Dart: == без hashCode в Set

class User {
  final int id;
  User(this.id);
  @override
  bool operator ==(Object other) => other is User && other.id == id;
}

class Fixed {
  final int id;
  Fixed(this.id);
  @override
  bool operator ==(Object other) => other is Fixed && other.id == id;
  @override
  int get hashCode => id.hashCode;
}

void main() {
  print(User(1) == User(1));
  print({User(1), User(1)}.length);
  print({Fixed(1), Fixed(1)}.length);
}