anchor.diff:    @override
     Future<List<SearchMatch>> searchMemberDeclarations(String name) async {
       List<SearchMatch> allDeclarations = [];
  -    for (AnalysisDriver driver in _drivers) {
  +    List<AnalysisDriver> drivers = _drivers.toList();
  +    for (AnalysisDriver driver in drivers) {
         List<Element> elements = await driver.search.classMembers(name);
         allDeclarations.addAll(elements.map(_SearchMatch.forElement));
       }
  
positive.code:   @override
    Future<List<SearchMatch>> searchMemberReferences(String name) async {
      List<SearchResult> allResults = [];
      for (AnalysisDriver driver in _drivers) {
        List<SearchResult> results =
            await driver.search.unresolvedMemberReferences(name);
        allResults.addAll(results);
  
negative.code:   @override
    Future<List<SearchMatch>> searchReferences(Element element) async {
      List<SearchResult> allResults = [];
      List<AnalysisDriver> drivers = _drivers.toList();
      for (AnalysisDriver driver in drivers) {
        List<SearchResult> results = await driver.search.references(element);
        allResults.addAll(results);
      }
  