How to mark platform dependent modules?

[sobolevn]

Now when I know about VERSIONS file I have a second question: what about platform specific modules?

Simple repro:

import winreg

Related #6733

[hauntsaninja]

We don't have a good solution for that. I'd be in favour of putting the whole module under a sys.platform check (we used to do this for sys.version_info before VERSIONS and it worked passably well).

Could also complicate the specification of VERSIONS, but it'd require support from all type checkers.

[AlexWaygood]

The whole of posix.pyi is under a sys.platform check: https://github.com/python/typeshed/blob/master/stdlib/posix.pyi

Seems sensible to do the same thing for winreg.

(Obviously there will still be false-negative type-checking errors with import winreg, but accessing anything from winreg on linux will at least cause an error.)

[sobolevn]

Ok, I will send a PR to winreg today!

Could also complicate the specification of VERSIONS, but it'd require support from all type checkers.

I think that using something like platform spec in pip might be a good idea.