From b7f38e45a68e7e2d94373c0417a2f176a9062ffe Mon Sep 17 00:00:00 2001
From: Thomas Lively <tlively@google.com>
Date: Fri, 8 May 2026 15:27:58 -0700
Subject: [PATCH] Fix crash in MinimizeRecGroups

We previously did not store type indices for public types. This caused a crash when the logic for comparing rec groups came across references to public types and assumed there would be indices to compare them by.
---
 src/passes/MinimizeRecGroups.cpp         |  2 +-
 test/lit/passes/minimize-rec-groups.wast | 40 ++++++++++++++++++++++++
 2 files changed, 41 insertions(+), 1 deletion(-)

diff --git a/src/passes/MinimizeRecGroups.cpp b/src/passes/MinimizeRecGroups.cpp
index 306426af5b9..a4d5e8211ac 100644
--- a/src/passes/MinimizeRecGroups.cpp
+++ b/src/passes/MinimizeRecGroups.cpp
@@ -311,10 +311,10 @@ struct MinimizeRecGroups : Pass {
     // generate new groups with the same shape.
     std::unordered_set<RecGroup> publicGroups;
     for (auto& [type, info] : typeInfo) {
+      typeIndices.insert({type, typeIndices.size()});
       if (info.visibility == ModuleUtils::Visibility::Private) {
         // We can optimize private types.
         types.push_back(type);
-        typeIndices.insert({type, typeIndices.size()});
       } else {
         publicGroups.insert(type.getRecGroup());
       }
diff --git a/test/lit/passes/minimize-rec-groups.wast b/test/lit/passes/minimize-rec-groups.wast
index 3483d1c9de3..963f655f20d 100644
--- a/test/lit/passes/minimize-rec-groups.wast
+++ b/test/lit/passes/minimize-rec-groups.wast
@@ -563,4 +563,44 @@
   ;; CHECK:      (global $privateB (ref null $privateB) (ref.null none))
   (global $privateB (ref null $privateB) (ref.null none))
 )
+
+;; Regression test for a bug where we crashed when comparing rec groups with
+;; references to public types because we did not store type indices for public
+;; types.
 ;; CHECK:      (export "g" (global $public))
+(module
+  (rec
+    ;; CHECK:      (rec
+    ;; CHECK-NEXT:  (type $public (sub (descriptor $desc) (struct)))
+    (type $public (sub (descriptor $desc) (struct)))
+    ;; CHECK:       (type $desc (sub (describes $public) (struct)))
+    (type $desc (sub (describes $public) (struct)))
+  )
+
+  ;; We should not crash when comparing these identical connected components.
+  (rec
+    ;; CHECK:      (rec
+    ;; CHECK-NEXT:  (type $private1 (sub $public (descriptor $desc1) (struct)))
+    (type $private1 (sub $public (descriptor $desc1) (struct)))
+    ;; CHECK:       (type $desc1 (sub $desc (describes $private1) (struct)))
+
+    ;; CHECK:      (rec
+    ;; CHECK-NEXT:  (type $4 (struct))
+
+    ;; CHECK:       (type $private2 (sub $public (descriptor $desc2) (struct)))
+    (type $private2 (sub $public (descriptor $desc2) (struct)))
+    (type $desc1 (sub $desc (describes $private1) (struct)))
+    ;; CHECK:       (type $desc2 (sub $desc (describes $private2) (struct)))
+    (type $desc2 (sub $desc (describes $private2) (struct)))
+  )
+
+  ;; CHECK:      (global $use1 (ref null $private1) (ref.null none))
+  (global $use1 (ref null $private1) (ref.null none))
+  ;; CHECK:      (global $use2 (ref null $private2) (ref.null none))
+  (global $use2 (ref null $private2) (ref.null none))
+  ;; CHECK:      (global $public (ref null $public) (ref.null none))
+  (global $public (ref null $public) (ref.null none))
+  ;; CHECK:      (export "public" (global $public))
+  (export "public" (global $public))
+)
+