LanguageFeatures/Private-fields-promotion/not_promotable_A01_t04 has incorrect expectation

[stereotype441]

LanguageFeatures/Private-fields-promotion/not_promotable_A01_t04 looks like this:

class A {
  void foo() {}
}

class C<T> {
   external final T _x;

  void test() {
    if (_x is A) {
      _x.foo();
//       ^^^^^
// [analyzer] unspecified
// [cfe] unspecified
    }
  }
}

main() {
  C c = C();
  if (c._x is A) {
    c._x.foo();
//       ^^^^^
// [analyzer] unspecified
// [cfe] unspecified
  }
  c.test();
}

The test is trying to verify that C._x does not type promote.

The first expectation (inside C.test) works fine, because inside an instance method of C, the unpromoted type of _x is T, and therefore trying to call _x.foo() is an effective way of verifying that _x wasn't promoted to A.

The second expectation (inside main) is problematic, because C c = C(); gets type inferred as C<dynamic> c = C();, therefore the unpromoted type of c._x is dynamic, and so the call to c._x.foo() works regardless of whether c._x has been type promoted.

One possible fix would be to change the first line of main to var c = C<Object>(). That would ensure that the unpromoted type of c._x is Object, and so the call to c._x.foo() would be an effective way of verifying that c._x hasn't been type promoted.