Improve error reporting: property setter in constructor expression - fixes #1112

Author: forki

src/fsharp/ConstraintSolver.fs

@@ -2010,10 +2010,22 @@ and ReportNoCandidatesError (csenv:ConstraintSolverEnv) (nUnnamedCallerArgs,nNam
 
     // One method, incorrect name/arg assignment 
     | _,_,_,_,([],[cmeth]) -> 
-        let msgNum,msgText = FSComp.SR.csRequiredSignatureIs(NicePrint.stringOfMethInfo amap m denv cmeth.Method)
+        let minfo = cmeth.Method
+        let msgNum,msgText = FSComp.SR.csRequiredSignatureIs(NicePrint.stringOfMethInfo amap m denv minfo)
         let msgNum,msgText,msgRange = 
             match cmeth.UnassignedNamedArgs with 
-            | CallerNamedArg(id,_) :: _ -> (msgNum,FSComp.SR.csMemberHasNoArgumentOrReturnProperty(methodName, id.idText, msgText),id.idRange)
+            | CallerNamedArg(id,_) :: _ -> 
+                if minfo.IsConstructor then
+                    let typ = minfo.DeclaringEntityRef
+
+                    let predictions =
+                        typ.AllInstanceFieldsAsList
+                        |> List.map (fun p -> p.Name.Replace("@",""))
+                        |> ErrorResolutionHints.FilterPredictions id.idText
+
+                    msgNum,FSComp.SR.csCtorHasNoArgumentOrReturnProperty(methodName, id.idText, msgText, ErrorResolutionHints.FormatPredictions predictions),id.idRange
+                else
+                    msgNum,FSComp.SR.csMemberHasNoArgumentOrReturnProperty(methodName, id.idText, msgText),id.idRange
             | [] -> (msgNum,msgText,m)
         ErrorD (Error ((msgNum,msgText),msgRange))
 

src/fsharp/FSComp.txt

@@ -334,6 +334,7 @@ csGenericConstructRequiresPublicDefaultConstructor,"A generic construct requires
 492,csMethodIsNotAStaticMethod,"%s is not a static method"
 493,csMethodIsNotAnInstanceMethod,"%s is not an instance method"
 csMemberHasNoArgumentOrReturnProperty,"The member or object constructor '%s' has no argument or settable return property '%s'. %s."
+csCtorHasNoArgumentOrReturnProperty,"The object constructor '%s' has no argument or settable return property '%s'. %s. %s"
 495,csRequiredSignatureIs,"The required signature is %s"
 496,csMemberSignatureMismatch,"The member or object constructor '%s' requires %d argument(s). The required signature is '%s'."
 497,csMemberSignatureMismatch2,"The member or object constructor '%s' requires %d additional argument(s). The required signature is '%s'."

tests/fsharpqa/Source/Warnings/SuggestFieldsInCtor.fs

@@ -0,0 +1,13 @@
+// #Warnings
+//<Expects status="Error" span="(11,17)" id="FS0495">The object constructor 'MyClass' has no argument or settable return property 'Property'.</Expects>
+//<Expects>Maybe you want one of the following:</Expects>
+//<Expects>MyProperty</Expects>
+
+type MyClass() =
+    member val MyProperty = "" with get, set 
+    member val MyProperty2 = "" with get, set
+    member val ABigProperty = "" with get, set
+
+let c = MyClass(Property = "")
+    
+exit 0

tests/fsharpqa/Source/Warnings/env.lst

@@ -7,6 +7,7 @@
 	SOURCE=ElseBranchHasWrongType.fs # ElseBranchHasWrongType.fs
 	SOURCE=MissingExpressionAfterLet.fs # MissingExpressionAfterLet.fs
 	SOURCE=AssignmentOnImmutable.fs # AssignmentOnImmutable.fs
+	SOURCE=SuggestFieldsInCtor.fs # SuggestFieldsInCtor.fs
 	SOURCE=RefCellInsteadOfNot.fs # RefCellInsteadOfNot.fs
 	SOURCE=RefCellInsteadOfNot2.fs # RefCellInsteadOfNot2.fs
 	SOURCE=UpcastInsteadOfDowncast.fs # UpcastInsteadOfDowncast.fs