Merge pull request #1275 from forki/refcell

Show better error when using ref cell instead of not

src/fsharp/CompileOps.fs

@@ -621,7 +621,7 @@ let OutputPhasedErrorR (os:System.Text.StringBuilder) (err:PhasedError) =
           (if m.StartLine <> m2.StartLine then 
              os.Append(SeeAlsoE().Format (stringOfRange m)) |> ignore )
       | ConstraintSolverTypesNotInEqualityRelation(denv,(TType_measure _ as t1),(TType_measure _ as t2),m,m2) -> 
-          // REVIEW: consider if we need to show _cxs (the type parameter constrants)
+          // REVIEW: consider if we need to show _cxs (the type parameter constraints)
           let t1, t2, _cxs = NicePrint.minimalStringsOfTwoTypes denv t1 t2
           os.Append(ConstraintSolverTypesNotInEqualityRelation1E().Format t1 t2 )  |> ignore
           (if m.StartLine <> m2.StartLine then 
@@ -633,7 +633,7 @@ let OutputPhasedErrorR (os:System.Text.StringBuilder) (err:PhasedError) =
           (if m.StartLine <> m2.StartLine then 
              os.Append(SeeAlsoE().Format (stringOfRange m)) |> ignore)
       | ConstraintSolverTypesNotInSubsumptionRelation(denv,t1,t2,m,m2) -> 
-          // REVIEW: consider if we need to show _cxs (the type parameter constrants)
+          // REVIEW: consider if we need to show _cxs (the type parameter constraints)
           let t1, t2, cxs= NicePrint.minimalStringsOfTwoTypes denv t1 t2
           os.Append(ConstraintSolverTypesNotInSubsumptionRelationE().Format t2 t1 cxs) |> ignore
           (if m.StartLine <> m2.StartLine then 
@@ -654,9 +654,12 @@ let OutputPhasedErrorR (os:System.Text.StringBuilder) (err:PhasedError) =
           match contextInfo with
           | ContextInfo.OmittedElseBranch -> os.Append(FSComp.SR.missingElseBranch(t2)) |> ignore
           | ContextInfo.ElseBranch -> os.Append(FSComp.SR.elseBranchHasWrongType(t1,t2)) |> ignore
-          | ContextInfo.TupleInRecordFields -> 
+          | ContextInfo.TupleInRecordFields ->
+                os.Append(ErrorFromAddingTypeEquation1E().Format t2 t1 tpcs) |> ignore
+                os.Append(System.Environment.NewLine + FSComp.SR.commaInsteadOfSemicolonInRecord()) |> ignore
+          | _ when t2 = "bool" && t1.EndsWith " ref" ->
                 os.Append(ErrorFromAddingTypeEquation1E().Format t2 t1 tpcs) |> ignore
-                os.Append(System.Environment.NewLine + FSComp.SR.commaInsteadOfSemicolonInRecord()) |> ignore                
+                os.Append(System.Environment.NewLine + FSComp.SR.derefInsteadOfNot()) |> ignore
           | _ -> os.Append(ErrorFromAddingTypeEquation1E().Format t2 t1 tpcs) |> ignore
       | ErrorFromAddingTypeEquation(_,_,_,_,((ConstraintSolverTypesNotInSubsumptionRelation _ | ConstraintSolverError _) as e), _, _)  ->  
           OutputExceptionR os e

src/fsharp/FSComp.txt

@@ -18,6 +18,7 @@ undefinedNamePatternDiscriminator,"The pattern discriminator '%s' is not defined
 missingElseBranch,"The 'if' expression is missing an 'else' branch. The 'then' branch has type '%s'. Because 'if' is an expression, and not a statement, add an 'else' branch which returns a value of the same type."
 elseBranchHasWrongType,"All branches of an 'if' expression must return the same type. This expression was expected to have type '%s' but here has type '%s'."
 commaInsteadOfSemicolonInRecord,"A ';' is used to separate field values in records. Consider replacing ',' with ';'."
+derefInsteadOfNot,"The '!' operator is used to dereference a ref cell. Consider using 'not expr' here."
 buildUnexpectedTypeArgs,"The non-generic type '%s' does not expect any type arguments, but here is given %d type argument(s)"
 returnUsedInsteadOfReturnBang,"Consider using 'return!' instead of 'return'."
 yieldUsedInsteadOfYieldBang,"Consider using 'yield!' instead of 'yield'."

tests/fsharpqa/Source/Warnings/RefCellInsteadOfNot.fs

@@ -0,0 +1,9 @@
+// #Warnings
+//<Expects status="Error" id="FS0001">This expression was expected to have type</Expects>
+//<Expects status="success">The '!' operator is used to dereference a ref cell. Consider using 'not expr' here.</Expects>
+
+let x = true
+if !x then
+    printfn "hello"
+
+exit 0

tests/fsharpqa/Source/Warnings/RefCellInsteadOfNot2.fs

@@ -0,0 +1,8 @@
+// #Warnings
+//<Expects status="Error" id="FS0001">This expression was expected to have type</Expects>
+//<Expects status="success">The '!' operator is used to dereference a ref cell. Consider using 'not expr' here.</Expects>
+
+let x = true
+let y = !x
+
+exit 0

tests/fsharpqa/Source/Warnings/env.lst

@@ -7,6 +7,8 @@
 	SOURCE=ElseBranchHasWrongType.fs # ElseBranchHasWrongType.fs
 	SOURCE=MissingExpressionAfterLet.fs # MissingExpressionAfterLet.fs
 	SOURCE=AssignmentOnImmutable.fs # AssignmentOnImmutable.fs
+	SOURCE=RefCellInsteadOfNot.fs # RefCellInsteadOfNot.fs
+	SOURCE=RefCellInsteadOfNot2.fs # RefCellInsteadOfNot2.fs
 	SOURCE=UpcastInsteadOfDowncast.fs # UpcastInsteadOfDowncast.fs
 	SOURCE=UpcastFunctionInsteadOfDowncast.fs # UpcastFunctionInsteadOfDowncast.fs
 	SOURCE=DowncastInsteadOfUpcast.fs # DowncastInsteadOfUpcast.fs