From 34da42d55a465e40e914c559077bab53a076e875 Mon Sep 17 00:00:00 2001
From: Alon Zakai <azakai@google.com>
Date: Wed, 15 Oct 2025 11:12:43 -0700
Subject: [PATCH] fix but why does fuzzer not find?

---
 src/tools/wasm-merge.cpp                   |  4 +++
 test/lit/merge/global_subtyping.wat        | 42 ++++++++++++++++++++++
 test/lit/merge/global_subtyping.wat.second | 14 ++++++++
 3 files changed, 60 insertions(+)
 create mode 100644 test/lit/merge/global_subtyping.wat
 create mode 100644 test/lit/merge/global_subtyping.wat.second

diff --git a/src/tools/wasm-merge.cpp b/src/tools/wasm-merge.cpp
index bfce9f0cdc2..149633c6958 100644
--- a/src/tools/wasm-merge.cpp
+++ b/src/tools/wasm-merge.cpp
@@ -568,6 +568,10 @@ void updateTypes(Module& wasm) {
       return std::make_unique<Updater>();
     }
 
+    void visitGlobalGet(GlobalGet* curr) {
+      curr->type = getModule()->getGlobal(curr->name)->type;
+    }
+
     void visitRefFunc(RefFunc* curr) {
       curr->finalize(getModule()->getFunction(curr->func)->type);
     }
diff --git a/test/lit/merge/global_subtyping.wat b/test/lit/merge/global_subtyping.wat
new file mode 100644
index 00000000000..0900fe8a399
--- /dev/null
+++ b/test/lit/merge/global_subtyping.wat
@@ -0,0 +1,42 @@
+;; NOTE: Assertions have been generated by update_lit_checks.py --all-items and should not be edited.
+
+;; RUN: wasm-merge %s primary %s.second secondary --skip-export-conflicts -all -S -o - | filecheck %s
+
+;; Export a global with a subtype. It is imported using the supertype, and
+;; after we merge, the type must be updated, including in the global.get from
+;; the second module (that goes from super to sub).
+(module
+ ;; CHECK:      (type $super (sub (func)))
+ (type $super (sub (func)))
+ ;; CHECK:      (type $sub (sub final $super (func)))
+ (type $sub (sub final $super (func)))
+
+ ;; CHECK:      (type $2 (func))
+
+ ;; CHECK:      (global $sub (ref $sub) (ref.func $sub))
+ (global $sub (ref $sub) (ref.func $sub))
+
+ ;; CHECK:      (export "sub" (global $sub))
+ (export "sub" (global $sub))
+
+ ;; CHECK:      (export "second-user" (func $second-user))
+
+ ;; CHECK:      (func $sub (type $sub)
+ ;; CHECK-NEXT:  (drop
+ ;; CHECK-NEXT:   (global.get $sub)
+ ;; CHECK-NEXT:  )
+ ;; CHECK-NEXT: )
+ (func $sub (type $sub)
+  (drop
+   (global.get $sub)
+  )
+ )
+)
+
+;; CHECK:      (func $second-user (type $2)
+;; CHECK-NEXT:  (drop
+;; CHECK-NEXT:   (block (result (ref $sub))
+;; CHECK-NEXT:    (global.get $sub)
+;; CHECK-NEXT:   )
+;; CHECK-NEXT:  )
+;; CHECK-NEXT: )
diff --git a/test/lit/merge/global_subtyping.wat.second b/test/lit/merge/global_subtyping.wat.second
new file mode 100644
index 00000000000..eb948e0d85d
--- /dev/null
+++ b/test/lit/merge/global_subtyping.wat.second
@@ -0,0 +1,14 @@
+(module
+ (type $second-super (sub (func)))
+
+ (import "primary" "sub" (global $import (ref $second-super)))
+
+ (func $second-user (export "second-user")
+  (drop
+   (block (result (ref $second-super))
+    (global.get $import)
+   )
+  )
+ )
+)
+