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
16class A {
17    data: string[] = ['a', 'b', 'c'];
18    $_iterator() {
19      return new DIterator(this);
20    }
21}
22
23class CIterator implements Iterator<string> {
24    index = 0;
25    base: A;
26    constructor (base: A) {
27        this.base = base;
28    }
29    next(): IteratorResult<string> {
30        if (this.index >= this.base.data.length) {
31            return {
32                done: true,
33                value: undefined
34            }
35        }
36        return {
37          done: this.index >= this.base.data.length,
38          value: this.base.data[this.index++]
39        }
40    }
41}
42
43class DIterator extends CIterator {
44    constructor (base: A) {
45            super(base);
46        }
47}
48
49function main(): void {
50    let res = "";
51    let a = new A();
52    for (let x of a) res += x;
53    assert(res == "abc");
54}
55