[Custom Descriptors] Fix TypeMerging sibling criteria#7842
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When merging sibling types, we must first partition the types by their supertypes and shapes. With custom descriptors, we consider full descriptor chains as single units to be merged. We had updated the shape partitioning to account for this, but not the supertype partitioning. As a result, we were incorrectly merging chains with different descriptor supertypes as long as the base described types had no supertype. Fix the bug by partitioning not just on the base described type's supertype, but the sequence of all supertypes in the chain.
kripken
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Aug 19, 2025
tlively
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Oct 3, 2025
Now that we have stricter validation for descriptor types, descriptor chains can only be subtypes of other descriptor chains if the base described type of the subtype chain is a subtype of the base described type of the supertype chain. We had previously handled more complicated cases where the base described type in the supertype chain could be a supertype of an arbitrary type in the subtype chain and where a subtype chain could even have several supertype chains. Simplify TypeMerging by reverting #7842 and #7764 now that we no longer need to handle these more complicated cases.
tlively
added a commit
that referenced
this pull request
Oct 3, 2025
Now that we have stricter validation for descriptor types, descriptor chains can only be subtypes of other descriptor chains if the base described type of the subtype chain is a subtype of the base described type of the supertype chain. We had previously handled more complicated cases where the base described type in the supertype chain could be a supertype of an arbitrary type in the subtype chain and where a subtype chain could even have several supertype chains. Simplify TypeMerging by reverting #7842 and #7764 now that we no longer need to handle these more complicated cases.
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When merging sibling types, we must first partition the types by their
supertypes and shapes. With custom descriptors, we consider full
descriptor chains as single units to be merged. We had updated the shape
partitioning to account for this, but not the supertype partitioning. As
a result, we were incorrectly merging chains with different descriptor
supertypes as long as the base described types had no supertype.
Fix the bug by partitioning not just on the base described type's
supertype, but the sequence of all supertypes in the chain.