[Wasm GC] Handle an unreachable br_on_cast_fail in DCE (#5418)

Without this we hit an assertion on unreachable not being a heap type.

1 files changed, 4 insertions, 1 deletions

diff --git a/src/wasm/wasm.cpp b/src/wasm/wasm.cpp
index 4a72f6ea6..fa1351541 100644
--- a/src/wasm/wasm.cpp
+++ b/src/wasm/wasm.cpp
@@ -1014,7 +1014,10 @@ Type BrOn::getSentType() {
         return castType;
       }
     case BrOnCastFail:
-      // The same as the result type of br_on_cast.
+      // The same as the result type of br_on_cast (if reachable).
+      if (ref->type == Type::unreachable) {
+        return Type::unreachable;
+      }
       if (castType.isNullable()) {
         return Type(ref->type.getHeapType(), NonNullable);
       } else {