typing: Use PEP 695 syntax in typing.py by JelleZijlstra · Pull Request #104553 · python/cpython

I think we shouldn't do this since it confuses scoping and much of the point of PEP 695 is to clarify scoping. We can use a callback protocol to spell this.

I'd brought this up somewhere before PEP 695 was accepted, but didn't get much of a response. Presumably since it's not the most common thing and I think e.g. pyre might not even support -> Callable[[T], T]