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NewType documentation is incorrect #11620
Description
The documentation for NewType at https://mypy.readthedocs.io/en/stable/more_types.html#newtypes states:
...the typing module provides a helper function
NewTypethat creates simple unique types with almost zero runtime overhead.
However, as the cpython documentation for NewType` states:
Changed in version 3.10:
NewTypeis now a class rather than a function. There is some additional runtime cost when callingNewTypeover a regular function. However, this cost will be reduced in 3.11.0.
In Python >=3.10, NewType is a class rather than a function, meaning the mypy documentation is now incorrect.
I'm not immediately sure how it could be rewritten in a more accurate way that is still concise, however.
Activity
JelleZijlstra commentedon Nov 26, 2021
We can just replace "function" with "object". The overhead is still tiny, and it doesn't matter to readers of the mypy documentation exactly how NewType is implemented.
Correct documentation for NewType
AlexWaygood commentedon Nov 26, 2021
Makes sense, thanks!
Correct documentation for NewType (#11621)
Correct documentation for NewType (python#11621)