From 094206a08d61b14abb2d6d28e6c59e0d316efc55 Mon Sep 17 00:00:00 2001
From: Peter Dimov <pdimov@gmail.com>
Date: Fri, 24 Mar 2023 11:58:56 +0200
Subject: [PATCH] Make mp_rename, mp_apply, mp_apply_q SFINAE-friendly

---
 include/boost/mp11/detail/mp_rename.hpp |  5 ++-
 test/Jamfile                            |  1 +
 test/mp_apply_q_sf.cpp                  | 49 +++++++++++++++++++++++++
 3 files changed, 53 insertions(+), 2 deletions(-)
 create mode 100644 test/mp_apply_q_sf.cpp

diff --git a/include/boost/mp11/detail/mp_rename.hpp b/include/boost/mp11/detail/mp_rename.hpp
index 8368ac6..5af6fc4 100644
--- a/include/boost/mp11/detail/mp_rename.hpp
+++ b/include/boost/mp11/detail/mp_rename.hpp
@@ -8,6 +8,8 @@
 //  See accompanying file LICENSE_1_0.txt or copy at
 //  http://www.boost.org/LICENSE_1_0.txt
 
+#include <boost/mp11/detail/mp_defer.hpp>
+
 namespace boost
 {
 namespace mp11
@@ -22,9 +24,8 @@ template<class A, template<class...> class B> struct mp_rename_impl
 // An error "no type named 'type'" here means that the first argument to mp_rename is not a list
 };
 
-template<template<class...> class A, class... T, template<class...> class B> struct mp_rename_impl<A<T...>, B>
+template<template<class...> class A, class... T, template<class...> class B> struct mp_rename_impl<A<T...>, B>: mp_defer<B, T...>
 {
-    using type = B<T...>;
 };
 
 } // namespace detail
diff --git a/test/Jamfile b/test/Jamfile
index 28ce8e9..8c8f683 100644
--- a/test/Jamfile
+++ b/test/Jamfile
@@ -41,6 +41,7 @@ run mp_replace_front.cpp ;
 run mp_replace_second.cpp ;
 run mp_replace_third.cpp ;
 run mp_apply_q.cpp ;
+run mp_apply_q_sf.cpp ;
 run mp_is_list.cpp ;
 run mp_list_c.cpp ;
 run mp_transform_front.cpp ;
diff --git a/test/mp_apply_q_sf.cpp b/test/mp_apply_q_sf.cpp
new file mode 100644
index 0000000..d30ce21
--- /dev/null
+++ b/test/mp_apply_q_sf.cpp
@@ -0,0 +1,49 @@
+// Copyright 2015, 2017, 2023 Peter Dimov
+// Distributed under the Boost Software License, Version 1.0.
+// https://www.boost.org/LICENSE_1_0.txt
+
+#include <boost/mp11/list.hpp>
+#include <boost/mp11/utility.hpp>
+#include <boost/mp11/detail/config.hpp>
+#include <boost/core/lightweight_test_trait.hpp>
+#include <type_traits>
+
+using boost::mp11::mp_apply_q;
+using boost::mp11::mp_list;
+using boost::mp11::mp_quote;
+using boost::mp11::mp_quote_trait;
+using boost::mp11::mp_valid;
+using boost::mp11::mp_identity;
+using boost::mp11::mp_identity_t;
+
+int main()
+{
+    BOOST_TEST_TRAIT_FALSE((mp_valid<mp_apply_q>));
+    BOOST_TEST_TRAIT_FALSE((mp_valid<mp_apply_q, void>));
+
+#if !BOOST_MP11_WORKAROUND( BOOST_MP11_MSVC, < 1920 )
+
+    BOOST_TEST_TRAIT_FALSE((mp_valid<mp_apply_q, void, void>));
+
+    BOOST_TEST_TRAIT_FALSE((mp_valid<mp_apply_q, void, mp_list<>>));
+    BOOST_TEST_TRAIT_FALSE((mp_valid<mp_apply_q, void, mp_list<void>>));
+    BOOST_TEST_TRAIT_FALSE((mp_valid<mp_apply_q, void, mp_list<void, void>>));
+
+#endif
+
+    using Qi = mp_quote<mp_identity_t>;
+
+    BOOST_TEST_TRAIT_FALSE((mp_valid<mp_apply_q, Qi, mp_list<>>));
+    BOOST_TEST_TRAIT_TRUE((mp_valid<mp_apply_q, Qi, mp_list<void>>));
+    BOOST_TEST_TRAIT_FALSE((mp_valid<mp_apply_q, Qi, mp_list<void, void>>));
+
+    using Qt = mp_quote_trait<mp_identity>;
+
+#if !BOOST_MP11_WORKAROUND( BOOST_MP11_MSVC, < 1900 )
+    BOOST_TEST_TRAIT_FALSE((mp_valid<mp_apply_q, Qt, mp_list<>>));
+#endif
+    BOOST_TEST_TRAIT_TRUE((mp_valid<mp_apply_q, Qt, mp_list<void>>));
+    BOOST_TEST_TRAIT_FALSE((mp_valid<mp_apply_q, Qt, mp_list<void, void>>));
+
+    return boost::report_errors();
+}