anchor.diff:  @pragma('vm:never-inline')
   @pragma('dart2js:noInline')
   Future<int> performAwaitCallsClosureTargetPolymorphic(
  -    FutureOr fun(int count)) async {
  +    FutureOr<int> fun(int count)) async {
     int sum = 0;
     for (int i = 0; i < iterationLimitAsync; ++i) {
       sum += await fun(i);
  
positive.code:     scheduleMicrotask(emit);
    }
  
    controller = StreamController(onListen: run, onResume: run, sync: true);
    return controller.stream;
  }
  
  
negative.code: @pragma('dart2js:noInline')
  Stream<int> generateNumbersManualAsync(int limit) {
    int current = 0;
    StreamController<int> controller = StreamController(sync: true);
    void emit() {
      while (true) {
        if (controller.isPaused || !controller.hasListener) return;
  