[WIP] trial fix for 9449

src/fsharp/ConstraintSolver.fs

@@ -248,6 +248,12 @@ type ConstraintSolverState =
       /// Indicates if the constraint solver is being run after type checking is complete,
       /// e.g. during codegen to determine solutions and witnesses for trait constraints.
       /// Suppresses the generation of certain errors such as missing constraint warnings.
+      afterTypeCheck: bool
+
+      /// Indicates if the constraint solver is being run at very last stage (ilxgen)
+      /// Allows constraints to be added to type parameters to produce a witness.
+      /// There is no really good reason this should be allowed nor should it be needed,
+      /// but it was in the codebase and remains active for legacy compat reasons.
       codegen: bool
 
       /// This table stores all unsolved, ungeneralized trait constraints, indexed by free type variable.
@@ -262,6 +268,7 @@ type ConstraintSolverState =
           amap = amap 
           ExtraCxs = HashMultiMap(10, HashIdentity.Structural)
           InfoReader = infoReader
+          afterTypeCheck = false
           codegen = false
           TcVal = tcVal } 
 
@@ -1952,7 +1959,7 @@ and AddConstraint (csenv: ConstraintSolverEnv) ndeep m2 trace tp newConstraint
             // will-be-made-rigid type variable. This is because the existence of these warnings
             // is relevant to the overload resolution rules (see 'candidateWarnCount' in the overload resolution
             // implementation).
-            if tp.Rigidity.WarnIfMissingConstraint  && not csenv.SolverState.codegen then
+            if tp.Rigidity.WarnIfMissingConstraint  && not csenv.SolverState.afterTypeCheck then
                 do! WarnD (ConstraintSolverMissingConstraint(denv, tp, newConstraint, m, m2))
 
             let newConstraints = 
@@ -3060,26 +3067,27 @@ let ApplyTyparDefaultAtPriority denv css priority (tp: Typar) =
                 |> RaiseOperationResult
         | _ -> ())
 
-let CreateCodegenState tcVal g amap = 
+let CreateCodegenState tcVal g amap codegen = 
     { g = g
       amap = amap
       TcVal = tcVal
       ExtraCxs = HashMultiMap(10, HashIdentity.Structural)
       InfoReader = new InfoReader(g, amap)
-      codegen = true }
+      codegen = codegen
+      afterTypeCheck = true }
 
 /// Generate a witness expression if none is otherwise available, e.g. in legacy non-witness-passing code
-let CodegenWitnessForTraitConstraint tcVal g amap m (traitInfo:TraitConstraintInfo) argExprs = trackErrors {
-    let css = CreateCodegenState tcVal g amap
+let CodegenWitnessForTraitConstraint tcVal g amap m (traitInfo:TraitConstraintInfo) argExprs codegen = trackErrors {
+    let css = CreateCodegenState tcVal g amap codegen
     let csenv = MakeConstraintSolverEnv ContextInfo.NoContext css m (DisplayEnv.Empty g)
     let! _res = SolveMemberConstraint csenv true PermitWeakResolution.Yes 0 m NoTrace traitInfo
     let sln = GenWitnessExpr amap g m traitInfo argExprs
     return sln
   }
 
 /// Generate the lambda argument passed for a use of a generic construct that accepts trait witnesses
-let CodegenWitnessesForTyparInst tcVal g amap m typars tyargs = trackErrors {
-    let css = CreateCodegenState tcVal g amap
+let CodegenWitnessesForTyparInst tcVal g amap m typars tyargs codegen = trackErrors {
+    let css = CreateCodegenState tcVal g amap codegen
     let csenv = MakeConstraintSolverEnv ContextInfo.NoContext css m (DisplayEnv.Empty g)
     let ftps, _renaming, tinst = FreshenTypeInst m typars
     let traitInfos = GetTraitConstraintInfosOfTypars g ftps 
@@ -3088,8 +3096,8 @@ let CodegenWitnessesForTyparInst tcVal g amap m typars tyargs = trackErrors {
   }
 
 /// Generate the lambda argument passed for a use of a generic construct that accepts trait witnesses
-let CodegenWitnessesForTraitWitness tcVal g amap m traitInfo = trackErrors {
-    let css = CreateCodegenState tcVal g amap
+let CodegenWitnessesForTraitWitness tcVal g amap m traitInfo codegen = trackErrors {
+    let css = CreateCodegenState tcVal g amap codegen
     let csenv = MakeConstraintSolverEnv ContextInfo.NoContext css m (DisplayEnv.Empty g)
     let! _res = SolveMemberConstraint csenv true PermitWeakResolution.Yes 0 m NoTrace traitInfo
     return MethodCalls.GenWitnessExprLambda amap g m traitInfo
@@ -3140,6 +3148,7 @@ let IsApplicableMethApprox g amap m (minfo: MethInfo) availObjTy =
               amap = amap
               TcVal = (fun _ -> failwith "should not be called")
               ExtraCxs = HashMultiMap(10, HashIdentity.Structural)
+              afterTypeCheck = false
               codegen = false
               InfoReader = new InfoReader(g, amap) }
         let csenv = MakeConstraintSolverEnv ContextInfo.NoContext css m (DisplayEnv.Empty g)

src/fsharp/ConstraintSolver.fsi

@@ -192,13 +192,13 @@ val SolveTypeAsError: DisplayEnv -> ConstraintSolverState -> range -> TType -> u
 val ApplyTyparDefaultAtPriority: DisplayEnv -> ConstraintSolverState -> priority: int -> Typar -> unit
 
 /// Generate a witness expression if none is otherwise available, e.g. in legacy non-witness-passing code
-val CodegenWitnessForTraitConstraint : TcValF -> TcGlobals -> ImportMap -> range -> TraitConstraintInfo -> Expr list -> OperationResult<Expr option>
+val CodegenWitnessForTraitConstraint : TcValF -> TcGlobals -> ImportMap -> range -> TraitConstraintInfo -> Expr list -> bool -> OperationResult<Expr option>
 
