// 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 We say that a type T is non-nullable if T <: Object. This is
/// equivalent to the syntactic criterion that T is any of:
///  Never
///  Any function type (including Function)
///  Any interface type except Null.
///  S* for some S where S is non-nullable
///  FutureOr<S> where S is non-nullable
///  X extends S where S is non-nullable
///  X & S where S is non-nullable
///
/// @description Check that type which is not subtype of Object cannot be
/// assigned to non-nullable type. Test X & S where S is non-nullable
/// @author sgrekhov@unipro.ru


class A {}
class S extends A {}

main() {
  A a = new S();
  if (a is S) {
    a = null;
//      ^^^^
// [analyzer] unspecified
// [cfe] unspecified
  }
}