Fix TypeIs narrowing for covariant generic Any - #21662
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This doesn't address why this works for contravariant typevars. Please don't duplicate code. |
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Updated, thanks. I removed the separate variance helper and route the TypeIs false-branch coverage check back through the existing type-parameter path instead. The new flag only changes variant parameter comparisons in this coverage check: invariant parameters stay exact/proper, while covariant and contravariant parameters use the existing declared-variance subtype logic. I also added the contravariant sibling regression case next to the covariant one, so the behavior that already worked stays covered. |
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According to mypy_primer, this change doesn't affect type check results on a corpus of open source code. ✅ |
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As per our policy we don't accept LLM generated PRs from new contributors. |
3 participants
Fixes #21641.
Summary
TypeIschecks according to declared variance.TypeIs[Source[object]]narrow awaySource[Any]whenSourceis covariant.Box[Any]is not removed byTypeIs[Box[str]].Tests
python runtests.py check-typeispython runtests.py check-typeguard check-narrowingpython -m pytest mypy/test/testsubtypes.py -qpython -m mypy --config-file mypy_self_check.ini mypy/subtypes.pypython -m ruff check mypy/subtypes.pypython -m black --check mypy/subtypes.pygit diff --checkPrepared with AI assistance.