anchor.diff:  
     Future<List<SearchResult>> _searchReferences(Element element) async {
       List<SearchResult> results = <SearchResult>[];
  -    await _addResults(results, element, IndexRelationKind.IS_REFERENCED_BY,
  -        SearchResultKind.REFERENCE);
  +    await _addResults(results, element,
  +        {IndexRelationKind.IS_REFERENCED_BY: SearchResultKind.REFERENCE});
       return results;
     }
   
  
positive.code:       element = (element as Member).baseElement;
      }
      List<SearchResult> results = <SearchResult>[];
      await _addResults(results, element, IndexRelationKind.IS_REFERENCED_BY,
          SearchResultKind.REFERENCE);
      await _addResults(results, element, IndexRelationKind.IS_INVOKED_BY,
          SearchResultKind.INVOCATION);
      return results;
    }
  
    Future<List<SearchResult>> _searchReferences_Getter(
        PropertyAccessorElement getter) async {
      List<SearchResult> results = <SearchResult>[];
      await _addResults(results, getter, IndexRelationKind.IS_REFERENCED_BY,
          SearchResultKind.REFERENCE);
      await _addResults(results, getter, IndexRelationKind.IS_INVOKED_BY,
          SearchResultKind.INVOCATION);
      return results;
    }
  
  
negative.code:     PropertyAccessorElement getter = field.getter;
      PropertyAccessorElement setter = field.setter;
      if (!field.isSynthetic) {
        await _addResults(results, field, {
          IndexRelationKind.IS_WRITTEN_BY: SearchResultKind.WRITE,
          IndexRelationKind.IS_REFERENCED_BY: SearchResultKind.REFERENCE
        });
      }
      if (getter != null) {
        await _addResults(results, getter, {
          IndexRelationKind.IS_REFERENCED_BY: SearchResultKind.READ,
          IndexRelationKind.IS_INVOKED_BY: SearchResultKind.INVOCATION
        });
      }
      if (setter != null) {
        await _addResults(results, setter,
            {IndexRelationKind.IS_REFERENCED_BY: SearchResultKind.WRITE});
      }
      return results;
    }
  