class Superclass {
  String method1(num argument1, num argument2) => "Superclass";
  String method2(num argument1, num argument2) => "Superclass";
  String method3(num argument1, covariant int argument2) => "Superclass";
  String method4(num argument1, covariant num argument2) => "Superclass";
}

class Mixin {
  String method1(num argument1, num argument2) => "Mixin";
  String method2(covariant int argument1, num argument2) => "Mixin";
  String method3(num argument1, num argument2) => "Mixin";
  String method4(covariant int argument1, int argument2) => "Mixin";
}

class Class extends Superclass with Mixin {}

main() {}
void expect(expected, actual) {}
void throws(void Function() f) {}