class MapLike<K, V> {
  final Map<K, V> _map = {};
  V get(Object key) => _map[key];
  V put(K key, V value) => _map[key] = value;
}
extension Extension<K, V> ( ){ }
on MapLike<K, V> (){ }
main() { }
implicit() { }
explicitWithTypeArguments() { }
explicitInferredTypeArguments() { }
expect(expected, actual) { }