InfoReader.fs

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


/// Select members from a type by name, searching the type hierarchy if needed
module internal FSharp.Compiler.InfoReader

open System
open System.Collections.Concurrent
open System.Collections.Generic
open Internal.Utilities.Library
open FSharp.Compiler 
open FSharp.Compiler.AbstractIL.IL
open FSharp.Compiler.AccessibilityLogic
open FSharp.Compiler.AttributeChecking
open FSharp.Compiler.DiagnosticsLogger
open FSharp.Compiler.Features
open FSharp.Compiler.Infos
open FSharp.Compiler.Syntax
open FSharp.Compiler.TcGlobals
open FSharp.Compiler.Text
open FSharp.Compiler.Text.Range
open FSharp.Compiler.TypedTree
open FSharp.Compiler.TypedTreeOps
open FSharp.Compiler.TypedTreeBasics
open FSharp.Compiler.TypeHierarchy
open FSharp.Compiler.TypeRelations
open Import

/// Use the given function to select some of the member values from the members of an F# type
let SelectImmediateMemberVals g optFilter f withExplicitImpl (tcref: TyconRef) = 
    let chooser (vref: ValRef) = 
        match vref.MemberInfo with 
        // The 'when' condition is a workaround for the fact that values providing 
        // override and interface implementations are published in inferred module types 
        // These cannot be selected directly via the "." notation. 
        // However, it certainly is useful to be able to publish these values, as we can in theory 
        // optimize code to make direct calls to these methods. 
        | Some membInfo when withExplicitImpl || not (ValRefIsExplicitImpl g vref) -> 
            f membInfo vref
        | _ ->  
            None

    match optFilter with 
    | None -> tcref.MembersOfFSharpTyconByName |> NameMultiMap.chooseRange chooser
    | Some nm -> tcref.MembersOfFSharpTyconByName |> NameMultiMap.find nm |> List.choose chooser

/// Check whether a name matches an optional filter
let private checkFilter optFilter (nm: string) = match optFilter with None -> true | Some n2 -> nm = n2

/// Try to select an F# value when querying members, and if so return a MethInfo that wraps the F# value.
let TrySelectMemberVal g optFilter ty pri _membInfo (vref: ValRef) =
    if checkFilter optFilter vref.LogicalName then 
        Some(FSMeth(g, ty, vref, pri))
    else 
        None

let rec GetImmediateIntrinsicMethInfosOfTypeAux (optFilter, ad) g amap m withExplicitImpl origTy metadataTy =

    let minfos =
        match metadataOfTy g metadataTy with 
#if !NO_TYPEPROVIDERS
        | ProvidedTypeMetadata info -> 
            let st = info.ProvidedType
            let meths = 
                match optFilter with
                | Some name ->  
                    st.PApplyFilteredArray ((fun st -> st.GetMethods()),(fun mi -> mi.Name = name), "GetMethods", m)                        
                | None -> st.PApplyArray ((fun st -> st.GetMethods()), "GetMethods", m)
            [   for mi in meths -> ProvidedMeth(amap, mi.Coerce(m), None, m) ]
#endif
        | ILTypeMetadata _ -> 
            let tinfo = ILTypeInfo.FromType g origTy
            let mdefs = tinfo.RawMetadata.Methods
            let mdefs = match optFilter with None -> mdefs.AsList() | Some nm -> mdefs.FindByName nm
            mdefs |> List.map (fun mdef -> MethInfo.CreateILMeth(amap, m, origTy, mdef)) 

        | FSharpOrArrayOrByrefOrTupleOrExnTypeMetadata -> 
            // Tuple types also support the methods get_Item1-8, get_Rest from the compiled tuple type.
            // In this case convert to the .NET Tuple type that carries metadata and try again
            if isAnyTupleTy g metadataTy then 
                let betterMetadataTy = convertToTypeWithMetadataIfPossible g metadataTy
                GetImmediateIntrinsicMethInfosOfTypeAux (optFilter, ad) g amap m withExplicitImpl origTy betterMetadataTy
            // Function types support methods FSharpFunc<_, _>.FromConverter and friends from .NET metadata,
            // but not instance methods (you can't write "f.Invoke(x)", you have to write "f x")
            elif isFunTy g metadataTy then 
                let betterMetadataTy = convertToTypeWithMetadataIfPossible g metadataTy
                GetImmediateIntrinsicMethInfosOfTypeAux (optFilter, ad) g amap m withExplicitImpl origTy betterMetadataTy
                  |> List.filter (fun minfo -> not minfo.IsInstance)
            else
                match tryTcrefOfAppTy g metadataTy with
                | ValueNone -> []
                | ValueSome tcref ->
                    SelectImmediateMemberVals g optFilter (TrySelectMemberVal g optFilter origTy None) withExplicitImpl tcref
    let minfos = minfos |> List.filter (IsMethInfoAccessible amap m ad)
    minfos

/// Query the immediate methods of an F# type, not taking into account inherited methods. The optFilter
/// parameter is an optional name to restrict the set of properties returned.
let GetImmediateIntrinsicMethInfosOfType (optFilter, ad) g amap m ty = 
    GetImmediateIntrinsicMethInfosOfTypeAux (optFilter, ad) g amap m false ty ty

let GetImmediateIntrinsicMethInfosWithExplicitImplOfType (optFilter, ad) g amap m ty = 
    GetImmediateIntrinsicMethInfosOfTypeAux (optFilter, ad) g amap m true ty ty

/// Query the immediate methods of an F# type, not taking into account inherited methods. The optFilter
/// parameter is an optional name to restrict the set of properties returned.
let GetImmediateTraitsInfosOfType optFilter g ty = 
    match tryDestTyparTy g ty with
    | ValueSome tp ->
        let infos = GetTraitConstraintInfosOfTypars g [tp]
        match optFilter with
        | None -> 
            [ for traitInfo in infos do
                match traitInfo.MemberFlags.MemberKind with
                | SynMemberKind.PropertySet ->
                    // A setter property trait only can be utilized via 
                    //   ^T.set_Property(v)
                    traitInfo.WithMemberKind(SynMemberKind.Member)
                | _ ->
                    traitInfo ]
        | Some nm ->
            [ for traitInfo in infos do
                match traitInfo.MemberFlags.MemberKind with
                | SynMemberKind.PropertyGet ->
                    // A getter property trait can be utilized via 
                    //   ^T.Property
                    //   ^T.get_Property()
                    // The latter doesn't appear in intellisense
                    if nm = traitInfo.MemberDisplayNameCore then
                        traitInfo
                    let traitInfo2 = traitInfo.WithMemberKind(SynMemberKind.Member)
                    if nm = traitInfo2.MemberDisplayNameCore then
                        traitInfo2
                | SynMemberKind.PropertySet ->
                    // A setter property trait only can be utilized via 
                    //   ^T.set_Property(v)
                    let traitInfo2 = traitInfo.WithMemberKind(SynMemberKind.Member)
                    if nm = traitInfo2.MemberDisplayNameCore then
                        traitInfo2
                | _ -> 
                    // Method traits can be utilized via
                    //   ^T.Member(v)
                    if nm = traitInfo.MemberDisplayNameCore then
                        traitInfo
                ]

    | _ ->
        []

/// A helper type to help collect properties.
///
/// Join up getters and setters which are not associated in the F# data structure 
type PropertyCollector(g, amap, m, ty, optFilter, ad) = 

    let hashIdentity = 
        HashIdentity.FromFunctions 
            (fun (pinfo: PropInfo) -> hash pinfo.PropertyName) 
            (fun pinfo1 pinfo2 -> 
                pinfo1.IsStatic = pinfo2.IsStatic &&
                PropInfosEquivByNameAndPartialSig EraseNone g amap m pinfo1 pinfo2 &&
                pinfo1.IsDefiniteFSharpOverride = pinfo2.IsDefiniteFSharpOverride )

    let props = ConcurrentDictionary<PropInfo, PropInfo>(hashIdentity)

    let add pinfo =
        match props.TryGetValue pinfo, pinfo with
        | (true, FSProp (_, ty, Some vref1, _)), FSProp (_, _, _, Some vref2)
        | (true, FSProp (_, ty, _, Some vref2)), FSProp (_, _, Some vref1, _) ->
            let pinfo = FSProp (g, ty, Some vref1, Some vref2)
            props[pinfo] <- pinfo 
        | (true, _), _ -> 
            // This assert fires while editing bad code. We will give a warning later in check.fs
            //assert ("unexpected case"= "")
            ()
        | _ ->
            props[pinfo] <- pinfo

    member _.Collect(membInfo: ValMemberInfo, vref: ValRef) = 
        match membInfo.MemberFlags.MemberKind with 
        | SynMemberKind.PropertyGet ->
            let pinfo = FSProp(g, ty, Some vref, None) 
            if checkFilter optFilter vref.PropertyName && IsPropInfoAccessible g amap m ad pinfo then
                add pinfo
        | SynMemberKind.PropertySet ->
            let pinfo = FSProp(g, ty, None, Some vref)
            if checkFilter optFilter vref.PropertyName  && IsPropInfoAccessible g amap m ad pinfo then 
                add pinfo
        | _ -> 
            ()

