anchor.diff:          base.Update (ci)
             
       override x.Update (ainfo:CommandArrayInfo) =
  -        match tryGetValidDoc with
  +        match tryGetValidDoc() with
           | None -> ()
           | Some doc ->
               if not (MDLanguageService.SupportedFileName (doc.FileName.ToString())) then ()
  
positive.code:         | [||] -> fileName
          | xs -> xs |> Array.last
  
      let tryGetValidDoc =
          let doc = IdeApp.Workbench.ActiveDocument
          if doc = null || doc.FileName = FilePath.Null || doc.ParsedDocument = null then None
          else Some doc
  
negative.code:                 |> ignore
  
              | Refactoring.SymbolDeclarationLocation.External docId ->
                  match symbolUse.Assembly.FileName with
                  | Some filename ->
                      IdeApp.ProjectOperations.JumpToMetadata(filename, docId)
                  | None -> 
                      ()
              | _ -> ()    
  
                  
  