anchor.diff:      Iterable<ParameterElement> requiredParam = parameters.where(
           (ParameterElement p) => p.parameterKind == ParameterKind.REQUIRED);
       int requiredCount = requiredParam.length;
  -    if (requiredCount > 0 && _isEmptyArgList(request)) {
  -      _addArgListSuggestion(requiredParam);
  -      return;
  -    }
       // TODO (jwren) _isAppendingToArgList can be split into two cases (with and
       // without preceded), then _isAppendingToArgList,
       // _isInsertingToArgListWithNoSynthetic and
  
positive.code:     }
    }
    return false;
  }
  
  /**
   * Determine if the completion target is an emtpy argument list.
   */
  bool _isEmptyArgList(DartCompletionRequest request) {
    AstNode node = request.target.containingNode;
    return node is ArgumentList &&
        node.leftParenthesis.next == node.rightParenthesis;
  }
  
  /**
  
negative.code:       return suggestions;
      }
      return EMPTY_LIST;
    }
  
    void _addDefaultParamSuggestions(Iterable<ParameterElement> parameters,
  