mock.patch generic incorrectly inferred from new= argument

[PeterJCLaw]

To Reproduce

from unittest import mock

x: mock._patch[int] = mock.patch(
    'something',
    new=2,
)

Results in error:

Incompatible types in assignment (expression has type "_patch[MagicMock]", variable has type "_patch[int]")

I've had a quick look at the typeshed (

typeshed/stdlib/unittest/mock.pyi

Lines 203 to 258 in af33b09

	class _patcher:
	TEST_PREFIX: str
	dict: Type[_patch_dict]
	if sys.version_info >= (3, 8):
	@overload
	def __call__( # type: ignore
	self,
	target: Any,
	*,
	spec: Optional[Any] = ...,
	create: bool = ...,
	spec_set: Optional[Any] = ...,
	autospec: Optional[Any] = ...,
	new_callable: Optional[Any] = ...,
	**kwargs: Any,
	) -> _patch[Union[MagicMock, AsyncMock]]: ...
	# This overload also covers the case, where new==DEFAULT. In this case, the return type is _patch[Any].
	# Ideally we'd be able to add an overload for it so that the return type is _patch[MagicMock],
	# but that's impossible with the current type system.
	@overload
	def __call__(
	self,
	target: Any,
	new: _T,
	spec: Optional[Any] = ...,
	create: bool = ...,
	spec_set: Optional[Any] = ...,
	autospec: Optional[Any] = ...,
	new_callable: Optional[Any] = ...,
	**kwargs: Any,
	) -> _patch[_T]: ...
	else:
	@overload
	def __call__( # type: ignore
	self,
	target: Any,
	*,
	spec: Optional[Any] = ...,
	create: bool = ...,
	spec_set: Optional[Any] = ...,
	autospec: Optional[Any] = ...,
	new_callable: Optional[Any] = ...,
	**kwargs: Any,
	) -> _patch[MagicMock]: ...
	@overload
	def __call__(
	self,
	target: Any,
	new: _T,
	spec: Optional[Any] = ...,
	create: bool = ...,
	spec_set: Optional[Any] = ...,
	autospec: Optional[Any] = ...,
	new_callable: Optional[Any] = ...,
	**kwargs: Any,
	) -> _patch[_T]: ...

) and it looks like it's doing the right thing, hence reporting as a mypy bug. I could definitely be convinced otherwise though.

Your Environment

• Mypy version used: 0.812
• Mypy command-line flags: none
• Python version used: 3.7.10
• Operating system and version: Ubuntu 20.04

[JelleZijlstra]

I wonder if the order of the two overloads should be flipped. Your code matches the first overload (the new just goes into **kwargs: Any) and also the second, but the second is what we want.

[hauntsaninja]

I think Jelle's right since if you pass the arg without keyword it works, opening a PR