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Wrong checking of overload for keyword-only args #1907
Description
While writing some stubs I found an issue that I simplified to the following:
from typing import overload
@overload
def f(*, out: str, flag: bool=False) -> str: ...
@overload
def f(*, flag: bool=False) -> bool: ...
reveal_type(f()) # I expect bool, get Any
reveal_type(f(flag=False)) # I expect bool, get Any
reveal_type(f(out="xxx")) # I expect str, get strThe checker shows a
error: Overloaded function signatures 1 and 2 overlap with incompatible return types
but actually the signatures do not overlap (there's no call that can match both the signatures).
Something that's also confusing is that if I change the order of the arguments like this
# Move the "out" argument to the end
@overload
def f(*, flag: bool=False, out: str) -> str: ...
@overload
def f(*, flag: bool=False) -> bool: ...I stop getting the "signature overlap" error, but I still get the "Any" type on the first two example calls. Given that these arguments are keyword only their positions shouldn't matter at all
(Comes from python/typing#248 )
Activity
euresti commentedon Dec 14, 2017
Very weirdly it's the kwonly that's causing issues:
This code has no issues:
But make those kwonly and boom:
Make overloads respect keyword-only args
Make overloads respect keyword-only args
Make overloads respect keyword-only args
Make overloads respect keyword-only args
ilevkivskyi commentedon May 17, 2018
The
Anyreturn is now fixed, but the overlap error still appears, so this is a false positive.Michael0x2a commentedon Jun 15, 2018
This took way way longer to resolve then I originally thought it would take, but the above examples are working as expected now in master after f61c2ba.
There's still a few todos related to handling edge cases w.r.t. star args, optional args, and such in #5163 that needs to land before we can really call this done, but I'm going to close this mostly so I can prune the list of overload-related things I have left to do.