Typing with ClassVar[Optional[Callable]] doesn't work if the callable has arguments
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Description
Typing an attribute in a base class with ClassVar[Optional[Callable]] results in a type error even though the typing is seemingly sound.
To Reproduce
Playground: https://mypy-play.net/?mypy=master&python=3.11&gist=4f52f561801eeb053b6d0a47c9afbc15
class BaseClass:
attr: ClassVar[Optional[Callable]] = None
class ChildClass2(BaseClass):
@staticmethod
def attr(s: str):
pass
Expected Behavior
Mypy shouldn't return any errors.
Additionally, the same should happen when Callable is also typed itself, e.g. Callable[[str], None]. Right now both fail when they shouldn't.
Actual Behavior
test.py:10: error: Signature of "attr" incompatible with supertype "BaseClass" [override]
Your Environment
- Mypy version used: 1.1.1, 1.2
- Mypy command-line flags: no relevant options
- Mypy configuration options from
mypy.ini(and other config files): no relevant options - Python version used: 3.11
Additional information
Interestingly, if the callable doesn't have any arguments, mypy doesn't fail:
class BaseClass:
attr: ClassVar[Optional[Callable]] = None
class ChildClass2(BaseClass):
@staticmethod
def attr():
pass
Contributor guide
First steps
- Read the whole issue, then the project's contributing guide.
- Comment on the issue to say you are picking it up — it saves two people doing the same work.
- Fork the repository and make your change on a branch.
- Open a pull request that references the issue number.
Research direction
Start with the linked mypy-play reproduction using Python 3.11 and compare the untyped and typed Callable cases. Trace the override-checking path for a ClassVar Optional Callable and verify that both staticmethod examples produce no incompatible-signature error.
Written by the indexing model from the issue text.
Assessment
- Tech stack
- python
- Domain
- devtools
- Issue type
- Bug
- Difficulty
- 4/5
- Estimated time
- 3-5 days
- Activity status
- Stale
- Clarity
- Clearly specified
- Newbie friendliness
- 35/100