2.4 Release Planning

[KevinRK29]

Release tracker for 2.4, the plan is to have it out by end of September.

Let me know if there's any PRs that you want to include in this release

[ilevkivskyi]

Here are the things I want to be included in the release (most of them don't have a PR yet, but I will most likely implement these in next couple weeks):

• [mypyc] Synchronize native-to-native imports #21887 should be reviewed and merged
• Finish switch to the native parser by default, see Make native parser the default #21823. This one will be hopefully done in next 2-3 days.
• Fix We need equivalent of parse_type_string() in native parser #21515 plus any possible fallout
• Use two-phase checking in sequential checking if --local-partial-types is set (i.e. by default)
• Add support for -n auto in parallel checking, see Detect number of CPUs with --num-workers auto #21477
• Change logic for variadic tuple[Any, ...] (this is a long-standing thing affecting NumPy, see e.g. tuple[*Ts] subtype with extra type parameter not gradually assignable to itself #19908)
• Fix remaining part of the performance regression from TypeForm, see Reduce TypeForm recognition slowdown (Take 3) #21833

Also (assuming -n auto will be done) we should announce that parallel checking will become default in a future release, and encourage people to use -n auto.

[KevinRK29]

It would also be nice to include support for PEP 718 in this release, using one of these implementations

• Draft implementation for PEP 718 -- function subscription #21880
• Alternate draft implementation for PEP 718 -- stricter rules #21881