提问：为什么在vscode上， v-for="item in list"的list会提醒(property) list?: ColumnProps[] | undefined，我断言了的呀

<template>
  <ul>
    <li v-for="item in list" :key="item.id">
      <img :src="item.avatar" alt="作者头像">
      <h5>{{ item.title }}</h5>
      <p>{{ item.description }}</p>
      <a href="#">进入专栏</a>
    </li>
  </ul>
</template>

<script lang="ts">
import { defineComponent, PropType } from 'vue'
export interface ColumnProps {
  id: string;
  title: string;
  avatar: string;
  description: string;
}
export default defineComponent({
  name: 'ColumnList',
  props: {
    list: {
      type: Array as PropType<ColumnProps[]>,
      requried: true
    }
  },