[Python-ideas] Moving typing out of the stdlib in Python 3.7?

[Guido van Rossum]

[A copy from https://github.com/python/typing/issues/495 to get more
people's attention to this issue.]

I'm wondering if we should remove typing from the stdlib. Now's the time to
think about this, as the feature freeze for 3.7 is about 12 weeks away.

Cons:

   - People have to depend on a PyPI package to use typing (but they do
   anyway for typing_extensions)
   - It's a backward incompatibility for users of Python 3.5 and 3.6 (but
   the typing module was always provisional)

Pros:

   - The typing module can evolve much faster outside the stdlib
   - We could get rid of typing_extensions (and maybe even mypy_extensions)

If we don't do this I worry that we're entering a period where many new
typesystem features end up in typing_extensions and users will be confused
about which items are in typing and which in typing_extensions (not to
mention mypy_extensions). Anything new to be added to typing (e.g. Const,
Final, Literal, or changing ABCs to Protocols) would have to be added to
typing_extensions instead, and users would be confused about which features
exist in which module. Moving typing out of the stdlib can make things
potentially simpler, at the cost of an extra pip install (but they'll need
one anyway for mypy).

Thoughts?

-- 
--Guido van Rossum (python.org/~guido)
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