anchor.diff:    final NullabilitySuffix _nullabilitySuffix;
     final LibraryElement _coreLibrary;
     final LibraryElement _asyncLibrary;
  +
  +  ClassElement _futureElement;
  +  ClassElement _futureOrElement;
  +  ClassElement _iterableElement;
  +  ClassElement _mapElement;
  +  ClassElement _streamElement;
   
     InterfaceType _boolType;
     InterfaceType _deprecatedType;
  
positive.code: 
    @override
    InterfaceType get streamDynamicType {
      _streamDynamicType ??= streamType.instantiate(<DartType>[dynamicType]);
      return _streamDynamicType;
    }
  
    @override
  
negative.code: 
    @override
    InterfaceType get iterableDynamicType {
      _iterableDynamicType ??= InterfaceTypeImpl.explicit(
        iterableElement,
        [dynamicType],
        nullabilitySuffix: _nullabilitySuffix,
      );
      return _iterableDynamicType;
    }
  
    ClassElement get iterableElement {
      return _iterableElement ??= _getClassElement(_coreLibrary, 'Iterable');
    }
  
    @override
    InterfaceType get iterableObjectType {
      _iterableObjectType ??= InterfaceTypeImpl.explicit(
        iterableElement,
        [objectType],
        nullabilitySuffix: _nullabilitySuffix,
      );
      return _iterableObjectType;
    }
  
  