Improve value restriction error message #1103

src/Compiler/Checking/CheckDeclarations.fs

@@ -5577,7 +5577,7 @@ let CheckValueRestriction denvAtEnd infoReader rootSigOpt implFileTypePriorToSig
                   // for example FSharp 1.0 3661.
                   (match v.ValReprInfo with None -> true | Some tvi -> tvi.HasNoArgs)) then 
                 match ftyvs with 
-                | tp :: _ -> errorR (ValueRestriction(denvAtEnd, infoReader, false, v, tp, v.Range))
+                | tp :: _ -> errorR (ValueRestriction(denvAtEnd, infoReader, v, tp, v.Range))
                 | _ -> ()
           mty.ModuleAndNamespaceDefinitions |> List.iter (fun v -> check v.ModuleOrNamespaceType) 
       try check implFileTypePriorToSig with RecoverableException e -> errorRecovery e m

src/Compiler/Checking/CheckExpressions.fs

@@ -94,7 +94,7 @@ exception UnionPatternsBindDifferentNames of range
 
 exception VarBoundTwice of Ident
 
-exception ValueRestriction of DisplayEnv * InfoReader * bool * Val * Typar * range
+exception ValueRestriction of DisplayEnv * InfoReader * Val * Typar * range
 
 exception ValNotMutable of DisplayEnv * ValRef * range
 

src/Compiler/Checking/CheckExpressions.fsi

@@ -75,7 +75,7 @@ exception UnionPatternsBindDifferentNames of range
 
 exception VarBoundTwice of Ident
 
-exception ValueRestriction of DisplayEnv * InfoReader * bool * Val * Typar * range
+exception ValueRestriction of DisplayEnv * InfoReader * Val * Typar * range
 
 exception ValNotMutable of DisplayEnv * ValRef * range
 

src/Compiler/Driver/CompilerDiagnostics.fs

@@ -145,7 +145,7 @@ type Exception with
         | IntfImplInIntrinsicAugmentation m
         | OverrideInExtrinsicAugmentation m
         | IntfImplInExtrinsicAugmentation m
-        | ValueRestriction(_, _, _, _, _, m)
+        | ValueRestriction(_, _, _, _, m)
         | LetRecUnsound(_, _, m)
         | ObsoleteError(_, m)
         | ObsoleteWarning(_, m)
@@ -579,11 +579,8 @@ module OldStyleMessages =
     let DeprecatedE () = Message("Deprecated", "%s")
     let LibraryUseOnlyE () = Message("LibraryUseOnly", "")
     let MissingFieldsE () = Message("MissingFields", "%s")
-    let ValueRestriction1E () = Message("ValueRestriction1", "%s%s%s")
-    let ValueRestriction2E () = Message("ValueRestriction2", "%s%s%s")
-    let ValueRestriction3E () = Message("ValueRestriction3", "%s")
-    let ValueRestriction4E () = Message("ValueRestriction4", "%s%s%s")
-    let ValueRestriction5E () = Message("ValueRestriction5", "%s%s%s")
+    let ValueRestrictionFunctionE () = Message("ValueRestrictionFunction", "%s%s%s")
+    let ValueRestrictionE () = Message("ValueRestriction", "%s%s%s")
     let RecoverableParseErrorE () = Message("RecoverableParseError", "")
     let ReservedKeywordE () = Message("ReservedKeyword", "%s")
     let IndentationProblemE () = Message("IndentationProblem", "%s")
@@ -1760,63 +1757,30 @@ type Exception with
 
         | MissingFields(sl, _) -> os.AppendString(MissingFieldsE().Format(String.concat "," sl + "."))
 
-        | ValueRestriction(denv, infoReader, hasSig, v, _, _) ->
+        | ValueRestriction(denv, infoReader, v, _, _) ->
             let denv =
                 { denv with
                     showInferenceTyparAnnotations = true
                 }
 
             let tau = v.TauType
 
-            if hasSig then
-                if isFunTy denv.g tau && (arityOfVal v).HasNoArgs then
-                    let msg =
-                        ValueRestriction1E().Format
-                            v.DisplayName
-                            (NicePrint.stringOfQualifiedValOrMember denv infoReader (mkLocalValRef v))
-                            v.DisplayName
+            if isFunTy denv.g tau && (arityOfVal v).HasNoArgs then
+                let msg =
+                    ValueRestrictionFunctionE().Format
+                        v.DisplayName
+                        (NicePrint.stringOfQualifiedValOrMember denv infoReader (mkLocalValRef v))
+                        v.DisplayName
 
