anchor.diff:          member _.SourceMap =
               mapGenerator.Force().toJSON()
   
  -        member _.WriteToFileIfChangedAsync(): Async<bool> = async {
  +        member _.WriteToFileIfChangedAsync(): Async<unit> = async {
               if memoryStream.Length = 0 then
  -                return false
  +                return ()
               elif not(IO.File.Exists(targetPath)) then
  -                return! WriteStreamToFileAsync(memoryStream, targetPath)
  +                do! WriteStreamToFileAsync(memoryStream, targetPath)
               else
                   let fileInfo = new IO.FileInfo(targetPath)
                   if fileInfo.Length <> memoryStream.Length then
  -                    return! WriteStreamToFileAsync(memoryStream, targetPath)
  +                    do! WriteStreamToFileAsync(memoryStream, targetPath)
                   else
                       match! IsMemoryStreamEqualToFileAsync() with
  -                    | false -> return! WriteStreamToFileAsync(memoryStream, targetPath)
  -                    | true -> return false
  +                    | false -> do! WriteStreamToFileAsync(memoryStream, targetPath)
  +                    | true -> return ()
             }
   
       let compileFile (com: CompilerImpl) (cliArgs: CliArgs) pathResolver isSilent = async {
  
positive.code:             member _.Write(str) =
                  async {
                      do! stream.WriteAsync(str) |> Async.AwaitTask
                      do! stream.FlushAsync() |> Async.AwaitTask
                  }
              member _.EscapeJsStringLiteral(str) =
  
negative.code:             use fileStream = new IO.StreamWriter(filePath)
              do! stream.CopyToAsync(fileStream.BaseStream) |> Async.AwaitTask
              do! fileStream.FlushAsync() |> Async.AwaitTask
  
              if cliArgs.SourceMaps then
                  let mapPath = filePath + ".map"
                  use fs = IO.File.Open(mapPath, IO.FileMode.Create)
                  let sourceMap = mapGenerator.Force().toJSON()
                  do! sourceMap.SerializeAsync(fs) |> Async.AwaitTask
          }
  
          let IsMemoryStreamEqualToFileAsync() = async {
  