fix #12025, fix a case where wrong warning was reported for a method arg, update baselines (#12028)

Co-authored-by: Don Syme <[email protected]>

Author: dsyme

src/fsharp/CheckExpressions.fs

@@ -5553,12 +5553,13 @@ and TcPropagatingExprLeafThenConvert cenv overallTy actualTy (env: TcEnv) (* can
     match overallTy with
     | MustConvertTo _ when cenv.g.langVersion.SupportsFeature LanguageFeature.AdditionalTypeDirectedConversions ->
         assert (cenv.g.langVersion.SupportsFeature LanguageFeature.AdditionalTypeDirectedConversions)
-        //if not canAdhoc then
-        //    AddCxTypeMustSubsumeType ContextInfo.NoContext env.DisplayEnv cenv.css m NoTrace reqdTy actualTy
+
         // 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
@@ -5575,15 +5576,16 @@ and TcPropagatingExprLeafThenConvert cenv overallTy actualTy (env: TcEnv) (* can
 /// 'processExpr' does the actual processing of the construct.
 ///
 /// Used for
-///  - tuple (exception is if overallTy is a tuple type, used to propagate structness from known type)
-///  - anon record (exception is if overallTy is an anon record type, similarly)
-///  - record (exception is (fun ty -> requiresCtor || haveCtor || isRecdTy cenv.g ty), similarly)
+///  - 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 TcPossiblyPropogatingExprLeafThenConvert isPropagating cenv (overallTy: OverallTy) (env: TcEnv) m processExpr =
     match overallTy with
     | MustConvertTo(_, reqdTy) when cenv.g.langVersion.SupportsFeature LanguageFeature.AdditionalTypeDirectedConversions && not (isPropagating reqdTy) ->
         TcNonPropagatingExprLeafThenConvert cenv overallTy env m (fun () ->
             let exprTy = NewInferenceType()
-            // Here 'processExpr' will do the unification with exprTy.
+
+            // Here 'processExpr' will eventually do the unification with exprTy.
             let expr, tpenv = processExpr exprTy
             expr, exprTy, tpenv)
     | _ ->
@@ -5601,8 +5603,10 @@ and TcPossiblyPropogatingExprLeafThenConvert isPropagating cenv (overallTy: Over
 and TcNonPropagatingExprLeafThenConvert 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 (* true  *) m expr
     expr2, tpenv
 
@@ -5750,7 +5754,7 @@ and TcExprUndelayed cenv (overallTy: OverallTy) env tpenv (synExpr: SynExpr) =
         expr, tpenv
 
     | SynExpr.Tuple (isExplicitStruct, args, _, m) ->
-        TcPossiblyPropogatingExprLeafThenConvert (isAnyTupleTy cenv.g) cenv overallTy env m (fun overallTy ->
+        TcPossiblyPropogatingExprLeafThenConvert (fun ty -> isAnyTupleTy cenv.g ty || isTyparTy cenv.g ty) cenv overallTy env m (fun overallTy ->
             let tupInfo, argTys = UnifyTupleTypeAndInferCharacteristics env.eContextInfo cenv env.DisplayEnv m overallTy isExplicitStruct args
 
             let flexes = argTys |> List.map (fun _ -> false)
@@ -5760,7 +5764,7 @@ and TcExprUndelayed cenv (overallTy: OverallTy) env tpenv (synExpr: SynExpr) =
         )
 
     | SynExpr.AnonRecd (isStruct, optOrigExpr, unsortedFieldExprs, mWholeExpr) ->
-        TcPossiblyPropogatingExprLeafThenConvert (isAnonRecdTy cenv.g) cenv overallTy env mWholeExpr (fun overallTy ->
+        TcPossiblyPropogatingExprLeafThenConvert (fun ty -> isAnonRecdTy cenv.g ty || isTyparTy cenv.g ty) cenv overallTy env mWholeExpr (fun overallTy ->
             TcAnonRecdExpr cenv overallTy env tpenv (isStruct, optOrigExpr, unsortedFieldExprs, mWholeExpr)
         )
 
