anchor.diff:  library TypedMessageTest;
   import "dart:async";
   import "package:expect/expect.dart";
  +import "package:async_helper/async_helper.dart";
   import "dart:isolate";
   
   void logMessages(SendPort replyTo) {
  
positive.code: }
  
  main() {
    ReceivePort receivePort = new ReceivePort();
    Future<Isolate> remote = Isolate.spawn(logMessages, receivePort.sendPort);
    List<int> msg = new List<int>(5);
  
negative.code:   }).then((b) {
      Expect.equals(1, iterator.current);
      receivePort.close();
      asyncEnd();
    });
  }
  