Fix crash involving Unpack-ed TypeVarTuple #20323
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hauntsaninja
commented
Nov 28, 2025
| @overload # E: Single overload definition, multiple required | ||
| def foo(x: int) -> None: ... | ||
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| def foo(*args: int, **kw: str) -> None: # E: Overloaded function implementation does not accept all possible arguments of signature 1 |
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Not really related to this PR, just adds #19619 (comment)
hauntsaninja
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Nov 28, 2025
mypy/types.py
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| typ = vararg.typ | ||
| if isinstance(typ, UnpackType): | ||
| # Similar to logic in ExpressionChecker.visit_tuple_index_helper | ||
| unpacked = get_proper_type(typ.type) |
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fixing this here could prevent crashes in other places that don't expect to be handling UnpackType, but may result in false positives because upper_bound is lossy
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Hmm, maybe this approach is too ambitious for now (e.g. thinking about |
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According to mypy_primer, this change doesn't affect type check results on a corpus of open source code. ✅ |
sterliakov
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Nov 29, 2025
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sterliakov
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sterliakov
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Certainly looks OK as a hotfix for a crashing result. The false positive just remains intact and should be tracked separately. Thanks!
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Fixes #20093
This fixes the crash, but not the false positive (the false positive existed prior to the regression that introduced the crash)