Function accepts callable, but a typeshed custom Protocol was passed

[Andrew-Chen-Wang]

Bug Report

(A clear and concise description of what the bug is.)

To Reproduce

I have some code like:

await asyncio.to_thread(
    shutil.rmtree, connector_folder, ignore_errors=False, onerror=None
)

But I'm getting mypy errors like

Argument 1 to "to_thread" has incompatible type "_RmtreeType"; expected "Callable[[Path, bool, None], None]"  [arg-type]

Expected Behavior

I would assume this is fine this callable is fine and this is passing.

Actual Behavior

Argument 1 to "to_thread" has incompatible type "_RmtreeType"; expected "Callable[[Path, bool, None], None]"  [arg-type]

Your Environment

• Mypy version used: 1.11.0
• Mypy command-line flags: pointing to pyproject.toml config
• Mypy configuration options from mypy.ini (and other config files): ignore_missing_imports = true
• Python version used: 3.12

I do NOT have Typeshed installed in my pip list, but I saw in typeshed that it may be bundled with mypy? Again I don't see it installed, but curious to know why this wouldn't work.

[TeamSpen210]

Indeed, mypy (and all other type checkers) bundle typeshed, since it’s where they get type definitions for everything in the standard library.

I can see the problem though: In 3.12, the stub specifies onerror as not accepting None. Though that’s the default anyway, so you could just omit it, or use the replacement onexc.

[Avasam]

You'll get this error only on Python 3.12+ because the typeshed definition didn't allow None for the onerror parameter on Python 3.12.

This is not a mypy issue and mypy is correctly interpreting the type here. Pyright has the same behaviour. The definition at

typeshed/stdlib/shutil.pyi

Lines 79 to 110 in 1d10860

	if sys.version_info >= (3, 12):
	@overload
	@deprecated("The `onerror` parameter is deprecated. Use `onexc` instead.")
	def __call__(
	self,
	path: StrOrBytesPath,
	ignore_errors: bool,
	onerror: _OnErrorCallback,
	*,
	onexc: None = None,
	dir_fd: int | None = None,
	) -> None: ...
	@overload
	@deprecated("The `onerror` parameter is deprecated. Use `onexc` instead.")
	def __call__(
	self,
	path: StrOrBytesPath,
	ignore_errors: bool = False,
	*,
	onerror: _OnErrorCallback,
	onexc: None = None,
	dir_fd: int | None = None,
	) -> None: ...
	@overload
	def __call__(
	self,
	path: StrOrBytesPath,
	ignore_errors: bool = False,
	*,
	onexc: _OnExcCallback | None = None,
	dir_fd: int | None = None,
	) -> None: ...

may be incorrect.

Do note however, that onerror is deprecated in favor of onexc