anchor.diff:                  | SlowStage.NoData (isUpdating = true) -> ()
                   | _ -> 
                       slowState.Swap (function
  -                        | SlowStage.Data data ->
  -                             SlowStage.Data { data with IsUpdating = true } 
  +                        | SlowStage.Data data -> SlowStage.Data { data with IsUpdating = true } 
                           | SlowStage.NoData _ -> SlowStage.NoData true) |> ignore
   
                       let cancelToken = newCancellationToken slowStageCancellationToken
  
positive.code: [<NoComparison>]
  type private FastStage =
      | NoData
      | Updating of oldData:FastStageData option * snapshot: ITextSnapshot
      | Data of FastStageData 
  
  [<NoComparison>]
  
negative.code:                 
          if needUpdate then
              let worker = async {
                  match getCurrentProject(), snapshot with
                  | Some currentProject, Some snapshot ->
                      debug "[SyntaxConstructClassifier] - Effective update"
                      let pf = Profiler()
  