Typing spec update: syntax and supported constructs for stub files

[rchen152]

Please consider this proposed change to the spec: https://github.com/python/typing/pull/1815.

The PR has already been reviewed by several people (thank you!). There are a few unresolved points on which discussion has stalled or petered out that I'm hoping the council can make a decision on.

• [Minor] Should pass in class and function bodies means the same thing as ..., or should the behavior of pass be undefined? Discussion
• [Minor] Should class-scoped type aliases be supported? Discussion
• [Controversial] What version of Python syntax should be supported? Discussion

Discuss thread here (but the discussion is all on the PR).