new Vue cannot infer mixin types

[gulewei]

Version

2.7.8

Reproduction link

codesandbox.io

Steps to reproduce

open CodeSandBox, and see line 14 in main.ts

What is expected?

type check without error.

What is actually happening?

Property 'helloThere' does not exist on type 'CombinedVueInstance<Vue<Record<string, any>, Record<string, any>, never, never, (event: string, ...args: any[]) => Vue<Record<string, any>, Record<string, any>, never, never, ...>>, ... 4 more ..., {}>'.ts(2339)