Release 1.3 planning

[wesleywright]

I'm aiming to make the 1.3 release by the end of April.

Please post here any issues you'd like to see fixed in the release, or PRs you'd like to have merged.

[ikonst]

#15050, #14849

[wesleywright]

Created a release branch for this release: https://github.com/python/mypy/tree/release-1.3

[wesleywright]

Looks like python/typeshed#10060 will be a blocker

[Viicos]

I would be grateful if #14471 could get fixed, I've spent some time trying to see what was failing but my knowledge of the mypy internals is too limited. It may be straightforward, as it is kind of reverting #7656 and this one doesn't have a large diff. More context here: #8330 (comment)

[cdce8p]

Would be awesome if the performance fix for union subtyping could be included

• Fix performance in union subtyping #15104

[emmatyping]

I'd love to get a review/merge on #14888 so that https://mypy.app can start using official mypy wheels.

[JelleZijlstra]

Merged #14888, would be good to cherry-pick.

[wesleywright]

Cherry-picked #14888 as well as python/typeshed#10061 to fix a known Typeshed bug

[wesleywright]

@cdce8p cherry-picked #15104.

@ikonst unfortunately it seems that #15050 has a conflict when I try to cherry-pick it; seems like that is related to 768ba66, which is pretty big, so I'm hesitant to cherry-pick that as well.

[wesleywright]

@JukkaL identified at least these two issues as potential blockers:

• Type ignore comments erroneously marked as unused by dmypy #15043
• More cases showing errors disappearing from dmypy reruns #15049

Will hold off on final release steps until Jukka's had a chance to assess these in more depth.