anchor.diff:    }
   
     invoke1(arg1) {
  -    return guardAsync(
  +    return _guardAsync(
           () {
             if (shouldCallBack()) {
               return callback(arg1);
  
positive.code:   }
  
    invoke2(arg1, arg2) {
      return guardAsync(
          () {
            if (shouldCallBack()) {
              return callback(arg1, arg2);
  
negative.code: 
    invoke([arg0 = sentinel, arg1 = sentinel, arg2 = sentinel,
            arg3 = sentinel, arg4 = sentinel]) {
      return _guardAsync(() {
        if (!shouldCallBack()) {
          return;
        } else if (arg0 == sentinel) {
  