Making a variable optional in an `else` block doesn't work for `try`/`else`
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Description
Bug Report
#11002 allowed making a variable optional in an else block; this appears not to work in an else block from a try.
To Reproduce
# t.py
def __() -> None:
try:
...
except ValueError as exc:
e = exc
else:
e = None
$ mypy t.py
t.py:7: error: Incompatible types in assignment (expression has type "None", variable has type "ValueError")
Found 1 error in 1 file (checked 1 source file)
Expected Behavior
I expect this to pass, as it would if it were an if/else
Actual Behavior
As above.
Your Environment
- Mypy version used: 0.950
- Mypy command-line flags: n/a
- Mypy configuration options from
mypy.ini(and other config files): n/a - Python version used: Python 3.10.4 (main, Apr 26 2022, 19:42:59) [Clang 13.1.6 (clang-1316.0.21.2)]
- Operating system and version: MacOS 12.3.1 (21E258)
I'm not sure if this is expected, and try/except was out of scope for the original feature, or whether this is a bug.
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 reported t.py example with mypy 0.950 and compare its try/except/else behavior with the if/else behavior described in issue #11002. Trace the type-checking path for assignments across try blocks, then add a regression test for the example and confirm mypy accepts the None assignment without introducing errors.
Written by the indexing model from the issue text.
Assessment
- Tech stack
- python
- Domain
- compilers, devtools
- Issue type
- Bug
- Difficulty
- 3/5
- Estimated time
- 1-2 days
- Activity status
- Stale
- Clarity
- Mostly clear
- Newbie friendliness
- 45/100