    member _.Close() = [ for KeyValue(_, pinfo) in props -> pinfo ]

let rec GetImmediateIntrinsicPropInfosOfTypeAux (optFilter, ad) g amap m withExplicitImpl origTy metadataTy =

    let pinfos =
        match metadataOfTy g metadataTy with 
#if !NO_TYPEPROVIDERS
        | ProvidedTypeMetadata info -> 
            let st = info.ProvidedType
            let matchingProps =
                match optFilter with
                |   Some name ->
                        match st.PApply((fun st -> st.GetProperty name), m) with
                        | Tainted.Null -> [||]
                        | Tainted.NonNull pi -> [|pi|]
                |   None ->
                        st.PApplyArray((fun st -> st.GetProperties()), "GetProperties", m)
            matchingProps
            |> Seq.map(fun pi -> ProvidedProp(amap, pi, m)) 
            |> List.ofSeq
#endif

        | ILTypeMetadata _ -> 
            let tinfo = ILTypeInfo.FromType g origTy
            let pdefs = tinfo.RawMetadata.Properties
            let pdefs = match optFilter with None -> pdefs.AsList() | Some nm -> pdefs.LookupByName nm
            pdefs |> List.map (fun pdef -> ILProp(ILPropInfo(tinfo, pdef))) 

        | FSharpOrArrayOrByrefOrTupleOrExnTypeMetadata -> 
            // Tuple types also support the properties Item1-8, Rest from the compiled tuple type
            // In this case convert to the .NET Tuple type that carries metadata and try again
            if isAnyTupleTy g metadataTy || isFunTy g metadataTy then 
                let betterMetadataTy = convertToTypeWithMetadataIfPossible g metadataTy
                GetImmediateIntrinsicPropInfosOfTypeAux (optFilter, ad) g amap m withExplicitImpl origTy betterMetadataTy
            else
                match tryTcrefOfAppTy g metadataTy with
                | ValueNone -> []
                | ValueSome tcref ->
                    let propCollector = PropertyCollector(g, amap, m, origTy, optFilter, ad)
                    SelectImmediateMemberVals g None (fun membInfo vref -> propCollector.Collect(membInfo, vref); None) withExplicitImpl tcref |> ignore
                    propCollector.Close()

    let pinfos = pinfos |> List.filter (IsPropInfoAccessible g amap m ad)
    pinfos

/// Query the immediate properties of an F# type, not taking into account inherited properties. The optFilter
/// parameter is an optional name to restrict the set of properties returned.
let GetImmediateIntrinsicPropInfosOfType (optFilter, ad) g amap m ty =
    GetImmediateIntrinsicPropInfosOfTypeAux (optFilter, ad) g amap m false ty ty

let GetImmediateIntrinsicPropInfosWithExplicitImplOfType (optFilter, ad) g amap m ty =
    GetImmediateIntrinsicPropInfosOfTypeAux (optFilter, ad) g amap m true ty ty

// Checks whether the given type has an indexer property.
let IsIndexerType g amap ty = 
    isArray1DTy g ty ||
    isListTy g ty ||
    match tryTcrefOfAppTy g ty with
    | ValueSome tcref ->
        let entityTy = generalizedTyconRef g tcref
        let props = GetImmediateIntrinsicPropInfosOfType (None, AccessibleFromSomeFSharpCode) g amap range0 entityTy
        props |> List.exists (fun x -> x.PropertyName = "Item")
    | ValueNone -> false

/// Get the items that are considered the most specific in the hierarchy out of the given items by type.
/// REVIEW: Note complexity O(N^2)
let GetMostSpecificItemsByType g amap f xs =
    [ for x in xs do
        match f x with
        | None -> ()
        | Some (xTy, m) ->
            let isEqual =
                xs
                |> List.forall (fun y ->
                    match f y with
                    | None -> true
                    | Some (yTy, _) ->
                        if typeEquiv g xTy yTy then true
                        else not (TypeFeasiblySubsumesType 0 g amap m xTy CanCoerce yTy))
            if isEqual then
                yield x ]

/// Finds the most specific methods from a method collection by a given method's signature.
let GetMostSpecificMethodInfosByMethInfoSig g amap m (ty, minfo) minfos =
    minfos
    |> GetMostSpecificItemsByType g amap (fun (ty2, minfo2) -> 
        let isEqual =
            typeEquiv g ty ty2 &&
            MethInfosEquivByPartialSig EraseNone true g amap m minfo minfo2
        if isEqual then
            Some(minfo2.ApparentEnclosingType, m)
        else
            None)

/// From the given method sets, filter each set down to the most specific ones. 
let FilterMostSpecificMethInfoSets g amap m (minfoSets: NameMultiMap<_>) : NameMultiMap<_> =
    minfoSets
    |> Map.map (fun _ minfos ->
        ([], minfos)
        ||> List.fold (fun minfoSpecifics (ty, minfo) ->
            let alreadySeen = 
                minfoSpecifics 
                |> List.exists (fun (tySpecific, minfoSpecific) -> 
                    typeEquiv g ty tySpecific &&
                    MethInfosEquivByPartialSig EraseNone true g amap m minfo minfoSpecific)
            if alreadySeen then
                minfoSpecifics
            else
                GetMostSpecificMethodInfosByMethInfoSig g amap m (ty, minfo) minfos @ minfoSpecifics))

/// Sets of methods up the hierarchy, ignoring duplicates by name and sig.
/// Used to collect sets of virtual methods, protected methods, protected
/// properties etc. 
type HierarchyItem = 
    | TraitItem of TraitConstraintInfo list
    | MethodItem of MethInfo list list
    | PropertyItem of PropInfo list list
    | RecdFieldItem of RecdFieldInfo
    | EventItem of EventInfo list
    | ILFieldItem of ILFieldInfo list

//-------------------------------------------------------------------------
// Collecting methods and properties taking into account hiding rules in the hierarchy

  
/// Indicates if we prefer overrides or abstract slots. 
type FindMemberFlag = 
    /// Prefer items toward the top of the hierarchy, which we do if the items are virtual 
    /// but not when resolving base calls. 
    | IgnoreOverrides 
    /// Get overrides instead of abstract slots when measuring whether a class/interface implements all its required slots. 
    | PreferOverrides
    /// Similar to "IgnoreOverrides", but filters the items bottom-to-top,
    /// and discards all when finds first non-virtual member which hides one above it in hierarchy.
    | DiscardOnFirstNonOverride

/// The input list is sorted from most-derived to least-derived type, so any System.Object methods 
/// are at the end of the list. Return a filtered list where prior/subsequent members matching by name and 
/// that are in the same equivalence class have been removed. We keep a name-indexed table to 
/// be more efficient when we check to see if we've already seen a particular named method. 
type private IndexedList<'T>(itemLists: 'T list list, itemsByName: NameMultiMap<'T>) = 
    
    /// Get the item sets
    member _.Items = itemLists

    /// Get the items with a particular name
    member _.ItemsWithName(nm)  = NameMultiMap.find nm itemsByName

    /// Add new items, extracting the names using the given function.
    member _.AddItems(items, nmf) = IndexedList<'T>(items :: itemLists, List.foldBack (fun x acc -> NameMultiMap.add (nmf x) x acc) items itemsByName )

    /// Get an empty set of items
    static member Empty = IndexedList<'T>([], NameMultiMap.empty)

    /// Filter a set of new items to add according to the content of the list.  Only keep an item
    /// if it passes 'keepTest' for all matching items already in the list.
    member x.FilterNewItems keepTest nmf itemsToAdd =
        // Have we already seen an item with the same name and that is in the same equivalence class?
        // If so, ignore this one. Note we can check against the original incoming 'ilist' because we are assuming that
        // none the elements of 'itemsToAdd' are equivalent. 
        itemsToAdd |> List.filter (fun item -> List.forall (keepTest item) (x.ItemsWithName(nmf item)))

/// An InfoReader is an object to help us read and cache infos. 
/// We create one of these for each file we typecheck. 
type InfoReader(g: TcGlobals, amap: ImportMap) as this =

    /// Get the declared IL fields of a type, not including inherited fields
    let GetImmediateIntrinsicILFieldsOfType (optFilter, ad) m ty =
        let infos =
            match metadataOfTy g ty with 
#if !NO_TYPEPROVIDERS
            | ProvidedTypeMetadata info -> 
                let st = info.ProvidedType
                match optFilter with
                |   None ->
                        [ for fi in st.PApplyArray((fun st -> st.GetFields()), "GetFields", m) -> ProvidedField(amap, fi, m) ]
                |   Some name ->
                        match st.PApply ((fun st -> st.GetField name), m) with
                        | Tainted.Null -> []
                        | Tainted.NonNull fi -> [  ProvidedField(amap, fi, m) ]
#endif
            | ILTypeMetadata _ -> 
                let tinfo = ILTypeInfo.FromType g ty
                let fdefs = tinfo.RawMetadata.Fields
                let fdefs = match optFilter with None -> fdefs.AsList() | Some nm -> fdefs.LookupByName nm
                fdefs |> List.map (fun pd -> ILFieldInfo(tinfo, pd)) 
            | FSharpOrArrayOrByrefOrTupleOrExnTypeMetadata -> 
                []
        let infos = infos |> List.filter (IsILFieldInfoAccessible g amap m  ad)
        infos           

