From 72825b9934fee6b9084d95df4f6f50d941aa6c18 Mon Sep 17 00:00:00 2001
From: Ana Hobden <operator@hoverbear.org>
Date: Fri, 27 Mar 2026 13:24:09 -0700
Subject: [PATCH] Mark code only used in nightly as nightly only

---
 compiler/rustc_abi/src/callconv.rs | 1 +
 1 file changed, 1 insertion(+)

diff --git a/compiler/rustc_abi/src/callconv.rs b/compiler/rustc_abi/src/callconv.rs
index 7ad7088b3089..bb959d2f2e8e 100644
--- a/compiler/rustc_abi/src/callconv.rs
+++ b/compiler/rustc_abi/src/callconv.rs
@@ -35,6 +35,7 @@ pub fn unit(self) -> Option<Reg> {
     /// Try to combine two `HomogeneousAggregate`s, e.g. from two fields in
     /// the same `struct`. Only succeeds if only one of them has any data,
     /// or both units are identical.
+    #[cfg(feature = "nightly")]
     fn merge(self, other: HomogeneousAggregate) -> Result<HomogeneousAggregate, Heterogeneous> {
         match (self, other) {
             (x, HomogeneousAggregate::NoData) | (HomogeneousAggregate::NoData, x) => Ok(x),