anchor.diff:    }
   
     test_const_topLevel_nullSafe_nullAware_propertyAccess() async {
  -    featureSet = enableNnbd;
  +    featureSet = featureSetNullSafe;
       var library = await checkLibrary(r'''
   const String? a = '';
   
  
positive.code:   }
  
    test_generic_function_type_nullability_question() async {
      featureSet = enableNnbd;
      var library = await checkLibrary('''
  void Function()? f;
  ''');
  
negative.code:   }
  
    test_class_ref_nullability_question() async {
      featureSet = featureSetNullSafe;
      var library = await checkLibrary('''
  class C {}
  C? c;
  