anchor.diff:  
     /// The names that are not to be made visible in the importing library even if
     /// they are defined in the imported library.
  -  List<String>? _hiddenNames;
  +  List<String> _hiddenNames = _Sentinel.string;
   
     HideElementCombinatorImpl()
         : linkedContext = null,
  
positive.code:       }
      }
  
      if (_constructors!.isEmpty) {
        var constructor = ConstructorElementImpl('', -1);
        constructor.isSynthetic = true;
        constructor.enclosingElement = this;
        _constructors = <ConstructorElement>[constructor];
      }
  
      return _constructors!;
    }
  
    /// Set the constructors contained in this class to the given [constructors].
  
negative.code: 
    @override
    List<PropertyAccessorElement> get accessors {
      if (!identical(_accessors, _Sentinel.propertyAccessorElement)) {
        return _accessors;
      }
  
      if (linkedNode != null) {
        if (linkedNode is ExtensionDeclaration) {
          _createPropertiesAndAccessors();
          return _accessors;
        }
      }
  
      return _accessors;
    }
  
    set accessors(List<PropertyAccessorElement> accessors) {
  