    /// Get the declared events of a type, not including inherited events, and not including F#-declared CLIEvents
    let ComputeImmediateIntrinsicEventsOfType (optFilter, ad) m ty =
        let infos =
            match metadataOfTy g ty with 
#if !NO_TYPEPROVIDERS
            | ProvidedTypeMetadata info -> 
                let st = info.ProvidedType
                match optFilter with
                |   None ->
                        [   for ei in st.PApplyArray((fun st -> st.GetEvents()), "GetEvents", m) -> ProvidedEvent(amap, ei, m) ]
                |   Some name ->
                        match st.PApply ((fun st -> st.GetEvent name), m) with
                        | Tainted.Null -> []
                        | Tainted.NonNull ei -> [  ProvidedEvent(amap, ei, m) ]
#endif
            | ILTypeMetadata _ -> 
                let tinfo = ILTypeInfo.FromType g ty
                let edefs = tinfo.RawMetadata.Events
                let edefs = match optFilter with None -> edefs.AsList() | Some nm -> edefs.LookupByName nm
                [ for edef in edefs   do
                    let ileinfo = ILEventInfo(tinfo, edef)
                    if IsILEventInfoAccessible g amap m ad ileinfo then 
                        yield ILEvent ileinfo ]
            | FSharpOrArrayOrByrefOrTupleOrExnTypeMetadata -> 
                []
        infos 

    /// Make a reference to a record or class field
    let MakeRecdFieldInfo g ty (tcref: TyconRef) fspec = 
        RecdFieldInfo(argsOfAppTy g ty, tcref.MakeNestedRecdFieldRef fspec)

    /// Get the F#-declared record fields or class 'val' fields of a type
    let GetImmediateIntrinsicRecdOrClassFieldsOfType (optFilter, _ad) _m ty =
        match tryTcrefOfAppTy g ty with 
        | ValueNone -> []
        | ValueSome tcref -> 
            // Note;secret fields are not allowed in lookups here, as we're only looking
            // up user-visible fields in name resolution.
            match optFilter with
            | Some nm ->
               match tcref.GetFieldByName nm with
               | Some rfield when not rfield.IsCompilerGenerated -> [MakeRecdFieldInfo g ty tcref rfield]
               | _ -> []
            | None -> 
                [ for fdef in tcref.AllFieldsArray do
                    if not fdef.IsCompilerGenerated then
                        yield MakeRecdFieldInfo g ty tcref fdef ]


    /// The primitive reader for the method info sets up a hierarchy
    let GetIntrinsicMethodSetsUncached ((optFilter, ad, allowMultiIntfInst), m, ty) =
        FoldPrimaryHierarchyOfType (fun ty acc -> GetImmediateIntrinsicMethInfosOfType (optFilter, ad) g amap m ty :: acc) g amap m allowMultiIntfInst ty []

    /// The primitive reader for the property info sets up a hierarchy
    let GetIntrinsicPropertySetsUncached ((optFilter, ad, allowMultiIntfInst), m, ty) =
        FoldPrimaryHierarchyOfType (fun ty acc -> GetImmediateIntrinsicPropInfosOfType (optFilter, ad) g amap m ty :: acc) g amap m allowMultiIntfInst ty []

    let GetIntrinsicILFieldInfosUncached ((optFilter, ad), m, ty) =
        FoldPrimaryHierarchyOfType (fun ty acc -> GetImmediateIntrinsicILFieldsOfType (optFilter, ad) m ty @ acc) g amap m AllowMultiIntfInstantiations.Yes ty []

    let GetIntrinsicEventInfosUncached ((optFilter, ad), m, ty) =
        FoldPrimaryHierarchyOfType (fun ty acc -> ComputeImmediateIntrinsicEventsOfType (optFilter, ad) m ty @ acc) g amap m AllowMultiIntfInstantiations.Yes ty []

    let GetIntrinsicRecdOrClassFieldInfosUncached ((optFilter, ad), m, ty) =
        FoldPrimaryHierarchyOfType (fun ty acc -> GetImmediateIntrinsicRecdOrClassFieldsOfType (optFilter, ad) m ty @ acc) g amap m AllowMultiIntfInstantiations.Yes ty []
    
    let GetEntireTypeHierarchyUncached (allowMultiIntfInst, m, ty) =
        FoldEntireHierarchyOfType (fun ty acc -> ty :: acc) g amap m allowMultiIntfInst ty  [] 

    let GetPrimaryTypeHierarchyUncached (allowMultiIntfInst, m, ty) =
        FoldPrimaryHierarchyOfType (fun ty acc -> ty :: acc) g amap m allowMultiIntfInst ty [] 

    /// The primitive reader for the named items up a hierarchy
    let GetIntrinsicNamedItemsUncached ((nm, ad, includeConstraints), m, ty) =
        if nm = ".ctor" then None else // '.ctor' lookups only ever happen via constructor syntax
        let optFilter = Some nm
        FoldPrimaryHierarchyOfType (fun ty acc -> 
             let qinfos = if includeConstraints then GetImmediateTraitsInfosOfType optFilter g ty else []
             let minfos = GetImmediateIntrinsicMethInfosOfType (optFilter, ad) g amap m ty
             let pinfos = GetImmediateIntrinsicPropInfosOfType (optFilter, ad) g amap m ty
             let finfos = GetImmediateIntrinsicILFieldsOfType (optFilter, ad) m ty 
             let einfos = ComputeImmediateIntrinsicEventsOfType (optFilter, ad) m ty 
             let rfinfos = GetImmediateIntrinsicRecdOrClassFieldsOfType (optFilter, ad) m ty 
             match acc with 
             | _ when not (isNil qinfos) -> Some(TraitItem qinfos)
             | Some(MethodItem(inheritedMethSets)) when not (isNil minfos) -> Some(MethodItem (minfos :: inheritedMethSets))
             | _ when not (isNil minfos) -> Some(MethodItem [minfos])
             | Some(PropertyItem(inheritedPropSets)) when not (isNil pinfos) -> Some(PropertyItem(pinfos :: inheritedPropSets))
             | _ when not (isNil pinfos) -> Some(PropertyItem([pinfos]))
             | _ when not (isNil finfos) -> Some(ILFieldItem(finfos))
             | _ when not (isNil einfos) -> Some(EventItem(einfos))
             | _ when not (isNil rfinfos) -> 
                match rfinfos with
                | [single] -> Some(RecdFieldItem(single))
                | _ -> failwith "Unexpected multiple fields with the same name" // Because an explicit name (i.e., nm) was supplied, there will be only one element at most.
             | _ -> acc)
          g amap m 
          AllowMultiIntfInstantiations.Yes
          ty
          None

    let GetImmediateIntrinsicOverrideMethodSetsOfType optFilter m (interfaceTys: TType list) ty acc =
        match tryAppTy g ty with
        | ValueSome (tcref, _) when tcref.IsILTycon && tcref.ILTyconRawMetadata.IsInterface ->
            let mimpls = tcref.ILTyconRawMetadata.MethodImpls.AsList()
            let mdefs = tcref.ILTyconRawMetadata.Methods

            // MethodImpls contains a list of methods that override.
            // OverrideBy is the method that does the overriding.
            // Overrides is the method being overridden.
            (acc, mimpls)
            ||> List.fold (fun acc ilMethImpl ->
                let overridesName = ilMethImpl.Overrides.MethodRef.Name
                let overrideBy = ilMethImpl.OverrideBy
                let canAccumulate =     
                    match optFilter with
                    | None -> true
                    | Some name when name = overridesName -> true
                    | _ -> false
                if canAccumulate then
                    match mdefs.TryFindInstanceByNameAndCallingSignature (overrideBy.Name, overrideBy.MethodRef.GetCallingSignature()) with
                    | Some mdef ->
                        let overridesILTy = ilMethImpl.Overrides.DeclaringType
                        let overridesTyFullName = overridesILTy.TypeRef.FullName
                        let overridesTyOpt = 
                            interfaceTys
                            |> List.tryPick (fun ty -> 
                                match tryTcrefOfAppTy g ty with
                                | ValueSome tcref when tcref.IsILTycon && tcref.ILTyconRawMetadata.Name = overridesTyFullName ->
                                    generalizedTyconRef g tcref
                                    |> Some
                                | _ -> 
                                    None)
                        match overridesTyOpt with
                        | Some overridesTy ->
                            NameMultiMap.add overridesName (overridesTy, MethInfo.CreateILMeth(amap, m, ty, mdef)) acc
                        | _ ->
                            acc
                    | _ ->
                        acc
                else
                    acc)
        | _ -> acc

    /// Visiting each type in the hierarchy and accumulate most specific methods that are the OverrideBy target from types.
    let GetIntrinsicMostSpecificOverrideMethodSetsUncached ((optFilter, _ad, allowMultiIntfInst), m, ty) : NameMultiMap<_> =
        let interfaceTys = 
            FoldPrimaryHierarchyOfType (fun ty acc ->
                if isInterfaceTy g ty then ty :: acc
                else acc) g amap m allowMultiIntfInst ty []

