anchor.diff:  
   /// A bazel worker loop that can compute full or summary kernel files.
   class KernelWorker extends AsyncWorkerLoop {
  -  fe.InitializedCompilerState previousState;
  +  fe.InitializedCompilerState? previousState;
   
     /// If [sendPort] is provided it is used for bazel worker communication
     /// instead of stdin/stdout.
  -  KernelWorker({SendPort sendPort})
  +  KernelWorker({SendPort? sendPort})
         : super(
               connection: sendPort == null
                   ? null
  
positive.code: 
  /// [sendPort] may be passed in when started in an isolate. If provided, it is
  /// used for bazel worker communication instead of stdin/stdout.
  main(List<String> args, SendPort sendPort) async {
    args = preprocessArgs(args);
  
    if (args.contains('--persistent_worker')) {
  
negative.code:     var outputBuffer = new StringBuffer();
      var response = new WorkResponse()..exitCode = 0;
      try {
        fe.InitializedCompilerState? previousStateToPass;
        if (request.arguments.contains("--reuse-compiler-result")) {
          previousStateToPass = previousState;
        } else {
  