From 90cda5339f8bea7d9bd0fc391ec4b9f4ae2a582f Mon Sep 17 00:00:00 2001
From: Peter Dimov <pdimov@gmail.com>
Date: Fri, 12 Mar 2021 23:40:14 +0200
Subject: [PATCH] Disable U&& constructor for derived types

---
 include/boost/variant2/variant.hpp | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/include/boost/variant2/variant.hpp b/include/boost/variant2/variant.hpp
index 06a0419..9609335 100644
--- a/include/boost/variant2/variant.hpp
+++ b/include/boost/variant2/variant.hpp
@@ -1581,7 +1581,7 @@ public:
 
     template<class U,
         class Ud = typename std::decay<U>::type,
-        class E1 = typename std::enable_if< !std::is_same<Ud, variant>::value && !detail::is_in_place_index<Ud>::value && !detail::is_in_place_type<Ud>::value >::type,
+        class E1 = typename std::enable_if< !std::is_same<Ud, variant>::value && !std::is_base_of<variant, Ud>::value && !detail::is_in_place_index<Ud>::value && !detail::is_in_place_type<Ud>::value >::type,
         class V = detail::resolve_overload_type<U&&, T...>,
         class E2 = typename std::enable_if<std::is_constructible<V, U&&>::value>::type
         >