Incompatible type "Type[ImportError]"; expected "Type[Exception]"
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Description
Bug Report
Mypy appears not to consider ImportError to be an exception type in some cases.
To Reproduce
y = [
# ValueError,
ImportError, # error: List item 0 has incompatible type "Type[ImportError]"; expected "Type[Exception]" [list-item]
AttributeError,
]
reveal_type(y) # note: Revealed type is "builtins.list[def (*args: builtins.object, *, name: Union[builtins.str, None] =, obj: Union[builtins.str, None] =) -> builtins.Exception]"
The ordering of the list elements doesn't seem to impact the behaviour.
If you un-comment the ValueError however:
y = [
ValueError,
ImportError,
AttributeError,
]
reveal_type(y) # note: Revealed type is "builtins.list[builtins.type]"
While this is perhaps less precise than I'd hope (I'd hope to get list[type[Exception]]) it feels more right to me.
Adding an annotation to the variable (y: list[type[Exception]]) does help mypy see that this is ok, however in my original use-case the list being constructed was passed to a decorator function, so there was no easy opportunity to annotate it.
Your Environment
- Mypy version used: 0.991
- Mypy command-line flags: none
- Mypy configuration options from
mypy.ini(and other config files): none - Python version used: 3.11
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 provided Python example with mypy 0.991 or a current checkout and compare the inferred types with and without ValueError. Trace the list-item inference and exception-type handling, then add a regression test showing that ImportError is accepted in the list and verify the expected revealed type.
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
- Mostly clear
- Newbie friendliness
- 38/100