTypars =
                 match uniqueAbstractMethSigs with
                 | uniqueAbstractMeth :: _ ->

                    // Overrides can narrow the retTy from nullable to not-null.
                     // By changing nullness to be variable we do not get in the way of eliminating nullness (=good).
                     // We only keep a WithNull nullness if it was part of an explicit type instantiation
                     let canChangeNullableRetTy = 
                        match g.checkNullness, renaming with
                        | false, _ -> false
                        | true, [] -> true
                        | true, _ -> not(uniqueAbstractMeth.HasGenericRetTy())

                     let uniqueAbstractMeth = uniqueAbstractMeth.Instantiate(cenv.amap, m, renaming)

                     let typarsFromAbsSlotAreRigid, typarsFromAbsSlot, argTysFromAbsSlot, retTyFromAbsSlot =
                         FreshenAbstractSlot g cenv.amap m synTyparDecls uniqueAbstractMeth

                     let declaredTypars = (if typarsFromAbsSlotAreRigid then typarsFromAbsSlot else declaredTypars)

                     let retTyFromAbsSlot = 
                        if canChangeNullableRetTy then
                            retTyFromAbsSlot |> changeWithNullReqTyToVariable g
                        else retTyFromAbsSlot 

                     let absSlotTy = mkMethodTy g argTysFromAbsSlot retTyFromAbsSlot

                     UnifyTypes cenv envinner m argsAndRetTy absSlotTy
                     declaredTypars
                 | _ -> declaredTypars

                 // Retained to ensure use of an FSComp.txt entry, can be removed at a later date: errorR(Error(FSComp.SR.tcDefaultAmbiguous(), memberId.idRange))

             // What's the type containing the abstract slot we're implementing? Used later on in MakeMemberDataAndMangledNameForMemberVal.
             // This type must be in terms of the enclosing type's formal type parameters, hence the application of revRenaming

             let optInferredImplSlotTys =
                 match intfSlotTyOpt with
                 | Some (x, _) -> [x]
                 | None -> uniqueAbstractMethSigs |> List.map (fun x -> x.ApparentEnclosingType)

             optInferredImplSlotTys, declaredTypars

        | SynMemberKind.PropertyGet
        | SynMemberKind.PropertySet as k ->
           let dispatchSlots = GetAbstractPropInfosForSynPropertyDecl(cenv.infoReader, ad, memberId, m, typToSearchForAbstractMembers, memberFlags)

           // Only consider those abstract slots where the get/set flags match the value we're defining
           let dispatchSlots =
               dispatchSlots
               |> List.filter (fun pinfo ->
                     (pinfo.HasGetter && k=SynMemberKind.PropertyGet) ||
                     (pinfo.HasSetter && k=SynMemberKind.PropertySet))

           // Find the unique abstract slot if it exists
           let uniqueAbstractPropSigs =
               match dispatchSlots with
               | [] when not (CompileAsEvent g attribs) ->
                   let instanceExpected = memberFlags.IsInstance
                   if instanceExpected then
                        errorR(Error(FSComp.SR.tcNoPropertyFoundForOverride(), memberId.idRange))
                   else
                        errorR (Error(FSComp.SR.tcNoStaticPropertyFoundForOverride (), memberId.idRange))
                   []
               | [uniqueAbstractProp] -> [uniqueAbstractProp]
               | _ ->
                   // We hit this case when it is ambiguous which abstract property is being implemented.
                   []

           // If we determined a unique member then utilize the type information from the slotsig
           uniqueAbstractPropSigs |> List.iter (fun uniqueAbstractProp ->

               let kIsGet = (k = SynMemberKind.PropertyGet)

               if not (if kIsGet then uniqueAbstractProp.HasGetter else uniqueAbstractProp.HasSetter) then
                   error(Error(FSComp.SR.tcAbstractPropertyMissingGetOrSet(if kIsGet then "getter" else "setter"), memberId.idRange))

               let uniqueAbstractMeth = if kIsGet then uniqueAbstractProp.GetterMethod else uniqueAbstractProp.SetterMethod

               let uniqueAbstractMeth = uniqueAbstractMeth.Instantiate(cenv.amap, m, renaming)

               let _, typarsFromAbsSlot, argTysFromAbsSlot, retTyFromAbsSlot =
                    FreshenAbstractSlot g cenv.amap m synTyparDecls uniqueAbstractMeth

               if not (isNil typarsFromAbsSlot) then
                   errorR(InternalError("Unexpected generic property", memberId.idRange))

               let absSlotTy =
                   if (memberFlags.MemberKind = SynMemberKind.PropertyGet) then
                       mkMethodTy g argTysFromAbsSlot retTyFromAbsSlot
                   else
                      match argTysFromAbsSlot with
                       | [argTysFromAbsSlot] ->
                           mkFunTy g (mkRefTupledTy g argTysFromAbsSlot) g.unit_ty
                       | _ ->
                           error(Error(FSComp.SR.tcInvalidSignatureForSet(), memberId.idRange))
                           mkFunTy g retTyFromAbsSlot g.unit_ty

               UnifyTypes cenv envinner m argsAndRetTy absSlotTy)

           // What's the type containing the abstract slot we're implementing? Used later on in MakeMemberDataAndMangledNameForMemberVal.
           // This type must be in terms of the enclosing type's formal type parameters, hence the application of revRenaming.

           let optInferredImplSlotTys =
               match intfSlotTyOpt with
               | Some (x, _) -> [ x ]
               | None -> uniqueAbstractPropSigs |> List.map (fun pinfo -> pinfo.ApparentEnclosingType)

           optInferredImplSlotTys, declaredTypars

        | _ ->
           match intfSlotTyOpt with
           | Some (x, _) -> [x], declaredTypars
           | None -> [], declaredTypars

    else

       [], declaredTypars

and CheckForNonAbstractInterface (g: TcGlobals) declKind tcref (memberFlags: SynMemberFlags) isMemberStatic m =
    if isInterfaceTyconRef tcref then
        if memberFlags.MemberKind = SynMemberKind.ClassConstructor then
            error(Error(FSComp.SR.tcStaticInitializersIllegalInInterface(), m))
        elif memberFlags.MemberKind = SynMemberKind.Constructor then
            error(Error(FSComp.SR.tcObjectConstructorsIllegalInInterface(), m))
        elif memberFlags.IsOverrideOrExplicitImpl then
            error(Error(FSComp.SR.tcMemberOverridesIllegalInInterface(), m))
        elif not (declKind = ExtrinsicExtensionBinding || memberFlags.IsDispatchSlot) then
            if not isMemberStatic then
                error(Error(FSComp.SR.tcConcreteMembersIllegalInInterface(), m))
            else
                checkLanguageFeatureError g.langVersion LanguageFeature.StaticMembersInInterfaces m

//-------------------------------------------------------------------------
// TcLetrecBindings - AnalyzeAndMakeAndPublishRecursiveValue s
//------------------------------------------------------------------------

and AnalyzeRecursiveStaticMemberOrValDecl
       (cenv: cenv,
        envinner: TcEnv,
        tpenv,
        declKind,
        synTyparDecls,
        newslotsOK,
        overridesOK,
        tcrefContainerInfo,
        vis1,
        id: Ident,
        vis2,
        declaredTypars,
        memberFlagsOpt: SynMemberFlags option,
        thisIdOpt,
        bindingAttribs,
        valSynInfo,
        ty,
        bindingRhs,
        mBinding,
        explicitTyparInfo) =

    let g = cenv.g
    let vis = CombineVisibilityAttribs vis1 vis2 mBinding

    // Check if we're defining a member, in which case generate the internal unique
    // name for the member and the information about which type it is augmenting

    match tcrefContainerInfo, memberFlagsOpt with
    | Some(MemberOrValContainerInfo(tcref, intfSlotTyOpt, _, _, declaredTyconTypars)), Some memberFlags
        when (match memberFlags.MemberKind with
              | SynMemberKind.Member -> true
              | SynMemberKind.PropertyGet -> true
              | SynMemberKind.PropertySet -> true
              | SynMemberKind.PropertyGetSet -> true
              | _ -> false) &&
             not memberFlags.IsInstance &&
             memberFlags.IsOverrideOrExplicitImpl ->

