highlight reference cells as mutables (#2470)

src/fsharp/vs/service.fs

@@ -1467,6 +1467,8 @@ type TypeCheckInfo
             // 'seq' in 'seq { ... }' gets colored as keywords
             | CNR(_, (Item.Value vref), ItemOccurence.Use, _, _, _, m) when valRefEq g g.seq_vref vref ->
                 Some (m, SemanticClassificationType.ComputationExpression)
+            | CNR(_, (Item.Value vref), _, _, _, _, m) when vref.IsMutable || Tastops.isRefCellTy g vref.Type ->
+                Some (m, SemanticClassificationType.MutableVar)
             | CNR(_, Item.Value KeywordIntrinsicValue, ItemOccurence.Use, _, _, _, m) ->
                 Some (m, SemanticClassificationType.IntrinsicFunction)
             | CNR(_, (Item.Value vref), _, _, _, _, m) when isFunction g vref.Type ->
@@ -1475,18 +1477,6 @@ type TypeCheckInfo
                 elif not (IsOperatorName vref.DisplayName) then
                     Some (m, SemanticClassificationType.Function)
                 else None
-            | CNR(_, (Item.Value vref), _, _, _, _, m) when vref.IsMutable ->
-                Some (m, SemanticClassificationType.MutableVar)
-            // todo here we should check if a `vref` is of type `ref`1`
-            // (the commented code does not work)
-
-            //| CNR(_, (Item.Value vref), _, _, _, _, m) ->
-            //    match vref.TauType with
-            //    | TType.TType_app(tref, _) ->  //  g.refcell_tcr_canon.t _refcell_tcr_canon canon.Deref.type vref ->
-            //        if g.refcell_tcr_canon.Deref.Stamp = tref.Deref.Stamp then
-            //            Some (m, SemanticClassificationType.MutableVar)
-            //        else None
-            //    | _ -> None
             | CNR(_, Item.RecdField rfinfo, _, _, _, _, m) when rfinfo.RecdField.IsMutable && rfinfo.LiteralValue.IsNone -> 
                 Some (m, SemanticClassificationType.MutableVar)
             | CNR(_, Item.MethodGroup(_, _, _), _, _, _, _, m) ->

vsintegration/src/FSharp.Editor/FSharp.Editor.resx

@@ -145,7 +145,7 @@
     <value>F# Functions / Methods</value>
   </data>
   <data name="FSharpMutableVarsClassificationType" xml:space="preserve">
-    <value>F# Mutable Variables</value>
+    <value>F# Mutable Variables / Reference Cells</value>
   </data>
   <data name="FSharpPrintfFormatClassificationType" xml:space="preserve">
     <value>F# Printf Format</value>