@@ -5837,7 +5841,7 @@ and TcExprUndelayed cenv (overallTy: OverallTy) env tpenv (synExpr: SynExpr) =
       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
-      TcPossiblyPropogatingExprLeafThenConvert (fun ty -> requiresCtor || haveCtor || isRecdTy cenv.g ty) cenv overallTy env mWholeExpr (fun overallTy ->
+      TcPossiblyPropogatingExprLeafThenConvert (fun ty -> requiresCtor || haveCtor || isRecdTy cenv.g ty || isTyparTy cenv.g ty) cenv overallTy env mWholeExpr (fun overallTy ->
         TcRecdExpr cenv overallTy env tpenv (inherits, optOrigExpr, flds, mWholeExpr)
       )
 

src/fsharp/ConstraintSolver.fs

@@ -2253,7 +2253,7 @@ and CanMemberSigsMatchUpToCheck
       alwaysCheckReturn // always check the return type?
       (unifyTypes: TType -> TType -> OperationResult<TypeDirectedConversionUsed>)   // used to equate the formal method instantiation with the actual method instantiation for a generic method, and the return types
       (subsumeTypes: TType -> TType -> OperationResult<TypeDirectedConversionUsed>)  // used to compare the "obj" type 
-      (subsumeOrConvertTypes: TType -> TType -> OperationResult<TypeDirectedConversionUsed>) // used to convert the "return" for MustConvertTo
+      (subsumeOrConvertTypes: bool -> TType -> TType -> OperationResult<TypeDirectedConversionUsed>) // used to convert the "return" for MustConvertTo
       (subsumeOrConvertArg: CalledArg -> CallerArg<_> -> OperationResult<TypeDirectedConversionUsed>)    // used to convert the arguments
       (reqdRetTyOpt: OverallTy option) 
       (calledMeth: CalledMeth<_>): OperationResult<TypeDirectedConversionUsed> =
@@ -2354,9 +2354,9 @@ and CanMemberSigsMatchUpToCheck
                     match reqdRetTyOpt with
                     | Some _  when ( (* minfo.IsConstructor || *) not alwaysCheckReturn && isNil unnamedCalledOutArgs) ->
                         ResultD TypeDirectedConversionUsed.No
-                    | Some (MustConvertTo(_, reqdTy)) when g.langVersion.SupportsFeature LanguageFeature.AdditionalTypeDirectedConversions ->
+                    | Some (MustConvertTo(isMethodArg, reqdTy)) when g.langVersion.SupportsFeature LanguageFeature.AdditionalTypeDirectedConversions ->
                         let methodRetTy = calledMeth.CalledReturnTypeAfterOutArgTupling
-                        subsumeOrConvertTypes reqdTy methodRetTy
+                        subsumeOrConvertTypes isMethodArg reqdTy methodRetTy
                     | Some reqdRetTy ->
                         let methodRetTy = calledMeth.CalledReturnTypeAfterOutArgTupling
                         unifyTypes reqdRetTy.Commit methodRetTy
@@ -2464,9 +2464,9 @@ and TypesMustSubsume (csenv: ConstraintSolverEnv) ndeep trace cxsln m calledArgT
         return TypeDirectedConversionUsed.No
     }
 
-and ReturnTypesMustSubsumeOrConvert (csenv: ConstraintSolverEnv) ad ndeep trace cxsln isConstraint m reqdTy actualTy = 
+and ReturnTypesMustSubsumeOrConvert (csenv: ConstraintSolverEnv) ad ndeep trace cxsln isConstraint m isMethodArg reqdTy actualTy = 
     trackErrors {
-        let reqdTy, usesTDC, eqn = AdjustRequiredTypeForTypeDirectedConversions csenv.InfoReader ad false isConstraint reqdTy actualTy m
+        let reqdTy, usesTDC, eqn = AdjustRequiredTypeForTypeDirectedConversions csenv.InfoReader ad isMethodArg isConstraint reqdTy actualTy m
         match eqn with 
         | Some (ty1, ty2, msg) ->
             do! SolveTypeEqualsType csenv ndeep m trace cxsln ty1 ty2 
@@ -2981,7 +2981,7 @@ and ResolveOverloading
                                 else
                                     match reqdRetTy with
                                     | MustConvertTo(isMethodArg, reqdRetTy) when g.langVersion.SupportsFeature LanguageFeature.AdditionalTypeDirectedConversions ->
-                                        let! _usesTDC = ReturnTypesMustSubsumeOrConvert csenv ad ndeep trace cxsln isMethodArg m reqdRetTy actualRetTy
+                                        let! _usesTDC = ReturnTypesMustSubsumeOrConvert csenv ad ndeep trace cxsln isMethodArg m isMethodArg reqdRetTy actualRetTy
                                         return ()
                                     | _ ->
                                         let! _usesTDC = TypesEquiv csenv ndeep trace cxsln reqdRetTy.Commit actualRetTy