        (NameMultiMap.Empty, interfaceTys)
        ||> List.fold (fun acc ty -> GetImmediateIntrinsicOverrideMethodSetsOfType optFilter m interfaceTys ty acc)
        |> FilterMostSpecificMethInfoSets g amap m

    /// Add all the items to the IndexedList, preferring the ones in the super-types. This is used to hide methods
    /// in super classes and/or hide overrides of methods in subclasses.
    ///
    /// Assume no items in 'items' are equivalent according to 'equivTest'. This is valid because each step in a
    /// .NET class hierarchy introduces a consistent set of methods, none of which hide each other within the 
    /// given set. This is an important optimization because it means we don't have filter for equivalence between the 
    /// large overload sets introduced by methods like System.WriteLine.
    ///
    /// Assume items can be given names by 'nmf', where two items with different names are
    /// not equivalent.

    static let FilterItemsInSubTypesBasedOnItemsInSuperTypes nmf keepTest itemLists = 
        let rec loop itemLists = 
            match itemLists with
            | [] -> IndexedList.Empty
            | items :: itemsInSuperTypes -> 
                let ilist = loop itemsInSuperTypes
                let itemsToAdd = ilist.FilterNewItems keepTest nmf items 
                ilist.AddItems(itemsToAdd, nmf)
        (loop itemLists).Items

    /// Add all the items to the IndexedList, preferring the ones in the sub-types.
    static let FilterItemsInSuperTypesBasedOnItemsInSubTypes nmf keepTest itemLists  = 
        let rec loop itemLists (indexedItemsInSubTypes: IndexedList<_>) = 
            match itemLists with
            | [] -> List.rev indexedItemsInSubTypes.Items
            | items :: itemsInSuperTypes -> 
                let itemsToAdd = items |> List.filter (fun item -> keepTest item (indexedItemsInSubTypes.ItemsWithName(nmf item)))            
                let ilist = indexedItemsInSubTypes.AddItems(itemsToAdd, nmf)
                loop itemsInSuperTypes ilist

        loop itemLists IndexedList.Empty

    static let ExcludeItemsInSuperTypesBasedOnEquivTestWithItemsInSubTypes nmf equivTest itemLists = 
        FilterItemsInSuperTypesBasedOnItemsInSubTypes nmf (fun item1 items -> not (items |> List.exists (fun item2 -> equivTest item1 item2))) itemLists 

    /// Filter the overrides of methods or properties, either keeping the overrides or keeping the dispatch slots.
    static let FilterOverrides findFlag (isVirt:'a->bool, isNewSlot, isDefiniteOverride, isFinal, isAbstract, equivSigs, nmf:'a->string) items = 
        let equivVirts x y = isVirt x && isVirt y && equivSigs x y
        let filterDefiniteOverrides = List.filter(isDefiniteOverride >> not)

        match findFlag with
        | DiscardOnFirstNonOverride ->
            items
            |> List.map filterDefiniteOverrides
            |> ExcludeItemsInSuperTypesBasedOnEquivTestWithItemsInSubTypes nmf (fun newItem priorItem ->
                equivSigs newItem priorItem &&
                isVirt newItem && not (isVirt priorItem)
            ) 
        | PreferOverrides ->
            items
            // For each F#-declared override, get rid of any equivalent abstract member in the same type
            // This is because F# abstract members with default overrides give rise to two members with the
            // same logical signature in the same type, e.g.
            // type ClassType1() =
            //      abstract VirtualMethod1: string -> int
            //      default x.VirtualMethod1(s) = 3
        
            |> List.map (fun items -> 
                let definiteOverrides = items |> List.filter isDefiniteOverride 
                items |> List.filter (fun item -> (isDefiniteOverride item || not (List.exists (equivVirts item) definiteOverrides))))
       
            // only keep virtuals that are not signature-equivalent to virtuals in subtypes
            |> ExcludeItemsInSuperTypesBasedOnEquivTestWithItemsInSubTypes nmf equivVirts 
        | IgnoreOverrides ->  
            let equivNewSlots x y = isNewSlot x && isNewSlot y && equivSigs x y
            items
              // Remove any F#-declared overrides. These may occur in the same type as the abstract member (unlike with .NET metadata)
              // Include any 'newslot' declared methods.
              |> List.map filterDefiniteOverrides

              // Remove any virtuals that are signature-equivalent to virtuals in subtypes, except for newslots
              // That is, keep if it's 
              //       (a) not virtual
              //       (b) is a new slot or 
              //       (c) not equivalent
              //       (d) is abstract (e.g. C# 'abstract override' re-abstracting a base virtual method)
              // We keep virtual finals around for error detection later on
              |> FilterItemsInSubTypesBasedOnItemsInSuperTypes nmf (fun newItem priorItem  ->
                     (isVirt newItem && isFinal newItem) || not (isVirt newItem) || isNewSlot newItem || isAbstract newItem || not (equivVirts newItem priorItem) )

              // Remove any abstract slots in supertypes that are (a) hidden by another newslot and (b) implemented
              // We leave unimplemented ones around to give errors, e.g. for
              // [<AbstractClass>]
              //   type PA() =
              //   abstract M : int -> unit
              // 
              //   [<AbstractClass>]
              //   type PB<'a>() =
              //       inherit PA()
              //       abstract M : 'a -> unit
              // 
              //   [<AbstractClass>]
              //   type PC() =
              //       inherit PB<int>()
              //       // Here, PA.M and PB<int>.M have the same signature, so PA.M is unimplementable.
              //       // REVIEW: in future we may give a friendly error at this point
              // 
              //   type PD() = 
              //       inherit PC()
              //       override this.M(x: int) = ()

              |> FilterItemsInSuperTypesBasedOnItemsInSubTypes nmf (fun item1 superTypeItems -> 
                      not (isNewSlot item1 && 
                           superTypeItems |> List.exists (equivNewSlots item1) &&
                           superTypeItems |> List.exists (fun item2 -> isDefiniteOverride item1 && equivVirts item1 item2))) 

    
    /// Filter the overrides of methods, either keeping the overrides or keeping the dispatch slots.
    static let FilterOverridesOfMethInfos findFlag g amap m minfos = 
        minfos 
        |> FilterOverrides findFlag 
            ((fun (minfo: MethInfo) -> minfo.IsVirtual),
             (fun minfo -> minfo.IsNewSlot),
             (fun minfo -> minfo.IsDefiniteFSharpOverride),
             (fun minfo -> minfo.IsFinal),
             (fun minfo -> minfo.IsAbstract),
             MethInfosEquivByNameAndSig EraseNone true g amap m,
             (fun minfo -> minfo.LogicalName)) 

    static let PropsGetterSetterEquiv innerEquality (p1:PropInfo) (p2:PropInfo)  : bool =
        p1.HasGetter = p2.HasGetter &&
        p1.HasSetter = p2.HasSetter &&
        innerEquality p1 p2

    /// Filter the overrides of properties, either keeping the overrides or keeping the dispatch slots.
    static let FilterOverridesOfPropInfos findFlag g amap m props = 
        props 
        |> FilterOverrides findFlag 
              ((fun (pinfo: PropInfo) -> pinfo.IsVirtualProperty),
               (fun pinfo -> pinfo.IsNewSlot),
               (fun pinfo -> pinfo.IsDefiniteFSharpOverride),
               (fun _ -> false), // isFinal
               (fun _ -> false), // isAbstract
               PropsGetterSetterEquiv (PropInfosEquivByNameAndSig EraseNone g amap m),
               (fun pinfo -> pinfo.PropertyName)) 

    //type A() =
    //    abstract E: int with get, set
    //    default val E = 0 with get
    // Will get (A::E with get, A::E with get, set)
    // -----
    //type A() =
    //    member val A = 0 with get, set
    //type B() =
    //    inherit A()
    //    static member val A = 0
    // Will get (static B::A, None)
    static let FilterOverridesOfPropInfosWithOverriddenProp findFlag g amap m props = 
        let checkProp prop prop2 =
            not(obj.ReferenceEquals(prop, prop2)) && 
            PropInfosEquivByNameAndSig EraseNone g amap m prop prop2 &&
            if prop.HasGetter && prop.HasSetter then false
            elif prop.HasGetter then prop2.HasSetter
            elif prop.HasSetter then prop2.HasGetter
            else false

        let rec findPropBefore prop hasMetTheProp =
            function
            | props :: t when hasMetTheProp -> 
                match props |> List.tryFind (checkProp prop) with
                | Some p -> ValueSome p
                | None -> findPropBefore prop true t
            | props :: t ->
                if props |> List.exists (fun i -> obj.ReferenceEquals(prop, i)) then
                    match props |> List.tryFind (checkProp prop) with
                    | Some p -> ValueSome p
                    | None -> findPropBefore prop true t
                else findPropBefore prop false t
            | _ -> ValueNone

        props
        |> FilterOverridesOfPropInfos findFlag g amap m
        |> List.map (List.map (fun prop -> struct(prop, if findFlag = FindMemberFlag.IgnoreOverrides || prop.IsNewSlot then ValueNone else findPropBefore prop false props)))

