Constrained composite fields refac

Strata/Languages/Laurel/ConstrainedTypeElim.lean

@@ -94,10 +94,6 @@ def mkConstraintFunc (ptMap : ConstrainedTypeMap) (ct : ConstrainedType) : Proce
     decreases := none
     preconditions := [] }
 
-private def wrap (stmts : List StmtExprMd) (src : Option FileRange)
-    : StmtExprMd :=
-  match stmts with | [s] => s | ss => ⟨.Block ss none, src⟩
-
 def resolveVariable (ptMap : ConstrainedTypeMap) (v : VariableMd) : VariableMd :=
   match v.val with
   | .Declare param => ⟨.Declare { param with type := resolveType ptMap param.type }, v.source⟩
@@ -128,130 +124,43 @@ def resolveExprNode (ptMap : ConstrainedTypeMap) (expr : StmtExprMd) : StmtExprM
   | .IsType t ty => ⟨.IsType t (resolveType ptMap ty), source⟩
   | _ => expr
 
-/-- If `target` is an assignment target of a constrained type, return that
-    constrained type together with an expression that reads the target back.
-    The declared type is taken from the `Declare` parameter or, for
-    `Local`/`Field` targets, from the semantic model.
-
-    Both `Local` and `Field` targets are resolved (they carry a `uniqueId`
-    after the resolution pass, which `constrainedTypeElimPass` requires), so the
-    model lookup reliably returns their declared type. -/
-def constrainedTargetReadback (ptMap : ConstrainedTypeMap) (model : SemanticModel)
-    (target : VariableMd) : Option (HighType × StmtExprMd) :=
-  let src := target.source
-  let check (ty : HighType) (ref : StmtExprMd) : Option (HighType × StmtExprMd) :=
-    if isConstrainedType ptMap ty then some (ty, ref) else none
-  match target.val with
-  | .Local name => check (model.get name).getType.val ⟨.Var (.Local name), src⟩
-  | .Declare param => check param.type.val ⟨.Var (.Local param.name), src⟩
-  | .Field tgt fieldName => check (model.get fieldName).getType.val ⟨.Var (.Field tgt fieldName), src⟩
-
-/-- Build `assert T$constraint(<read-back of target>)` for an assignment
-    `target` of constrained type `T`, or `none` if the target's type is not
-    constrained. This is the single point that turns any assignment target
-    (`Local`, `Declare`, or `Field`) into its constraint check, used by both the
-    statement-position handler (`elimStmt`) and the expression-position handler
-    (`wrapAssignNode`).
-
-    `src` is the source range reported on the generated assertion (and its
-    constraint call); it defaults to the target's own source but callers pass
-    the enclosing assignment's source so a failed check points at the whole
-    assignment. -/
-def constrainedTargetAssert (ptMap : ConstrainedTypeMap) (model : SemanticModel)
-    (target : VariableMd) (src : Option FileRange := target.source) : Option StmtExprMd :=
-  (constrainedTargetReadback ptMap model target).bind fun (ty, ref) =>
-    (constraintCallForExpr ptMap ty ref (src := src)).map fun c =>
-      ⟨.Assert { condition := c }, src⟩
-
-/-- Wrap an assignment that appears in *expression* position so that the
-    constraint of any constrained-typed target is checked.
-
-    For `x := v` where `x : T` is constrained, produces the block expression
-    `{ x := v; assert T$constraint(x); x }`, whose value is the assigned value.
-    The constraint is asserted on a read-back of the target (after the
-    assignment) rather than on the value `v`, so `v` is evaluated exactly once
-    and the check is semantics-preserving.
-
-    `elimStmt` already handles assignments that appear as statements; this covers
-    assignments nested inside expressions (e.g. `y := (x := -1) + 1`), which are
-    only hoisted to statement level by the later `LiftExpressionAssignments`
-    pass. That pass preserves the order of side-effecting statements within an
-    expression-position block, so the assertion stays after the assignment.
-    Non-`Assign` nodes are returned unchanged. -/
-def wrapAssignNode (ptMap : ConstrainedTypeMap) (model : SemanticModel)
-    (node : StmtExprMd) : StmtExprMd :=
+/-- Per-node constrained-type elimination, applied bottom-up (with flattening)
+    by `mapStmtExprFlattenM`. `resultUsed` is `true` when the node occupies a
+    value position.
+
+    - Uninitialized constrained declaration `var x: T;` → assume its constraint.
+    - Assignment to constrained target(s) → emit the assignment followed by an
+      `assert T$constraint(<read-back>)` per constrained target. The constraint
+      is checked on a *read-back* of the target rather than on the RHS, so the
+      RHS is evaluated exactly once. In value position the read-back is also
+      appended as the final statement, so the resulting value-block evaluates to
