anchor.diff:    }
   
     @override
  -  Object visitAssignmentExpression(AssignmentExpression node) {
  +  visitAssignmentExpression(AssignmentExpression node) {
       _recordOperatorReference(node.operator, node.bestElement);
  -    return super.visitAssignmentExpression(node);
  -  }
  -
  -  @override
  -  Object visitBinaryExpression(BinaryExpression node) {
  +    super.visitAssignmentExpression(node);
  +  }
  +
  +  @override
  +  visitBinaryExpression(BinaryExpression node) {
       _recordOperatorReference(node.operator, node.bestElement);
  -    return super.visitBinaryExpression(node);
  -  }
  -
  -  @override
  -  Object visitClassDeclaration(ClassDeclaration node) {
  +    super.visitBinaryExpression(node);
  +  }
  +
  +  @override
  +  visitClassDeclaration(ClassDeclaration node) {
       ClassElement element = node.element;
       enterScope(element);
       try {
  
positive.code:       }
      }
      _recordImportElementReferenceWithoutPrefix(node);
      return super.visitSimpleIdentifier(node);
    }
  
    @override
    Object visitSuperConstructorInvocation(SuperConstructorInvocation node) {
      ConstructorElement element = node.staticElement;
      Location location;
      if (node.constructorName != null) {
  
negative.code:     if (fieldName != null) {
        Element element = fieldName.staticElement;
        Location location = _createLocationForNode(fieldName);
        _store.recordRelationship(
            element,
            IndexConstants.IS_WRITTEN_BY,
            location);
      }
      // index expression
      if (expression != null) {
  