           CheckMemberFlags intfSlotTyOpt newslotsOK overridesOK memberFlags id.idRange
           CheckForNonAbstractInterface g declKind tcref memberFlags true id.idRange

           let isExtrinsic = (declKind = ExtrinsicExtensionBinding)
           let tcrefObjTy, enclosingDeclaredTypars, renaming, _, _ = FreshenObjectArgType cenv mBinding TyparRigidity.WillBeRigid tcref isExtrinsic declaredTyconTypars
           let envinner = AddDeclaredTypars CheckForDuplicateTypars enclosingDeclaredTypars envinner
           let envinner = MakeInnerEnvForTyconRef envinner tcref isExtrinsic

           let (ExplicitTyparInfo(_, declaredTypars, infer)) = explicitTyparInfo

           let optInferredImplSlotTys, declaredTypars =
               ApplyAbstractSlotInference cenv envinner None (ty, mBinding, synTyparDecls, declaredTypars, id, tcrefObjTy, renaming, intfSlotTyOpt, valSynInfo, memberFlags, bindingAttribs)

           let explicitTyparInfo = ExplicitTyparInfo(declaredTypars, declaredTypars, infer)

           let memberInfo = MakeMemberDataAndMangledNameForMemberVal(g, tcref, isExtrinsic, bindingAttribs, optInferredImplSlotTys, memberFlags, valSynInfo, id, false)

           envinner, tpenv, id, None, Some memberInfo, vis, vis2, None, enclosingDeclaredTypars, None, explicitTyparInfo, bindingRhs, declaredTypars

    | Some(MemberOrValContainerInfo(tcref, intfSlotTyOpt, baseValOpt, _safeInitInfo, declaredTyconTypars)), Some memberFlags ->
        assert (Option.isNone intfSlotTyOpt)

        CheckMemberFlags None newslotsOK overridesOK memberFlags id.idRange
        CheckForNonAbstractInterface g declKind tcref memberFlags true id.idRange

        if memberFlags.MemberKind = SynMemberKind.Constructor && tcref.Deref.IsFSharpException then
            error(Error(FSComp.SR.tcConstructorsDisallowedInExceptionAugmentation(), id.idRange))

        let isExtrinsic = (declKind = ExtrinsicExtensionBinding)
        let _, enclosingDeclaredTypars, _, objTy, thisTy = FreshenObjectArgType cenv mBinding TyparRigidity.WillBeRigid tcref isExtrinsic declaredTyconTypars
        let envinner = AddDeclaredTypars CheckForDuplicateTypars enclosingDeclaredTypars envinner
        let envinner = MakeInnerEnvForTyconRef envinner tcref isExtrinsic

        let safeThisValOpt, baseValOpt =
            match memberFlags.MemberKind with

            // Explicit struct or class constructor
            | SynMemberKind.Constructor ->
                // A fairly adhoc place to put this check
                if tcref.IsStructOrEnumTycon && (match valSynInfo with SynValInfo([[]], _) -> true | _ -> false) then
                    errorR(Error(FSComp.SR.tcStructsCannotHaveConstructorWithNoArguments(), mBinding))

                if not tcref.IsFSharpObjectModelTycon then
                    errorR(Error(FSComp.SR.tcConstructorsIllegalForThisType(), id.idRange))

                let safeThisValOpt = MakeAndPublishSafeThisVal cenv envinner thisIdOpt thisTy

                // baseValOpt is the 'base' variable associated with the inherited portion of a class
                // It is declared once on the 'inheritedTys clause, but a fresh binding is made for
                // each member that may use it.
                let baseValOpt =
                    match GetSuperTypeOfType g cenv.amap mBinding objTy with
                    | Some superTy -> MakeAndPublishBaseVal cenv envinner (match baseValOpt with None -> None | Some v -> Some v.Id) superTy
                    | None -> None

                let domainTy = NewInferenceType g

                // This is the type we pretend a constructor has, because its implementation must ultimately appear to return a value of the given type
                // This is somewhat awkward later in codegen etc.
                UnifyTypes cenv envinner mBinding ty (mkFunTy g domainTy objTy)

                safeThisValOpt, baseValOpt

            | _ ->
                None, None

        let memberInfo =
            let isExtrinsic = (declKind = ExtrinsicExtensionBinding)
            MakeMemberDataAndMangledNameForMemberVal(g, tcref, isExtrinsic, bindingAttribs, [], memberFlags, valSynInfo, id, false)

        envinner, tpenv, id, None, Some memberInfo, vis, vis2, safeThisValOpt, enclosingDeclaredTypars, baseValOpt, explicitTyparInfo, bindingRhs, declaredTypars

    // non-member bindings. How easy.
    | _ ->
        envinner, tpenv, id, None, None, vis, vis2, None, [], None, explicitTyparInfo, bindingRhs, declaredTypars

and AnalyzeRecursiveInstanceMemberDecl
       (cenv: cenv,
        envinner: TcEnv,
        tpenv,
        declKind,
        synTyparDecls,
        valSynInfo,
        explicitTyparInfo: ExplicitTyparInfo,
        newslotsOK,
        overridesOK,
        vis1,
        thisId,
        memberId: Ident,
        toolId: Ident option,
        bindingAttribs,
        vis2,
        tcrefContainerInfo,
        memberFlagsOpt,
        ty,
        bindingRhs,
        mBinding) =

    let g = cenv.g
    let vis = CombineVisibilityAttribs vis1 vis2 mBinding
    let (ExplicitTyparInfo(_, declaredTypars, infer)) = explicitTyparInfo
    match tcrefContainerInfo, memberFlagsOpt with
     // Normal instance members.
     | Some(MemberOrValContainerInfo(tcref, intfSlotTyOpt, baseValOpt, _safeInitInfo, declaredTyconTypars)), Some memberFlags ->

         CheckMemberFlags intfSlotTyOpt newslotsOK overridesOK memberFlags mBinding

         if Option.isSome vis && memberFlags.IsOverrideOrExplicitImpl then
            errorR(Error(FSComp.SR.tcOverridesCannotHaveVisibilityDeclarations(), memberId.idRange))

         // Syntactically push the "this" variable across to be a lambda on the right
         let bindingRhs = PushOnePatternToRhs cenv true (mkSynThisPatVar thisId) bindingRhs

         // The type being augmented tells us the type of 'this'
         let isExtrinsic = (declKind = ExtrinsicExtensionBinding)
         let tcrefObjTy, enclosingDeclaredTypars, renaming, objTy, thisTy = FreshenObjectArgType cenv mBinding TyparRigidity.WillBeRigid tcref isExtrinsic declaredTyconTypars

         let envinner = AddDeclaredTypars CheckForDuplicateTypars enclosingDeclaredTypars envinner

         // If private, the member's accessibility is related to 'tcref'
         let envinner = MakeInnerEnvForTyconRef envinner tcref isExtrinsic

         let baseValOpt = if tcref.IsFSharpObjectModelTycon then baseValOpt else None

         // Apply the known type of 'this'
         let argsAndRetTy = NewInferenceType g
         UnifyTypes cenv envinner mBinding ty (mkFunTy g thisTy argsAndRetTy)

         CheckForNonAbstractInterface g declKind tcref memberFlags false memberId.idRange

         // Determine if a uniquely-identified-override exists based on the information
         // at the member signature. If so, we know the type of this member, and the full slotsig
         // it implements. Apply the inferred slotsig.
         let optInferredImplSlotTys, declaredTypars =
             ApplyAbstractSlotInference cenv envinner baseValOpt (argsAndRetTy, mBinding, synTyparDecls, declaredTypars, memberId, tcrefObjTy, renaming, intfSlotTyOpt, valSynInfo, memberFlags, bindingAttribs)

