Exception variable can leak to other scopes causing strange error messages
Open
Nobody has claimed this yet.
priority-2-low
topic-runtime-semantics
topic-usability
topic-variable-scope
- Dominant language
- Python
- Stars
- 20.6k
- Forks
- 3.3k
- PR merge metrics
- PR metrics pending
Description
Consider this example:
def test() -> None:
print(e)
try:
pass
except Exception as e:
pass
I would expect Name 'e' is not defined, but instead mypy gives Trying to read deleted variable 'e', which may be confusing.
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 with the supplied Python reproducer and search the codebase for the diagnostic text "Trying to read deleted variable". Trace how exception variables are reported, then add a regression test showing that the out-of-scope reference produces the expected undefined-name message.
Written by the indexing model from the issue text.
Assessment
- Tech stack
- python
- Domain
- compilers
- Issue type
- Bug
- Difficulty
- 3/5
- Estimated time
- 1-2 days
- Activity status
- Stale
- Clarity
- Mostly clear
- Newbie friendliness
- 42/100