T hest1<T>() => throw "hest";

class A2 {
  String? foo;
}

class A5 {
  String? operator [](int index) => null;
  void operator []=(int index, String? value) {}
}

class A7 {
  String? bar;
  String foo = "foo";
}

class B5 extends A5 {
  test5() {}
}

extension E6 on double {
  String? operator [](int index) => null;
  void operator []=(int index, String? value) {}
}

main() {}
test1() {}
test2(A2 a) {}
test3() {}
test4() {}
test6() {}
test7(A7? a) {}