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Author kj
Recipients Ofekmeister, kj
Date 2021-01-19.14:20:04
SpamBayes Score -1.0
Marked as misclassified Yes
Message-id <>
Hello, this issue is a byproduct of issue42195. It has already been fixed on Python 3.10, and on Python 3.9.2 (which isn't out yet). You can see the what's new for it here

The expected release date for Python 3.9.2 is Monday, 2021-02-15 according to PEP 596

For now, I guess you'll have to use the old typing.Callable, then update it in newer versions of Python.

On Python 3.10a4:
>>> from typing import Optional
>>> from import Callable
>>> Optional[Callable[[bytes], bytes]]
typing.Optional[[[bytes], bytes]]
Date User Action Args
2021-01-19 14:20:04kjsetrecipients: + kj, Ofekmeister
2021-01-19 14:20:04kjsetmessageid: <>
2021-01-19 14:20:04kjlinkissue42965 messages
2021-01-19 14:20:04kjcreate