[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`.

Author: aheejin

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;
+            }
           }
         }
       }

test/lit/passes/translate-to-new-eh.wast

@@ -2211,4 +2211,79 @@
       )
     )
   )
+
+  ;; CHECK:      (func $try-catch-rethrow-with-inner-delegate (type $1)
+  ;; CHECK-NEXT:  (local $0 exnref)
+  ;; CHECK-NEXT:  (block $outer2
+  ;; CHECK-NEXT:   (local.set $0
+  ;; CHECK-NEXT:    (block $catch3 (result exnref)
+  ;; CHECK-NEXT:     (try_table (catch_ref $e-empty $catch3)
+  ;; CHECK-NEXT:      (call $foo)
+  ;; CHECK-NEXT:     )
+  ;; CHECK-NEXT:     (br $outer2)
+  ;; CHECK-NEXT:    )
+  ;; CHECK-NEXT:   )
+  ;; CHECK-NEXT:   (block
+  ;; CHECK-NEXT:    (block $outer1
+  ;; CHECK-NEXT:     (try_table
+  ;; CHECK-NEXT:      (throw_ref
+  ;; CHECK-NEXT:       (block $l10 (result exnref)
+  ;; CHECK-NEXT:        (try_table (catch_all_ref $l10)
+  ;; CHECK-NEXT:         (call $foo)
+  ;; CHECK-NEXT:        )
+  ;; CHECK-NEXT:        (br $outer1)
+  ;; CHECK-NEXT:       )
+  ;; CHECK-NEXT:      )
+  ;; CHECK-NEXT:     )
+  ;; CHECK-NEXT:    )
+  ;; CHECK-NEXT:    (throw_ref
+  ;; CHECK-NEXT:     (local.get $0)
+  ;; CHECK-NEXT:    )
+  ;; CHECK-NEXT:   )
+  ;; CHECK-NEXT:  )
+  ;; CHECK-NEXT: )
+  ;; STACKIR-OPT:      (func $try-catch-rethrow-with-inner-delegate (type $1)
+  ;; STACKIR-OPT-NEXT:  (local $0 exnref)
+  ;; STACKIR-OPT-NEXT:  block $outer2
+  ;; STACKIR-OPT-NEXT:   block $catch3 (result exnref)
+  ;; STACKIR-OPT-NEXT:    try_table (catch_ref $e-empty $catch3)
+  ;; STACKIR-OPT-NEXT:     call $foo
+  ;; STACKIR-OPT-NEXT:    end
+  ;; STACKIR-OPT-NEXT:    br $outer2
+  ;; STACKIR-OPT-NEXT:   end
+  ;; STACKIR-OPT-NEXT:   block $outer1
+  ;; STACKIR-OPT-NEXT:    try_table
+  ;; STACKIR-OPT-NEXT:     block $l10 (result exnref)
+  ;; STACKIR-OPT-NEXT:      try_table (catch_all_ref $l10)
+  ;; STACKIR-OPT-NEXT:       call $foo
+  ;; STACKIR-OPT-NEXT:      end
+  ;; STACKIR-OPT-NEXT:      br $outer1
+  ;; STACKIR-OPT-NEXT:     end
+  ;; STACKIR-OPT-NEXT:     throw_ref
+  ;; STACKIR-OPT-NEXT:    end
+  ;; STACKIR-OPT-NEXT:    unreachable
+  ;; STACKIR-OPT-NEXT:   end
+  ;; STACKIR-OPT-NEXT:   throw_ref
+  ;; STACKIR-OPT-NEXT:  end
+  ;; STACKIR-OPT-NEXT: )
+  (func $try-catch-rethrow-with-inner-delegate
+    (try $l0
+      (do
+        (call $foo)
+      )
+      (catch $e-empty
+        (try $l1
+          (do
+            (try
+              (do
+                (call $foo)
+              )
+              (delegate $l1)
+            )
+          )
+        )
+        (rethrow $l0)
+      )
+    )
+  )
 )