class A extends Enum {
  int get foo => index;
}

class B implements Enum {
  int get foo => index;
}

abstract class EnumInterface implements Enum {}

class EnumClass extends EnumInterface {
  int get index => 0;
}

abstract class AbstractEnumClass extends EnumInterface {}

class EnumClass2 extends AbstractEnumClass {}

mixin EnumMixin on Enum {}

abstract class AbstractEnumClass2 with EnumMixin {}

class EnumClass3 extends AbstractEnumClass2 {}

main() {}