    /// Exclude methods from super types which have the same signature as a method in a more specific type.
    static let ExcludeHiddenOfMethInfosImpl g amap m (minfos: MethInfo list list) = 
        minfos
        |> ExcludeItemsInSuperTypesBasedOnEquivTestWithItemsInSubTypes 
            (fun minfo -> minfo.LogicalName)
            (fun m1 m2 -> 
                 // only hide those truly from super classes 
                 not (tyconRefEq g m1.DeclaringTyconRef m2.DeclaringTyconRef) &&
                 MethInfosEquivByNameAndPartialSig EraseNone true g amap m m1 m2)
        
        |> List.concat

    /// Exclude properties from super types which have the same name as a property in a more specific type.
    static let ExcludeHiddenOfPropInfosImpl g amap m pinfos = 
        pinfos 
        |> ExcludeItemsInSuperTypesBasedOnEquivTestWithItemsInSubTypes (fun (pinfo: PropInfo) -> pinfo.PropertyName) (PropsGetterSetterEquiv (PropInfosEquivByNameAndPartialSig EraseNone g amap m)) 
        |> List.concat

    /// Make a cache for function 'f' keyed by type (plus some additional 'flags') that only 
    /// caches computations for monomorphic types.

    let MakeInfoCache name f (flagsEq : IEqualityComparer<_>) = 
        MemoizationTable<_, _>
             (name, compute=f,
              // Only cache closed, monomorphic types (closed = all members for the type
              // have been processed). Generic type instantiations could be processed if we had 
              // a decent hash function for these.

              // Nullness of `ty` (TType_app) is not considered here, as the info is used to load members of the type
              // It would matter for different generic instantiations of the same type, but we don't cache that here - TType_app is always matched for `[]` typars.
              canMemoize=(fun (_flags, _: range, ty) -> 
                                    match stripTyEqns g ty with 
                                    | TType_app(tcref, [], _) -> tcref.TypeContents.tcaug_closed
                                    | _ -> false),
              
              keyComparer=
                 { new IEqualityComparer<_> with 
                       member _.GetHashCode((flags, _, ty)) =
                                    // Ignoring the ranges - that's OK.
                                    flagsEq.GetHashCode flags + 
                                    (match stripTyEqns g ty with 
                                     | TType_app(tcref, [], _) -> hash tcref.LogicalName
                                     | _ -> 0)
                       member _.Equals((flags1, _, ty1), (flags2, _, ty2)) =
                                    // Ignoring the ranges - that's OK.
                                    flagsEq.Equals(flags1, flags2) && 
                                    match stripTyEqns g ty1, stripTyEqns g ty2 with 
                                    | TType_app(tcref1, [], _),TType_app(tcref2, [], _) -> tyconRefEq g tcref1 tcref2
                                    | _ -> false })
    
    let FindImplicitConversionsUncached (ad, m, ty) = 
        if isTyparTy g ty then 
            [] 
        // F# ignores the op_Implicit conversions defined on the 'Option' and 'ValueOption' types
        elif isOptionTy g ty || isValueOptionTy g ty then
            []
        else
            this.TryFindIntrinsicMethInfo m ad "op_Implicit" ty

    let IsInterfaceTypeWithMatchingStaticAbstractMemberUncached ((ad, nm), m, ty) = 
        ExistsInEntireHierarchyOfType (fun parentTy -> 
            let meths = this.TryFindIntrinsicMethInfo m ad nm parentTy
            meths |> List.exists (fun meth ->
                not meth.IsInstance &&
                meth.IsDispatchSlot &&
                isInterfaceTy g meth.ApparentEnclosingAppType
            ))
           g amap m AllowMultiIntfInstantiations.Yes ty

    let GetUnimplementedStaticAbstractMemberOfTypeUncached (_flags, m, interfaceTy) =
        if not (isInterfaceTy g interfaceTy) then
            None
        else
            let checkMembersOfInterface (ty: TType) =
                let meths = this.GetIntrinsicMethInfosOfType None AccessibleFromSomeFSharpCode AllowMultiIntfInstantiations.Yes IgnoreOverrides m ty
                meths |> List.tryPick (fun (minfo: MethInfo) ->
                    // Static abstract non-sealed (non-DIM) members
                    if not minfo.IsInstance && minfo.IsAbstract && not minfo.IsFinal then
                        Some minfo.DisplayNameCore
                    else
                        None
                )

            match checkMembersOfInterface interfaceTy with
            | Some name -> Some name
            | None ->
                let baseInterfaces = AllInterfacesOfType g amap m AllowMultiIntfInstantiations.Yes interfaceTy
                baseInterfaces |> List.tryPick checkMembersOfInterface

    let hashFlags0 = 
        { new IEqualityComparer<string option * AccessorDomain * AllowMultiIntfInstantiations> with 
               member _.GetHashCode((filter: string option, ad: AccessorDomain, _allowMultiIntfInst1)) = hash filter + AccessorDomain.CustomGetHashCode ad
               member _.Equals((filter1, ad1, allowMultiIntfInst1), (filter2, ad2, allowMultiIntfInst2)) = 
                   (filter1 = filter2) && AccessorDomain.CustomEquals(g, ad1, ad2) && allowMultiIntfInst1 = allowMultiIntfInst2 }

    let hashFlags1 = 
        { new IEqualityComparer<string option * AccessorDomain> with 
               member _.GetHashCode((filter: string option, ad: AccessorDomain)) = hash filter + AccessorDomain.CustomGetHashCode ad
               member _.Equals((filter1, ad1), (filter2, ad2)) = (filter1 = filter2) && AccessorDomain.CustomEquals(g, ad1, ad2) }

    let hashFlags2 = 
        { new IEqualityComparer<string * AccessorDomain * bool> with 
               member _.GetHashCode((nm: string, ad: AccessorDomain, includeConstraints)) =
                   hash nm + AccessorDomain.CustomGetHashCode ad + hash includeConstraints
               member _.Equals((nm1, ad1, includeConstraints1), (nm2, ad2, includeConstraints2)) =
                   (nm1 = nm2) && AccessorDomain.CustomEquals(g, ad1, ad2) && (includeConstraints1 = includeConstraints2) }
                         
    let hashFlags3 = 
        { new IEqualityComparer<AccessorDomain> with 
               member _.GetHashCode((ad: AccessorDomain)) = AccessorDomain.CustomGetHashCode ad
               member _.Equals(ad1, ad2) = nullSafeEquality ad1 ad2 (fun ad1 ad2 -> AccessorDomain.CustomEquals(g, ad1, ad2)) }
                         
    let hashFlags4 = 
        { new IEqualityComparer<AccessorDomain * string> with 
               member _.GetHashCode((ad, nm)) = AccessorDomain.CustomGetHashCode ad + hash nm
               member _.Equals((ad1, nm1), (ad2, nm2)) = AccessorDomain.CustomEquals(g, ad1, ad2) && (nm1 = nm2) }
                         
    let methodInfoCache = MakeInfoCache "methodInfoCache" GetIntrinsicMethodSetsUncached hashFlags0
    let propertyInfoCache = MakeInfoCache "propertyInfoCache" GetIntrinsicPropertySetsUncached hashFlags0
    let recdOrClassFieldInfoCache =  MakeInfoCache "recdOrClassFieldInfoCache" GetIntrinsicRecdOrClassFieldInfosUncached hashFlags1
    let ilFieldInfoCache = MakeInfoCache "ilFieldInfoCache" GetIntrinsicILFieldInfosUncached hashFlags1
    let eventInfoCache = MakeInfoCache "eventInfoCache" GetIntrinsicEventInfosUncached hashFlags1
    let namedItemsCache = MakeInfoCache "namedItemsCache" GetIntrinsicNamedItemsUncached hashFlags2
    let mostSpecificOverrideMethodInfoCache = MakeInfoCache "mostSpecificOverrideMethodInfoCache" GetIntrinsicMostSpecificOverrideMethodSetsUncached hashFlags0

    let entireTypeHierarchyCache = MakeInfoCache "entireTypeHierarchyCache" GetEntireTypeHierarchyUncached HashIdentity.Structural
    let primaryTypeHierarchyCache = MakeInfoCache "primaryTypeHierarchyCache" GetPrimaryTypeHierarchyUncached HashIdentity.Structural
    let implicitConversionCache = MakeInfoCache "implicitConversionCache" FindImplicitConversionsUncached hashFlags3
    let isInterfaceWithStaticAbstractMethodCache = MakeInfoCache "isInterfaceWithStaticAbstractMethodCache" IsInterfaceTypeWithMatchingStaticAbstractMemberUncached hashFlags4
    let unimplementedStaticAbstractMemberCache =
        MakeInfoCache
            "unimplementedStaticAbstractMemberCache"
            GetUnimplementedStaticAbstractMemberOfTypeUncached
            hashFlags0

