anchor.diff:      throw 0;
     }
   }
  +
  +abstract class ListMixin<E> implements List<E> { }
  +
  +abstract class MapMixin<K, V> implements Map<K, V> { }
  +
  +abstract class SetMixin<E> implements Set<E> { }
   ''',
     )
   ]);
  
positive.code:   const JsonCodec();
    String encode(Object? value, {Object? toEncodable(dynamic object)?}) => '';
  }
  ''',
      )
    ],
  
negative.code:   Iterator<E> get iterator;
    int get length;
  
    const Iterable();
  
    const factory Iterable.empty() => EmptyIterable<E>();
  
    bool contains(Object? element);
  
    Iterable<T> expand<T>(Iterable<T> f(E element));
  
  