LanguageFeatures/Constant-update-2018/EqualityOperator_A01_t01.dart

// 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 The [==] operator in constant expressions was defined such that
/// [e1 != null] was only allowed if [e1] had one of the "primitive" system
/// types. Users had to rewrite their code to [!identical(e1, null)]. This was
/// changed so that the [==] expression is always allowed as long as one of the
/// operands is [null].
/// @description Checks that [==] operator is allowed if one of the operands is
/// [null] in potentially constant or compile-time constant.
/// @author iarkh@unipro.ru

import "../../Utils/expect.dart";

const str1 = "test";
const str2 = null;

class MyClass {
  final String option;
  const MyClass(String? str) : assert(str == null), this.option = "OK";
}

main() {
  const bool res1 = (str1 == null);
  Expect.isFalse(res1);

  const bool res2 = (str2 == null);
  Expect.isTrue(res2);

  const MyClass c = MyClass(null);
  Expect.equals("OK", c.option);
}