python / python/typing_extensions
Bug: `typing_extensions.Generic` not support `TypeVar` defaults
Open
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- Dominant language
- Python
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- 583
- Forks
- 146
- Avg merge
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- Merged PRs (30d)
- 5
Description
Work MRE.
Setup
>> python version: 3.13.5 (main, Jun 21 2025, 09:35:00) [GCC 15.1.1 20250425]
MRE
from typing import TypeVar, Generic, get_args
R = TypeVar("R")
T = TypeVar("T", default=int)
class A(Generic[R, T]):
pass
assert get_args(A[str]) == (str, int)
Not work MRE.
Setup
>> python version: 3.10.17 (main, Apr 9 2025, 04:03:39) [Clang 20.1.0 ]
>> uv pip show typing-extensions
Name: typing-extensions
Version: 4.15.0
MRE
from typing_extensions import TypeVar, Generic, get_args
R = TypeVar("R")
T = TypeVar("T", default=int)
class A(Generic[R, T]):
pass
assert get_args(A[str]) == (str,)
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 running the Python 3.13 MRE and the typing_extensions MRE to compare their get_args results. Trace the TypeVar default handling used by Generic in typing_extensions, then verify that A[str] includes int as in the standard-library example.
Written by the indexing model from the issue text.
Assessment
- Tech stack
- python
- Domain
- tooling
- Issue type
- Bug
- Difficulty
- 3/5
- Estimated time
- 1-2 days
- Activity status
- Stale
- Clarity
- Clearly specified
- Newbie friendliness
- 45/100