Report protocol problems in no_variant_matches_arguments if possible

Feature

Report protocol problems in no_variant_matches_arguments if possible.

Pitch

Given following example:

from typing import Protocol, overload


class Foo(Protocol):
    def some_method(self, value: int = 0) -> None: ...


class Bar:
    def some_method(self, value: int) -> None:
        pass


@overload
def accept_foo(value: Foo, v: int) -> None:
    pass


@overload
def accept_foo(value: Foo, v: float) -> None:
    pass


def accept_foo(value: Foo, v: int | float) -> None:
    pass


accept_foo(Bar(), 1)

The Bar has conflict with the Protocol Foo, but currently Mypy won't report the protocol problems. This is the current error report:

protocol_example.py:27: error: No overload variant of "accept_foo" matches argument types "Bar", "int"  [call-overload]
protocol_example.py:27: note: Possible overload variants:
protocol_example.py:27: note:     def accept_foo(value: Foo, v: int) -> None
protocol_example.py:27: note:     def accept_foo(value: Foo, v: float) -> None
Found 1 error in 1 file (checked 1 source file)

If we can report the protocol problems in this case, it may save developers time to figure out what' wrong.

I did a proof-of-concept implementation here: https://github.com/python/mypy/commit/a2040d3680320afbac6e13b3b04593a7965242bc. This is the updated error report:

protocol_example.py:27: error: No overload variant of "accept_foo" matches argument types "Bar", "int"  [call-overload]
protocol_example.py:27: note: Following member(s) of "Bar" have conflicts:
protocol_example.py:27: note:     Expected:
protocol_example.py:27: note:         def some_method(self, value: int = ...) -> None
protocol_example.py:27: note:     Got:
protocol_example.py:27: note:         def some_method(self, value: int) -> None
protocol_example.py:27: note:     Expected:
protocol_example.py:27: note:         def some_method(self, value: int = ...) -> None
protocol_example.py:27: note:     Got:
protocol_example.py:27: note:         def some_method(self, value: int) -> None
protocol_example.py:27: note: Possible overload variants:
protocol_example.py:27: note:     def accept_foo(value: Foo, v: int) -> None
protocol_example.py:27: note:     def accept_foo(value: Foo, v: float) -> None
Found 1 error in 1 file (checked 1 source file)

If this is OK, I'd happy to refine the implementation and submit a PR.

Thanks.

Commencez au point d'entrée no_variant_matches_arguments et examinez le commit de preuve de concept lié dans l'issue. Reproduisez l'exemple fourni de Protocol et overload, puis vérifiez que le diagnostic signale correctement les membres en conflit, sans sortie en double ni trompeuse.