Bug report (Regression): bad overload resolution in `--strict` mode
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Description
Bug Report
The following code type-checked with mypy 1.16.1 in --strict mode but does not type-check with mypy 1.17 and the master branch (currently eb07c060c) in --strict mode. Bisecting points to the commit 33d1eedc0.
Note that the problem does not occur if --strict mode is disabled.
To Reproduce
import inspect
import typing
from typing import Any, ClassVar
def is_classvar(cls: type, scope: dict[Any, type]) -> bool:
ann = inspect.get_annotations(cls, eval_str=True, locals=scope).get("kind")
if ann is None:
raise Exception("Should be annotated.")
return typing.get_origin(ann) is not ClassVar
Actual Behavior
mypy --strict test_any.py
test_any.py:9: error: Non-overlapping identity check (left operand type: "ParamSpec", right operand type: "<typing special form>") [comparison-overlap]
Found 1 error in 1 file (checked 1 source file)
Your Environment
- Mypy version used:
mypy 1.17andmaster(bad),mypy 1.16.1(good) - Mypy command-line flags:
--strict - Mypy configuration options from
mypy.ini(and other config files): - Python version used:
3.13
Note that reveal_type(ann) gives Any | None and that annotating ann: Any | None solves the problem.
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 reproducer in test_any.py and the behavior introduced by commit 33d1eedc0. Run mypy --strict against the example on the affected and previously working versions; done means the example type-checks under --strict without requiring an explicit ann: Any | None annotation.
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
- Stale
- Clarity
- Clearly specified
- Newbie friendliness
- 52/100