是说ValidateForm.vue没有导出该模块吗？

ValidateForm.vue

<script lang="ts">
import { defineComponent, onUnmounted } from 'vue'
import mitt from 'mitt'
export const emitter = mitt()

export default defineComponent({
  emits: ['form-submit'],
  setup (props, context) {
    const submitForm = () => {
      context.emit('form-submit', true)
    }

    const callback = (text?: string) => {
      console.log(text)
    }

    emitter.on('form-item-created', callback)

    onUnmounted(() => {
      emitter.off('form-item-created', callback)
    })

    return {
      submitForm
    }
  }
})
</script>

ValidateInput.vue

<script lang="ts">
import { defineComponent, reactive, PropType, onMounted } from 'vue'
import { emitter } from './ValidateForm.vue'
const emailReg = /^[a-zA-Z0-9.!#$%&'*+/=?^_`{|}~-]+@[a-zA-Z0-9-]+(?:\.[a-zA-Z0-9-]+)*$/
interface RuleProp {
  type: 'required' | 'email';
  message: string;
}
export type RulesProp = RuleProp[]
</script>

上面贴了js的局部代码。

在ValidateInput.vue引入emitter的时候就报错了。

mitt的版本是 2.1.0