tests/fsharp/core/auto-widen/preview-default-warns/test.bsl

@@ -3,10 +3,6 @@ test.fsx(147,18,147,19): typecheck error FS3391: This expression uses the implic
 
 test.fsx(149,39,149,41): typecheck error FS3391: This expression uses the implicit conversion 'Xml.Linq.XNamespace.op_Implicit(namespaceName: string) : Xml.Linq.XNamespace' to convert type 'string' to type 'Xml.Linq.XNamespace'. See https://aka.ms/fsharp-implicit-convs. This warning may be disabled using '#nowarn "3391".
 
-test.fsx(172,18,172,21): typecheck error FS3391: This expression uses the implicit conversion 'static member Y.op_Implicit : y:Y -> X' to convert type 'Y' to type 'X'. See https://aka.ms/fsharp-implicit-convs. This warning may be disabled using '#nowarn "3391".
-
-test.fsx(172,18,172,21): typecheck error FS3391: This expression uses the implicit conversion 'static member Y.op_Implicit : y:Y -> X' to convert type 'Y' to type 'X'. See https://aka.ms/fsharp-implicit-convs. This warning may be disabled using '#nowarn "3391".
-
 test.fsx(178,20,178,21): typecheck error FS3391: This expression uses the implicit conversion 'static member C.op_Implicit : x:'T -> C<'T>' to convert type 'int' to type 'C<int>'. See https://aka.ms/fsharp-implicit-convs. This warning may be disabled using '#nowarn "3391".
 
 test.fsx(180,15,180,16): typecheck error FS3391: This expression uses the implicit conversion 'static member C.op_Implicit : x:'T -> C<'T>' to convert type 'int' to type 'C<int>'. See https://aka.ms/fsharp-implicit-convs. This warning may be disabled using '#nowarn "3391".
@@ -26,26 +22,10 @@ test.fsx(482,18,482,21): typecheck error FS3387: This expression has type 'B' an
    static member B.op_Implicit : x:B -> C
    static member C.op_Implicit : x:B -> C
 
-test.fsx(482,18,482,21): typecheck error FS3391: This expression uses the implicit conversion 'static member B.op_Implicit : x:B -> C' to convert type 'B' to type 'C'. See https://aka.ms/fsharp-implicit-convs. This warning may be disabled using '#nowarn "3391".
-
 test.fsx(482,18,482,21): typecheck error FS3387: This expression has type 'B' and is only made compatible with type 'C' through an ambiguous implicit conversion. Consider using an explicit call to 'op_Implicit'. The applicable implicit conversions are:
    static member B.op_Implicit : x:B -> C
    static member C.op_Implicit : x:B -> C
 
-test.fsx(482,18,482,21): typecheck error FS3391: This expression uses the implicit conversion 'static member B.op_Implicit : x:B -> C' to convert type 'B' to type 'C'. See https://aka.ms/fsharp-implicit-convs. This warning may be disabled using '#nowarn "3391".
-
-test.fsx(507,18,507,21): typecheck error FS3391: This expression uses the implicit conversion 'static member C.op_Implicit : x:B -> C' to convert type 'B' to type 'C'. See https://aka.ms/fsharp-implicit-convs. This warning may be disabled using '#nowarn "3391".
-
-test.fsx(507,18,507,21): typecheck error FS3391: This expression uses the implicit conversion 'static member C.op_Implicit : x:B -> C' to convert type 'B' to type 'C'. See https://aka.ms/fsharp-implicit-convs. This warning may be disabled using '#nowarn "3391".
-
-test.fsx(519,18,519,21): typecheck error FS3391: This expression uses the implicit conversion 'static member B.op_Implicit : x:B -> C' to convert type 'B' to type 'C'. See https://aka.ms/fsharp-implicit-convs. This warning may be disabled using '#nowarn "3391".
-
-test.fsx(519,18,519,21): typecheck error FS3391: This expression uses the implicit conversion 'static member B.op_Implicit : x:B -> C' to convert type 'B' to type 'C'. See https://aka.ms/fsharp-implicit-convs. This warning may be disabled using '#nowarn "3391".
-
-test.fsx(538,18,538,21): typecheck error FS3391: This expression uses the implicit conversion 'static member C.op_Implicit : x:B -> C' to convert type 'B' to type 'C'. See https://aka.ms/fsharp-implicit-convs. This warning may be disabled using '#nowarn "3391".
-
-test.fsx(538,18,538,21): typecheck error FS3391: This expression uses the implicit conversion 'static member C.op_Implicit : x:B -> C' to convert type 'B' to type 'C'. See https://aka.ms/fsharp-implicit-convs. This warning may be disabled using '#nowarn "3391".
-
 test.fsx(546,30,546,31): typecheck error FS0001: This expression was expected to have type
     'float32'    
 but here has type

