[EH] Fix assumption that all throw_refs are created from rethrows (#6524)

`shouldBeRef` incorrectly assumed that all `throw_ref`s within a `catch`
body had been generated from `rethrow`s, which was not true, because
`throw_ref`s are also created when translating `try`-`delegate`s:
https://github.com/WebAssembly/binaryen/blob/219e668e87b012c0634043ed702534b8be31231f/src/passes/TranslateEH.cpp#L304

This fixes the assumption and changes `cast` to `dynCast`.

1 files changed, 7 insertions, 5 deletions

diff --git a/src/passes/TranslateEH.cpp b/src/passes/TranslateEH.cpp
index f8e059624..42cea6199 100644
--- a/src/passes/TranslateEH.cpp
+++ b/src/passes/TranslateEH.cpp
@@ -359,11 +359,13 @@ struct TranslateToNewEH : public WalkerPass<PostWalker<TranslateToNewEH>> {
       std::optional<Index> local = localAssigner->getExnrefLocal(curr->name);
       if (local) {
         for (auto* throwRef : FindAll<ThrowRef>(catchBody).list) {
-          // All throw_refs generated in this pass has a local.get as its child.
-          // See visitRethrow().
-          auto* localGet = throwRef->exnref->cast<LocalGet>();
-          if (localGet->index == *local) {
-            return true;
+          // All rethrows within this catch body have already been converted to
+          // throw_refs, which contains a local.get as its child.(See
+          // visitRethrow() for details).
+          if (auto* localGet = throwRef->exnref->dynCast<LocalGet>()) {
+            if (localGet->index == *local) {
+              return true;
+            }
           }
         }
       }