Description
Bug Report
When trying to use a match
pattern and bind to a variable with the same name as an except ... as
bind, mypy starts returning an error.
If I remove the try/except
block or don't try to attempt to reassign the variable, the issue goes away.
I've tried to search for other similar issues, but couldn't find much. Hope it's not a duplicate.
To Reproduce
def main() -> None:
try:
pass
except Exception as exc:
print(exc)
result = Exception() # this could for example be the result of `asyncio.gather(..., return_exceptions=True)`
match result:
case Exception() as exc:
print("got exception", exc)
case _:
print("got something else", result)
main()
Gist URL: https://gist.github.com/mypy-play/4d9bc9f42141eb6093823efcbc0dafd7
Playground URL: https://mypy-play.net/?mypy=master&python=3.13&gist=4d9bc9f42141eb6093823efcbc0dafd7&flags=allow-redefinition
Tried with various versions of mypy (1.8.0, 1.15.0, master) and Python (3.10, 3.11, 3.13).
Tried with --allow-redefinition
and without.
Expected Behavior
No error from mypy, at least when using --allow-redefinition
.
Actual Behavior
main.py:9: error: Incompatible types in capture pattern (pattern captures type "Exception", variable has type <deleted>) [misc]
main.py:10: error: Trying to read deleted variable "exc" [misc]
Found 2 errors in 1 file (checked 1 source file)
Your Environment
- Mypy version used: 1.8.0, 1.15.0, master
- Mypy command-line flags: --allow-redefinition
- Mypy configuration options from
mypy.ini
(and other config files): N/A - Python version used: 3.10, 3.11, 3.13