Issue 29316: Keep typing.py provisional for the duration of the Python 3.6 release cycle

The 3.6 what's new (https://docs.python.org/3/whatsnew/3.6.html#whatsnew36-typing) claims typing.py is no longer provisional, but I don't think it's quite ready yet. There are a number of things that I'd like to merge into typing.py over the duration of 3.6's lifetime. Nothing backwards incompatible, but definitely new features.

See also https://github.com/python/typing/issues/247

I don't have any strong opinion on this. If others don't object then I am perfectly fine with keeping typing provisional for 3.6.

There are three specific areas I can identify that are missing from the typing module at the moment:
* support for structural typing (protocols)
* support for typing heterogenous dictionaries (dictionary "schema")
* support for typing arbitrary callables

There are also minor things like NoReturn, typing_inspect helpers(?) etc. 

The main good point I see for keeping typing provisional is we could iterate fast and come up with more "settled" and robust API in time for 3.7.

+1 for keeping this provisional.  The code is still maturing and needs to be iterated while we gain experience with it.

Keeping it provisional sounds reasonable to me, especially if it helps land protocol support.

As far as I can tell, the only places that typing was declared as provisional were in PEP 484 and twice in the 3.5 What's New document (https://docs.python.org/3.5/whatsnew/3.5.html); it doesn't appear to have been mentioned in the library reference (https://docs.python.org/3.5/library/typing.html) and probably should have been.  FTR, it looks like there was some discussion of removing typing's provisional status in https://github.com/python/typing/issues/278 and https://github.com/python/typing/issues/247.  While it seems somewhat unusual to reinstate a feature's provisional status, I don't have an objection as 3.6 release manager since it is clear that typing is still a new and evolving module.  To make the change in status, the 3.6 What's New document should be updated, a Misc/NEWS entry added for 3.6.1, and the provisional status added to Docs/library/typing.rst.

Thanks everybody! We'll make typing.py provisional again for 3.6. @levkivskyi do you have the stomach to upload a patch here?

Yes, I attached the patch.

New changeset 72c64b6e5486 by Ned Deily in branch '3.6':
Issue #29316: Restore the provisional status of typing module and add
https://hg.python.org/cpython/rev/72c64b6e5486

New changeset ef416878495f by Ned Deily in branch 'default':
Issue #29316: merge 3.6
https://hg.python.org/cpython/rev/ef416878495f

Patch LGTM, thanks Ivan!

stage: patch review -> resolved

stage: needs patch -> patch review

messages: + msg285760

components: + Library (Lib)
keywords: + 3.6regression