Take double conversions into account for overload resolution

Fixes test failures for cases where separate overloads have args like Nullable<int> and Nullable<int64> in the same position

src/Compiler/Checking/CheckExpressions.fs

@@ -780,7 +780,7 @@ let UnifyOverallType cenv (env: TcEnv) m overallTy actualTy =
             | None -> ()
 
             match usesTDC with
-            | TypeDirectedConversionUsed.Yes warn -> warning(warn env.DisplayEnv)
+            | TypeDirectedConversionUsed.Yes(warn, _) -> warning(warn env.DisplayEnv)
             | TypeDirectedConversionUsed.No -> ()
 
             if AddCxTypeMustSubsumeTypeUndoIfFailed env.DisplayEnv cenv.css m reqdTy2 actualTy then

src/Compiler/Checking/ConstraintSolver.fs

@@ -2738,7 +2738,7 @@ and ArgsMustSubsumeOrConvert
         msg csenv.DisplayEnv
     | None -> ()
     match usesTDC with 
-    | TypeDirectedConversionUsed.Yes warn -> do! WarnD(warn csenv.DisplayEnv)
+    | TypeDirectedConversionUsed.Yes(warn, _) -> do! WarnD(warn csenv.DisplayEnv)
     | TypeDirectedConversionUsed.No -> ()
     do! SolveTypeSubsumesTypeWithReport csenv ndeep m trace cxsln (Some calledArg.CalledArgumentType) calledArgTy callerArg.CallerArgumentType
     if calledArg.IsParamArray && isArray1DTy g calledArgTy && not (isArray1DTy g callerArg.CallerArgumentType) then 
@@ -2769,7 +2769,7 @@ and ArgsMustSubsumeOrConvertWithContextualReport
             msg csenv.DisplayEnv
         | None -> ()
         match usesTDC with 
-        | TypeDirectedConversionUsed.Yes warn -> do! WarnD(warn csenv.DisplayEnv)
+        | TypeDirectedConversionUsed.Yes(warn, _) -> do! WarnD(warn csenv.DisplayEnv)
         | TypeDirectedConversionUsed.No -> ()
         do! SolveTypeSubsumesTypeWithWrappedContextualReport csenv ndeep m trace cxsln (Some calledArg.CalledArgumentType) calledArgTy callerArgTy (fun e -> ArgDoesNotMatchError(e :?> _, calledMeth, calledArg, callerArg))  
         return usesTDC
@@ -2796,7 +2796,7 @@ and ReturnTypesMustSubsumeOrConvert (csenv: ConstraintSolverEnv) ad ndeep trace
             msg csenv.DisplayEnv
         | None -> ()
         match usesTDC with 
-        | TypeDirectedConversionUsed.Yes warn -> do! WarnD(warn csenv.DisplayEnv)
+        | TypeDirectedConversionUsed.Yes(warn, _) -> do! WarnD(warn csenv.DisplayEnv)
         | TypeDirectedConversionUsed.No -> ()
         do! SolveTypeSubsumesTypeWithReport csenv ndeep m trace cxsln None reqdTy actualTy 
         return usesTDC
@@ -2813,7 +2813,7 @@ and ArgsEquivOrConvert (csenv: ConstraintSolverEnv) ad ndeep trace cxsln isConst
             msg csenv.DisplayEnv
         | None -> ()
         match usesTDC with 
-        | TypeDirectedConversionUsed.Yes warn -> do! WarnD(warn csenv.DisplayEnv)
+        | TypeDirectedConversionUsed.Yes(warn, _) -> do! WarnD(warn csenv.DisplayEnv)
         | TypeDirectedConversionUsed.No -> ()
         if not (typeEquiv csenv.g calledArgTy callerArgTy) then 
             return! ErrorD(Error(FSComp.SR.csArgumentTypesDoNotMatch(), m))
@@ -3223,6 +3223,10 @@ and GetMostApplicableOverload csenv ndeep candidates applicableMeths calledMethG
         // Prefer methods that don't use type-directed conversion
         let c = compare (match usesTDC1 with TypeDirectedConversionUsed.No -> 1 | _ -> 0) (match usesTDC2 with TypeDirectedConversionUsed.No -> 1 | _ -> 0)
         if c <> 0 then c else
+
+        // Prefer methods that need less type-directed conversion
+        let c = compare (match usesTDC1 with TypeDirectedConversionUsed.Yes(_, false) -> 1 | _ -> 0) (match usesTDC2 with TypeDirectedConversionUsed.Yes(_, false) -> 1 | _ -> 0)
+        if c <> 0 then c else
 