         // Update the ExplicitTyparInfo to reflect the declaredTypars inferred from the abstract slot
         let explicitTyparInfo = ExplicitTyparInfo(declaredTypars, declaredTypars, infer)

         // baseValOpt is the 'base' variable associated with the inherited portion of a class
         // It is declared once on the 'inheritedTys clause, but a fresh binding is made for
         // each member that may use it.
         let baseValOpt =
             match GetSuperTypeOfType g cenv.amap mBinding objTy with
             | Some superTy -> MakeAndPublishBaseVal cenv envinner (match baseValOpt with None -> None | Some v -> Some v.Id) superTy
             | None -> None

         let memberInfo = MakeMemberDataAndMangledNameForMemberVal(g, tcref, isExtrinsic, bindingAttribs, optInferredImplSlotTys, memberFlags, valSynInfo, memberId, false)
         // We used to factored in the 'get' or 'set' as the identifier for a property declaration using "with get () = ... and set v = ..."
         // It has been removed from FSharp.Compiler.Service because we want the property name to be the location of
         // the definition of these symbols.
         //
         // See https://github.com/fsharp/FSharp.Compiler.Service/issues/79.

         envinner, tpenv, memberId, toolId, Some memberInfo, vis, vis2, None, enclosingDeclaredTypars, baseValOpt, explicitTyparInfo, bindingRhs, declaredTypars
     | _ ->
         error(Error(FSComp.SR.tcRecursiveBindingsWithMembersMustBeDirectAugmentation(), mBinding))

and AnalyzeRecursiveDecl
        (cenv,
         envinner,
         tpenv,
         declKind,
         synTyparDecls,
         declaredTypars,
         thisIdOpt,
         valSynInfo,
         explicitTyparInfo,
         newslotsOK,
         overridesOK,
         vis1,
         declPattern,
         bindingAttribs,
         tcrefContainerInfo,
         memberFlagsOpt,
         ty,
         bindingRhs,
         mBinding) =

    let rec analyzeRecursiveDeclPat tpenv pat =
        match pat with
        | SynPat.FromParseError(innerPat, _) -> analyzeRecursiveDeclPat tpenv innerPat
        | SynPat.Typed(innerPat, tgtTy, _) ->
            let tgtTyR, tpenv = TcTypeAndRecover cenv NewTyparsOK CheckCxs ItemOccurrence.UseInType WarnOnIWSAM.Yes envinner tpenv tgtTy
            UnifyTypes cenv envinner mBinding ty tgtTyR
            analyzeRecursiveDeclPat tpenv innerPat
        | SynPat.Attrib(_innerPat, _attribs, m) ->
            error(Error(FSComp.SR.tcAttributesInvalidInPatterns(), m))

        // This is for the construct 'let rec x = ... and do ... and y = ...' (DEPRECATED IN pars.mly )
        //
        // Also for
        //    module rec M =
        //        printfn "hello" // side effects in recursive modules
        //        let x = 1
        | SynPat.Const (SynConst.Unit, m) | SynPat.Wild m ->
             let id = ident (cenv.niceNameGen.FreshCompilerGeneratedName("doval", m), m)
             analyzeRecursiveDeclPat tpenv (SynPat.Named (SynIdent(id, None), false, None, m))

        | SynPat.Named (SynIdent(id,_), _, vis2, _) ->
            AnalyzeRecursiveStaticMemberOrValDecl
                (cenv, envinner, tpenv, declKind, synTyparDecls,
                 newslotsOK, overridesOK, tcrefContainerInfo,
                 vis1, id, vis2, declaredTypars,
                 memberFlagsOpt, thisIdOpt, bindingAttribs,
                 valSynInfo, ty, bindingRhs, mBinding, explicitTyparInfo)

        | SynPat.InstanceMember(thisId, memberId, toolId, vis2, _) ->
            AnalyzeRecursiveInstanceMemberDecl
                (cenv, envinner, tpenv, declKind,
                 synTyparDecls, valSynInfo, explicitTyparInfo, newslotsOK,
                 overridesOK, vis1, thisId, memberId, toolId,
                 bindingAttribs, vis2, tcrefContainerInfo,
                 memberFlagsOpt, ty, bindingRhs, mBinding)

        | SynPat.Paren(_, m) -> error(Error(FSComp.SR.tcInvalidMemberDeclNameMissingOrHasParen(), m))

        | _ -> error(Error(FSComp.SR.tcOnlySimplePatternsInLetRec(), mBinding))

    analyzeRecursiveDeclPat tpenv declPattern


/// This is a major routine that generates the Val for a recursive binding
/// prior to the analysis of the definition of the binding. This includes
/// members of all flavours (including properties, implicit class constructors
/// and overrides). At this point we perform override inference, to infer
/// which method we are overriding, in order to add constraints to the
/// implementation of the method.
and AnalyzeAndMakeAndPublishRecursiveValue
        overridesOK
        isGeneratedEventVal
        (cenv: cenv)
        (env: TcEnv)
        (tpenv, recBindIdx)
        (NormalizedRecBindingDefn(containerInfo, newslotsOK, declKind, binding)) =

    let g = cenv.g

    // Pull apart the inputs
    let (NormalizedBinding(vis1, bindingKind, isInline, isMutable, bindingSynAttribs, bindingXmlDoc, synTyparDecls, valSynData, declPattern, bindingRhs, mBinding, debugPoint)) = binding
    let (NormalizedBindingRhs(_, _, bindingExpr)) = bindingRhs
    let (SynValData(memberFlagsOpt, valSynInfo, thisIdOpt)) = valSynData
    let (ContainerInfo(altActualParent, tcrefContainerInfo)) = containerInfo

    let attrTgt = declKind.AllowedAttribTargets memberFlagsOpt

    // Check the attributes on the declaration
    let bindingAttribs = TcAttributes cenv env attrTgt bindingSynAttribs

    // Allocate the type inference variable for the inferred type
    let ty = NewInferenceType g

    let inlineFlag = ComputeInlineFlag memberFlagsOpt isInline isMutable g bindingAttribs mBinding

    if isMutable then errorR(Error(FSComp.SR.tcOnlyRecordFieldsAndSimpleLetCanBeMutable(), mBinding))

    // Typecheck the typar decls, if any
    let explicitTyparInfo, tpenv = TcBindingTyparDecls false cenv env tpenv synTyparDecls
    let (ExplicitTyparInfo(_, declaredTypars, _)) = explicitTyparInfo
    let envinner = AddDeclaredTypars CheckForDuplicateTypars declaredTypars env

    // OK, analyze the declaration and return lots of information about it
    let envinner, tpenv, bindingId, toolIdOpt, memberInfoOpt, vis, vis2, safeThisValOpt, enclosingDeclaredTypars, baseValOpt, explicitTyparInfo, bindingRhs, declaredTypars =

        AnalyzeRecursiveDecl (cenv, envinner, tpenv, declKind, synTyparDecls, declaredTypars, thisIdOpt, valSynInfo,
                              explicitTyparInfo,
                              newslotsOK, overridesOK, vis1, declPattern, bindingAttribs, tcrefContainerInfo,
                              memberFlagsOpt, ty, bindingRhs, mBinding)

    let optionalArgsOK = Option.isSome memberFlagsOpt

    // Assert the types given in the argument patterns
    ApplyTypesFromArgumentPatterns(cenv, envinner, optionalArgsOK, ty, mBinding, tpenv, bindingRhs, memberFlagsOpt)

    // Do the type annotations give the full and complete generic type?
    // If so, generic recursion can be used when using this type.
    let isComplete = ComputeIsComplete enclosingDeclaredTypars declaredTypars ty

