Revert dotnet#4173 (i.e. reapply dotnet#1650 and dotnet#3366)"

This reverts commit f9893b6.

src/fsharp/ConstraintSolver.fs

@@ -372,6 +372,7 @@ let ShowAccessDomain ad =
 // Solve
 
 exception NonRigidTypar of DisplayEnv * string option * range * TType * TType * range
+exception LocallyAbortOperationThatFailsToResolveOverload
 exception LocallyAbortOperationThatLosesAbbrevs 
 let localAbortD = ErrorD LocallyAbortOperationThatLosesAbbrevs
 
@@ -740,19 +741,19 @@ and solveTypMeetsTyparConstraints (csenv:ConstraintSolverEnv) ndeep m2 trace ty
               | Some destTypar ->
                   AddConstraint csenv ndeep m2 trace destTypar (TyparConstraint.DefaultsTo(priority, dty, m))
 
-      | TyparConstraint.SupportsNull m2                 -> SolveTypSupportsNull               csenv ndeep m2 trace ty
-      | TyparConstraint.IsEnum(underlying, m2)          -> SolveTypIsEnum                     csenv ndeep m2 trace ty underlying
-      | TyparConstraint.SupportsComparison(m2)          -> SolveTypeSupportsComparison        csenv ndeep m2 trace ty
-      | TyparConstraint.SupportsEquality(m2)            -> SolveTypSupportsEquality           csenv ndeep m2 trace ty
+      | TyparConstraint.SupportsNull m2                -> SolveTypSupportsNull               csenv ndeep m2 trace ty
+      | TyparConstraint.IsEnum(underlying, m2)         -> SolveTypIsEnum                     csenv ndeep m2 trace ty underlying
+      | TyparConstraint.SupportsComparison(m2)         -> SolveTypeSupportsComparison        csenv ndeep m2 trace ty
+      | TyparConstraint.SupportsEquality(m2)           -> SolveTypSupportsEquality           csenv ndeep m2 trace ty
       | TyparConstraint.IsDelegate(aty, bty, m2)        -> SolveTypIsDelegate                 csenv ndeep m2 trace ty aty bty
-      | TyparConstraint.IsNonNullableStruct m2          -> SolveTypIsNonNullableValueType     csenv ndeep m2 trace ty
-      | TyparConstraint.IsUnmanaged m2                  -> SolveTypIsUnmanaged                csenv ndeep m2 trace ty
-      | TyparConstraint.IsReferenceType m2              -> SolveTypIsReferenceType            csenv ndeep m2 trace ty
-      | TyparConstraint.RequiresDefaultConstructor m2   -> SolveTypRequiresDefaultConstructor csenv ndeep m2 trace ty
+      | TyparConstraint.IsNonNullableStruct m2         -> SolveTypIsNonNullableValueType     csenv ndeep m2 trace ty
+      | TyparConstraint.IsUnmanaged m2                 -> SolveTypIsUnmanaged                csenv ndeep m2 trace ty
+      | TyparConstraint.IsReferenceType m2             -> SolveTypIsReferenceType            csenv ndeep m2 trace ty
+      | TyparConstraint.RequiresDefaultConstructor m2  -> SolveTypRequiresDefaultConstructor csenv ndeep m2 trace ty
       | TyparConstraint.SimpleChoice(tys, m2)           -> SolveTypChoice                     csenv ndeep m2 trace ty tys
       | TyparConstraint.CoercesTo(ty2, m2)              -> SolveTypSubsumesTypKeepAbbrevs     csenv ndeep m2 trace None ty2 ty
-      | TyparConstraint.MayResolveMember(traitInfo, m2) ->
-          SolveMemberConstraint csenv false ndeep m2 trace traitInfo ++ (fun _ -> CompleteD)
+      | TyparConstraint.MayResolveMember(traitInfo, m2) -> 
+          SolveMemberConstraint csenv false false ndeep m2 trace traitInfo ++ (fun _ -> CompleteD) 
     )))
 
 
@@ -762,14 +763,15 @@ and SolveTypEqualsTyp (csenv:ConstraintSolverEnv) ndeep m2 (trace: OptionalTrace
     let ndeep = ndeep + 1
     let aenv = csenv.EquivEnv
     let g = csenv.g
-    if ty1 === ty2 then CompleteD else
 
     match cxsln with
     | Some (traitInfo, traitSln) when traitInfo.Solution.IsNone -> 
         // If this is an overload resolution at this point it's safe to assume the candidate member being evaluated solves this member constraint.
         TransactMemberConstraintSolution traitInfo trace traitSln
     | _ -> ()
 