+      the assigned value (this covers expression-position assignments such as
+      `y := (x := -1) + 1`); in statement position it is omitted.
+    - All other nodes are returned unchanged; the traversal handles recursion. -/
+def elimNode (ptMap : ConstrainedTypeMap) (model : SemanticModel)
+    (resultUsed : Bool) (node : StmtExprMd) : List StmtExprMd :=
+  let source := node.source
   match node.val with
-  | .Assign targets _value =>
-    match targets.filterMap (constrainedTargetReadback ptMap model) with
-    | [] => node
-    | (_, resultRef) :: _ =>
-      let src := node.source
-      let asserts : List StmtExprMd := targets.filterMap (constrainedTargetAssert ptMap model · (src := src))
-      ⟨.Block ([node] ++ asserts ++ [resultRef]) none, src⟩
-  | _ => node
-
-/-- Insert constraint assertions for every assignment to a constrained-typed
-    target that appears within an expression. A no-op on expressions that
-    contain no such assignment. -/
-def wrapExprAssigns (ptMap : ConstrainedTypeMap) (model : SemanticModel)
-    (expr : StmtExprMd) : StmtExprMd :=
-  mapStmtExpr (wrapAssignNode ptMap model) expr
-
-def elimStmt (ptMap : ConstrainedTypeMap) (model : SemanticModel)
-    (stmt : StmtExprMd) : List StmtExprMd :=
-  let source := stmt.source
-
-  match _h : stmt.val with
   | .Var (.Declare param) =>
-    -- Uninitialized constrained-typed declaration (`var x: T;`): assume its
-    -- constraint, since the variable's value is otherwise unconstrained.
     let check := (constraintCallFor ptMap param.type.val param.name (src := source)).toList.map
       fun c => ⟨.Assume c, source⟩
-    [stmt] ++ check
-
-  | .Assign targets value =>
-    -- Wrap any assignments nested in the value expression (expression-position
-    -- assignments) so their constrained-type constraints are checked too.
-    let value := wrapExprAssigns ptMap model value
-    let stmt' : StmtExprMd := ⟨.Assign targets value, source⟩
-    -- Assert the constraint of every constrained-typed target, uniformly across
-    -- `Local`, `Declare`, and `Field` targets via `constrainedTargetAssert`.
-    --
-    -- The constraint is asserted on a *read-back* of the target (after the
-    -- write) rather than on `value`. `value` is the full RHS expression, already
-    -- emitted as the assignment statement above; re-using it would emit it a
-    -- second time, so any side effect in the RHS would run twice (e.g.
-    -- `c#count := (x := x + 1) + 1` would increment `x` twice). Reading the
-    -- target back evaluates the RHS exactly once.
-    let checks := targets.filterMap (constrainedTargetAssert ptMap model · (src := source))
-    [stmt'] ++ checks
-
-  | .Block stmts sep =>
-    let stmtss := stmts.map (elimStmt ptMap model)
-    [⟨.Block stmtss.flatten sep, source⟩]
-
-  | .IfThenElse cond thenBr (some elseBr) =>
-    let cond := wrapExprAssigns ptMap model cond
-    let thenSs := elimStmt ptMap model thenBr
-    let elseSs := elimStmt ptMap model elseBr
-    [⟨.IfThenElse cond (wrap thenSs source) (some (wrap elseSs source)), source⟩]
-  | .IfThenElse cond thenBr none =>
-    let cond := wrapExprAssigns ptMap model cond
-    let thenSs := elimStmt ptMap model thenBr
-    [⟨.IfThenElse cond (wrap thenSs source) none, source⟩]
-
-  | .While cond inv dec body =>
-    let cond := wrapExprAssigns ptMap model cond
-    let bodySs := elimStmt ptMap model body
-    [⟨.While cond inv dec (wrap bodySs source), source⟩]
-
-  | _ => [stmt]
-termination_by sizeOf stmt
-decreasing_by
-  all_goals simp_wf
-  all_goals (try have := AstNode.sizeOf_val_lt stmt)
-  all_goals (try term_by_mem)
-  all_goals omega
+    [node] ++ check
+  | .Assign targets _value =>
+    let asserts: List StmtExprMd := targets.filterMap (fun target =>
+      let ref : StmtExprMd := VariableMd.toReadbackExpr target
+      let ty : HighType := (computeExprType model ref).val
+      (constraintCallForExpr ptMap ty ref (src := source)).map (⟨.Assert { condition := · }, source⟩))
+    let suffix := match targets with
+      | [single] => if resultUsed then [VariableMd.toReadbackExpr single] else []
+      | _ => []
+    [node] ++ asserts ++ suffix
+  | _ => [node]
+
+/-- Apply `elimNode` across a body via the flattening, `resultUsed`-aware
+    traversal. A procedure body is a statement, so the top-level `resultUsed`
+    is `false`. -/
+def elimStmts (ptMap : ConstrainedTypeMap) (model : SemanticModel) (body : StmtExprMd) : StmtExprMd :=
+  mapStmtExprFlattenM (m := Id) (fun _ _ => none) (elimNode ptMap model) false body
 
