Ken Jin <kenjin4...@gmail.com> added the comment:
Sorry, I don't think this is a typing module issue.
The NameError stems from what you mentioned: 'A' not being defined since
TYPE_CHECKING evaluates to false at runtime. This would raise an error in any
Python code, not just typing. The equivalent is this::
>>> A
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
NameError: name 'A' is not defined
Without the future import, def f(a: A): ... already throws that NameError. The
reason why it works in your example is because 'A' isn't evaluated at function
declaration time with the future import.
To appease your static type checker and not cause runtime errors, you might
want to try:
f(cast("A", "anything"))
Which seems to work in mypy and pycharm. (Sorry, I don't have
pyre/pytype/pyright to check with, though I would be surprised if this didn't
pass on them.)
Please correct me if you feel anything I wrote was incorrect :).
----------
nosy: +gvanrossum, kj, levkivskyi
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<https://bugs.python.org/issue42377>
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