    // NOTE: The type scheme here is normally not 'complete'!!!! The type is more or less just a type variable at this point.
    // NOTE: top arity, type and typars get fixed-up after inference
    let prelimTyscheme = GeneralizedType(enclosingDeclaredTypars@declaredTypars, ty)
    let prelimValReprInfo = TranslateSynValInfo cenv mBinding (TcAttributes cenv envinner) valSynInfo
    let valReprInfo, valReprInfoForDisplay = UseSyntacticValReprInfo declKind prelimTyscheme prelimValReprInfo
    let hasDeclaredTypars = not (List.isEmpty declaredTypars)
    let prelimValScheme = ValScheme(bindingId, prelimTyscheme, valReprInfo, valReprInfoForDisplay, memberInfoOpt, false, inlineFlag, NormalVal, vis, false, false, false, hasDeclaredTypars)

    // Check the literal r.h.s., if any
    let _, literalValue = TcLiteral cenv ty envinner tpenv (bindingAttribs, bindingExpr)

    let extraBindings, extraValues, tpenv, recBindIdx =
       let extraBindings =
          [ for extraBinding in EventDeclarationNormalization.GenerateExtraBindings cenv (bindingAttribs, binding) do
               yield NormalizedRecBindingDefn(containerInfo, newslotsOK, declKind, extraBinding) ]
       let res, (tpenv, recBindIdx) = List.mapFold (AnalyzeAndMakeAndPublishRecursiveValue overridesOK true cenv env) (tpenv, recBindIdx) extraBindings
       let extraBindings, extraValues = List.unzip res
       List.concat extraBindings, List.concat extraValues, tpenv, recBindIdx

    // Create the value
    let vspec = MakeAndPublishVal cenv envinner (altActualParent, false, declKind, ValInRecScope isComplete, prelimValScheme, bindingAttribs, bindingXmlDoc, literalValue, isGeneratedEventVal)

    // Suppress hover tip for "get" and "set" at property definitions, where toolId <> bindingId
    match toolIdOpt with
    | Some tid when not tid.idRange.IsSynthetic && not (equals tid.idRange bindingId.idRange) ->
        let item = Item.Value (mkLocalValRef vspec)
        CallNameResolutionSink cenv.tcSink (tid.idRange, env.NameEnv, item, emptyTyparInst, ItemOccurrence.RelatedText, env.eAccessRights)
    | _ -> ()

    let mangledId = ident(vspec.LogicalName, vspec.Range)
    // Reconstitute the binding with the unique name
    let revisedBinding = NormalizedBinding (vis1, bindingKind, isInline, isMutable, bindingSynAttribs, bindingXmlDoc, synTyparDecls, valSynData, mkSynPatVar vis2 mangledId, bindingRhs, mBinding, debugPoint)

    // Create the RecursiveBindingInfo to use in later phases
    let rbinfo =
        let safeInitInfo =
            match tcrefContainerInfo with
            | Some(MemberOrValContainerInfo(_, _, _, safeInitInfo, _)) -> safeInitInfo
            | _ -> NoSafeInitInfo

        RecursiveBindingInfo(recBindIdx, containerInfo, enclosingDeclaredTypars, inlineFlag, vspec, explicitTyparInfo, prelimValReprInfo, memberInfoOpt, baseValOpt, safeThisValOpt, safeInitInfo, vis, ty, declKind)

    let recBindIdx = recBindIdx + 1

    // Done - add the declared name to the List.map and return the bundle for use by TcLetrecBindings
    let primaryBinding: PreCheckingRecursiveBinding =
        { SyntacticBinding = revisedBinding
          RecBindingInfo = rbinfo }

    ((primaryBinding :: extraBindings), (vspec :: extraValues)), (tpenv, recBindIdx)

and AnalyzeAndMakeAndPublishRecursiveValues overridesOK cenv env tpenv binds =
    let recBindIdx = 0
    let res, tpenv = List.mapFold (AnalyzeAndMakeAndPublishRecursiveValue overridesOK false cenv env) (tpenv, recBindIdx) binds
    let bindings, values = List.unzip res
    List.concat bindings, List.concat values, tpenv


//-------------------------------------------------------------------------
// TcLetrecBinding
//-------------------------------------------------------------------------

and TcLetrecBinding
         (cenv: cenv, envRec: TcEnv, scopem, extraGeneralizableTypars: Typars, reqdThisValTyOpt: TType option)

         // The state of the left-to-right iteration through the bindings
         (envNonRec: TcEnv,
          generalizedRecBinds: PostGeneralizationRecursiveBinding list,
          preGeneralizationRecBinds: PreGeneralizationRecursiveBinding list,
          tpenv,
          uncheckedRecBindsTable: Map<Stamp, PreCheckingRecursiveBinding>)

         // This is the actual binding to check
         (rbind: PreCheckingRecursiveBinding) =

    let g = cenv.g

    let (RecursiveBindingInfo(_, _, enclosingDeclaredTypars, _, vspec, explicitTyparInfo, _, _, baseValOpt, safeThisValOpt, safeInitInfo, _, tau, declKind)) = rbind.RecBindingInfo

    let allDeclaredTypars = enclosingDeclaredTypars @ rbind.RecBindingInfo.DeclaredTypars

    // Notes on FSharp 1.0, 3187:
    //    - Progressively collect the "eligible for early generalization" set of bindings -- DONE
    //    - After checking each binding, check this set to find generalizable bindings
    //    - The only reason we can't generalize is if a binding refers to type variables to which
    //      additional constraints may be applied as part of checking a later binding
    //    - Compute the set by iteratively knocking out bindings that refer to type variables free in later bindings
    //    - Implementation notes:
    //         - Generalize by remap/substitution
    //         - Pass in "free in later bindings" by passing in the set of inference variables for the bindings, i.e. the binding types
    //         - For classes the bindings will include all members in a recursive group of types
    //

    //  Example 1:
    //    let f() = g()   f: unit -> ?b
    //    and g() = 1     f: unit -> int, can generalize (though now monomorphic)

    //  Example 2:
    //    let f() = g()   f: unit -> ?b
    //    and g() = []    f: unit -> ?c list, can generalize

    //  Example 3:
    //    let f() = []   f: unit -> ?b, can generalize immediately
    //    and g() = []
    let envRec = Option.foldBack (AddLocalVal g cenv.tcSink scopem) baseValOpt envRec
    let envRec = Option.foldBack (AddLocalVal g cenv.tcSink scopem) safeThisValOpt envRec

    // Members can access protected members of parents of the type, and private members in the type
    let envRec = MakeInnerEnvForMember envRec vspec

    let checkedBind, tpenv =
        TcNormalizedBinding declKind cenv envRec tpenv tau safeThisValOpt safeInitInfo (enclosingDeclaredTypars, explicitTyparInfo) rbind.SyntacticBinding

    (try UnifyTypes cenv envRec vspec.Range (allDeclaredTypars +-> tau) vspec.Type
     with e -> error (Recursion(envRec.DisplayEnv, vspec.Id, tau, vspec.Type, vspec.Range)))

    // Inside the incremental class syntax we assert the type of the 'this' variable to be precisely the same type as the
    // this variable for the implicit class constructor. For static members, we assert the type variables associated
    // for the class to be identical to those used for the implicit class constructor and the static class constructor.
    match reqdThisValTyOpt with
    | None -> ()
    | Some reqdThisValTy ->
        let reqdThisValTy, actualThisValTy, rangeForCheck =
            match GetInstanceMemberThisVariable (vspec, checkedBind.Expr) with
            | None ->
                let reqdThisValTy = if isByrefTy g reqdThisValTy then destByrefTy g reqdThisValTy else reqdThisValTy
                let enclosingTyconRef = tcrefOfAppTy g reqdThisValTy
                reqdThisValTy, (mkWoNullAppTy enclosingTyconRef (List.map mkTyparTy enclosingDeclaredTypars)), vspec.Range
            | Some thisVal ->
                reqdThisValTy, thisVal.Type, thisVal.Range
        if not (AddCxTypeEqualsTypeUndoIfFailed envRec.DisplayEnv cenv.css rangeForCheck actualThisValTy reqdThisValTy) then
            errorR (Error(FSComp.SR.tcNonUniformMemberUse vspec.DisplayName, vspec.Range))

    let preGeneralizationRecBind =
        { RecBindingInfo = rbind.RecBindingInfo
          CheckedBinding= checkedBind
          ExtraGeneralizableTypars= extraGeneralizableTypars }

