V2版 @Event @Param 装饰器， 如何完美实现V1版 @Link 的功能？

@ComponentV2
struct Child {
  @Param index: number = 0;
  @Event changeIndex: (val: number) => void;

  build() {
    Column() {
      Text(`Child index: ${this.index}`)
        .onClick(() => {
          this.changeIndex(20);
          console.log(`after changeIndex ${this.index}`);
        })
    }
  }
}
@Entry
@ComponentV2
struct Index {
  @Local index: number = 0;

  build() {
      Column() {
        Child({
          index: this.index,
          changeIndex: (val: number) => {
            this.index = val;
          console.log(`in changeIndex ${this.index}`);
          }
        })
      }
  }
}
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in changeIndex 20
after changeIndex 0
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