-                    os.AppendString msg
-                else
-                    let msg =
-                        ValueRestriction2E().Format
-                            v.DisplayName
-                            (NicePrint.stringOfQualifiedValOrMember denv infoReader (mkLocalValRef v))
-                            v.DisplayName
-
-                    os.AppendString msg
+                os.AppendString msg
             else
-                match v.MemberInfo with
-                | Some membInfo when
-                    (match membInfo.MemberFlags.MemberKind with
-                     | SynMemberKind.PropertyGet
-                     | SynMemberKind.PropertySet
-                     | SynMemberKind.Constructor -> true // can't infer extra polymorphism
-                     // can infer extra polymorphism
-                     | _ -> false)
-                    ->
-                    let msg =
-                        ValueRestriction3E()
-                            .Format(NicePrint.stringOfQualifiedValOrMember denv infoReader (mkLocalValRef v))
-
-                    os.AppendString msg
-                | _ ->
-                    if isFunTy denv.g tau && (arityOfVal v).HasNoArgs then
-                        let msg =
-                            ValueRestriction4E().Format
-                                v.DisplayName
-                                (NicePrint.stringOfQualifiedValOrMember denv infoReader (mkLocalValRef v))
-                                v.DisplayName
-
-                        os.AppendString msg
-                    else
-                        let msg =
-                            ValueRestriction5E().Format
-                                v.DisplayName
-                                (NicePrint.stringOfQualifiedValOrMember denv infoReader (mkLocalValRef v))
-                                v.DisplayName
+                let msg =
+                    ValueRestrictionE().Format
+                        v.DisplayName
+                        (NicePrint.stringOfQualifiedValOrMember denv infoReader (mkLocalValRef v))
+                        v.DisplayName
 
-                        os.AppendString msg
+                os.AppendString msg
 
         | Parsing.RecoverableParseError -> os.AppendString(RecoverableParseErrorE().Format)
 

src/Compiler/FSStrings.resx

@@ -1029,20 +1029,11 @@
   <data name="MissingFields" xml:space="preserve">
     <value>The following fields require values: {0}</value>
   </data>
-  <data name="ValueRestriction1" xml:space="preserve">
-    <value>Value restriction. The value '{0}' has generic type\n    {1}    \nEither make the arguments to '{2}' explicit or, if you do not intend for it to be generic, add a type annotation.</value>
+  <data name="ValueRestrictionFunction" xml:space="preserve">
+    <value>Value restriction: The value '{0}' has an inferred generic function type\n    {1}\nHowever, values cannot have generic type variables like '_a in "let f: '_a". You should define '{2}' as a function instead by doing one of the following:\n- Add an explicit parameter that is applied instead of using a partial application "let f param"\n- Add a unit parameter like "let f()"\n- Write explicit type parameters like "let f&lt;'a&gt;"\nor if you do not intend for it to be generic, either:\n- Add an explicit type annotation like "let f : obj -&gt; obj"\n- Apply arguments of non-generic types to the function value in later code for type inference like "do f()".\nThis error is because a let binding without parameters defines a value, not a function. Values cannot be generic because reading a value is assumed to result in the same everywhere but generic type parameters may invalidate this assumption by enabling type-dependent results.</value>
   </data>
-  <data name="ValueRestriction2" xml:space="preserve">
-    <value>Value restriction. The value '{0}' has generic type\n    {1}    \nEither make '{2}' into a function with explicit arguments or, if you do not intend for it to be generic, add a type annotation.</value>
-  </data>
-  <data name="ValueRestriction3" xml:space="preserve">
-    <value>Value restriction. This member has been inferred to have generic type\n    {0}    \nConstructors and property getters/setters cannot be more generic than the enclosing type.  Add a type annotation to indicate the exact types involved.</value>
-  </data>
-  <data name="ValueRestriction4" xml:space="preserve">
-    <value>Value restriction. The value '{0}' has been inferred to have generic type\n    {1}    \nEither make the arguments to '{2}' explicit or, if you do not intend for it to be generic, add a type annotation.</value>
-  </data>
-  <data name="ValueRestriction5" xml:space="preserve">
-    <value>Value restriction. The value '{0}' has been inferred to have generic type\n    {1}    \nEither define '{2}' as a simple data term, make it a function with explicit arguments or, if you do not intend for it to be generic, add a type annotation.</value>
+  <data name="ValueRestriction" xml:space="preserve">
+    <value>Value restriction: The value '{0}' has an inferred generic type\n    {1}\nHowever, values cannot have generic type variables like '_a in "let x: '_a". You can do one of the following:\n- Define it as a simple data term like an integer literal, a string literal or a union case like "let x = 1"\n- Add an explicit type annotation like "let x : int"\n- Use the value as a non-generic type in later code for type inference like "do x"\nor if you still want type-dependent results, you can define '{2}' as a function instead by doing either:\n- Add a unit parameter like "let x()"\n- Write explicit type parameters like "let x&lt;'a&gt;".\nThis error is because a let binding without parameters defines a value, not a function. Values cannot be generic because reading a value is assumed to result in the same everywhere but generic type parameters may invalidate this assumption by enabling type-dependent results.</value>
   </data>
   <data name="RecoverableParseError" xml:space="preserve">
     <value>syntax error</value>