Unwrap type[...] before intersection narrowing for TypeIs/TypeGuard#21678
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ygale wants to merge 2 commits into
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Unwrap type[...] before intersection narrowing for TypeIs/TypeGuard#21678ygale wants to merge 2 commits into
ygale wants to merge 2 commits into
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issubclass()/isinstance() narrowing unwraps type[...] before computing an ad-hoc intersection and rewraps the result. TypeIs/TypeGuard narrowing never did this, so a TypeIs[type[M]] guard on a type[A] expression silently failed to narrow.
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Diff from mypy_primer, showing the effect of this PR on open source code: koda-validate (https://github.com/keithasaurus/koda-validate)
+ koda_validate/dataclasses.py:117: error: Redundant cast to "type[_DCT]" [redundant-cast]
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Fixes #21677
issubclass()/isinstance() narrowing unwraps type[...] before computing an ad-hoc intersection and rewraps the result. TypeIs/TypeGuard narrowing never did this, so a TypeIs[type[M]] guard on a type[A] expression silently failed to narrow.
LLM Disclosure
I was assisted by Claude (Sonnet 5), under my close guidance and supervision. The work is mine.