1/*
2 * Copyright (c) 2024 Huawei Device Co., Ltd.
3 * Licensed under the Apache License, Version 2.0 (the "License");
4 * you may not use this file except in compliance with the License.
5 * You may obtain a copy of the License at
6 *
7 * http://www.apache.org/licenses/LICENSE-2.0
8 *
9 * Unless required by applicable law or agreed to in writing, software
10 * distributed under the License is distributed on an "AS IS" BASIS,
11 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
12 * See the License for the specific language governing permissions and
13 * limitations under the License.
14 */
15 
16 class A {
17    returnHello(op?: string): string {
18        const extra: string = op ? op as string : ""
19        return "hello A " + extra;
20    }
21}
22
23class B extends A {
24    returnHello(op?: string): string {
25        const extra: string = op ? op as string : ""
26        return "hello B " + extra;
27    }
28}
29
30function main(): void {
31    let b: A = new B()
32    assert b.returnHello() == "hello B "
33}
34