From 7cc7f940072629d901b859631fe29e6adf21ab93 Mon Sep 17 00:00:00 2001
From: jzmaddock <john@johnmaddock.co.uk>
Date: Thu, 7 Oct 2021 13:05:15 +0100
Subject: [PATCH] Update for present, but broken <concepts> on latest MacOS
 clang.

---
 include/boost/config/stdlib/libcpp.hpp | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/include/boost/config/stdlib/libcpp.hpp b/include/boost/config/stdlib/libcpp.hpp
index c7daab1f..fe4a48d2 100644
--- a/include/boost/config/stdlib/libcpp.hpp
+++ b/include/boost/config/stdlib/libcpp.hpp
@@ -157,6 +157,9 @@
 #if !defined(__cpp_lib_semaphore) || (__cpp_lib_semaphore < 201907L)
 #  define BOOST_NO_CXX20_HDR_SEMAPHORE
 #endif
+#if !defined(__cpp_lib_concepts) || (__cpp_lib_concepts < 202002L)
+#  define BOOST_NO_CXX20_HDR_CONCEPTS
+#endif
 
 #if(_LIBCPP_VERSION < 9000) && !defined(BOOST_NO_CXX20_HDR_SPAN)
 // as_writable_bytes is missing.