mixin M {
  String toString() => "M";
}

abstract class A {
  String toString() => "A";
}

abstract class B implements Enum {
  String toString() => "B";
}

enum E1 with M { element }

enum E2 with M {
  element;

  String toString() => "E2";
}

enum E3 {
  element;

  String toString() => "E3";
}

enum E4 implements B { element }

enum E5 implements B {
  element;

  String toString() => "E5";
}

enum E6 with A { element }

enum E7 with A {
  element;

  String toString() => "E7";
}

checkEqual(x, y) {}
main() {}