2 files changed, 8 insertions, 1 deletions
diff --git a/src/ir/type-updating.cpp b/src/ir/type-updating.cpp
index 00f313a2a..67ec4a5c0 100644
--- a/src/ir/type-updating.cpp
+++ b/src/ir/type-updating.cpp
@@ -89,7 +89,7 @@ void GlobalTypeRewriter::update() {
     }
 
     // Apply a super, if there is one
-    if (auto super = type.getSuperType()) {
+    if (auto super = getSuperType(type)) {
       if (auto it = typeIndices.find(*super); it != typeIndices.end()) {
         assert(it->second < i);
         typeBuilder[i].subTypeOf(typeBuilder[it->second]);
diff --git a/src/ir/type-updating.h b/src/ir/type-updating.h
index 5cd8eef47..e1b5e42a9 100644
--- a/src/ir/type-updating.h
+++ b/src/ir/type-updating.h
@@ -357,6 +357,13 @@ public:
   virtual void modifyArray(HeapType oldType, Array& array) {}
   virtual void modifySignature(HeapType oldType, Signature& sig) {}
 
+  // Subclasses can override this method to modify supertypes. The new
+  // supertype, if any, must be a supertype (or the same as) the original
+  // supertype.
+  virtual std::optional<HeapType> getSuperType(HeapType oldType) {
+    return oldType.getSuperType();
+  }
+
   // Map an old type to a temp type. This can be called from the above hooks,
   // so that they can use a proper temp type of the TypeBuilder while modifying
   // things.