no error when value of type `type` (aka `type[Any]`) passed to function with generic with constraint, generic inferred as the first constraint
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bug
topic-type-variables
- Dominant language
- Python
- Stars
- 20.6k
- Forks
- 3.3k
- PR merge metrics
- PR metrics pending
Description
from typing import TypeVar
T = TypeVar("T", int, str)
def foo(cls: type[T]) -> T:
...
asdf: type
reveal_type(type) # error: Expression type contains "Any"
a = foo(asdf) # no error
reveal_type(a) # int
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First steps
- Read the whole issue, then the project's contributing guide.
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- Open a pull request that references the issue number.
Research direction
Start with the supplied mypy-play reproducer and confirm the diagnostics for asdf: type, foo(asdf), and reveal_type(a). Trace generic inference for constrained TypeVar arguments in mypy, then add a regression test covering this case. Done means the call no longer silently infers int without an appropriate error or corrected inference.
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
- Mostly clear
- Newbie friendliness
- 35/100