anchor.diff:    f(s: null);
   }
   ''';
  -    _checkSingleFileChanges(content, expected);
  +    await _checkSingleFileChanges(content, expected);
     }
   
     test_named_parameter_no_default_used_non_null_option2_assume_nullable() async {
  
positive.code:   f();
  }
  ''';
      _checkSingleFileChanges(content, expected);
    }
  
    test_named_parameter_no_default_used_null_option2() async {
  
negative.code: f(int i) => null; // TODO(danrubel): suggest type
  int? g(int i) => f(i);
  ''';
      await _checkSingleFileChanges(content, expected);
    }
  
    test_discard_simple_condition() async {
  