F811 (redefinition of unused variable) incorrectly triggered with @overload decorator

PEP 484 introduced the @overload decorator for type annotations.

[...] a series of @overload-decorated definitions must be followed by exactly one non-@overload-decorated definition (for the same function/method). The @overload-decorated definitions are for the benefit of the type checker only, since they will be overwritten by the non-@overload-decorated definition, while the latter is used at runtime but should be ignored by a type checker.

The following should pass PyFlakes without errors, but currently triggers F811 errors:

from typing import overload


@overload
def utf8(value: None) -> None:
    pass


@overload
def utf8(value: bytes) -> bytes:
    pass


@overload
def utf8(value: str) -> bytes:
    pass


def utf8(value):
    pass  # actual implementation

test.py:9:1: F811 redefinition of unused 'utf8' from line 4
test.py:14:1: F811 redefinition of unused 'utf8' from line 9
test.py:19:1: F811 redefinition of unused 'utf8' from line 14

facing the same issue. do you have a workaround?

~~Added this to .pydocstyle~~

~~[pydocstyle] ignore-decorators = overload~~
We ended up adding `# noqa: F811` comments.

How does pydocstyle config fix a pyflakes bug?

I took a stab at this: #371

Hi, it's good to see #371 solved this partially, but overloads on classes is still incorrectly triggered

import typing
from typing import overload


class Foo:
    @overload
    def f(self, s):  # type: (None) -> None
        pass

    @overload
    def f(self, s):  # type: (int) -> int
        pass

    def f(self, s):
        return s

    @typing.overload
    def g(self, s):  # type: (None) -> None
        pass

    @typing.overload
    def g(self, s):  # type: (int) -> int
        pass

    def g(self, s):
        return s

☁  shm  pyflakes a.py 
a.py:11: redefinition of unused 'f' from line 6
a.py:16: redefinition of unused 'f' from line 10
☁  shm  pyflakes --version
2.1.1 Python 3.6.7 on Linux

I'm now working around this by using full typing.overload name

@feisuzhu

@feisuzhu try master, I've already fixed this: #435

I still have this issue when the overload decorator is wrapped by another decorator.

def my_decorator(func):
    return typing.overload(func)

@my_decorator
def utf8(value: None) -> None:
    pass

@my_decorator
def utf8(value: bytes) -> bytes:
    pass

def utf8(value):
    pass  # actual implementation

that's not possible to detect statically -- I'd suggest not doing that (I don't think mypy can detect that either)

I'd suggest explicitly using the overload decorator

Gotcha. I don't think this works either.

from typing import overload

def my_decorator(func):
    return func

@overload
@my_decorator
def utf8(value: None) -> None:
    pass

@overload
@my_decorator
def utf8(value: bytes) -> bytes:
    pass

def utf8(value):
    pass  # actual implementation

Have you tried on master? it works for me

actually, it even works with the released version of pyflakes so you're probably on an old one

This is my version info that doesn't work:

3.7.8 (flake8-comprehensions: 2.1.0, flake8-mypy: 17.8.0, mccabe: 0.6.1, pycodestyle: 2.5.0, pyflakes: 2.1.1) CPython 3.6.8 on Linux

What do you think about counting a decorator as a use of a function? Edit: the redefinition error would still exist even if the unused wouldn't

actually, I'm wrong about it being already released -- it is fixed on master though, please try that and confirm

see #435

yea works on master, thanks!

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F811 (redefinition of unused variable) incorrectly triggered with @overload decorator #320

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F811 (redefinition of unused variable) incorrectly triggered with @overload decorator #320

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tscholak commented on Feb 13, 2018

bartvm commented on Feb 13, 2018

sigmavirus24 commented on Feb 13, 2018

asottile commented on Oct 14, 2018

feisuzhu commented on Mar 4, 2019

asottile commented on Mar 4, 2019

eellison commented on Aug 6, 2019

asottile commented on Aug 6, 2019

eellison commented on Aug 6, 2019

asottile commented on Aug 6, 2019

asottile commented on Aug 6, 2019

eellison commented on Aug 6, 2019

asottile commented on Aug 6, 2019

asottile commented on Aug 6, 2019

eellison commented on Aug 6, 2019

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