anchor.diff:  library xml.reader;
  +
  +import 'dart:collection';
   
   import 'package:petitparser/petitparser.dart';
   import 'package:xml/xml/nodes/attribute.dart';
  
positive.code:     return context.success(null, context.position + 1);
    }
  }
  
negative.code: import 'package:xml/xml/production.dart';
  import 'package:xml/xml/utils/name.dart';
  import 'package:xml/xml/utils/node_list.dart';
  import 'package:xml/xml/utils/node_type.dart';
  import 'package:xml/xml/utils/token.dart';
  
  // Definition of the XML productions.
  