Support PEP 647: TypeGuard

[JelleZijlstra]

I'd like to start using https://www.python.org/dev/peps/pep-0647/ in typeshed. Do you have any plans in that direction already?

I can look into adding basic support to unblock typeshed, which would mean simply interpreting TypeGuard[...] as an alias for bool.

[rchen152]

No plans yet, but as you said, it shouldn't be too difficult for us to just interpret TypeGuard as bool for now.

[rchen152]

I should have some time to do this tomorrow afternoon.

[JelleZijlstra]

Thanks!

[rchen152]

I've implemented rewriting TypeGuard[X] to bool in stubs; I'll try to do a release tomorrow.

[rchen152]

Ok, pytype 2021.05.14 is out. Please let me know if you run into any issues using TypeGuard in stubs.

[JelleZijlstra]

Thanks again!

[rchen152]

We've got a basic implementation of TypeGuard done. It'll be in the next release, hopefully tomorrow.