From 989ee9bca6228e31e9ea1128d167f498cd931766 Mon Sep 17 00:00:00 2001
From: Alon Zakai <azakai@google.com>
Date: Thu, 19 Mar 2026 13:42:39 -0700
Subject: [PATCH 1/2] fix

---
 src/ir/type-updating.h                 |  2 +-
 test/lit/passes/type-merging-cont.wast | 27 ++++++++++++++++++++++++++
 2 files changed, 28 insertions(+), 1 deletion(-)

diff --git a/src/ir/type-updating.h b/src/ir/type-updating.h
index 52a3e09027f..0e050becc59 100644
--- a/src/ir/type-updating.h
+++ b/src/ir/type-updating.h
@@ -502,7 +502,7 @@ class TypeMapper : public GlobalTypeRewriter {
   HeapType getNewHeapType(HeapType type) {
     auto iter = mapping.find(type);
     if (iter != mapping.end()) {
-      return iter->second;
+      type = iter->second;
     }
     return getTempHeapType(type);
   }
diff --git a/test/lit/passes/type-merging-cont.wast b/test/lit/passes/type-merging-cont.wast
index c7b57669d17..3acacc047f5 100644
--- a/test/lit/passes/type-merging-cont.wast
+++ b/test/lit/passes/type-merging-cont.wast
@@ -45,3 +45,30 @@
   )
 )
 
+;; A chain of continuations. During merging here we map types that are being
+;; rebuilt, and should not error while doing so. We can merge the function
+;; types, and all but two of the continuations.
+(module
+  (rec
+    ;; CHECK:      (rec
+    ;; CHECK-NEXT:  (type $func (sub (func)))
+    (type $func (sub (func)))
+    ;; CHECK:       (type $cont (sub (cont $func)))
+    (type $cont (sub (cont $func)))
+    (type $contB (sub $cont (cont $func)))
+    (type $contC (sub $contB (cont $func)))
+    (type $funcB (sub $func (func)))
+    ;; CHECK:       (type $contD (sub final $cont (cont $func)))
+    (type $contD (sub final $contC (cont $funcB)))
+  )
+
+  ;; CHECK:       (type $3 (func))
+
+  ;; CHECK:      (func $use-rec-group (type $3)
+  ;; CHECK-NEXT:  (local $t (ref null $contD))
+  ;; CHECK-NEXT: )
+  (func $use-rec-group
+   (local $t (ref null $contD))
+  )
+)
+

From dfb13eaf7d423d0d486805774b36d4a0ecc29a4e Mon Sep 17 00:00:00 2001
From: Alon Zakai <azakai@google.com>
Date: Thu, 19 Mar 2026 14:04:08 -0700
Subject: [PATCH 2/2] improve test

---
 test/lit/passes/type-merging-cont.wast | 18 ++++++++++++++----
 1 file changed, 14 insertions(+), 4 deletions(-)

diff --git a/test/lit/passes/type-merging-cont.wast b/test/lit/passes/type-merging-cont.wast
index 3acacc047f5..a9c479f5a8c 100644
--- a/test/lit/passes/type-merging-cont.wast
+++ b/test/lit/passes/type-merging-cont.wast
@@ -64,11 +64,21 @@
 
   ;; CHECK:       (type $3 (func))
 
-  ;; CHECK:      (func $use-rec-group (type $3)
-  ;; CHECK-NEXT:  (local $t (ref null $contD))
+  ;; CHECK:      (func $uses (type $3)
+  ;; CHECK-NEXT:  (local $func (ref $func))
+  ;; CHECK-NEXT:  (local $funcB (ref $func))
+  ;; CHECK-NEXT:  (local $cont (ref $cont))
+  ;; CHECK-NEXT:  (local $contB (ref $cont))
+  ;; CHECK-NEXT:  (local $contC (ref $cont))
+  ;; CHECK-NEXT:  (local $contD (ref $contD))
   ;; CHECK-NEXT: )
-  (func $use-rec-group
-   (local $t (ref null $contD))
+  (func $uses
+    (local $func (ref $func))
+    (local $funcB (ref $funcB))
+    (local $cont (ref $cont))
+    (local $contB (ref $contB))
+    (local $contC (ref $contC))
+    (local $contD (ref $contD))
   )
 )