lambda changes the behavior of `type`
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bug
- Dominant language
- Python
- Stars
- 20.6k
- Forks
- 3.3k
- PR merge metrics
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Description
from typing import TypeVar, Callable
T = TypeVar("T")
T2 = TypeVar("T2")
def f(it: T, fn: Callable[[T], T2]) -> T2: ...
reveal_type(f(1, type)) # type
reveal_type(f(1, lambda x: type(x))) # type[int]
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 example in the linked mypy-play playground and compare the revealed types for type and the lambda expression. Start by tracing the callable/type-inference behavior involved; done means the issue's intended behavior is clarified and the two cases produce the expected, consistent revealed types.
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
- Needs clarification
- Newbie friendliness
- 35/100