[Wasm GC] Allow subtyping in arguments to struct.get etc. Fixes #3636 (#3644)

Note that Binaryen "canonicalizes" the type, so in the test output here
we end up with $grandchild twice. This is a consequence of us not
storing the heap type as an extra field. I can't think of a downside to
this canonicalization, aside from losing perfect roundtripping, but I think
that's a worthwhile tradeoff for efficiency as we've been thinking so far.

Fixes #3636

1 files changed, 1 insertions, 1 deletions

diff --git a/src/wasm/wasm-binary.cpp b/src/wasm/wasm-binary.cpp
index 1f54a0038..d5579eedf 100644
--- a/src/wasm/wasm-binary.cpp
+++ b/src/wasm/wasm-binary.cpp
@@ -6417,7 +6417,7 @@ void WasmBinaryBuilder::validateHeapTypeUsingChild(Expression* child,
     return;
   }
   if ((!child->type.isRef() && !child->type.isRtt()) ||
-      child->type.getHeapType() != heapType) {
+      !HeapType::isSubType(child->type.getHeapType(), heapType)) {
     throwError("bad heap type: expected " + heapType.toString() +
                " but found " + child->type.toString());
   }