class A {
  foo(int x) => x;
}

class B {
  foo(int x, {int? y}) => y;
}

class C extends A implements B {
  noSuchMethod(i) {}
}

class D {
  foo(int x) => x;
}

class E extends D {
  foo(int x, {int? y});
  noSuchMethod(i) {}
}

main() {}