Property 'formData' does not exist on type 'CreateComponentPublicInstance<{ [x: string & on${string}]: ((...args: any[]) => any) | undefined; } | { [x: string & on${string}]: undefined; }, {}, {}, {}, {}, ComponentOptionsMixin, ComponentOptionsMixin, ... 10 more ..., {}>'. Property 'formData' does not exist on type '{ $: ComponentInternalInstance; $data: {}; $props: { [x: string & on${string}]: ((...args: any[]) => any) | undefined; } | { [x: string & on${string}]: undefined; }; ... 10 more ...; $watch(source: string | Function, cb: Function, options?: WatchOptions<...> | undefined): WatchStopHandle; } & ... 4 more ... & Co...'.Vetur(2339)

[any86]

{
  computed:{
    canSubmit() {
      return !!this.formData.username
    },
  },
}

这是因为计算属性必须标注返回值

{
  computed:{
    canSubmit() :boolean{
      return !!this.formData.username
    },
  },
}