Component's props cannot correctly validate required on a Boolean prop

[kuanyui]

Version

3.0.7

Reproduction link

https://jsfiddle.net/cafpskt5/22/

Steps to reproduce

1. Define a required boolean prop in component (e.g. bool: { type: Boolean, required: true } in props)
2. Use this component, but don't pass any prop to it.

What is expected?

Gives a warning [Vue warn]: Missing required prop: \"bool\""

What is actually happening?

No warning message output.

---

1. But if you give :bool= a string or number, it indeed can be validated and gives a warning message ([Vue warn]: Invalid prop: type check failed for prop \"bool\". Expected Boolean, got String with value \"1\".).
2. Other types (Number, String, Object) work well and have no similar bugs like this.

[Kingbultsea]

bool is set to false by default.
is this about #3337 ?

[HcySunYang]

Yeah, by default if the boolean props are absent then they will be cast to false, but we still need to raise a warning if it is required.