From f586dc88484fea8ad790218c9f02489aa936015b Mon Sep 17 00:00:00 2001
From: Peter Dimov <pdimov@gmail.com>
Date: Fri, 12 Mar 2021 20:15:09 +0200
Subject: [PATCH 1/2] Add test for inherited constructors (refs #26)

---
 test/Jamfile                       |  2 ++
 test/variant_derived_construct.cpp | 33 ++++++++++++++++++++++++++++++
 2 files changed, 35 insertions(+)
 create mode 100644 test/variant_derived_construct.cpp

diff --git a/test/Jamfile b/test/Jamfile
index 682b862..d104a1b 100644
--- a/test/Jamfile
+++ b/test/Jamfile
@@ -119,3 +119,5 @@ run variant_visit_r.cpp : : :
     <toolset>gcc,<target-os>windows:<variant>release
     <toolset>gcc,<target-os>cygwin:<variant>release
     ;
+
+compile variant_derived_construct.cpp ;
diff --git a/test/variant_derived_construct.cpp b/test/variant_derived_construct.cpp
new file mode 100644
index 0000000..6844336
--- /dev/null
+++ b/test/variant_derived_construct.cpp
@@ -0,0 +1,33 @@
+// Copyright 2021 Peter Dimov.
+// Distributed under the Boost Software License, Version 1.0.
+// https://www.boost.org/LICENSE_1_0.txt
+
+#include <boost/variant2/variant.hpp>
+
+using namespace boost::variant2;
+
+template<class... T> class X: variant<T...>
+{
+    using base = variant<T...>;
+    using base::base;
+};
+
+struct Y
+{
+    Y( Y const& rhs ) = default;
+
+    template<class T> Y( T const& t )
+    {
+        t.bar();
+    }
+};
+
+int main()
+{
+    using W = X<int, double, Y>;
+
+    W a( 1 );
+    W b( a );
+
+    (void)b;
+}

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 2/2] 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
         >