anchor.diff:      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.
  
positive.code:       }
      }
      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,
  
negative.code:   Future<List<Assist>> compute() async {
      // TODO(brianwilkerson) Determine whether this await is necessary.
      await null;
      if (!_setupCompute()) {
        return assists;
      }
  
  