abstract class Const {
  const factory Const.impl() = _ConstImpl;
}

class Class {
  Class(
      {this.constants = const [
        Const.impl(),
        Alias.impl(),
        ImplAlias<String>()
      ]});
  final List<Const> constants;
}

class _ConstImpl<T> implements Const {
  const _ConstImpl();
}

main() {}
typedef Alias = Const;
typedef ImplAlias<T extends num> = _ConstImpl<T>;