    // Remove one binding from the unchecked list
    let uncheckedRecBindsTable =
        assert (uncheckedRecBindsTable.ContainsKey rbind.RecBindingInfo.Val.Stamp)
        uncheckedRecBindsTable.Remove rbind.RecBindingInfo.Val.Stamp

    // Add one binding to the candidates eligible for generalization
    let preGeneralizationRecBinds = (preGeneralizationRecBind :: preGeneralizationRecBinds)

    // Incrementally generalize as many bindings as we can
    TcIncrementalLetRecGeneralization cenv scopem (envNonRec, generalizedRecBinds, preGeneralizationRecBinds, tpenv, uncheckedRecBindsTable)

and TcIncrementalLetRecGeneralization cenv scopem
         // The state of the left-to-right iteration through the bindings
         (envNonRec: TcEnv,
          generalizedRecBinds: PostGeneralizationRecursiveBinding list,
          preGeneralizationRecBinds: PreGeneralizationRecursiveBinding list,
          tpenv,
          uncheckedRecBindsTable: Map<Stamp, PreCheckingRecursiveBinding>) =

    let g = cenv.g
    let denv = envNonRec.DisplayEnv

    // Recompute the free-in-environment in case any type variables have been instantiated
    let freeInEnv = GeneralizationHelpers.ComputeUngeneralizableTypars envNonRec

    // Attempt to actually generalize some of the candidates eligible for generalization.
    // Compute which bindings are now eligible for early generalization.
    // Do this by computing a greatest fixed point by iteratively knocking out bindings that refer
    // to type variables free in later bindings. Look for ones whose type doesn't involve any of the other types
    let newGeneralizedRecBinds, preGeneralizationRecBinds, tpenv =

        //printfn "\n---------------------\nConsidering early generalization after type checking binding %s" vspec.DisplayName

        // Get the type variables free in bindings that have not yet been checked.
        //
        // The naive implementation of this is to iterate all the forward bindings, but this is quadratic.
        //
        // It turns out we can remove the quadratic behaviour as follows.
        // -    During type checking we already keep a table of recursive uses of values, indexed by target value.
        // -    This table is usually much smaller than the number of remaining forward declarations ? e.g. in the pathological case you mentioned below this table is size 1.
        // -    If a forward declaration does not have an entry in this table then its type can't involve any inference variables from the declarations we have already checked.
        // -    So by scanning the domain of this table we can reduce the complexity down to something like O(n * average-number-of-forward-calls).
        // -    For a fully connected programs or programs where every forward declaration is subject to a forward call, this would be quadratic. However we do not expect call graphs to be like this in practice
        //
        // Hence we use the recursive-uses table to guide the process of scraping forward references for frozen types
        // If the is no entry in the recursive use table then a forward binding has never been used and
        // the type of a binding will not contain any inference variables.
        //
        // We do this lazily in case it is "obvious" that a binding can be generalized (e.g. its type doesn't
        // involve any type inference variables)
        //
        // The forward uses table will always be smaller than the number of potential forward bindings except in extremely
        // pathological situations
        let freeInUncheckedRecBinds =
            lazy ((emptyFreeTyvars, cenv.recUses.Contents) ||> Map.fold (fun acc vStamp _ ->
                       match uncheckedRecBindsTable.TryGetValue vStamp with
                       | true, fwdBind ->
                           accFreeInType CollectAllNoCaching fwdBind.RecBindingInfo.Val.Type acc
                       | _ ->
                           acc))

        let rec loop (preGeneralizationRecBinds: PreGeneralizationRecursiveBinding list,
                      frozenBindings: PreGeneralizationRecursiveBinding list) =

            let frozenBindingTypes = frozenBindings |> List.map (fun pgrbind -> pgrbind.RecBindingInfo.Val.Type)

            let freeInFrozenAndLaterBindings =
                if frozenBindingTypes.IsEmpty then
                    freeInUncheckedRecBinds
                else
                    lazy (accFreeInTypes CollectAllNoCaching frozenBindingTypes (freeInUncheckedRecBinds.Force()))

            let preGeneralizationRecBinds, newFrozenBindings =

                preGeneralizationRecBinds |> List.partition (fun pgrbind ->

                    //printfn "(testing binding %s)" pgrbind.RecBindingInfo.Val.DisplayName

                    // Get the free type variables in the binding
                    //
                    // We use the TauType here because the binding may already have been pre-generalized because it has
                    // a fully type-annotated type signature. We effectively want to generalize the binding
                    // again here, properly - for example this means adjusting the expression for the binding to include
                    // a Expr_tlambda. If we use Val.Type then the type will appear closed.
                    let freeInBinding = (freeInType CollectAllNoCaching pgrbind.RecBindingInfo.Val.TauType).FreeTypars

                    // Is the binding free of type inference variables? If so, it can be generalized immediately
                    if freeInBinding.IsEmpty then true else

                    //printfn "(failed generalization test 1 for binding for %s)" pgrbind.RecBindingInfo.Val.DisplayName
                    // Any declared type parameters in an type are always generalizable
                    let freeInBinding = Zset.diff freeInBinding (Zset.ofList typarOrder (NormalizeDeclaredTyparsForEquiRecursiveInference g pgrbind.ExtraGeneralizableTypars))

                    if freeInBinding.IsEmpty then true else

                    //printfn "(failed generalization test 2 for binding for %s)" pgrbind.RecBindingInfo.Val.DisplayName

                    // Any declared method parameters can always be generalized
                    let freeInBinding = Zset.diff freeInBinding (Zset.ofList typarOrder (NormalizeDeclaredTyparsForEquiRecursiveInference g pgrbind.RecBindingInfo.DeclaredTypars))

                    if freeInBinding.IsEmpty then true else

                    //printfn "(failed generalization test 3 for binding for %s)" pgrbind.RecBindingInfo.Val.DisplayName

                    // Type variables free in the non-recursive environment do not stop us generalizing the binding,
                    // since they can't be generalized anyway
                    let freeInBinding = Zset.diff freeInBinding freeInEnv

                    if freeInBinding.IsEmpty then true else

                    //printfn "(failed generalization test 4 for binding for %s)" pgrbind.RecBindingInfo.Val.DisplayName

                    // Type variables free in unchecked bindings do stop us generalizing
                    let freeInBinding = Zset.inter (freeInFrozenAndLaterBindings.Force().FreeTypars) freeInBinding

                    if freeInBinding.IsEmpty then true else

                    //printfn "(failed generalization test 5 for binding for %s)" pgrbind.RecBindingInfo.Val.DisplayName

                    false)
                    //if canGeneralize then
                    //    printfn "YES: binding for %s can be generalized early" pgrbind.RecBindingInfo.Val.DisplayName
                    //else
                    //    printfn "NO: binding for %s can't be generalized early" pgrbind.RecBindingInfo.Val.DisplayName

            // Have we reached a fixed point?
            if newFrozenBindings.IsEmpty then
                preGeneralizationRecBinds, frozenBindings
            else
                // if not, then repeat
                loop(preGeneralizationRecBinds, newFrozenBindings@frozenBindings)

        // start with no frozen bindings
        let newGeneralizableBindings, preGeneralizationRecBinds = loop(preGeneralizationRecBinds, [])