    // Runtime feature support

    let isRuntimeFeatureSupported runtimeFeature =
        match g.System_Runtime_CompilerServices_RuntimeFeature_ty with
        | Some runtimeFeatureTy ->
            GetIntrinsicILFieldInfosUncached ((None, AccessorDomain.AccessibleFromEverywhere), range0, runtimeFeatureTy)
            |> List.exists (fun (ilFieldInfo: ILFieldInfo) -> ilFieldInfo.FieldName = runtimeFeature)
        | _ ->
            false

    let isRuntimeFeatureDefaultImplementationsOfInterfacesSupported =
        lazy isRuntimeFeatureSupported "DefaultImplementationsOfInterfaces"

    let isRuntimeFeatureVirtualStaticsInInterfacesSupported =
        lazy isRuntimeFeatureSupported "VirtualStaticsInInterfaces"

    member _.g = g
    member _.amap = amap

    /// Read the raw method sets of a type, including inherited ones. Cache the result for monomorphic types
    member _.GetRawIntrinsicMethodSetsOfType (optFilter, ad, allowMultiIntfInst, m, ty) =
        methodInfoCache.Apply(((optFilter, ad, allowMultiIntfInst), m, ty))

    /// Read the raw property sets of a type, including inherited ones. Cache the result for monomorphic types
    member _.GetRawIntrinsicPropertySetsOfType (optFilter, ad, allowMultiIntfInst, m, ty) =
        propertyInfoCache.Apply(((optFilter, ad, allowMultiIntfInst), m, ty))

    /// Read the record or class fields of a type, including inherited ones. Cache the result for monomorphic types.
    member _.GetRecordOrClassFieldsOfType (optFilter, ad, m, ty) =
        recdOrClassFieldInfoCache.Apply(((optFilter, ad), m, ty))

    /// Read the IL fields of a type, including inherited ones. Cache the result for monomorphic types.
    member _.GetILFieldInfosOfType (optFilter, ad, m, ty) =
        ilFieldInfoCache.Apply(((optFilter, ad), m, ty))

    member _.GetImmediateIntrinsicEventsOfType (optFilter, ad, m, ty) =
        ComputeImmediateIntrinsicEventsOfType (optFilter, ad) m ty

    /// Read the events of a type, including inherited ones. Cache the result for monomorphic types.
    member _.GetEventInfosOfType (optFilter, ad, m, ty) =
        eventInfoCache.Apply(((optFilter, ad), m, ty))

    /// Try and find a record or class field for a type.
    member _.TryFindRecdOrClassFieldInfoOfType (nm, m, ty) =
        match recdOrClassFieldInfoCache.Apply((Some nm, AccessibleFromSomewhere), m, ty) with
        | [] -> ValueNone
        | [single] -> ValueSome single
        | flds ->
            // multiple fields with the same name can come from different classes,
            // so filter them by the given type name
            match tryTcrefOfAppTy g ty with 
            | ValueNone -> ValueNone
            | ValueSome tcref ->
                match flds |> List.filter (fun rfinfo -> tyconRefEq g tcref rfinfo.TyconRef) with
                | [] -> ValueNone
                | [single] -> ValueSome single
                | _ -> failwith "unexpected multiple fields with same name" // Because it should have been already reported as duplicate fields

    /// Try and find an item with the given name in a type.
    member _.TryFindNamedItemOfType ((nm, ad, includeConstraints), m, ty) =
        namedItemsCache.Apply(((nm, ad, includeConstraints), m, ty))

    /// Read the raw method sets of a type that are the most specific overrides. Cache the result for monomorphic types
    member _.GetIntrinsicMostSpecificOverrideMethodSetsOfType (optFilter, ad, allowMultiIntfInst, m, ty) =
        mostSpecificOverrideMethodInfoCache.Apply(((optFilter, ad, allowMultiIntfInst), m, ty))

    /// Get the super-types of a type, including interface types.
    member _.GetEntireTypeHierarchy (allowMultiIntfInst, m, ty) =
        entireTypeHierarchyCache.Apply((allowMultiIntfInst, m, ty))

    /// Get the super-types of a type, excluding interface types.
    member _.GetPrimaryTypeHierarchy (allowMultiIntfInst, m, ty) =
        primaryTypeHierarchyCache.Apply((allowMultiIntfInst, m, ty))

    /// Check if the given language feature is supported by the runtime.
    member _.IsLanguageFeatureRuntimeSupported langFeature =
        match langFeature with
        // Both default and static interface method consumption features are tied to the runtime support of DIMs.
        | LanguageFeature.DefaultInterfaceMemberConsumption -> isRuntimeFeatureDefaultImplementationsOfInterfacesSupported.Value
        | LanguageFeature.InterfacesWithAbstractStaticMembers -> isRuntimeFeatureVirtualStaticsInInterfacesSupported.Value
        | _ -> true
            
    /// Get the declared constructors of any F# type
    member infoReader.GetIntrinsicConstructorInfosOfTypeAux m origTy metadataTy = 
      protectAssemblyExploration [] (fun () -> 
        let g = infoReader.g
        let amap = infoReader.amap 
        match metadataOfTy g metadataTy with 
    #if !NO_TYPEPROVIDERS
        | ProvidedTypeMetadata info -> 
            let st = info.ProvidedType
            [ for ci in st.PApplyArray((fun st -> st.GetConstructors()), "GetConstructors", m) do
                    yield ProvidedMeth(amap, ci.Coerce(m), None, m) ]
    #endif
        | ILTypeMetadata _ -> 
            let tinfo = ILTypeInfo.FromType g origTy
            tinfo.RawMetadata.Methods.FindByName ".ctor" 
            |> List.filter (fun md -> md.IsConstructor) 
            |> List.map (fun mdef -> MethInfo.CreateILMeth (amap, m, origTy, mdef)) 

        | FSharpOrArrayOrByrefOrTupleOrExnTypeMetadata -> 
            // Tuple types also support constructors. In this case convert to the .NET Tuple type that carries metadata and try again
            // Function types also support constructors. In this case convert to the FSharpFunc type that carries metadata and try again
            if isAnyTupleTy g metadataTy || isFunTy g metadataTy then 
                let betterMetadataTy = convertToTypeWithMetadataIfPossible g metadataTy
                infoReader.GetIntrinsicConstructorInfosOfTypeAux m origTy betterMetadataTy
            else
                match tryTcrefOfAppTy g metadataTy with
                | ValueNone -> []
                | ValueSome tcref -> 
                    tcref.MembersOfFSharpTyconByName 
                    |> NameMultiMap.find ".ctor"
                    |> List.choose(fun vref -> 
                        match vref.MemberInfo with 
                        | Some membInfo when (membInfo.MemberFlags.MemberKind = SynMemberKind.Constructor) -> Some vref 
                        | _ -> None) 
                    |> List.map (fun x -> FSMeth(g, origTy, x, None)) 
      )    

    static member ExcludeHiddenOfMethInfos g amap m minfos = 
        ExcludeHiddenOfMethInfosImpl g amap m minfos

    static member ExcludeHiddenOfPropInfos g amap m pinfos = 
        ExcludeHiddenOfPropInfosImpl g amap m pinfos

    /// Get the sets of intrinsic methods in the hierarchy (not including extension methods)
    member infoReader.GetIntrinsicMethInfoSetsOfType optFilter ad allowMultiIntfInst findFlag m ty = 
        infoReader.GetRawIntrinsicMethodSetsOfType(optFilter, ad, allowMultiIntfInst, m, ty)
        |> FilterOverridesOfMethInfos findFlag infoReader.g infoReader.amap m
  
    /// Get the sets intrinsic properties in the hierarchy (not including extension properties)
    member infoReader.GetIntrinsicPropInfoSetsOfType optFilter ad allowMultiIntfInst findFlag m ty = 
        infoReader.GetRawIntrinsicPropertySetsOfType(optFilter, ad, allowMultiIntfInst, m, ty) 
        |> FilterOverridesOfPropInfos findFlag infoReader.g infoReader.amap m

    /// Get the flattened list of intrinsic methods in the hierarchy
    member infoReader.GetIntrinsicMethInfosOfType optFilter ad allowMultiIntfInst findFlag m ty = 
        infoReader.GetIntrinsicMethInfoSetsOfType optFilter ad allowMultiIntfInst findFlag m ty |> List.concat
  
    /// Get the flattened list of intrinsic properties in the hierarchy
    member infoReader.GetIntrinsicPropInfosOfType optFilter ad allowMultiIntfInst findFlag m ty = 
        infoReader.GetIntrinsicPropInfoSetsOfType optFilter ad allowMultiIntfInst findFlag m ty  |> List.concat

    /// Get the flattened list of intrinsic properties in the hierarchy
    member infoReader.GetIntrinsicPropInfoWithOverriddenPropOfType optFilter ad allowMultiIntfInst findFlag m ty = 
        infoReader.GetRawIntrinsicPropertySetsOfType(optFilter, ad, allowMultiIntfInst, m, ty) 
        |> FilterOverridesOfPropInfosWithOverriddenProp findFlag infoReader.g infoReader.amap m
        |> List.concat

    member _.GetTraitInfosInType optFilter ty = 
        GetImmediateTraitsInfosOfType optFilter g ty

    member infoReader.TryFindIntrinsicNamedItemOfType (nm, ad, includeConstraints) findFlag m ty = 
        match infoReader.TryFindNamedItemOfType((nm, ad, includeConstraints), m, ty) with
        | Some item -> 
            match item with 
            | PropertyItem psets -> Some(PropertyItem (psets |> FilterOverridesOfPropInfos findFlag infoReader.g infoReader.amap m))
            | MethodItem msets -> Some(MethodItem (msets |> FilterOverridesOfMethInfos findFlag infoReader.g infoReader.amap m))
            | _ -> Some(item)
        | None -> None

