Reduce import time part 3: remove typing import

[hukkin]

No description provided.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 100.00%. Comparing base (4188188) to head (32af4fd).
Report is 1 commits behind head on master.

Additional details and impacted files

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  Coverage   100.00%   100.00%           
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  Files            4         4           
  Lines          525       526    +1     
  Branches        97        97           
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+ Hits           525       526    +1     

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[hauntsaninja]

Does TYPE_CHECKING = False not work? Only mypy will understand MYPY = False

[hukkin]

I actually only tried MYPY. My interpretation of mypy docs is that only MYPY is officially promised to work here, and TYPE_CHECKING only when imported from typing.

[hauntsaninja]

Let's do python/mypy#18443 :-)
https://github.com/python/mypy/blob/master/mypy/reachability.py#L152

[hukkin]

Great! Switched to TYPE_CHECKING here.

[hukkin]

According to my tests, making Output inherit from object rather than typing.NamedTuple doesn't hurt performance (of pure Python or mypyc whels), so merging this doesn't appear to have a downside.