From 6bdd3e39ca5d2d29b78cf2ac38e22657490273c9 Mon Sep 17 00:00:00 2001
From: Chris Tate <chris@ctate.dev>
Date: Mon, 26 Oct 2026 16:20:12 -0500
Subject: [PATCH] Fix the self-hosting build of the arena runtime

---
 packages/compiler/src/backend/llvm/region-groups.ts | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/packages/compiler/src/backend/llvm/region-groups.ts b/packages/compiler/src/backend/llvm/region-groups.ts
index 70e4168ed..ce8354c92 100644
--- a/packages/compiler/src/backend/llvm/region-groups.ts
+++ b/packages/compiler/src/backend/llvm/region-groups.ts
@@ -438,7 +438,11 @@ export function analyzeRegionGroups(mod: IrModule): RegionGroups {
       const info: UseInfo = {};
       const use = useOf(parents[index]!, parents.slice(0, index), false, info);
       if (use !== "internal") {
-        Object.assign(out, info);
+        // Field by field: an Object.assign onto a record makes the
+        // self-hosted compiler read class and record properties dynamically.
+        if (info.bound !== undefined) out.bound = info.bound;
+        if (info.at !== undefined) out.at = info.at;
+        if (info.target !== undefined) out.target = info.target;
         return use;
       }
       index = info.at!;