From 786e316de5c25a3fddeaa2003f6efb64fb5ab4a9 Mon Sep 17 00:00:00 2001
From: Nathan Myers <ncm@cantrip.org>
Date: Fri, 6 Feb 2026 03:09:39 -0500
Subject: [PATCH] libstdc++: fix C++17 regression in concept
 __heterogeneous_key

The commit 3f7905550483408a2c4c5096a1adc8d7e863eb12 defined a
concept using a name not defined in C++17. This is fixed by
using an older name.

https://gcc.gnu.org/pipermail/gcc-patches/2026-February/707814.html

libstdc++-v3/ChangeLog
	* include/bits/stl_function.h (__heterogeneous_key): Use
	C++17-defined remove_cvref<>::type instead.
---
 libstdc++-v3/include/bits/stl_function.h | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/libstdc++-v3/include/bits/stl_function.h b/libstdc++-v3/include/bits/stl_function.h
index edbbfe11b96..657f40bca2e 100644
--- a/libstdc++-v3/include/bits/stl_function.h
+++ b/libstdc++-v3/include/bits/stl_function.h
@@ -1533,7 +1533,8 @@ template <typename _Kt, typename _Container>
 
 template <typename _Kt, typename _Container>
   concept __heterogeneous_key =
-    (!is_same_v<typename _Container::key_type, remove_cvref_t<_Kt>>) &&
+    (!is_same_v<typename _Container::key_type,
+		typename remove_cvref<_Kt>::type>) &&
     __not_container_iterator<_Kt, _Container>;
 #endif