| //===----------------------------------------------------------------------===// |
| // |
| // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. |
| // See https://llvm.org/LICENSE.txt for license information. |
| // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception |
| // |
| //===----------------------------------------------------------------------===// |
| |
| #ifndef _LIBCPP___TYPE_TRAITS_IS_ASSIGNABLE_H |
| #define _LIBCPP___TYPE_TRAITS_IS_ASSIGNABLE_H |
| |
| #include <__config> |
| #include <__type_traits/integral_constant.h> |
| |
| #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER) |
| # pragma GCC system_header |
| #endif |
| |
| _LIBCPP_BEGIN_NAMESPACE_STD |
| |
| template<typename, typename _Tp> struct __select_2nd { typedef _LIBCPP_NODEBUG _Tp type; }; |
| |
| #if __has_keyword(__is_assignable) |
| |
| template<class _Tp, class _Up> |
| struct _LIBCPP_TEMPLATE_VIS is_assignable : _BoolConstant<__is_assignable(_Tp, _Up)> { }; |
| |
| #if _LIBCPP_STD_VER > 14 |
| template <class _Tp, class _Arg> |
| inline constexpr bool is_assignable_v = __is_assignable(_Tp, _Arg); |
| #endif |
| |
| #else // __has_keyword(__is_assignable) |
| |
| template <class _Tp, class _Arg> |
| typename __select_2nd<decltype((declval<_Tp>() = declval<_Arg>())), true_type>::type |
| __is_assignable_test(int); |
| |
| template <class, class> |
| false_type __is_assignable_test(...); |
| |
| |
| template <class _Tp, class _Arg, bool = is_void<_Tp>::value || is_void<_Arg>::value> |
| struct __is_assignable_imp |
| : public decltype((_VSTD::__is_assignable_test<_Tp, _Arg>(0))) {}; |
| |
| template <class _Tp, class _Arg> |
| struct __is_assignable_imp<_Tp, _Arg, true> |
| : public false_type |
| { |
| }; |
| |
| template <class _Tp, class _Arg> |
| struct is_assignable |
| : public __is_assignable_imp<_Tp, _Arg> {}; |
| |
| #if _LIBCPP_STD_VER > 14 |
| template <class _Tp, class _Arg> |
| inline constexpr bool is_assignable_v = is_assignable<_Tp, _Arg>::value; |
| #endif |
| |
| #endif // __has_keyword(__is_assignable) |
| |
| _LIBCPP_END_NAMESPACE_STD |
| |
| #endif // _LIBCPP___TYPE_TRAITS_IS_ASSIGNABLE_H |