Set[T] is incompatible with Set[Optional[T]] - Set[None]
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feature
priority-2-low
- Dominant language
- Python
- Stars
- 20.6k
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- 3.3k
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Description
Tested with 0.761.
MWE:
from typing import Optional, Set
class Foo:
pass
bar: Set[Optional[Foo]] = set()
baz: Set[Foo] = bar - {None}
# Incompatible types in assignment (expression has type "Set[Optional[Foo]]",
# variable has type "Set[Foo]")
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
Reproduce the issue with the provided MWE using mypy 0.761 or a current checkout, then trace how set subtraction is typed for Set[Optional[Foo]] and {None}. Done means the assignment to Set[Foo] is handled according to the intended type-checking behavior, with a regression test for the example.
Written by the indexing model from the issue text.
Assessment
- Tech stack
- python
- Domain
- devtools
- Issue type
- Bug
- Difficulty
- 4/5
- Estimated time
- 3-5 days
- Activity status
- Stale
- Clarity
- Mostly clear
- Newbie friendliness
- 35/100