如何在Vue组件中声明其它组件的方法(Typescript)？

Question

子组件

<script lang="ts">
import { Vue } from 'vue-property-decorator'

export default class Child extends Vue {
  public func(): void {
    //
  }
}
</script>

父组件

<template>
  <child ref="child" />
</template>

<script lang="ts">
import { Vue } from 'vue-property-decorator'
import Child from './child.vue'

export default Parent extends Vue {
  public create (): void {
    (this.$refs.child as typeof Child).func()
  }
}
</script>

TSLint报错：

Property 'func' does not exist on type 'Component<DefaultData<never>, DefaultMethods<never>, DefaultComputed, DefaultProps>'.