Fixes #3170 (#3173)

* cleanup

* Fixes #3170

* Adding a test

src/fsharp/TypeChecker.fs

@@ -9931,7 +9931,7 @@ and TcMethodApplication
 and TcUnnamedMethodArgs cenv env lambdaPropagationInfo tpenv args =  
     List.mapiFoldSquared (TcUnnamedMethodArg cenv env) (lambdaPropagationInfo,tpenv) args 
 
-and TcUnnamedMethodArg  cenv env  (lambdaPropagationInfo,tpenv) (i,j,CallerArg(argTy,mArg,isOpt,argExpr)) = 
+and TcUnnamedMethodArg cenv env  (lambdaPropagationInfo,tpenv) (i,j,CallerArg(argTy,mArg,isOpt,argExpr)) = 
     // Try to find the lambda propagation info for the corresponding unnamed argument at this position
     let lambdaPropagationInfoForArg = 
         [| for (unnamedInfo,_) in lambdaPropagationInfo -> 
@@ -9958,14 +9958,14 @@ and TcMethodArg  cenv env  (lambdaPropagationInfo,tpenv) (lambdaPropagationInfoF
     // Apply the F# 3.1 rule for extracting information for lambdas
     //
     // Before we check the argument, check to see if we can propagate info from a called lambda expression into the arguments of a received lambda
-    begin
-        if lambdaPropagationInfoForArg.Length > 0 then 
-            let allOverloadsAreFuncOrMismatchForThisArg = 
-                lambdaPropagationInfoForArg |> Array.forall (function ArgDoesNotMatch | CallerLambdaHasArgTypes _ -> true | NoInfo | CalledArgMatchesType _ -> false)
-
-            if allOverloadsAreFuncOrMismatchForThisArg then 
-              let overloadsWhichAreFuncAtThisPosition = lambdaPropagationInfoForArg |> Array.choose (function CallerLambdaHasArgTypes r -> Some (List.toArray r) | _ -> None)
-              if overloadsWhichAreFuncAtThisPosition.Length > 0 then 
+    if lambdaPropagationInfoForArg.Length > 0 then 
+        let allOverloadsAreNotCalledArgMatchesForThisArg = 
+            lambdaPropagationInfoForArg 
+            |> Array.forall (function ArgDoesNotMatch | CallerLambdaHasArgTypes _ | NoInfo -> true | CalledArgMatchesType _ -> false)
+
+        if allOverloadsAreNotCalledArgMatchesForThisArg then 
+            let overloadsWhichAreFuncAtThisPosition = lambdaPropagationInfoForArg |> Array.choose (function CallerLambdaHasArgTypes r -> Some (List.toArray r) | _ -> None)
+            if overloadsWhichAreFuncAtThisPosition.Length > 0 then 
                 let minFuncArity = overloadsWhichAreFuncAtThisPosition |> Array.minBy Array.length |> Array.length
                 let prefixOfLambdaArgsForEachOverload = overloadsWhichAreFuncAtThisPosition |> Array.map (Array.take minFuncArity)
           
@@ -9987,7 +9987,6 @@ and TcMethodArg  cenv env  (lambdaPropagationInfo,tpenv) (lambdaPropagationInfoF
                                         loop callerLambdaRangeTy (lambdaVarNum + 1)
                                 | None -> ()
                     loop argTy 0
-    end
 
     let e',tpenv = TcExpr cenv argTy env tpenv argExpr
 

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

+// #Conformance #DeclarationElements #MemberDefinitions #Overloading 
+// inference failed for Linq .ToDictionary(fun,fun) - #3170
+
+open System
+open System.Linq
+
+type GuidWrapper = GuidWrapper of Guid
+    with member x.Id =
+            let (GuidWrapper id) = x
+            x
+
+let id = Guid.NewGuid()
+let map = [GuidWrapper id, GuidWrapper id] |> Map
+
+let y = map.ToDictionary((fun m -> m.Key.Id), (fun m -> m.Value.Id))
+
+printfn "%A" y
+
+exit 0

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

@@ -24,6 +24,8 @@ NOMONO,NoMT	SOURCE=ConsumeOverloadGenericMethods.fs SCFLAGS="-r:lib.dll" PRECMD=
 	SOURCE=OperatorOverloading04.fs						# OperatorOverloading04.fs
 	SOURCE=E_OperatorOverloading01.fs SCFLAGS="--test:ErrorRanges"		# E_OperatorOverloading01.fs
 
+	SOURCE=InferenceForLambdaArgs.fs						# InferenceForLambdaArgs.fs
+
 	SOURCE=SlowOverloadResolution.fs						# SlowOverloadResolution.fs
 
 	SOURCE=E_OverloadCurriedFunc.fs		# E_OverloadCurriedFunc.fs