Explicit type aliases fail in typeshed

[srittau]

I can't reproduce this locally, but please have a look at the CI failures of python/typeshed#7534. The change is adding explicit type aliases to _typeshed/*. CI runs mypy 0.941 with all Python versions.

[JelleZijlstra]

For reference #11305 added PEP 613 support.

[AlexWaygood]

Happy to confirm that #12431 solved this issue — now only the pytype test is failing in typeshed's CI (python/typeshed#7534) 🎉