From 9d4cc20dda5fc242e6286ff14b41b2c5735bec3b Mon Sep 17 00:00:00 2001
From: Alon Zakai <azakai@google.com>
Date: Thu, 14 Aug 2025 12:55:09 -0700
Subject: [PATCH 1/3] fix

---
 src/wasm/wasm-binary.cpp       |  4 +++-
 test/lit/basic/cont-no-gc.wast | 20 ++++++++++++++++++++
 2 files changed, 23 insertions(+), 1 deletion(-)
 create mode 100644 test/lit/basic/cont-no-gc.wast

diff --git a/src/wasm/wasm-binary.cpp b/src/wasm/wasm-binary.cpp
index 5d32f52d726..c5d14336123 100644
--- a/src/wasm/wasm-binary.cpp
+++ b/src/wasm/wasm-binary.cpp
@@ -1863,7 +1863,9 @@ void WasmBinaryWriter::writeHeapType(HeapType type, Exactness exactness) {
   if (!wasm->features.hasCustomDescriptors()) {
     exactness = Inexact;
   }
-  if (!wasm->features.hasGC()) {
+  // GC can refer to full heap types for many things; Stack Switching can do so
+  // for functions (continuation types refer to function types).
+  if (!wasm->features.hasGC() && !wasm->features.hasStackSwitching()) {
     type = type.getTop();
   }
   assert(!type.isBasic() || exactness == Inexact);
diff --git a/test/lit/basic/cont-no-gc.wast b/test/lit/basic/cont-no-gc.wast
new file mode 100644
index 00000000000..c70d80c378b
--- /dev/null
+++ b/test/lit/basic/cont-no-gc.wast
@@ -0,0 +1,20 @@
+;; NOTE: Assertions have been generated by update_lit_checks.py and should not be edited.
+
+;; Test that we can write a binary without erroring when using stack switching
+;; without GC. This verifies we can emit continuation types properly even when
+;; GC is disabled
+
+;; RUN: wasm-opt %s --enable-stack-switching --roundtrip -S -o - | filecheck %s
+
+(module
+ (type $proc (func))
+ (type $cont (cont $proc))
+
+ (func $main
+  (drop
+   (cont.new $cont
+    (ref.func $main)
+   )
+  )
+ )
+)

From 997579ec6c2454d74c6b1c6ece655a2032a163c4 Mon Sep 17 00:00:00 2001
From: Alon Zakai <azakai@google.com>
Date: Thu, 14 Aug 2025 12:59:02 -0700
Subject: [PATCH 2/3] fix

---
 test/lit/basic/cont-no-gc.wast | 11 ++++++++++-
 1 file changed, 10 insertions(+), 1 deletion(-)

diff --git a/test/lit/basic/cont-no-gc.wast b/test/lit/basic/cont-no-gc.wast
index c70d80c378b..f7fe3f27e1d 100644
--- a/test/lit/basic/cont-no-gc.wast
+++ b/test/lit/basic/cont-no-gc.wast
@@ -4,12 +4,21 @@
 ;; without GC. This verifies we can emit continuation types properly even when
 ;; GC is disabled
 
-;; RUN: wasm-opt %s --enable-stack-switching --roundtrip -S -o - | filecheck %s
+;; RUN: wasm-opt %s --enable-stack-switching --enable-reference-types --roundtrip -S -o - | filecheck %s
 
 (module
+ ;; CHECK:      (type $proc (func))
  (type $proc (func))
+ ;; CHECK:      (type $cont (cont $proc))
  (type $cont (cont $proc))
 
+ ;; CHECK:      (func $main
+ ;; CHECK-NEXT:  (drop
+ ;; CHECK-NEXT:   (cont.new $cont
+ ;; CHECK-NEXT:    (ref.func $main)
+ ;; CHECK-NEXT:   )
+ ;; CHECK-NEXT:  )
+ ;; CHECK-NEXT: )
  (func $main
   (drop
    (cont.new $cont

From 1759b0330e398c03e7dd04e405201c2f6e5d1b71 Mon Sep 17 00:00:00 2001
From: Alon Zakai <azakai@google.com>
Date: Thu, 14 Aug 2025 13:21:20 -0700
Subject: [PATCH 3/3] bettr

---
 src/wasm/wasm-binary.cpp | 6 ++----
 src/wasm/wasm-stack.cpp  | 4 +++-
 2 files changed, 5 insertions(+), 5 deletions(-)

diff --git a/src/wasm/wasm-binary.cpp b/src/wasm/wasm-binary.cpp
index c5d14336123..0b03c5824e9 100644
--- a/src/wasm/wasm-binary.cpp
+++ b/src/wasm/wasm-binary.cpp
@@ -310,7 +310,7 @@ void WasmBinaryWriter::writeTypes() {
         break;
       case HeapTypeKind::Cont:
         o << uint8_t(BinaryConsts::EncodedType::Cont);
-        writeHeapType(type.getContinuation().type, Inexact);
+        writeIndexedHeapType(type.getContinuation().type);
         break;
       case HeapTypeKind::Basic:
         WASM_UNREACHABLE("unexpected kind");
@@ -1863,9 +1863,7 @@ void WasmBinaryWriter::writeHeapType(HeapType type, Exactness exactness) {
   if (!wasm->features.hasCustomDescriptors()) {
     exactness = Inexact;
   }
-  // GC can refer to full heap types for many things; Stack Switching can do so
-  // for functions (continuation types refer to function types).
-  if (!wasm->features.hasGC() && !wasm->features.hasStackSwitching()) {
+  if (!wasm->features.hasGC()) {
     type = type.getTop();
   }
   assert(!type.isBasic() || exactness == Inexact);
diff --git a/src/wasm/wasm-stack.cpp b/src/wasm/wasm-stack.cpp
index 529bb1db19c..bfc0d8191ae 100644
--- a/src/wasm/wasm-stack.cpp
+++ b/src/wasm/wasm-stack.cpp
@@ -135,7 +135,9 @@ void BinaryInstWriter::visitCallIndirect(CallIndirect* curr) {
   Index tableIdx = parent.getTableIndex(curr->table);
   int8_t op =
     curr->isReturn ? BinaryConsts::RetCallIndirect : BinaryConsts::CallIndirect;
-  o << op << U32LEB(parent.getTypeIndex(curr->heapType)) << U32LEB(tableIdx);
+  o << op;
+  parent.writeIndexedHeapType(curr->heapType);
+  o << U32LEB(tableIdx);
 }
 
 void BinaryInstWriter::visitLocalGet(LocalGet* curr) {