 def elimProc (ptMap : ConstrainedTypeMap) (model : SemanticModel) (proc : Procedure) : Procedure :=
   let inputRequires : List Condition := proc.inputs.filterMap fun p =>
@@ -262,14 +171,13 @@ def elimProc (ptMap : ConstrainedTypeMap) (model : SemanticModel) (proc : Proced
       fun c => { condition := ⟨c.val, p.type.source⟩ }
   let body' := match proc.body with
   | .Transparent bodyExpr =>
-    let stmts := elimStmt ptMap model bodyExpr
-    let body := wrap stmts bodyExpr.source
+    let body := elimStmts ptMap model bodyExpr
     if outputEnsures.isEmpty then .Transparent body
     else
       let retBody := if proc.isFunctional then ⟨.Return (some body), bodyExpr.source⟩ else body
       .Opaque outputEnsures (some retBody) []
   | .Opaque postconds impl modif =>
-    let impl' := impl.map fun b => wrap (elimStmt ptMap model b) b.source
+    let impl' := impl.map (elimStmts ptMap model)
     .Opaque (postconds ++ outputEnsures) impl' modif
   | .Abstract postconds => .Abstract (postconds ++ outputEnsures)
   | .External => .External

Strata/Languages/Laurel/LaurelAST.lean

@@ -748,6 +748,21 @@ def StmtExpr.constructorName (e : StmtExpr) : String :=
   | .Hole .. => "Hole"
   | .IncrDecr .. => "IncrDecr"
 
+/-- Build an expression that reads back the value of a variable reference.
+
+    The result is always a `Var` expression that evaluates to the variable's
+    value. A `Declare` is read back as a `Local` reference to the declared name
+    (so a declaration target reads back the variable it introduces). -/
+def Variable.toReadbackExpr : Variable → StmtExpr
+  | .Local name => .Var (.Local name)
+  | .Declare param => .Var (.Local param.name)
+  | .Field target fieldName => .Var (.Field target fieldName)
+
+/-- Source-preserving read-back expression for a `VariableMd`
+    (see `Variable.toReadbackExpr`). -/
+def VariableMd.toReadbackExpr (v : VariableMd) : StmtExprMd :=
+  ⟨ v.val.toReadbackExpr, v.source ⟩
+
 /-- Check whether a single modifies entry is the wildcard (`*`). -/
 def StmtExprMd.isWildcard (m : StmtExprMd) : Bool := match m.val with | .All => true | _ => false