diff options
Diffstat (limited to 'libstdc++-v3/include/std/tuple')
| -rw-r--r-- | libstdc++-v3/include/std/tuple | 24 |
1 files changed, 22 insertions, 2 deletions
diff --git a/libstdc++-v3/include/std/tuple b/libstdc++-v3/include/std/tuple index 2e69af1..b39ce71 100644 --- a/libstdc++-v3/include/std/tuple +++ b/libstdc++-v3/include/std/tuple @@ -2939,19 +2939,39 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION #endif #ifdef __cpp_lib_make_from_tuple // C++ >= 17 + template <typename _Tp, typename _Tuple, typename _Seq + = make_index_sequence<tuple_size_v<remove_reference_t<_Tuple>>>> + constexpr bool __can_make_from_tuple = false; + + // _GLIBCXX_RESOLVE_LIB_DEFECTS + // 3528. make_from_tuple can perform (the equivalent of) a C-style cast + template <typename _Tp, typename _Tuple, size_t... _Idx> + constexpr bool __can_make_from_tuple<_Tp, _Tuple, index_sequence<_Idx...>> + = is_constructible_v<_Tp, + decltype(std::get<_Idx>(std::declval<_Tuple>()))...>; + template <typename _Tp, typename _Tuple, size_t... _Idx> constexpr _Tp __make_from_tuple_impl(_Tuple&& __t, index_sequence<_Idx...>) - { return _Tp(std::get<_Idx>(std::forward<_Tuple>(__t))...); } + { + static_assert(__can_make_from_tuple<_Tp, _Tuple, index_sequence<_Idx...>>); + return _Tp(std::get<_Idx>(std::forward<_Tuple>(__t))...); + } #if __cpp_lib_tuple_like // >= C++23 template <typename _Tp, __tuple_like _Tuple> #else template <typename _Tp, typename _Tuple> #endif - constexpr _Tp + constexpr auto make_from_tuple(_Tuple&& __t) noexcept(__unpack_std_tuple<is_nothrow_constructible, _Tp, _Tuple>) +#ifdef __cpp_concepts // >= C++20 + -> _Tp + requires __can_make_from_tuple<_Tp, _Tuple> +#else + -> __enable_if_t<__can_make_from_tuple<_Tp, _Tuple>, _Tp> +#endif { constexpr size_t __n = tuple_size_v<remove_reference_t<_Tuple>>; #if __has_builtin(__reference_constructs_from_temporary) |