unexpected "var-annotated" when using constrained TypeVar
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bug
topic-type-variables
- Dominant language
- Python
- Stars
- 20.6k
- Forks
- 3.3k
- PR merge metrics
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Description
Bug Report
I expect to not need to annotate the example below
To Reproduce
class C[T: (int, str)]:
def __init__(self, x: T) -> None:
self.x = x
Expected Behavior
no errors
Actual Behavior
$ ./venv/bin/mypy t.py
t.py:3: error: Need type annotation for "x" [var-annotated]
Your Environment
- Mypy version used: 1.17.1
- Mypy command-line flags: n/a
- Mypy configuration options from
mypy.ini(and other config files): n/a - Python version used: 3.13.1
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
Reproduce the report with the provided t.py example and the mypy command using a constrained TypeVar. Trace how the assignment to self.x is inferred, then verify that the example completes without a var-annotated error.
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
- 45/100