New submission from Peilonrayz <peilonr...@gmail.com>:
The documentation for `typing.overload` says in a non-stub file the last
definition shouldn't be typed. However running that through `mypy --strict`
fails. I opened an issue on mypy a couple of days ago, however was told to
report this on CPython.
```
>>> import typing
>>> help(typing.overload)
Help on function overload in module typing:
overload(func)
Decorator for overloaded functions/methods.
In a stub file, place two or more stub definitions for the same
function in a row, each decorated with @overload. For example:
@overload
def utf8(value: None) -> None: ...
@overload
def utf8(value: bytes) -> bytes: ...
@overload
def utf8(value: str) -> bytes: ...
In a non-stub file (i.e. a regular .py file), do the same but
follow it with an implementation. The implementation should *not*
be decorated with @overload. For example:
@overload
def utf8(value: None) -> None: ...
@overload
def utf8(value: bytes) -> bytes: ...
@overload
def utf8(value: str) -> bytes: ...
def utf8(value):
# implementation goes here
```
The typing docs and PEP 484 say similar things.
typing docs - https://docs.python.org/3/library/typing.html#typing.overload
PEP 484 - https://www.python.org/dev/peps/pep-0484/#function-method-overloading
Jelle Zijlstra told me to report this here.
https://github.com/python/mypy/issues/9633#issuecomment-716201251
> You should annotate the implementation. The example in the typing docs should
> perhaps also add an annotation, but that's an issue for the CPython repo, not
> for mypy.
Either way mypy errors which can be seen in the following playgrounds.
docs -
https://mypy-play.net/?mypy=latest&python=3.9&flags=strict&gist=cffb94a2de9d5d55142da5e7d960102f
```
main.py:9: error: Function is missing a type annotation
Found 1 error in 1 file (checked 1 source file)
```
proper way? -
https://mypy-play.net/?mypy=latest&python=3.9&gist=bfadffe92571b4faad04ea151b2b1c54
```
main.py:3: error: An overloaded function outside a stub file must have an
implementation
Found 1 error in 1 file (checked 1 source file)
```
Is all the documentation on `typing.overload` wrong - should the implementation
be annotated?
----------
assignee: docs@python
components: Documentation
messages: 379754
nosy: docs@python, peilonrayz
priority: normal
severity: normal
status: open
title: Apparently all documentation on @typing.overload is wrong
versions: Python 3.10, Python 3.6, Python 3.7, Python 3.8, Python 3.9
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Python tracker <rep...@bugs.python.org>
<https://bugs.python.org/issue42169>
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