no `Any` errors when type inferred from value passed to `type[T]` with no type arguments
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bug
topic-disallow-any
- Dominant language
- Python
- Stars
- 20.6k
- Forks
- 3.3k
- PR merge metrics
- PR metrics pending
Description
from typing import cast, TypeVar, Any
T = TypeVar("T")
def get_value(type_: type[T]) -> T:
...
foo = get_value(list) # no error
bar: list # correct error (Missing type parameters for generic type "list" [type-arg])
reveal_type(foo[0]) # no error
reveal_type(bar[0]) # correct error (Expression type contains "Any" (has type "List[Any]") [misc])
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 minimal example in the issue, using the linked mypy playground and its strictness flags. Trace how mypy infers T for get_value(list) and compare it with the annotated list case; done means the inferred value no longer silently permits the Any-related operations described in the report.
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