anchor.diff:    }
   
     invoke0() {
  -    return guardAsync(
  +    return _guardAsync(
           () {
             if (shouldCallBack()) {
               return callback();
  
positive.code:  *
   * The value returned by [tryBody] (if any) is returned by [guardAsync].
   */
  guardAsync(Function tryBody, [Function finallyBody, int testNum = -1]) {
    if (testNum < 0) testNum = _currentTest;
    try {
      return tryBody();
    } catch (e, trace) {
  
negative.code:   }
  
    invoke2(arg1, arg2) {
      return _guardAsync(
          () {
            if (shouldCallBack()) {
              return callback(arg1, arg2);
  