anchor.diff:  
                       snapshot <-
                           use edit = subjectBuffer.CreateEdit()
  +
  +                        edit.Insert(closingSnapshotPoint.Position, closingBrace.ToString()) |> ignore
                       
                           if edit.HasFailedChanges then
                               Debug.Fail("Unable to insert closing brace")
  
positive.code:                                 editorOperationsFactoryService, 
                                  editorSession) :> IBraceCompletionSession
  
              match session with
              | null -> false
              | _ -> true
negative.code: 
              let textSnapshot = openingPoint.Snapshot
  
              let newSession =
                  match textSnapshot.GetOpenDocumentInCurrentContextWithChanges() with
                  | null -> null
                  | document ->
  