PEP 544: Specify usage of modules as subtypes of protocols

[ilevkivskyi]

See python/mypy#5018 for motivation.

Attn: @gvanrossum @JukkaL @ambv

[gvanrossum]

LG, but let's wait until the implementation has landed. We might find some unexpected issue.

Also, when next publishing PEP 544 for review on python-dev this should be mentioned in the summary of changes since the last publication. (Don't worry, this isn't going to be another PEP 572. :-)

[ilevkivskyi]

See python/mypy#5322

[gvanrossum]

Whoa. If you don't feel like working on this, fine, but there's no need to close the PR.

(This PR is waiting for the implementation, one of the items at python/mypy#5322 (comment).)

[brettcannon]

I tweaked the title to say "WIP" so people know it's still open on purpose.

[ilevkivskyi]

As we discussed recently, there is no need to wait for full implementation before acceptance (this part of the PEP is not implemented in mypy). I looked at this again, and seems to me this can be merged as is, the current proposal matches the discussion in python/mypy#5322.