    /// Try to detect the existence of a method on a type.
    member infoReader.TryFindIntrinsicMethInfo m ad nm ty : MethInfo list = 
        infoReader.GetIntrinsicMethInfosOfType (Some nm) ad AllowMultiIntfInstantiations.Yes IgnoreOverrides m ty 

    /// Try to find a particular named property on a type. Only used to ensure that local 'let' definitions and property names
    /// are distinct, a somewhat adhoc check in tc.fs.
    member infoReader.TryFindIntrinsicPropInfo m ad nm ty = 
        infoReader.GetIntrinsicPropInfosOfType (Some nm) ad AllowMultiIntfInstantiations.Yes IgnoreOverrides m ty 

    member _.FindImplicitConversions m ad ty = 
        implicitConversionCache.Apply((ad, m, ty))

    member _.IsInterfaceTypeWithMatchingStaticAbstractMember m nm ad ty = 
        isInterfaceWithStaticAbstractMethodCache.Apply((ad, nm), m, ty)

    member _.TryFindUnimplementedStaticAbstractMemberOfType (m: range) (interfaceTy: TType) : string option =
        if not (isInterfaceTy g interfaceTy) then
            None
        elif not (g.langVersion.SupportsFeature LanguageFeature.InterfacesWithAbstractStaticMembers) then
            None
        else
            unimplementedStaticAbstractMemberCache.Apply(((None, AccessibleFromSomewhere, AllowMultiIntfInstantiations.Yes), m, interfaceTy))

let checkLanguageFeatureRuntimeAndRecover (infoReader: InfoReader) langFeature m =
    if not (infoReader.IsLanguageFeatureRuntimeSupported langFeature) then
        let featureStr = LanguageVersion.GetFeatureString langFeature
        errorR (Error(FSComp.SR.chkFeatureNotRuntimeSupported featureStr, m))

let GetIntrinsicConstructorInfosOfType (infoReader: InfoReader) m ty = 
    infoReader.GetIntrinsicConstructorInfosOfTypeAux m ty ty

let ExcludeHiddenOfMethInfos g amap m (minfos: MethInfo list list) = 
    InfoReader.ExcludeHiddenOfMethInfos g amap m minfos

let ExcludeHiddenOfPropInfos g amap m pinfos = 
    InfoReader.ExcludeHiddenOfPropInfos g amap m pinfos

let GetIntrinsicMethInfoSetsOfType (infoReader:InfoReader) optFilter ad allowMultiIntfInst findFlag m ty = 
    infoReader.GetIntrinsicMethInfoSetsOfType optFilter ad allowMultiIntfInst findFlag m ty
  
let GetIntrinsicPropInfoSetsOfType (infoReader:InfoReader) optFilter ad allowMultiIntfInst findFlag m ty = 
    infoReader.GetIntrinsicPropInfoSetsOfType optFilter ad allowMultiIntfInst findFlag m ty

let GetIntrinsicMethInfosOfType (infoReader: InfoReader) optFilter ad allowMultiIntfInst findFlag m ty = 
    infoReader.GetIntrinsicMethInfosOfType optFilter ad allowMultiIntfInst findFlag m ty 
  
let GetIntrinsicPropInfosOfType (infoReader: InfoReader) optFilter ad allowMultiIntfInst findFlag m ty = 
    infoReader.GetIntrinsicPropInfosOfType optFilter ad allowMultiIntfInst findFlag m ty

let GetIntrinsicPropInfoWithOverriddenPropOfType (infoReader: InfoReader) optFilter ad allowMultiIntfInst findFlag m ty = 
    infoReader.GetIntrinsicPropInfoWithOverriddenPropOfType optFilter ad allowMultiIntfInst findFlag m ty

let TryFindIntrinsicNamedItemOfType (infoReader: InfoReader) (nm, ad, includeConstraints) findFlag m ty = 
    infoReader.TryFindIntrinsicNamedItemOfType (nm, ad, includeConstraints) findFlag m ty

let TryFindIntrinsicMethInfo (infoReader: InfoReader) m ad nm ty = 
    infoReader.TryFindIntrinsicMethInfo m ad nm ty

let TryFindIntrinsicPropInfo (infoReader: InfoReader) m ad nm ty = 
    infoReader.TryFindIntrinsicPropInfo m ad nm ty

/// Get a set of most specific override methods.
let GetIntrinsicMostSpecificOverrideMethInfoSetsOfType (infoReader: InfoReader) m ty =
    infoReader.GetIntrinsicMostSpecificOverrideMethodSetsOfType (None, AccessibleFromSomewhere, AllowMultiIntfInstantiations.Yes, m, ty)

//-------------------------------------------------------------------------
// Helpers related to delegates and events - these use method searching hence are in this file
//------------------------------------------------------------------------- 

/// The Invoke MethInfo, the function argument types, the function return type 
/// and the overall F# function type for the function type associated with a .NET delegate type
[<NoEquality;NoComparison>]
type SigOfFunctionForDelegate =
    SigOfFunctionForDelegate of
        delInvokeMeth: MethInfo *
        delArgTys: TType list *
        delRetTy: TType *
        delFuncTy: TType

/// Given a delegate type work out the minfo, argument types, return type 
/// and F# function type by looking at the Invoke signature of the delegate. 
let GetSigOfFunctionForDelegate (infoReader: InfoReader) delTy m ad =
    let g = infoReader.g
    let amap = infoReader.amap
    let delInvokeMeth = 
        match GetIntrinsicMethInfosOfType infoReader (Some "Invoke") ad AllowMultiIntfInstantiations.Yes IgnoreOverrides m delTy with 
        | [h] -> h
        | [] -> error(Error(FSComp.SR.noInvokeMethodsFound (), m))
        | h :: _ -> warning(InternalError(FSComp.SR.moreThanOneInvokeMethodFound (), m)); h
    
    let minst = []   // a delegate's Invoke method is never generic 

    let delArgTys = 
        match delInvokeMeth.GetParamTypes(amap, m, minst) with 
        | [args] -> args
        | _ -> error(Error(FSComp.SR.delegatesNotAllowedToHaveCurriedSignatures (), m))

    let fsharpViewOfDelArgTys = 
        match delArgTys with 
        | [] -> [g.unit_ty] 
        | _ -> delArgTys

    let delRetTy = delInvokeMeth.GetFSharpReturnType(amap, m, minst)

    CheckMethInfoAttributes g m None delInvokeMeth |> CommitOperationResult

    let delFuncTy = mkIteratedFunTy g fsharpViewOfDelArgTys delRetTy

    SigOfFunctionForDelegate(delInvokeMeth, delArgTys, delRetTy, delFuncTy)

/// Try and interpret a delegate type as a "standard" .NET delegate type associated with an event, with a "sender" parameter.
let TryDestStandardDelegateType (infoReader: InfoReader) m ad delTy =
    let g = infoReader.g
    let (SigOfFunctionForDelegate(_, delArgTys, delRetTy, _)) = GetSigOfFunctionForDelegate infoReader delTy m ad
    match delArgTys with 
    | senderTy :: argTys when (isObjTyAnyNullness g senderTy) && not (List.exists (isByrefTy g) argTys)  -> Some(mkRefTupledTy g argTys, delRetTy)
    | _ -> None


/// Indicates if an event info is associated with a delegate type that is a "standard" .NET delegate type
/// with a sender parameter.
//
// In the F# design, we take advantage of the following idiom to simplify away the bogus "object" parameter of the
// of the "Add" methods associated with events.  If you want to access it you
// can use AddHandler instead.
   
