import "package:expect/expect.dart";

class A<N, S, U> {
  final List<U?>? field;
  A(N n, S s) : field = <U>[] {}
  A.empty() : field = null {}
  factory A.f(S s) {}
  const A.c(U u, S s) : field = const <Null>[null];
  List<U?>? get getter {}
  void set setter(S s) {}
}

abstract class J<Aa, B> {}

abstract class I<H, C, K> extends J<C, K> {}

main() {}