Repro of volar issue #704

Parent.vue

<script lang="ts">
import { defineComponent } from 'vue';
import SubComponent from './Sub.vue';

export default defineComponent({
  components: {
    SubComponent,
  },
  setup() {
    function handleChange(n: number) {
      console.log(n);
    }
    return {
      handleChange,
    };
  },
});
</script>

<template>
  <sub-component @change="handleChange" />
</template>

Sub.vue

<script lang="ts">
import { defineComponent } from 'vue';
export default defineComponent({
    emits: {
        change(n: boolean) {
            return true;
        },
    },
    props: {
        a: {
            type: String,
            required: false,
        },
    },
    setup(props) {},
});
</script>
<template>
Sub
</template>