Added thirdparty: boost library

thirdparty/include/boost/pfr/detail/rvalue_t.hpp

@@ -0,0 +1,35 @@
+// Copyright (c) 2016-2023 Antony Polukhin
+//
+// Distributed under the Boost Software License, Version 1.0. (See accompanying
+// file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
+
+#ifndef BOOST_PFR_DETAIL_RVALUE_T_HPP
+#define BOOST_PFR_DETAIL_RVALUE_T_HPP
+#pragma once
+
+#include <type_traits>
+#include <utility>      // std::enable_if_t
+
+// This header provides aliases rvalue_t and lvalue_t.
+//
+// Usage: template <class T> void foo(rvalue<T> rvalue);
+//
+// Those are useful for
+//  * better type safety - you can validate at compile time that only rvalue reference is passed into the function
+//  * documentation and readability - rvalue_t<T> is much better than T&&+SFINAE
+
+namespace boost { namespace pfr { namespace detail {
+
+/// Binds to rvalues only, no copying allowed.
+template <class T
+#ifdef BOOST_PFR_DETAIL_STRICT_RVALUE_TESTING
+    , class = std::enable_if_t<std::is_rvalue_reference<T&&>::value>
+#endif
+>
+using rvalue_t = T&&;
+
+/// Binds to mutable lvalues only
+
+}}} // namespace boost::pfr::detail
+
+#endif // BOOST_PFR_DETAIL_RVALUE_T_HPP