tests/fsharp/core/auto-widen/preview/test.bsl

@@ -165,9 +165,9 @@ test.fsx(165,18,165,19): typecheck error FS3390: This expression uses the implic
 
 test.fsx(165,18,165,19): typecheck error FS3388: This expression implicitly converts type 'int' to type 'C'. See https://aka.ms/fsharp-implicit-convs.
 
-test.fsx(172,18,172,21): typecheck error FS3391: This expression uses the implicit conversion 'static member Y.op_Implicit : y:Y -> X' to convert type 'Y' to type 'X'. See https://aka.ms/fsharp-implicit-convs. This warning may be disabled using '#nowarn "3391".
+test.fsx(172,18,172,21): typecheck error FS3390: This expression uses the implicit conversion 'static member Y.op_Implicit : y:Y -> X' to convert type 'Y' to type 'X'.
 
-test.fsx(172,18,172,21): typecheck error FS3391: This expression uses the implicit conversion 'static member Y.op_Implicit : y:Y -> X' to convert type 'Y' to type 'X'. See https://aka.ms/fsharp-implicit-convs. This warning may be disabled using '#nowarn "3391".
+test.fsx(172,18,172,21): typecheck error FS3390: This expression uses the implicit conversion 'static member Y.op_Implicit : y:Y -> X' to convert type 'Y' to type 'X'.
 
 test.fsx(178,20,178,21): typecheck error FS3391: This expression uses the implicit conversion 'static member C.op_Implicit : x:'T -> C<'T>' to convert type 'int' to type 'C<int>'. See https://aka.ms/fsharp-implicit-convs. This warning may be disabled using '#nowarn "3391".
 
@@ -602,25 +602,25 @@ test.fsx(482,18,482,21): typecheck error FS3387: This expression has type 'B' an
    static member B.op_Implicit : x:B -> C
    static member C.op_Implicit : x:B -> C
 
-test.fsx(482,18,482,21): typecheck error FS3391: This expression uses the implicit conversion 'static member B.op_Implicit : x:B -> C' to convert type 'B' to type 'C'. See https://aka.ms/fsharp-implicit-convs. This warning may be disabled using '#nowarn "3391".
+test.fsx(482,18,482,21): typecheck error FS3390: This expression uses the implicit conversion 'static member B.op_Implicit : x:B -> C' to convert type 'B' to type 'C'.
 
 test.fsx(482,18,482,21): typecheck error FS3387: This expression has type 'B' and is only made compatible with type 'C' through an ambiguous implicit conversion. Consider using an explicit call to 'op_Implicit'. The applicable implicit conversions are:
    static member B.op_Implicit : x:B -> C
    static member C.op_Implicit : x:B -> C
 
-test.fsx(482,18,482,21): typecheck error FS3391: This expression uses the implicit conversion 'static member B.op_Implicit : x:B -> C' to convert type 'B' to type 'C'. See https://aka.ms/fsharp-implicit-convs. This warning may be disabled using '#nowarn "3391".
+test.fsx(482,18,482,21): typecheck error FS3390: This expression uses the implicit conversion 'static member B.op_Implicit : x:B -> C' to convert type 'B' to type 'C'.
 
-test.fsx(507,18,507,21): typecheck error FS3391: This expression uses the implicit conversion 'static member C.op_Implicit : x:B -> C' to convert type 'B' to type 'C'. See https://aka.ms/fsharp-implicit-convs. This warning may be disabled using '#nowarn "3391".
+test.fsx(507,18,507,21): typecheck error FS3390: This expression uses the implicit conversion 'static member C.op_Implicit : x:B -> C' to convert type 'B' to type 'C'.
 