        // Some of the bindings may now have been marked as 'generalizable' (which means they now transition
        // from PreGeneralization --> PostGeneralization, since we won't get any more information on
        // these bindings by processing later bindings). But this doesn't mean we
        // actually generalize all the individual type variables occurring in these bindings - for example, some
        // type variables may be free in the environment, and some definitions
        // may be value definitions which can't be generalized, e.g.
        //   let rec f x = g x
        //   and g = id f
        // Here the type variables in 'g' can't be generalized because it's a computation on the right.
        //
        // Note that in the normal case each binding passes IsGeneralizableValue. Properties and
        // constructors do not pass CanInferExtraGeneralizedTyparsForRecBinding.

        let freeInEnv =
            (freeInEnv, newGeneralizableBindings) ||> List.fold (fun freeInEnv pgrbind ->
                if GeneralizationHelpers.IsGeneralizableValue g pgrbind.CheckedBinding.Expr then
                    freeInEnv
                else
                    let freeInBinding = (freeInType CollectAllNoCaching pgrbind.RecBindingInfo.Val.TauType).FreeTypars
                    let freeInBinding = Zset.diff freeInBinding (Zset.ofList typarOrder (NormalizeDeclaredTyparsForEquiRecursiveInference g pgrbind.ExtraGeneralizableTypars))
                    let freeInBinding = Zset.diff freeInBinding (Zset.ofList typarOrder (NormalizeDeclaredTyparsForEquiRecursiveInference g pgrbind.RecBindingInfo.DeclaredTypars))
                    Zset.union freeInBinding freeInEnv)

        // Process the bindings marked for transition from PreGeneralization --> PostGeneralization
        let newGeneralizedRecBinds, tpenv =
            if newGeneralizableBindings.IsEmpty then
                [], tpenv
            else

                let supportForBindings = newGeneralizableBindings |> List.collect (TcLetrecComputeSupportForBinding cenv)
                CanonicalizePartialInferenceProblem cenv.css denv scopem supportForBindings

                let generalizedTyparsL = newGeneralizableBindings |> List.map (TcLetrecComputeAndGeneralizeGenericTyparsForBinding cenv denv freeInEnv)

                // Generalize the bindings.
                let newGeneralizedRecBinds = (generalizedTyparsL, newGeneralizableBindings) ||> List.map2 (TcLetrecGeneralizeBinding cenv denv )
                let tpenv = HideUnscopedTypars (List.concat generalizedTyparsL) tpenv
                newGeneralizedRecBinds, tpenv


        newGeneralizedRecBinds, preGeneralizationRecBinds, tpenv

    let envNonRec = envNonRec |> AddLocalVals g cenv.tcSink scopem (newGeneralizedRecBinds |> List.map (fun b -> b.RecBindingInfo.Val))
    let generalizedRecBinds = newGeneralizedRecBinds @ generalizedRecBinds

    (envNonRec, generalizedRecBinds, preGeneralizationRecBinds, tpenv, uncheckedRecBindsTable)

//-------------------------------------------------------------------------
// TcLetrecComputeAndGeneralizeGenericTyparsForBinding
//-------------------------------------------------------------------------

/// Compute the type variables which may be generalized and perform the generalization
and TcLetrecComputeAndGeneralizeGenericTyparsForBinding cenv denv freeInEnv (pgrbind: PreGeneralizationRecursiveBinding) =

    let g = cenv.g

    let freeInEnv = Zset.diff freeInEnv (Zset.ofList typarOrder (NormalizeDeclaredTyparsForEquiRecursiveInference g pgrbind.ExtraGeneralizableTypars))

    let rbinfo = pgrbind.RecBindingInfo
    let vspec = rbinfo.Val
    let (CheckedBindingInfo(inlineFlag, _, _, _, _, _, expr, _, _, m, _, _, _, _)) = pgrbind.CheckedBinding
    let (ExplicitTyparInfo(rigidCopyOfDeclaredTypars, declaredTypars, _)) = rbinfo.ExplicitTyparInfo
    let allDeclaredTypars = rbinfo.EnclosingDeclaredTypars @ declaredTypars

    // The declared typars were not marked rigid to allow equi-recursive type inference to unify
    // two declared type variables. So we now check that, for each binding, the declared
    // type variables can be unified with a rigid version of the same and undo the results
    // of this unification.
    CheckDeclaredTypars denv cenv.css m rigidCopyOfDeclaredTypars declaredTypars

    let memFlagsOpt = vspec.MemberInfo |> Option.map (fun memInfo -> memInfo.MemberFlags)
    let isCtor = (match memFlagsOpt with None -> false | Some memberFlags -> memberFlags.MemberKind = SynMemberKind.Constructor)

    GeneralizationHelpers.CheckDeclaredTyparsPermitted(memFlagsOpt, declaredTypars, m)
    let canInferTypars = CanInferExtraGeneralizedTyparsForRecBinding pgrbind

    let tau = vspec.TauType
    let maxInferredTypars = freeInTypeLeftToRight g false tau

    let canGeneralizeConstrained = GeneralizationHelpers.CanGeneralizeConstrainedTyparsForDecl rbinfo.DeclKind
    let generalizedTypars = GeneralizationHelpers.ComputeAndGeneralizeGenericTypars (cenv, denv, m, freeInEnv, canInferTypars, canGeneralizeConstrained, inlineFlag, Some expr, allDeclaredTypars, maxInferredTypars, tau, isCtor)
    generalizedTypars

/// Compute the type variables which may have member constraints that need to be canonicalized prior to generalization
and TcLetrecComputeSupportForBinding cenv (pgrbind: PreGeneralizationRecursiveBinding) =
    let g = cenv.g
    let rbinfo = pgrbind.RecBindingInfo
    let allDeclaredTypars = rbinfo.EnclosingDeclaredTypars @ rbinfo.DeclaredTypars
    let maxInferredTypars = freeInTypeLeftToRight g false rbinfo.Val.TauType
    allDeclaredTypars @ maxInferredTypars

//-------------------------------------------------------------------------
// TcLetrecGeneralizeBinding
//------------------------------------------------------------------------

// Generalise generalizedTypars from checkedBind.
and TcLetrecGeneralizeBinding cenv denv generalizedTypars (pgrbind: PreGeneralizationRecursiveBinding) : PostGeneralizationRecursiveBinding =

    let g = cenv.g
    let (RecursiveBindingInfo(_, _, enclosingDeclaredTypars, _, vspec, explicitTyparInfo, prelimValReprInfo, memberInfoOpt, _, _, _, vis, _, declKind)) = pgrbind.RecBindingInfo
    let (CheckedBindingInfo(inlineFlag, _, _, _, _, _, expr, argAttribs, _, _, _, isCompGen, _, isFixed)) = pgrbind.CheckedBinding

    if isFixed then
        errorR(Error(FSComp.SR.tcFixedNotAllowed(), expr.Range))

    let _, tau = vspec.GeneralizedType

    let prelimVal1 = PrelimVal1(vspec.Id, explicitTyparInfo, tau, Some prelimValReprInfo, memberInfoOpt, false, inlineFlag, NormalVal, argAttribs, vis, isCompGen)
    let prelimVal2 = GeneralizeVal cenv denv enclosingDeclaredTypars generalizedTypars prelimVal1

    let valscheme = UseCombinedValReprInfo g declKind expr prelimVal2
    AdjustRecType vspec valscheme

