TypeUpdating: Fix heap type updates on heap type children #7848
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tlively
approved these changes
Aug 20, 2025
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| // XXX This will not scan HeapType children that are not also children of | ||
| // Type children, which happens with Continuation (has a HeapType | ||
| // child that is not a Type). |
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It's unclear to me whether this is a problem that needs to be fixed or just a helpful note to inform any future changes.
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I think this will be a problem if we have features that depend on it. Atm I think we don't.
I was just auditing this code and realized that this was a potential future bug. And, regardless, the right thing here is to scan heap types, not types.
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GlobalTypeRewriter::getTempTypehad the right logic to handle aType, which included the right logic to handle the HeapType of a
Type: Look in
typeIndicesand use that mapping if it is present. Weneed the same thing for HeapTypes as well, which this adds in a
new
getTempHeapType.This was not noticed before because Continuations are the first
thing to have a direct HeapType child which is not through a Type.
So Types worked before, but not direct HeapType children, which
ended up mapped to the old type before the rewriting.
Changes to
wasm-type.hare NFC but I think make it easier to read,as it makes that logic entirely parallel to the lines above it.
One existing test has an update, which fixes it by removing the
ref to the old type.