LanguageFeatures/Private-fields-promotion/not_promotable_A01_t04.dart

// Copyright (c) 2023, the Dart project authors.  Please see the AUTHORS file
// for details. All rights reserved. Use of this source code is governed by a
// BSD-style license that can be found in the LICENSE file.

/// @assertion An instance field is promotable if all the following conditions
/// hold:
/// - It refers to a field (not a getter)
/// - The field is private
/// - The field is final
/// - There is no getter with the same name elsewhere in the library
/// - There is no non-final field with the same name elsewhere in the library
/// - There is no implicit noSuchMethod forwarder with the same name elsewhere
///   in the library.
///
/// @description Checks that an instance field is not promotable if it is
/// external
/// @author sgrekhov22@gmail.com

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