    { ValScheme = valscheme
      CheckedBinding = pgrbind.CheckedBinding
      RecBindingInfo = pgrbind.RecBindingInfo }

and TcLetrecComputeCtorSafeThisValBind (cenv: cenv) safeThisValOpt =
    let g = cenv.g
    match safeThisValOpt with
    | None -> None
    | Some (v: Val) ->
        let m = v.Range
        let ty = destRefCellTy g v.Type
        Some (mkCompGenBind v (mkRefCell g m ty (mkNull m ty)))

and MakeCheckSafeInitField g tinst thisValOpt rfref reqExpr (expr: Expr) =
    let m = expr.Range
    let availExpr =
        match thisValOpt with
        | None -> mkStaticRecdFieldGet (rfref, tinst, m)
        | Some thisVar ->
            // This is an instance method, it must have a 'this' var
            mkRecdFieldGetViaExprAddr (exprForVal m thisVar, rfref, tinst, m)
    let failureExpr = match thisValOpt with None -> mkCallFailStaticInit g m | Some _ -> mkCallFailInit g m
    mkCompGenSequential m (mkIfThen g m (mkILAsmClt g m availExpr reqExpr) failureExpr) expr

and MakeCheckSafeInit g tinst safeInitInfo reqExpr expr =
    match safeInitInfo with
    | SafeInitField (rfref, _) -> MakeCheckSafeInitField g tinst None rfref reqExpr expr
    | NoSafeInitInfo -> expr

// Given a method binding (after generalization)
//
//    method M = (fun <tyargs> <args> -> <body>)
//
// wrap the following around it if needed
//
//    method M = (fun <tyargs> baseVal <args> ->
//                      check ctorSafeInitInfo
//                      let ctorSafeThisVal = ref null
//                      <body>)
//
// The "check ctorSafeInitInfo" is only added for non-constructor instance members in a class where at least one type in the
// hierarchy has HasSelfReferentialConstructor
//
// The "let ctorSafeThisVal = ref null" is only added for explicit constructors with a self-reference parameter (Note: check later code for exact conditions)
// For implicit constructors the binding is added to the bindings of the implicit constructor

and TcLetrecAdjustMemberForSpecialVals (cenv: cenv) (pgrbind: PostGeneralizationRecursiveBinding) : PostSpecialValsRecursiveBinding =

    let g = cenv.g
    let (RecursiveBindingInfo(_, _, _, _, vspec, _, _, _, baseValOpt, safeThisValOpt, safeInitInfo, _, _, _)) = pgrbind.RecBindingInfo
    let expr = pgrbind.CheckedBinding.Expr
    let debugPoint = pgrbind.CheckedBinding.DebugPoint

    // Add the safe-init check for access to 'this' to the member if necessary
    let expr =
        match TcLetrecComputeCtorSafeThisValBind cenv safeThisValOpt with
        | None -> expr
        | Some bind ->
            let m = expr.Range
            let tps, vsl, body, returnTy = stripTopLambda (expr, vspec.Type)
            mkMultiLambdas g m tps vsl (mkLetBind m bind body, returnTy)

    // Add a call to CheckInit if necessary for instance members
    let expr =
        if vspec.IsInstanceMember && not vspec.IsExtensionMember && not vspec.IsConstructor then
            match safeInitInfo with
            | SafeInitField (rfref, _) ->
                let m = expr.Range
                let tps, vsl, body, returnTy = stripTopLambda (expr, vspec.Type)
                // This is an instance member, it must have a 'this'
                let thisVar = vsl.Head.Head
                let thisTypeInst = argsOfAppTy g thisVar.Type
                let newBody = MakeCheckSafeInitField g thisTypeInst (Some thisVar) rfref (mkOne g m) body
                mkMultiLambdas g m tps vsl (newBody, returnTy)
            | NoSafeInitInfo ->
                expr

        else
            expr

    // Add the base value to the lambda if necessary
    let expr =
        match baseValOpt with
        | None -> expr
        | _ ->
            let m = expr.Range
            let tps, vsl, body, returnTy = stripTopLambda (expr, vspec.Type)
            mkMemberLambdas g m tps None baseValOpt vsl (body, returnTy)

    { ValScheme = pgrbind.ValScheme
      Binding = TBind(vspec, expr, debugPoint) }

and FixupLetrecBind (cenv: cenv) denv generalizedTyparsForRecursiveBlock (bind: PostSpecialValsRecursiveBinding) =
    let g = cenv.g
    let (TBind(vspec, expr, debugPoint)) = bind.Binding

    // Check coherence of generalization of variables for memberInfo members in generic classes
    match vspec.MemberInfo with
    | Some _ ->
       match PartitionValTyparsForApparentEnclosingType g vspec with
       | Some(parentTypars, memberParentTypars, _, _, _) ->
          // Temporarily strip extra nullness constraints (e.g. NotSupportsNull) from member type params
          // before checking signature conformance against parent type params.
          // These constraints may be inferred by the solver but are not present on the parent,
          // causing false signature mismatch errors. We restore the original constraints afterward.
          let savedConstraints = memberParentTypars |> List.map (fun tp -> tp, tp.Constraints)

          if g.checkNullness then
              (memberParentTypars, parentTypars)
              ||> List.iter2 (fun mtp ptp ->
                  let parentHasConstraint c =
                      List.exists (typarConstraintsAEquiv g TypeEquivEnv.EmptyIgnoreNulls c) ptp.Constraints

                  mtp.SetConstraints(
                      mtp.Constraints
                      |> List.filter (fun c -> not (isConstraintAllowedAsExtra c) || parentHasConstraint c)
                  ))

          ignore(SignatureConformance.Checker(g, cenv.amap, denv, SignatureRepackageInfo.Empty, false).CheckTypars vspec.Range TypeEquivEnv.EmptyIgnoreNulls memberParentTypars parentTypars)

          for tp, cs in savedConstraints do
              tp.SetConstraints cs
       | None ->
          errorR(Error(FSComp.SR.tcMemberIsNotSufficientlyGeneric(), vspec.Range))
    | _ -> ()

    // Fixup recursive references...
    let fixupPoints = GetAllUsesOfRecValue cenv vspec

    AdjustAndForgetUsesOfRecValue cenv (mkLocalValRef vspec) bind.ValScheme

    let expr = mkGenericBindRhs g vspec.Range generalizedTyparsForRecursiveBlock bind.ValScheme.GeneralizedType expr

    let finalBinding = TBind(vspec, expr, debugPoint)

    { FixupPoints = fixupPoints
      Binding = finalBinding }

//-------------------------------------------------------------------------
// TcLetrecBindings - for both expressions and class-let-rec-declarations
//------------------------------------------------------------------------

and unionGeneralizedTypars typarSets = List.foldBack (ListSet.unionFavourRight typarEq) typarSets []

and TcLetrecBindings overridesOK (cenv: cenv) env tpenv (binds, bindsm, scopem) =

    let g = cenv.g

    // Create prelimRecValues for the recursive items (includes type info from LHS of bindings) *)
    let normalizedBinds = binds |> List.map (fun (RecDefnBindingInfo(a, b, c, bind)) -> NormalizedRecBindingDefn(a, b, c, BindingNormalization.NormalizeBinding ValOrMemberBinding cenv env bind))

    let uncheckedRecBinds, prelimRecValues, (tpenv, _) = AnalyzeAndMakeAndPublishRecursiveValues overridesOK cenv env tpenv normalizedBinds

    let envRec = AddLocalVals g cenv.tcSink scopem prelimRecValues env

    // Typecheck bindings
    let uncheckedRecBindsTable = uncheckedRecBinds |> List.map (fun rbind -> rbind.RecBindingInfo.Val.Stamp, rbind) |> Map.ofList

    let _, generalizedRecBinds, preGeneralizationRecBinds, tpenv, _ =
        ((env, [], [], tpenv, uncheckedRecBindsTable), uncheckedRecBinds) ||> List.fold (TcLetrecBinding (cenv, envRec, scopem, [], None))

    // There should be no bindings that have not been generalized since checking the vary last binding always
    // results in the generalization of all remaining ungeneralized bindings, since there are no remaining unchecked bindings
    // to prevent the generalization
    assert preGeneralizationRecBinds.IsEmpty

    let generalizedRecBinds = generalizedRecBinds |> List.sortBy (fun pgrbind -> pgrbind.RecBindingInfo.Index)
    let generalizedTyparsForRecursiveBlock =
         generalizedRecBinds
            |> List.map (fun pgrbind -> pgrbind.GeneralizedTypars)
            |> unionGeneralizedTypars

    let vxbinds = generalizedRecBinds |> List.map (TcLetrecAdjustMemberForSpecialVals cenv)

