From 0d7d9c72efc3675a81c8ca60b521c570f6020a6a Mon Sep 17 00:00:00 2001
From: Peter Dimov <pdimov@pdimov.com>
Date: Sat, 25 Aug 2018 15:36:29 +0300
Subject: [PATCH] Add comment describing the use of noncopyable_::base_token

---
 include/boost/type_traits/is_noncopyable.hpp | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/include/boost/type_traits/is_noncopyable.hpp b/include/boost/type_traits/is_noncopyable.hpp
index ff0076f..787103e 100644
--- a/include/boost/type_traits/is_noncopyable.hpp
+++ b/include/boost/type_traits/is_noncopyable.hpp
@@ -19,6 +19,10 @@ namespace boost
 #ifndef BOOST_NONCOPYABLE_BASE_TOKEN_DEFINED
 #define BOOST_NONCOPYABLE_BASE_TOKEN_DEFINED
 
+// boost::noncopyable derives from noncopyable_::base_token to enable us
+// to recognize it. The definition is macro-guarded so that we can replicate
+// it here without including boost/core/noncopyable.hpp, which is in Core.
+
 namespace noncopyable_
 {
     struct base_token {};