anchor.diff:     * in the given completion context may not be resolved.
      */
     void _update(
  -      CompletionRequest request, Iterable<CompletionSuggestion> suggestions) {
  +      CompletionRequest request, Iterable<CompletionSuggestion> suggestions) async {
           var target = _getCompletionTarget(request);
           _log.info("completionTarget: $target");
   
  
positive.code: // log.Logger _log = new log.Logger("common_usage_sorter");
  
  class _log {
    static info(String l) {
      log.info("common_usage_sorter", l);
    }
  }
  
  
negative.code: 
    @override
    Future sort(DartCompletionRequest request,
        Iterable<CompletionSuggestion> suggestions) async {
      _update(request, suggestions);
      return new Future.value();
    }
  