Fix determinism bug when mapping type names - #8956
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When we rewrite module types, we must associate the old type names and indices with the new types they are being mapped to. The code for this was previously sensitive to the iteration order over the old-to-new type map because it modified the module's type names as it traversed them and because visitation order determined which name was kept in cases where multiple old types map to the same new type. Fix both problems by keeping the lesser names and indices in the case of merges and by not updating the module type names until after the new type names have been fully populated.
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Split off from #8953, as suggested. |
kripken
approved these changes
Jul 30, 2026
| return seenTypeNames.insert(name).second; | ||
| }); | ||
| } | ||
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No test needed updating after this? Odd...
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No, the only pass that merged types previously was TypeMerging, which I guess must handle this itself somehow.
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When we rewrite module types, we must associate the old type names and indices with the new types they are being mapped to. The code for this was previously sensitive to the iteration order over the old-to-new type map because it modified the module's type names as it traversed them and because visitation order determined which name was kept in cases where multiple old types map to the same new type. Fix both problems by keeping the lesser names and indices in the case of merges and by not updating the module type names until after the new type names have been fully populated.