False positive with disallow-any-explicit and `...` in `Callable` in bound of type var
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bug
priority-2-low
topic-calls
topic-disallow-any
- Dominant language
- Python
- Stars
- 20.6k
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Description
I want a generic function type, but I don't want to get spurious Any errors on every usage.
from typing import Callable, TypeVar
Fn = TypeVar("Fn", bound=Callable[..., object])
mypy --disallow-any-explicit .
error: Explicit "Any" is not allowed
Fn = TypeVar("Fn", bound=Callable[..., object])
^
I understand that this is actually usable as unsafe Any garbage:
def foo(fn: Fn) -> Fn: # type safe usage
fn(1) # not type safe usage
So this should be the only place where the error appears.
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 by reproducing the issue with mypy --disallow-any-explicit on the shown TypeVar("Fn", bound=Callable[..., object]) example, then trace how explicit Any diagnostics handle ... in a Callable bound. Done means the bound is diagnosed as the intentional unsafe Any case without producing spurious errors at every use of Fn.
Written by the indexing model from the issue text.
Assessment
- Tech stack
- python
- Domain
- devtools
- Issue type
- Bug
- Difficulty
- 3/5
- Estimated time
- 1-2 days
- Activity status
- Quiet
- Clarity
- Mostly clear
- Newbie friendliness
- 48/100