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: 
    invoke([arg0 = sentinel, arg1 = sentinel, arg2 = sentinel,
            arg3 = sentinel, arg4 = sentinel]) {
      return _guardAsync(() {
        if (!shouldCallBack()) {
          return;
        } else if (arg0 == sentinel) {
  