// The .NET Framework guidelines indicate that the delegate type used for
// an event should take two parameters, an "object source" parameter
// indicating the source of the event, and an "e" parameter that
// encapsulates any additional information about the event. The type of
// the "e" parameter should derive from the EventArgs class. For events
// that do not use any additional information, the .NET Framework has
// already defined an appropriate delegate type: EventHandler.
// (from http://msdn.microsoft.com/library/default.asp?url=/library/en-us/csref/html/vcwlkEventsTutorial.asp)
let IsStandardEventInfo (infoReader: InfoReader) m ad (einfo: EventInfo) =
    let delTy = einfo.GetDelegateType(infoReader.amap, m)
    match TryDestStandardDelegateType infoReader m ad delTy with
    | Some _ -> true
    | None -> false

/// Get the (perhaps tupled) argument type accepted by an event 
let ArgsTypeOfEventInfo (infoReader: InfoReader) m ad (einfo: EventInfo)  =
    let amap = infoReader.amap
    let delTy = einfo.GetDelegateType(amap, m)
    match TryDestStandardDelegateType infoReader m ad delTy with
    | Some(argTys, _) -> argTys
    | None -> error(nonStandardEventError einfo.EventName m)

/// Get the type of the event when looked at as if it is a property 
/// Used when displaying the property in Intellisense 
let PropTypeOfEventInfo (infoReader: InfoReader) m ad (einfo: EventInfo) =  
    let g = infoReader.g
    let amap = infoReader.amap
    let delTy = einfo.GetDelegateType(amap, m)
    let argsTy = ArgsTypeOfEventInfo infoReader m ad einfo 
    mkIEventType g delTy argsTy

/// Try to find the name of the metadata file for this external definition 
let TryFindMetadataInfoOfExternalEntityRef (infoReader: InfoReader) m eref = 
    let g = infoReader.g
    match eref with 
    | ERefLocal _ -> None
    | ERefNonLocal nlref -> 
        // Generalize to get a formal signature 
        let formalTypars = eref.Typars m
        let formalTypeInst = generalizeTypars formalTypars
        let ty = TType_app(eref, formalTypeInst, KnownAmbivalentToNull)
        if isILAppTy g ty then
            let formalTypeInfo = ILTypeInfo.FromType g ty
            Some(nlref.Ccu.FileName, formalTypars, formalTypeInfo)
        else None

/// Try to find the xml doc associated with the assembly name and xml doc signature
let TryFindXmlDocByAssemblyNameAndSig (infoReader: InfoReader) assemblyName xmlDocSig =
    infoReader.amap.assemblyLoader.TryFindXmlDocumentationInfo(assemblyName)
    |> Option.bind (fun xmlDocInfo ->
        xmlDocInfo.TryGetXmlDocBySig(xmlDocSig)
    )

let private libFileOfEntityRef x =
    match x with
    | ERefLocal _ -> None
    | ERefNonLocal nlref -> nlref.Ccu.FileName 

let GetXmlDocSigOfEntityRef infoReader m (eref: EntityRef) = 
    if eref.IsILTycon then 
        match TryFindMetadataInfoOfExternalEntityRef infoReader m eref  with
        | None -> None
        | Some (ccuFileName, _, formalTypeInfo) -> Some(ccuFileName, "T:"+formalTypeInfo.ILTypeRef.FullName)
    else
        let ccuFileName = libFileOfEntityRef eref
        let m = eref.Deref
        if String.IsNullOrEmpty(m.XmlDocSig) then
            m.XmlDocSig <- XmlDocSigOfEntity eref
        Some (ccuFileName, m.XmlDocSig)

let GetXmlDocSigOfScopedValRef g (tcref: TyconRef) (vref: ValRef) = 
    let ccuFileName = libFileOfEntityRef tcref
    let v = vref.Deref
    if String.IsNullOrEmpty(v.XmlDocSig) && v.HasDeclaringEntity then
        let ap = buildAccessPath vref.DeclaringEntity.CompilationPathOpt
        let path =
            if vref.DeclaringEntity.IsModule then
                let sep = if ap.Length > 0 then "." else ""
                ap + sep + vref.DeclaringEntity.CompiledName
            else
                ap
        v.XmlDocSig <- XmlDocSigOfVal g false path v
    Some (ccuFileName, v.XmlDocSig)                

let GetXmlDocSigOfRecdFieldRef (rfref: RecdFieldRef) = 
    let tcref = rfref.TyconRef
    let ccuFileName = libFileOfEntityRef tcref 
    if String.IsNullOrEmpty(rfref.RecdField.XmlDocSig) then
        rfref.RecdField.XmlDocSig <- XmlDocSigOfProperty [tcref.CompiledRepresentationForNamedType.FullName; rfref.RecdField.LogicalName]
    Some (ccuFileName, rfref.RecdField.XmlDocSig)

let GetXmlDocSigOfUnionCaseRef (ucref: UnionCaseRef) = 
    let tcref =  ucref.TyconRef
    let ccuFileName = libFileOfEntityRef tcref
    if String.IsNullOrEmpty(ucref.UnionCase.XmlDocSig) then
        ucref.UnionCase.XmlDocSig <- XmlDocSigOfUnionCase [tcref.CompiledRepresentationForNamedType.FullName; ucref.CaseName]
    Some (ccuFileName, ucref.UnionCase.XmlDocSig)

[<TailCall>]
let rec GetXmlDocSigOfMethInfo (infoReader: InfoReader)  m (minfo: MethInfo) = 
    let amap = infoReader.amap
    match minfo with
    | FSMeth (g, _, vref, _) ->
        GetXmlDocSigOfScopedValRef g minfo.DeclaringTyconRef vref
    | ILMeth (g, ilminfo, _) ->            
        let actualTypeName = ilminfo.DeclaringTyconRef.CompiledRepresentationForNamedType.FullName
        let fmtps = ilminfo.FormalMethodTypars            
        let genericArity = if fmtps.Length=0 then "" else sprintf "``%d" fmtps.Length

        match TryFindMetadataInfoOfExternalEntityRef infoReader m ilminfo.DeclaringTyconRef  with 
        | None -> None
        | Some (ccuFileName, formalTypars, formalTypeInfo) ->
            let filminfo = ILMethInfo(g, IlType formalTypeInfo, ilminfo.RawMetadata, fmtps) 
            let args = 
                if ilminfo.IsILExtensionMethod then
                    filminfo.GetRawArgTypes(amap, m, minfo.FormalMethodInst)
                else
                    filminfo.GetParamTypes(amap, m, minfo.FormalMethodInst)

            // http://msdn.microsoft.com/en-us/library/fsbx0t7x.aspx
            // If the name of the item itself has periods, they are replaced by the hash-sign ('#'). 
            // It is assumed that no item has a hash-sign directly in its name. For example, the fully 
            // qualified name of the String constructor would be "System.String.#ctor".
            let normalizedName = ilminfo.ILName.Replace(".", "#")

            Some (ccuFileName, "M:"+actualTypeName+"."+normalizedName+genericArity+XmlDocArgsEnc g (formalTypars, fmtps) args)

    | MethInfoWithModifiedReturnType(mi,_) -> GetXmlDocSigOfMethInfo infoReader m mi
    | DefaultStructCtor(g, ty) ->
        match tryTcrefOfAppTy g ty with
        | ValueSome tcref ->
            Some(None, $"M:{tcref.CompiledRepresentationForNamedType.FullName}.#ctor")
        | _ -> None

#if !NO_TYPEPROVIDERS
    | ProvidedMeth _ -> None
#endif

let GetXmlDocSigOfValRef g (vref: ValRef) =
    if not vref.IsLocalRef then
        let ccuFileName = vref.nlr.Ccu.FileName
        let v = vref.Deref
        if String.IsNullOrEmpty(v.XmlDocSig) && v.HasDeclaringEntity then
            v.XmlDocSig <- XmlDocSigOfVal g false vref.DeclaringEntity.CompiledRepresentationForNamedType.Name v
        Some (ccuFileName, v.XmlDocSig)
    else 
        match vref.ApparentEnclosingEntity with
        | Parent tcref ->
            GetXmlDocSigOfScopedValRef g tcref vref
        | _ ->
            None

let GetXmlDocSigOfProp infoReader m (pinfo: PropInfo) =
    let g = pinfo.TcGlobals
    match pinfo with 
#if !NO_TYPEPROVIDERS
    | ProvidedProp _ -> None // No signature is possible. If an xml comment existed it would have been returned by PropInfo.XmlDoc in infos.fs
#endif
    | FSProp _ as fspinfo -> 
        match fspinfo.ArbitraryValRef with 
        | None -> None
        | Some vref -> GetXmlDocSigOfScopedValRef g pinfo.DeclaringTyconRef vref
    | ILProp(ILPropInfo(_, pdef)) -> 
        match TryFindMetadataInfoOfExternalEntityRef infoReader m pinfo.DeclaringTyconRef with
        | Some (ccuFileName, formalTypars, formalTypeInfo) ->
            let filpinfo = ILPropInfo(formalTypeInfo, pdef)
            Some (ccuFileName, "P:"+formalTypeInfo.ILTypeRef.FullName+"."+pdef.Name+XmlDocArgsEnc g (formalTypars, []) (filpinfo.GetParamTypes(infoReader.amap, m)))
        | _ -> None

let GetXmlDocSigOfEvent infoReader m (einfo: EventInfo) =
    match einfo with
    | ILEvent _ ->
        match TryFindMetadataInfoOfExternalEntityRef infoReader m einfo.DeclaringTyconRef with 
        | Some (ccuFileName, _, formalTypeInfo) -> 
            Some(ccuFileName, "E:"+formalTypeInfo.ILTypeRef.FullName+"."+einfo.EventName)
        | _ -> None
    | _ -> None

let GetXmlDocSigOfILFieldInfo infoReader m (finfo: ILFieldInfo) =
    match TryFindMetadataInfoOfExternalEntityRef infoReader m finfo.DeclaringTyconRef with
    | Some (ccuFileName, _, formalTypeInfo) ->
        Some(ccuFileName, "F:"+formalTypeInfo.ILTypeRef.FullName+"."+finfo.FieldName)
    | _ -> None