// Copyright (c) 2019, 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 It is a warning to use a null aware operator (?., ?.., ??, ??=,
/// or ...?) on an expression of type T if T is strictly non-nullable.
///
/// @description Check it is a warning to use a null aware operator (?., ?.., ??,
/// ??=, or ...?) on a strictly non-nullable receiver. Test if (t is Object) {…}
/// @author sgrekhov@unipro.ru
/// @issue 39598
/// @issue 39714

class A {
}
class C extends A {}

test(var a, C c) {
  if (a is Object) {
    a?.toString();
//   ^^
// [analyzer] STATIC_WARNING.INVALID_NULL_AWARE_OPERATOR
    a?..toString();
//   ^^^
// [analyzer] STATIC_WARNING.INVALID_NULL_AWARE_OPERATOR
    a ?? c;
//       ^
// [analyzer] STATIC_WARNING.DEAD_NULL_AWARE_EXPRESSION
    a ??= c;
//        ^
// [analyzer] STATIC_WARNING.DEAD_NULL_AWARE_EXPRESSION
  }
}

main() {
  A? a = A();
  C c = C();
  test(a, c);
}