PEP 604: Remove some more uses of Union/Optional

[JelleZijlstra]

Mypy seems fine with these. Aliases that use type[] or variadic tuple[]
still break mypy.

[AlexWaygood]

Some of these mypy is cool with on >= 3.10, but can't handle on <3.10.

(I'm planning to write up bug reports soon; haven't got round to it yet.)

[JelleZijlstra]

Right. Looks like these are the patterns:

1. type[] at top level fails
2. tuple[T1, T2] at top level fails (but tuple[T1, ...] is fine)
3. T1 | Callable[..., T2 | T3] fails, but only <=3.9

Still ended up with a few fixes. I didn't look at @python2.

[AlexWaygood]

Right. Looks like these are the patterns:

1. type[] at top level fails
2. tuple[T1, T2] at top level fails (but tuple[T1, ...] is fine)
3. T1 | Callable[..., T2 | T3] fails, but only <=3.9

Still ended up with a few fixes. I didn't look at @python2.

Of these, as far as I'm aware, only (2) is tracked over at mypy (in python/mypy#11098); (1) and (3) need to have bug reports filed.

(3) is obviously only relevant to stub files, as it isn't valid syntax in .py files in Python <3.10. That's probably why it hasn't been reported yet.

[github-actions]

According to mypy_primer, this change has no effect on the checked open source code. 🤖🎉

[AlexWaygood]

LGTM

[JelleZijlstra]

I created https://github.com/python/mypy/labels/topic-pep-604 so we can track these better. Going to spend some time today organizing the mypy issue tracker.

[AlexWaygood]

I created https://github.com/python/mypy/labels/topic-pep-604 so we can track these better. Going to spend some time today organizing the mypy issue tracker.

python/mypy#11887 (fixed for stubs but not for .py files) could do with that label being added 👍

[AlexWaygood]

Mypy bugs for (1) and (3) have been filled:

• False-positive errors when using type[T] (or Type[T]) in a PEP 604 type alias mypy#12392
• False-positive error when using Callable in a PEP 604 type alias mypy#12393

[JelleZijlstra]

Thanks!