[match-case] Fix narrowing of class pattern with union-argument. #19473
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randolf-scholz
changed the title
randolf-scholz
commented
Jul 17, 2025
| current_type = try_expanding_sum_type_to_union(current_type, enum_name) | ||
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| current_type = get_proper_type(current_type) | ||
| if isinstance(current_type, UnionType) and (default == current_type): |
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The default == current_type was necessary, otherwise quite a few tests break.
Adding or (default is None) and passing default=None in the recursive call also seems to break stuff. Not entirely sure what's going on there.
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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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isinstancecall. #19468testMatchNarrowDownUnionUsingClassPatternI added factorization over
UnionTypeinside theconditional_typesfunction.Then
try_expanding_sum_type_to_unionneeded to move to the start of the function so that we expandcurrent_typebefore attempting factorizating the union type.I also reformatted the docstring for better legibility.