Fix crash on unnormalized tuples in deferred type alias - #22096
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According to mypy_primer, this change doesn't affect type check results on a corpus of open source code. ✅ |
ilevkivskyi
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JukkaL
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Oct 5, 2026
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Fixes #21933
It is crucial that
TypeAliasnode is created once, and then modified in-place in case of deferrals. This is how recursive types were implemented, and a lot of code relies on this. However,rvalue.analyzed(ands.alias_nodefor new-style aliases) were getting a new alias node each time. And these are the waysMixedTraverserfinds type aliases to perform type normalization. Therefore, we could get non-normalized tuples (and other problematic types) in case of a deferred type alias.