vue3中间定义的数组对象为什么用不了？？？（原来在vue2中就没有问题）求大神帮助---标黑的地方报警

<template>
<div class="header">
<ul>
<li v-for="(item,index) in activeList(0)" :class="[{active:item.isShow}]" @click.stop="changeli(index,item)">
{{item.menuname}}
<ul v-show="item.isShow">
<li v-for="(childitem,index) in activeList(item.menuid)" :class="[{activeItem:childitem.showItem}]"

<script lang="ts">
import {computed} from 'vue'
export default {
name: "tmenu",
props: {
data: Array,
default:()=>[]

    },  
    setup(props,) {