LanguageFeatures/nnbd/override_checking_A01_t24.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 In an unmigrated library, override checking is done using legacy
 * types. This means that an unmigrated library can bring together otherwise
 * incompatible methods. When choosing the most specific signature during
 * interface computation, all nullability and requiredness annotations are
 * ignored, and the [Never] type is treated as [Null].
 *
 * @description Check that if legacy class extends opted-in class, legacy field
 * can accept null values if corresponding parent field is of both nullable or
 * non-nullable type.
 *
 * @author iarkh@unipro.ru
 */
// SharedOptions=--enable-experiment=non-nullable
// @dart=2.6

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

class A1 implements A {
  String field1 = "c";
  String field2 = "d";

  void test_nullable(int i) {}
  void test_required({int i = 1}) {}
  void test_never(Null i) {}
  int test_return_nullable() => 1;
  Null test_return_never() => null;
  String get get_field1 => field1;
  String get get_field2 => field1;
  void set set_field1(String str) { field1 = str; }
  void set set_field2(String str) { field2 = str; }
}

class A2 implements A {
  String field1 = null;
  String field2 = null;

  void test_nullable(int i) {}
  void test_required({int i = 1}) {}
  void test_never(Null i) {}
  int test_return_nullable() => 1;
  Null test_return_never() => null;
  String get get_field1 => field1;
  String get get_field2 => field1;
  void set set_field1(String str) { field1 = str; }
  void set set_field2(String str) { field2 = str; }
}

class A3 implements A {
  String field1;
  String field2;

  void test_nullable(int i) {}
  void test_required({int i = 1}) {}
  void test_never(Null i) {}
  int test_return_nullable() => 1;
  Null test_return_never() => null;
  String get get_field1 => field1;
  String get get_field2 => field1;
  void set set_field1(String str) { field1 = str; }
  void set set_field2(String str) { field2 = str; }
}

main() {
  A1 a1 = A1();
  a1.field1 = null;
  Expect.isNull(a1.field1);
  a1.field2 = null;
  Expect.isNull(a1.field2);

  A2 a2 = A2();
  Expect.isNull(a2.field1);
  Expect.isNull(a2.field2);

  A3 a3 = A3();
  Expect.isNull(a3.field1);
  Expect.isNull(a3.field2);
}