    // Now that we know what we've generalized we can adjust the recursive references
    let vxbinds = vxbinds |> List.map (FixupLetrecBind cenv env.DisplayEnv generalizedTyparsForRecursiveBlock)

    // Now eliminate any initialization graphs
    let binds =
        let bindsWithoutLaziness = vxbinds
        let mustHaveValReprInfo =
            match uncheckedRecBinds with
            | [] -> false
            | rbind :: _ -> rbind.RecBindingInfo.DeclKind.MustHaveValReprInfo

        let results =
           EliminateInitializationGraphs
             g
             mustHaveValReprInfo
             env.DisplayEnv
             bindsWithoutLaziness
             //(fun
             (fun doBindings bindings -> doBindings bindings)
             id
             (fun doBindings bindings -> [doBindings bindings])
             bindsm
        List.concat results

    // Post letrec env
    let envbody = AddLocalVals g cenv.tcSink scopem prelimRecValues env
    binds, envbody, tpenv

//-------------------------------------------------------------------------
// Bind specifications of values
//-------------------------------------------------------------------------

let private PublishArguments (cenv: cenv) (env: TcEnv) vspec (synValSig: SynValSig) numEnclosingTypars =
    let arities = arityOfVal vspec
    let _tps, _witnessInfos, curriedArgInfos, _retTy, _ = GetValReprTypeInCompiledForm cenv.g arities numEnclosingTypars vspec.Type vspec.DefinitionRange

    let argInfos =
        // Drop "this" argument for instance methods
        match vspec.IsInstanceMember, curriedArgInfos with
        | true, _::args
        | _, args -> args

    let synArgInfos = synValSig.SynInfo.CurriedArgInfos
    let argData =
        (synArgInfos, argInfos)
        ||> Seq.zip
        |> Seq.collect (fun x -> x ||> Seq.zip)
        |> Seq.choose (fun (synArgInfo, argInfo) -> synArgInfo.Ident |> Option.map (pair argInfo))

    for (argTy, argReprInfo), ident in argData do
        let item = Item.OtherName (Some ident, argTy, Some argReprInfo, None, ident.idRange)
        CallNameResolutionSink cenv.tcSink (ident.idRange, env.NameEnv, item, emptyTyparInst, ItemOccurrence.Binding, env.AccessRights)

let TcAndPublishValSpec (cenv: cenv, env, containerInfo: ContainerInfo, declKind : DeclKind, memFlagsOpt, tpenv, synValSig) =

    let g = cenv.g

    let (SynValSig (attributes=Attributes synAttrs; explicitTypeParams=explicitTypeParams; isInline=isInline; isMutable=mutableFlag; xmlDoc=xmlDoc; accessibility=vis; synExpr=literalExprOpt; range=m)) = synValSig
    let (ValTyparDecls (synTypars, _, synCanInferTypars)) = explicitTypeParams
    let declaredTypars = TcTyparDecls cenv env synTypars

    GeneralizationHelpers.CheckDeclaredTyparsPermitted(memFlagsOpt, declaredTypars, m)

    let canInferTypars = GeneralizationHelpers.ComputeCanInferExtraGeneralizableTypars (containerInfo.ParentRef, synCanInferTypars, memFlagsOpt)

    let attrTgt = declKind.AllowedAttribTargets memFlagsOpt

    let attrs = TcAttributes cenv env attrTgt synAttrs
    let newOk = if canInferTypars then NewTyparsOK else NoNewTypars

    let valinfos, tpenv = TcValSpec cenv env declKind newOk containerInfo memFlagsOpt None tpenv synValSig attrs
    let denv = env.DisplayEnv
    let viss = 
        match memFlagsOpt with
        | Some {MemberKind = SynMemberKind.PropertyGetSet as propKind} ->
            let getterAccess, setterAccess = getGetterSetterAccess vis propKind g.langVersion
            List.init valinfos.Length (fun i -> if i = 0 then getterAccess else setterAccess)
        | Some {MemberKind = SynMemberKind.PropertyGet as propKind} ->
            let getterAccess, _ = getGetterSetterAccess vis propKind g.langVersion
            List.init valinfos.Length (fun _ -> getterAccess)
        | Some {MemberKind = SynMemberKind.PropertySet as propKind} ->
            let _, setterAccess = getGetterSetterAccess vis propKind g.langVersion
            List.init valinfos.Length (fun _ -> setterAccess)
        | _ ->
            List.init valinfos.Length (fun _ -> vis.SingleAccess())
    let valinfos = List.zip valinfos viss

    (tpenv, valinfos) ||> List.mapFold (fun tpenv (valSpecResult, vis) ->

        let (ValSpecResult (altActualParent, memberInfoOpt, id, enclosingDeclaredTypars, declaredTypars, ty, prelimValReprInfo, declKind)) = valSpecResult

        let inlineFlag = ComputeInlineFlag (memberInfoOpt |> Option.map (fun (PrelimMemberInfo(memberInfo, _, _)) -> memberInfo.MemberFlags)) isInline mutableFlag g attrs m

        let freeInType = freeInTypeLeftToRight g false ty

        let allDeclaredTypars = enclosingDeclaredTypars @ declaredTypars

        let explicitTyparInfo = ExplicitTyparInfo(declaredTypars, declaredTypars, synCanInferTypars)

        let generalizedTypars =
            GeneralizationHelpers.ComputeAndGeneralizeGenericTypars(cenv, denv, id.idRange,
                emptyFreeTypars, canInferTypars, CanGeneralizeConstrainedTypars, inlineFlag,
                None, allDeclaredTypars, freeInType, ty, false)

        let valscheme1 = PrelimVal1(id, explicitTyparInfo, ty, Some prelimValReprInfo, memberInfoOpt, mutableFlag, inlineFlag, NormalVal, noArgOrRetAttribs, vis, false)

        let valscheme2 = GeneralizeVal cenv denv enclosingDeclaredTypars generalizedTypars valscheme1

        let tpenv = HideUnscopedTypars generalizedTypars tpenv

        let valscheme = BuildValScheme declKind (Some prelimValReprInfo) valscheme2

        let literalValue =
            match literalExprOpt with
            | None ->
                let hasLiteralAttr =
                    attribsHaveValFlag g WellKnownValAttributes.LiteralAttribute attrs
                if hasLiteralAttr then
                    errorR(Error(FSComp.SR.tcLiteralAttributeRequiresConstantValue(), m))
                None

            | Some e ->
                let hasLiteralAttr, literalValue = TcLiteral cenv ty env tpenv (attrs, e)
                if not hasLiteralAttr then
                    errorR(Error(FSComp.SR.tcValueInSignatureRequiresLiteralAttribute(), e.Range))
                literalValue

        let paramNames =
            match valscheme.ValReprInfo with
            | None -> None
            | Some valReprInfo -> Some valReprInfo.ArgNames

        let checkXmlDocs = cenv.diagnosticOptions.CheckXmlDocs
        let xmlDoc = xmlDoc.ToXmlDoc(checkXmlDocs, paramNames)
        let isGeneratedEventVal =
            CompileAsEvent g attrs
            && (id.idText.StartsWithOrdinal("add_") || id.idText.StartsWithOrdinal("remove_"))

        let vspec = MakeAndPublishVal cenv env (altActualParent, true, declKind, ValNotInRecScope, valscheme, attrs, xmlDoc, literalValue, isGeneratedEventVal)

        PublishArguments cenv env vspec synValSig allDeclaredTypars.Length

        assert(vspec.InlineInfo = inlineFlag)

        vspec, tpenv)