allow runtime-broken stuff under "if TYPE_CHECKING"
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feature
- Dominant language
- Python
- Stars
- 20.6k
- Forks
- 3.3k
- PR merge metrics
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Description
Feature
Sometimes mypy emits warnings because Python won't understand something at runtime. These shouldn't happen under if TYPE_CHECKING.
Pitch
In Python 3.7, the following code needs a type: ignore comment on the erroring line:
from __future__ import annotations
from typing import TYPE_CHECKING
if TYPE_CHECKING:
Point = tuple[int, int] # mypy error: "tuple" is not subscriptable
def foo(p: Point) -> None:
print(p)
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 Python 3.7 example and trace how mypy processes the if TYPE_CHECKING block. Done means the runtime-invalid tuple[int, int] expression inside that block no longer requires a type: ignore comment, while the annotation remains usable.
Written by the indexing model from the issue text.
Assessment
- Tech stack
- python
- Domain
- devtools
- Issue type
- Feature
- Difficulty
- 4/5
- Estimated time
- 3-5 days
- Activity status
- Stale
- Clarity
- Mostly clear
- Newbie friendliness
- 35/100