pfr/detail/possible_reflectable.hpp

0001 // Copyright (c) 2022 Denis Mikhailov
0002 //
0003 // Distributed under the Boost Software License, Version 1.0. (See accompanying
0004 // file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
0005
0006 #ifndef BOOST_PFR_DETAIL_POSSIBLE_REFLECTABLE_HPP
0007 #define BOOST_PFR_DETAIL_POSSIBLE_REFLECTABLE_HPP
0008 #pragma once
0009
0010 #include <boost/pfr/detail/config.hpp>
0011 #include <boost/pfr/traits_fwd.hpp>
0012
0013 #ifdef BOOST_PFR_HAS_STD_MODULE
0014 import std;
0015 #else
0016 #include <type_traits> // for std::is_aggregate
0017 #endif
0018
0019 namespace boost { namespace pfr { namespace detail {
0020
0021 ///////////////////// Returns false when the type exactly wasn't be reflectable
0022 template <class T, class WhatFor>
0023 constexpr decltype(is_reflectable<T, WhatFor>::value) possible_reflectable(long) noexcept {
0024     return is_reflectable<T, WhatFor>::value;
0025 }
0026
0027 #if BOOST_PFR_ENABLE_IMPLICIT_REFLECTION
0028
0029 template <class T, class WhatFor>
0030 constexpr bool possible_reflectable(int) noexcept {
0031 #   if  defined(__cpp_lib_is_aggregate)
0032     using type = std::remove_cv_t<T>;
0033     return std::is_aggregate<type>();
0034 #   else
0035     return true;
0036 #   endif
0037 }
0038
0039 #else
0040
0041 template <class T, class WhatFor>
0042 constexpr bool possible_reflectable(int) noexcept {
0043     // negative answer here won't change behaviour in PFR-dependent libraries(like Fusion)
0044     return false;
0045 }
0046
0047 #endif
0048
0049 }}} // namespace boost::pfr::detail
0050
0051 #endif // BOOST_PFR_DETAIL_POSSIBLE_REFLECTABLE_HPP
0052
0053