+    if ty1 === ty2 then CompleteD else
+
     let canShortcut = not trace.HasTrace
     let sty1 = stripTyEqnsA csenv.g canShortcut ty1
     let sty2 = stripTyEqnsA csenv.g canShortcut ty2
@@ -943,7 +945,7 @@ and SolveDimensionlessNumericType (csenv:ConstraintSolverEnv) ndeep m2 trace ty
 /// We pretend int and other types support a number of operators.  In the actual IL for mscorlib they 
 /// don't, however the type-directed static optimization rules in the library code that makes use of this 
 /// will deal with the problem. 
-and SolveMemberConstraint (csenv:ConstraintSolverEnv) permitWeakResolution ndeep m2 trace (TTrait(tys,nm,memFlags,argtys,rty,sln)) :  OperationResult<bool> =
+and SolveMemberConstraint (csenv:ConstraintSolverEnv) ignoreUnresolvedOverload permitWeakResolution ndeep m2 trace (TTrait(tys, nm, memFlags, argtys, rty, sln)): OperationResult<bool> =
     // Do not re-solve if already solved
     if sln.Value.IsSome then ResultD true else
     let g = csenv.g
@@ -1300,9 +1302,12 @@ and SolveMemberConstraint (csenv:ConstraintSolverEnv) permitWeakResolution ndeep
                   let frees = GetFreeTyparsOfMemberConstraint csenv traitInfo
 
                   // If there's nothing left to learn then raise the errors 
-                  (if (permitWeakResolution && isNil support) || isNil frees then errors
-                  // Otherwise re-record the trait waiting for canonicalization 
-                   else AddMemberConstraint csenv ndeep m2 trace traitInfo support frees) ++ (fun () -> ResultD TTraitUnsolved)
+                  (if (permitWeakResolution && isNil support) || isNil frees then errors  
+                   // Otherwise re-record the trait waiting for canonicalization 
+                   else AddMemberConstraint csenv ndeep m2 trace traitInfo support frees) ++ (fun () -> 
+                       match errors with
+                       | ErrorResult (_, UnresolvedOverloading _) when not ignoreUnresolvedOverload && (not (nm = "op_Explicit" || nm = "op_Implicit")) -> ErrorD LocallyAbortOperationThatFailsToResolveOverload
+                       | _ -> ResultD TTraitUnsolved)
     ) 
     ++ 
     (fun res -> RecordMemberConstraintSolution csenv.SolverState m trace traitInfo res))
@@ -1444,7 +1449,7 @@ and SolveRelevantMemberConstraintsForTypar (csenv:ConstraintSolverEnv) ndeep per
     cxs 
     |> AtLeastOneD (fun (traitInfo, m2) -> 
         let csenv = { csenv with m = m2 }
-        SolveMemberConstraint csenv permitWeakResolution (ndeep+1) m2 trace traitInfo)
+        SolveMemberConstraint csenv true permitWeakResolution (ndeep+1) m2 trace traitInfo)
 
 and CanonicalizeRelevantMemberConstraints (csenv:ConstraintSolverEnv) ndeep trace tps =
     SolveRelevantMemberConstraints csenv ndeep true trace tps
@@ -1959,18 +1964,22 @@ and CanMemberSigsMatchUpToCheck
 // to allow us to report the outer types involved in the constraint 
 and private SolveTypSubsumesTypWithReport (csenv:ConstraintSolverEnv) ndeep m trace cxsln ty1 ty2 =
     TryD (fun () -> SolveTypSubsumesTypKeepAbbrevs csenv ndeep m trace cxsln ty1 ty2)
-         (fun res ->
-            match csenv.eContextInfo with
-            | ContextInfo.RuntimeTypeTest isOperator ->
-                // test if we can cast other way around
+         (function
+          | LocallyAbortOperationThatFailsToResolveOverload -> CompleteD
+          | res ->
+                match csenv.eContextInfo with
+                | ContextInfo.RuntimeTypeTest isOperator ->
+                    // test if we can cast other way around
                     match CollectThenUndo (fun newTrace -> SolveTypSubsumesTypKeepAbbrevs csenv ndeep m (OptionalTrace.WithTrace newTrace) cxsln ty2 ty1) with 
                     | OkResult _ -> ErrorD (ErrorsFromAddingSubsumptionConstraint(csenv.g, csenv.DisplayEnv, ty1, ty2, res, ContextInfo.DowncastUsedInsteadOfUpcast isOperator, m))
                     | _ -> ErrorD (ErrorsFromAddingSubsumptionConstraint(csenv.g, csenv.DisplayEnv, ty1, ty2, res, ContextInfo.NoContext, m))
                 | _ -> ErrorD (ErrorsFromAddingSubsumptionConstraint(csenv.g, csenv.DisplayEnv, ty1, ty2, res, csenv.eContextInfo, m)))
 
