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Wrong "Overloaded function implementation does not accept all possible arguments" #11004
Closed as not planned
Description
Bug Report
The following example (reduced from psycopg 3) seems to be a false positive:
To Reproduce
from typing import Any, Callable, Generic, overload, Optional, TypeVar, Tuple, Union
Row = TypeVar("Row")
class Connection(Generic[Row]):
@overload
def connect(
self, *, row_factory: Callable[[], Row], **kwargs: Union[None, int, str]
) -> "Connection[Row]":
...
@overload
def connect(
self, **kwargs: Union[None, int, str],
) -> "Connection[Tuple[Any, ...]]":
...
def connect(
self, *, row_factory: Optional[Callable[[], Row]] = None, **kwargs: Any,
) -> "Connection[Any]":
raise NotImplementedErrorThe file is flagged with the error:
bug_mypy.py:18: error: Overloaded function implementation does not accept all possible arguments of signature 2 [misc]
Your Environment
- Mypy version used: 0.910
- Python version used: 3.8
- Operating system and version: Linux
Activity
erictraut commentedon Aug 21, 2021
You may have already figured this out, but there is a simple workaround. If you change the second overload to include an explicit
row_factoryparameter, it will type check without errors.dvarrazzo commentedon Aug 21, 2021
@erictraut No, I didn't notice that, thank you. It is interesting, however I prefer to use a
type: ignorerather than a dummy parameter.Another thing that makes the error go is to use
**kwargs: Anyin the second signature.dlax commentedon Aug 23, 2021
I think that's the issue I tried to resolve in #10390.
dvarrazzo commentedon Aug 23, 2021
Amazing @dlax, didn't know you had looked into it so much to propose a MR! 🙂
adam-grant-hendry commentedon Jul 5, 2022
@dlax Do you plan to merge the change soon?
dlax commentedon Jul 6, 2022
@adam-grant-hendry, the PR is still pending review; and then possible merge by a project member.
sterliakov commentedon Mar 26, 2025
This isn't a bug? As currently written, the second overload accepts
Connection().connect(row_factory=10)and the implementation signature does not, somypywarns about a real problem.