do not simplify open statements (#4068)

src/fsharp/NameResolution.fs

@@ -1223,6 +1223,8 @@ type ItemOccurence =
     | Implemented
     /// Result gets suppressed over this text range
     | RelatedText
+    /// This is a usage of a module or namespace name in open statement
+    | Open
   
 type OpenDeclaration =
     { LongId: Ident list

src/fsharp/NameResolution.fsi

@@ -246,6 +246,7 @@ type internal ItemOccurence =
     | Pattern 
     | Implemented 
     | RelatedText
+    | Open
   
 /// Check for equality, up to signature matching
 val ItemsAreEffectivelyEqual : TcGlobals -> Item -> Item -> bool

src/fsharp/TypeChecker.fs

@@ -466,7 +466,7 @@ let OpenModulesOrNamespaces tcSink g amap scopem root env mvvs openDeclaration =
                 loop acc rest
         
         for item, range in loop [] (List.rev openDeclaration.LongId) do
-            CallNameResolutionSink tcSink (range, env.NameEnv, item, item, emptyTyparInst, ItemOccurence.Use, env.DisplayEnv, env.eAccessRights)
+            CallNameResolutionSink tcSink (range, env.NameEnv, item, item, emptyTyparInst, ItemOccurence.Open, env.DisplayEnv, env.eAccessRights)
     env
 
 let AddRootModuleOrNamespaceRefs g amap m env modrefs =

src/fsharp/symbols/Symbols.fs

@@ -2281,11 +2281,11 @@ type FSharpSymbolUse(g:TcGlobals, denv: DisplayEnv, symbol:FSharpSymbol, itemOcc
     member __.Symbol  = symbol
     member __.DisplayContext  = FSharpDisplayContext(fun _ -> denv)
     member x.IsDefinition = x.IsFromDefinition
-    member __.IsFromDefinition = (match itemOcc with ItemOccurence.Binding -> true | _ -> false)
-    member __.IsFromPattern = (match itemOcc with ItemOccurence.Pattern -> true | _ -> false)
-    member __.IsFromType = (match itemOcc with ItemOccurence.UseInType -> true | _ -> false)
-    member __.IsFromAttribute = (match itemOcc with ItemOccurence.UseInAttribute -> true | _ -> false)
-    member __.IsFromDispatchSlotImplementation = (match itemOcc with ItemOccurence.Implemented -> true | _ -> false)
+    member __.IsFromDefinition = itemOcc = ItemOccurence.Binding
+    member __.IsFromPattern = itemOcc = ItemOccurence.Pattern
+    member __.IsFromType = itemOcc = ItemOccurence.UseInType
+    member __.IsFromAttribute = itemOcc = ItemOccurence.UseInAttribute
+    member __.IsFromDispatchSlotImplementation = itemOcc = ItemOccurence.Implemented
     member __.IsFromComputationExpression = 
         match symbol.Item, itemOcc with 
         // 'seq' in 'seq { ... }' gets colored as keywords
@@ -2293,7 +2293,7 @@ type FSharpSymbolUse(g:TcGlobals, denv: DisplayEnv, symbol:FSharpSymbol, itemOcc
         // custom builders, custom operations get colored as keywords
         | (Item.CustomBuilder _ | Item.CustomOperation _), ItemOccurence.Use ->  true
         | _ -> false
-
+    member __.IsFromOpenStatement = itemOcc = ItemOccurence.Open
     member __.FileName = range.FileName
     member __.Range = Range.toZ range
     member __.RangeAlternate = range

src/fsharp/symbols/Symbols.fsi

@@ -1125,6 +1125,9 @@ type internal FSharpSymbolUse =
     /// Indicates if the reference is either a builder or a custom operation in a computation expression
     member IsFromComputationExpression : bool
 
+    /// Indicates if the reference is in open statement
+    member IsFromOpenStatement : bool
+
     /// The file name the reference occurs in 
     member FileName: string 
 

vsintegration/src/FSharp.Editor/Diagnostics/SimplifyNameDiagnosticAnalyzer.fs

@@ -66,6 +66,7 @@ type internal SimplifyNameDiagnosticAnalyzer() =
                     let mutable result = ResizeArray()
                     let symbolUses =
                         symbolUses
+                        |> Array.filter (fun symbolUse -> not symbolUse.IsFromOpenStatement)
                         |> Array.Parallel.map (fun symbolUse ->
                             let lineStr = sourceText.Lines.[Line.toZ symbolUse.RangeAlternate.StartLine].ToString()
                             // for `System.DateTime.Now` it returns ([|"System"; "DateTime"|], "Now")