 and private SolveTypEqualsTypWithReport (csenv:ConstraintSolverEnv) ndeep  m trace cxsln ty1 ty2 = 
     TryD (fun () -> SolveTypEqualsTypKeepAbbrevsWithCxsln csenv ndeep m trace cxsln ty1 ty2)
-         (fun res -> ErrorD (ErrorFromAddingTypeEquation(csenv.g, csenv.DisplayEnv, ty1, ty2, res, m)))
+         (function
+          | LocallyAbortOperationThatFailsToResolveOverload -> CompleteD
+          | res -> ErrorD (ErrorFromAddingTypeEquation(csenv.g, csenv.DisplayEnv, ty1, ty2, res, m)))
 
 and ArgsMustSubsumeOrConvert 
         (csenv:ConstraintSolverEnv)
@@ -2536,7 +2545,7 @@ let AddCxTypeMustSubsumeType contextInfo denv css m trace ty1 ty2 =
     |> RaiseOperationResult
 
 let AddCxMethodConstraint denv css m trace traitInfo  =
-    TryD (fun () -> SolveMemberConstraint (MakeConstraintSolverEnv ContextInfo.NoContext css m denv) false 0 m trace traitInfo ++ (fun _ -> CompleteD))
+    TryD (fun () -> SolveMemberConstraint (MakeConstraintSolverEnv ContextInfo.NoContext css m denv) true false 0 m trace traitInfo ++ (fun _ -> CompleteD))
          (fun res -> ErrorD (ErrorFromAddingConstraint(denv, res, m)))
     |> RaiseOperationResult
 
@@ -2594,7 +2603,7 @@ let CodegenWitnessThatTypSupportsTraitConstraint tcVal g amap m (traitInfo:Trait
           InfoReader = new InfoReader(g, amap) }
 
     let csenv = MakeConstraintSolverEnv ContextInfo.NoContext css m (DisplayEnv.Empty g)
-    SolveMemberConstraint csenv true 0 m NoTrace traitInfo ++ (fun _res -> 
+    SolveMemberConstraint csenv true true 0 m NoTrace traitInfo ++ (fun _res -> 
         let sln = 
               match traitInfo.Solution with 
               | None -> Choice4Of4()
@@ -2719,4 +2728,5 @@ let IsApplicableMethApprox g amap m (minfo:MethInfo) availObjTy =
             |> CommitOperationResult
         | _ -> true
     else
-        true
+        true
+

tests/fsharpqa/Source/Conformance/DeclarationElements/MemberDefinitions/OverloadingMembers/SlowOverloadResolution.fs

@@ -1,6 +1,6 @@
 // #Conformance #DeclarationElements #MemberDefinitions #Overloading 
 // https://github.com/Microsoft/visualfsharp/issues/351 - slow overlaod resolution
-//<Expects id="FS0001" status="error">No overloads match</Expects>
+//<Expects id="FS0003" status="error">This value is not a function and cannot be applied</Expects>
 type Switcher = Switcher
 
 let inline checker< ^s, ^r when (^s or ^r) : (static member pass : ^r -> unit)> (s : ^s) (r : ^r) = ()
@@ -22,4 +22,4 @@ let main argv =
     let res : unit = format () "text" 5 "more text" ()
     printfn "%A" res
     System.Console.ReadKey()
-    0 // return an integer exit code
+    0 // return an integer exit code

tests/fsharpqa/Source/Conformance/DeclarationElements/MemberDefinitions/OverloadingMembers/env.lst

@@ -27,8 +27,6 @@ NOMONO,NoMT	SOURCE=ConsumeOverloadGenericMethods.fs SCFLAGS="-r:lib.dll" PRECMD=
 	SOURCE=InferenceForLambdaArgs.fs						# InferenceForLambdaArgs.fs
 
 	SOURCE=SlowOverloadResolution.fs						# SlowOverloadResolution.fs
-	SOURCE=RecursiveOverload01.fs							# RecursiveOverload01.fs
-	SOURCE=OverloadsAndSRTPs01.fs							# OverloadsAndSRTPs01.fs
 
 	SOURCE=E_OverloadCurriedFunc.fs		# E_OverloadCurriedFunc.fs
 	SOURCE=NoWarningWhenOverloadingInSubClass01.fs SCFLAGS="--warnaserror"		# NoWarningWhenOverloadingInSubClass01.fs