-test.fsx(507,18,507,21): typecheck error FS3391: This expression uses the implicit conversion 'static member C.op_Implicit : x:B -> C' to convert type 'B' to type 'C'. See https://aka.ms/fsharp-implicit-convs. This warning may be disabled using '#nowarn "3391".
+test.fsx(507,18,507,21): typecheck error FS3390: This expression uses the implicit conversion 'static member C.op_Implicit : x:B -> C' to convert type 'B' to type 'C'.
 
-test.fsx(519,18,519,21): typecheck error FS3391: This expression uses the implicit conversion 'static member B.op_Implicit : x:B -> C' to convert type 'B' to type 'C'. See https://aka.ms/fsharp-implicit-convs. This warning may be disabled using '#nowarn "3391".
+test.fsx(519,18,519,21): typecheck error FS3390: This expression uses the implicit conversion 'static member B.op_Implicit : x:B -> C' to convert type 'B' to type 'C'.
 
-test.fsx(519,18,519,21): typecheck error FS3391: This expression uses the implicit conversion 'static member B.op_Implicit : x:B -> C' to convert type 'B' to type 'C'. See https://aka.ms/fsharp-implicit-convs. This warning may be disabled using '#nowarn "3391".
+test.fsx(519,18,519,21): typecheck error FS3390: This expression uses the implicit conversion 'static member B.op_Implicit : x:B -> C' to convert type 'B' to type 'C'.
 
-test.fsx(538,18,538,21): typecheck error FS3391: This expression uses the implicit conversion 'static member C.op_Implicit : x:B -> C' to convert type 'B' to type 'C'. See https://aka.ms/fsharp-implicit-convs. This warning may be disabled using '#nowarn "3391".
+test.fsx(538,18,538,21): typecheck error FS3390: This expression uses the implicit conversion 'static member C.op_Implicit : x:B -> C' to convert type 'B' to type 'C'.
 
-test.fsx(538,18,538,21): typecheck error FS3391: This expression uses the implicit conversion 'static member C.op_Implicit : x:B -> C' to convert type 'B' to type 'C'. See https://aka.ms/fsharp-implicit-convs. This warning may be disabled using '#nowarn "3391".
+test.fsx(538,18,538,21): typecheck error FS3390: This expression uses the implicit conversion 'static member C.op_Implicit : x:B -> C' to convert type 'B' to type 'C'.
 
 test.fsx(543,30,543,31): typecheck error FS0001: This expression was expected to have type
     'float32'    

tests/fsharp/core/auto-widen/preview/test.fsx

@@ -169,7 +169,7 @@ module ConvertViaOpImplicit5 =
         static member M1(x:X) = 1
     type Y() =
         static member op_Implicit(y:Y) = X()
-    let x = X.M1(Y())
+    let x = X.M1(Y()) // Note this counts as a use in a method arg position, when processing the return type of 'Y'
 
 module ConvertViaOpImplicitGeneric =
     type C<'T>() = 
@@ -543,6 +543,54 @@ module TestNoWidening =
     let x4 : float32 list = [1;2;3;4]
     let x5 : float64 list = [1.0f;2.0f;3.0f;4.0f]
 #endif
+
+
+module TestRecursiveInferenceForPropagatingCases =
+
+    module Bug1 = 
+        type RecordTypeA =
+            { Name: string
+              FieldA: string }
+
+        type RecordTypeB =
+            { Name: string
+              FieldB: int}
+
+        // When the record expression is encountered, it must commit to "RecordTypeA"
+        // because the return type of "f" is, at that point, a variable type
+        // and must be correctly inferred by the point where we process the subsequence 
+        // dot-notation "f().Name"
+        let rec f() =
+            { Name=""
+              FieldA =  f().Name  
+            }
+
+    module Bug2 = 
+
+        type RecordTypeB =
+            { Name: string
+              FieldB: int}
+
+        // When the anonymous record expression is encountered, it must commit to "RecordTypeA".
+        // The return type of "f" is, at that point, a variable type
+        // and must be correctly inferred by the point where we process the subsequence 
+        // dot-notation "f().Name"
+        let rec f() =
+            {| Name=""
+               FieldA =  f().Name  
+            |}
+
+    module Test3 = 
+
+        // Check the return type of 'f' is known by the time we process "f().Length"
+        let rec f() = [ f().Length  ]
+
+    module Test4 = 
+
+        // Check the return type of 'f' is known by the time we process "f().CompareTo(y)"
+        let rec f() = { new System.IComparable with member x.CompareTo(y) = f().CompareTo(y) }
+
+
 printfn "test done"
 
 let aa =