LanguageFeatures/nnbd/weak/overriding/override_checking_A03_t05.dart

// Copyright (c) 2020, 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 Members inherited in a class in an opted-in library, which are
/// inherited via a class or mixin defined in a legacy library are viewed with
/// their erased legacy signature, even if they were original defined in an
/// opted-in library. Note that if a class which is defined in a legacy library
/// inherits a member with the same name from multiple super-interfaces, then
/// error checking is done as usual using the legacy typing rules which ignore
/// nullability. This means that it is valid for a legacy class to inherit the
/// same member signature with contradictory nullability information. For the
/// purposes of member lookup within a legacy library, nullability information is
/// ignored, and so it is valid to simply erase the nullability information
/// within the legacy library. When referenced from an opted-in library, the same
/// erasure is performed, and the member is seen at its legacy type.
///
/// We use legacy subtyping when checking inherited member signature coherence in
/// classes because opted out libraries may bring together otherwise incompatible
/// member signatures without causing an error.
///
/// @description Check that legacy class can inherit the same method with return
/// value from two opted in classes with contradictory nullability information.
///
/// @author iarkh@unipro.ru

// Requirements=nnbd-weak

import "../../../../Utils/expect.dart";
import "override_checking_A03_opted_out_lib.dart";
import "override_checking_A03_opted_in_lib.dart";

main() {
  LEGACY_RETURN_1 x1 = LEGACY_RETURN_1();
  Expect.isNull(x1.getInt());
  Expect.isNull(x1.getObject());
  Expect.isNull(x1.getFunction());

  LEGACY_RETURN_2 x2 = LEGACY_RETURN_2();
  Expect.equals(1, x2.getInt());
  Expect.equals(1, x2.getObject());
  Expect.equals(testme, x2.getFunction());
}