anchor.diff:        }
       }
       return null;
  -  }
  -
  -  bool setupCompute() {
  -    try {
  -      utils = new CorrectionUtils(unit);
  -    } catch (e) {
  -      throw new CancelCorrectionException(exception: e);
  -    }
  -
  -    bool success = true;
  -    node = new NodeLocator(selectionOffset, selectionEnd).searchWithin(unit);
  -    if (node == null) {
  -      success = false;
  -    }
  -    return success;
     }
   
     void _addAssistFromBuilder(DartChangeBuilder builder, AssistKind kind,
  
positive.code:   Future<List<Assist>> compute() async {
      // TODO(brianwilkerson) Determine whether this await is necessary.
      await null;
      if (!setupCompute()) {
        return assists;
      }
  
  
negative.code:     return utils.getRangeText(range);
    }
  
    bool _setupCompute() {
      try {
        utils = new CorrectionUtils(unit);
      } catch (e) {
        throw new CancelCorrectionException(exception: e);
      }
  
      node = new NodeLocator(selectionOffset, selectionEnd).searchWithin(unit);
      return node != null;
    }
  
    Future<void> _swapParentAndChild(InstanceCreationExpression parent,
        InstanceCreationExpression child, AssistKind kind) async {
      // TODO(brianwilkerson) Determine whether this await is necessary.
  