         // Prefer methods that don't give "this code is less generic" warnings
         // Note: Relies on 'compare' respecting true > false

src/Compiler/Checking/MethodCalls.fs

@@ -236,12 +236,15 @@ type TypeDirectedConversion =
 
 [<RequireQualifiedAccess>]
 type TypeDirectedConversionUsed =
-    | Yes of (DisplayEnv -> exn)
+    | Yes of (DisplayEnv -> exn) * isDoubleConversion: bool
     | No
     static member Combine a b =
-        match a with 
-        | Yes _ -> a
-        | No -> b
+        match a, b with 
+        | Yes(_,true), _ -> a
+        | _, Yes(_,true) -> b
+        | Yes _, _ -> a
+        | _, Yes _ -> b
+        | No, No -> a
 
 let MapCombineTDCD mapper xs =
     MapReduceD mapper TypeDirectedConversionUsed.No TypeDirectedConversionUsed.Combine xs
@@ -279,33 +282,33 @@ let rec AdjustRequiredTypeForTypeDirectedConversions (infoReader: InfoReader) ad
 
     // Adhoc int32 --> int64
     elif g.langVersion.SupportsFeature LanguageFeature.AdditionalTypeDirectedConversions && typeEquiv g g.int64_ty reqdTy && typeEquiv g g.int32_ty actualTy then 
-        g.int32_ty, TypeDirectedConversionUsed.Yes(warn TypeDirectedConversion.BuiltIn), None
+        g.int32_ty, TypeDirectedConversionUsed.Yes(warn TypeDirectedConversion.BuiltIn, false), None
 
     // Adhoc int32 --> nativeint
     elif g.langVersion.SupportsFeature LanguageFeature.AdditionalTypeDirectedConversions && typeEquiv g g.nativeint_ty reqdTy && typeEquiv g g.int32_ty actualTy then 
-        g.int32_ty, TypeDirectedConversionUsed.Yes(warn TypeDirectedConversion.BuiltIn), None
+        g.int32_ty, TypeDirectedConversionUsed.Yes(warn TypeDirectedConversion.BuiltIn, false), None
 
     // Adhoc int32 --> float64
     elif g.langVersion.SupportsFeature LanguageFeature.AdditionalTypeDirectedConversions && typeEquiv g g.float_ty reqdTy && typeEquiv g g.int32_ty actualTy then 
-        g.int32_ty, TypeDirectedConversionUsed.Yes(warn TypeDirectedConversion.BuiltIn), None
+        g.int32_ty, TypeDirectedConversionUsed.Yes(warn TypeDirectedConversion.BuiltIn, false), None
 
     elif g.langVersion.SupportsFeature LanguageFeature.NullableOptionalInterop && isMethodArg && isNullableTy g reqdTy && not (isNullableTy g actualTy) then 
         let underlyingTy = destNullableTy g reqdTy
         // shortcut
         if typeEquiv g underlyingTy actualTy then
-            actualTy, TypeDirectedConversionUsed.Yes(warn TypeDirectedConversion.BuiltIn), None
+            actualTy, TypeDirectedConversionUsed.Yes(warn TypeDirectedConversion.BuiltIn, false), None
         else
             let adjustedTy, _, _ = AdjustRequiredTypeForTypeDirectedConversions infoReader ad isMethodArg isConstraint underlyingTy actualTy m
             if typeEquiv g adjustedTy actualTy then 
-                actualTy, TypeDirectedConversionUsed.Yes(warn TypeDirectedConversion.BuiltIn), None
+                actualTy, TypeDirectedConversionUsed.Yes(warn TypeDirectedConversion.BuiltIn, true), None
             else 
                 reqdTy, TypeDirectedConversionUsed.No, None
 
     // Adhoc based on op_Implicit, perhaps returing a new equational type constraint to 
     // eliminate articifical constrained type variables.
     elif g.langVersion.SupportsFeature LanguageFeature.AdditionalTypeDirectedConversions then
          match TryFindRelevantImplicitConversion infoReader ad reqdTy actualTy m with
-         | Some (minfo, _staticTy, eqn) -> actualTy, TypeDirectedConversionUsed.Yes(warn (TypeDirectedConversion.Implicit minfo)), Some eqn
+         | Some (minfo, _staticTy, eqn) -> actualTy, TypeDirectedConversionUsed.Yes(warn (TypeDirectedConversion.Implicit minfo), false), Some eqn
          | None -> reqdTy, TypeDirectedConversionUsed.No, None
 
     else reqdTy, TypeDirectedConversionUsed.No, None

src/Compiler/Checking/MethodCalls.fsi

@@ -119,7 +119,7 @@ type CallerArgs<'T> =
 /// has been used in F# code
 [<RequireQualifiedAccess>]
 type TypeDirectedConversionUsed =
-    | Yes of (DisplayEnv -> exn)
+    | Yes of (DisplayEnv -> exn) * isDoubleConversion: bool
     | No
 
     static member Combine: TypeDirectedConversionUsed -> TypeDirectedConversionUsed -> TypeDirectedConversionUsed