Fix match statement narrowing for self-matching class patterns with literal arguments - #21918
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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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Fixes #21780
This was likely because join_types was being used to combine two possible remaining types (e.g. tuple[int, int] and int), and it would collapse those into object instead of keeping both, which is why mypy couldn't narrow down to a bottom type (Never).
This PR replaces join_types with make_simplified_union, and adds a regression test based on the repro in the issue.
Could be a better fix than this, I would welcome it.