[RT] Support expressions in element segments (#3666)

This PR adds support for `ref.null t` as a valid element segment
item. The abbreviated format of `(elem ... func $f $g...)` is kept in
both printing and binary emitting if all items are `ref.func`s. Public
APIs aren't updated in this PR.

1 files changed, 3 insertions, 0 deletions

diff --git a/src/wasm-traversal.h b/src/wasm-traversal.h
index 7dcf2d146..1f307c318 100644
--- a/src/wasm-traversal.h
+++ b/src/wasm-traversal.h
@@ -196,6 +196,9 @@ struct Walker : public VisitorType {
     if (segment->table.is()) {
       walk(segment->offset);
     }
+    for (auto* expr : segment->data) {
+      walk(expr);
+    }
     static_cast<SubType*>(this)->visitElementSegment(segment);
   }