[TSX] Functional component does not accept known attributes

[wonderful-panda]

Version

3.0.0-beta.18

Reproduction link

https://codesandbox.io/s/vue-tsx-typeerror-repro-q2j4r?file=/src/main.tsx

Steps to reproduce

const HelloWorld = (props: { msg: string }) => (<div>{props.msg}</div>);
const vm = <HelloWorld msg="foo" key="1" />; 

What is expected?

No compilation error

What is actually happening?

Compilation error at second line

Type '{ msg: string; key: string; }' is not assignable to type '{ foo: string; }'.
  Property 'key' does not exist on type '{ msg: string; }'.ts(2322)