 /// Generate the arguments passed when using a generic construct that accepts traits witnesses
-val CodegenWitnessesForTyparInst : TcValF -> TcGlobals -> ImportMap -> range -> Typars -> TType list -> OperationResult<Choice<TraitConstraintInfo, Expr> list>
+val CodegenWitnessesForTyparInst : TcValF -> TcGlobals -> ImportMap -> range -> Typars -> TType list -> bool -> OperationResult<Choice<TraitConstraintInfo, Expr> list>
 
 /// Generate the lambda argument passed for a use of a generic construct that accepts trait witnesses
-val CodegenWitnessesForTraitWitness : TcValF -> TcGlobals -> ImportMap -> range -> TraitConstraintInfo -> OperationResult<Choice<TraitConstraintInfo, Expr>>
+val CodegenWitnessesForTraitWitness : TcValF -> TcGlobals -> ImportMap -> range -> TraitConstraintInfo -> bool -> OperationResult<Choice<TraitConstraintInfo, Expr>>
 
 /// For some code like "let f() = ([] = [])", a free choice is made for a type parameter
 /// for an interior type variable.  This chooses a solution for a type parameter subject

src/fsharp/IlxGen.fs

@@ -3114,7 +3114,7 @@ and GenWitnessArgFromTraitInfo cenv cgbuf eenv m traitInfo =
     match storage with 
     | None ->
         let witnessExpr =
-           ConstraintSolver.CodegenWitnessesForTraitWitness cenv.tcVal g cenv.amap m traitInfo 
+           ConstraintSolver.CodegenWitnessesForTraitWitness cenv.tcVal g cenv.amap m traitInfo true
             |> CommitOperationResult
         match witnessExpr with
         | Choice1Of2 _traitInfo ->
@@ -3152,7 +3152,7 @@ and GenWitnessArgs cenv cgbuf eenv m tps tyargs =
     // Witness arguments are only generated in emitted 'inline' code where witness parameters are available.
     if generateWitnesses then 
         let mwitnesses = 
-            ConstraintSolver.CodegenWitnessesForTyparInst cenv.tcVal g cenv.amap m tps tyargs 
+            ConstraintSolver.CodegenWitnessesForTyparInst cenv.tcVal g cenv.amap m tps tyargs true
             |> CommitOperationResult
 
         for witnessArg in mwitnesses do
@@ -4084,7 +4084,7 @@ and GenTraitCall (cenv: cenv) cgbuf eenv (traitInfo: TraitConstraintInfo, argExp
     // If witnesses are available, we should now always find trait witnesses in scope
     assert not generateWitnesses
 
-    let minfoOpt = CommitOperationResult (ConstraintSolver.CodegenWitnessForTraitConstraint cenv.tcVal g cenv.amap m traitInfo argExprs)
+    let minfoOpt = CommitOperationResult (ConstraintSolver.CodegenWitnessForTraitConstraint cenv.tcVal g cenv.amap m traitInfo argExprs true)
     match minfoOpt with
     | None ->
         let exnArg = mkString g m (FSComp.SR.ilDynamicInvocationNotSupported(traitInfo.MemberName))

src/fsharp/Optimizer.fs

@@ -520,9 +520,9 @@ let BindInternalLocalVal cenv (v: Val) vval env =
         env
 
 let BindExternalLocalVal cenv (v: Val) vval env = 
-#if CHECKED
-    CheckInlineValueIsComplete v vval
-#endif
+//#if CHECKED
+    CheckInlineValueIsComplete v vval.ValExprInfo
+//#endif
 
     let vval = if v.IsMutable then {vval with ValExprInfo=UnknownValue } else vval
     let env = 
@@ -2451,7 +2451,7 @@ and OptimizeWhileLoop cenv env (spWhile, marker, e1, e2, m) =
 and OptimizeTraitCall cenv env (traitInfo, args, m) =
 
     // Resolve the static overloading early (during the compulsory rewrite phase) so we can inline. 
-    match ConstraintSolver.CodegenWitnessForTraitConstraint cenv.TcVal cenv.g cenv.amap m traitInfo args with
+    match ConstraintSolver.CodegenWitnessForTraitConstraint cenv.TcVal cenv.g cenv.amap m traitInfo args false with
 
     | OkResult (_, Some expr) -> OptimizeExpr cenv env expr
 

src/fsharp/QuotationTranslator.fs

@@ -249,7 +249,7 @@ and GetWitnessArgs cenv (env : QuotationTranslationEnv) m tps tyargs =
     let g = cenv.g
     if g.generateWitnesses && not env.suppressWitnesses then 
         let witnessExprs = 
-            ConstraintSolver.CodegenWitnessesForTyparInst cenv.tcVal g cenv.amap m tps tyargs 
+            ConstraintSolver.CodegenWitnessesForTyparInst cenv.tcVal g cenv.amap m tps tyargs false
             |> CommitOperationResult
         let env = { env with suppressWitnesses = true }
         witnessExprs |> List.map (fun arg -> 
@@ -737,7 +737,7 @@ and private ConvExprCore cenv (env : QuotationTranslationEnv) (expr: Expr) : QP.
 
                 let minfoOpt =
                     if g.generateWitnesses then 
-                        ConstraintSolver.CodegenWitnessForTraitConstraint cenv.tcVal g cenv.amap m traitInfo args |> CommitOperationResult 
+                        ConstraintSolver.CodegenWitnessForTraitConstraint cenv.tcVal g cenv.amap m traitInfo args false |> CommitOperationResult 
                     else
                         None
                 match minfoOpt with