1 //===----------------------------------------------------------------------===// 2 // 3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. 4 // See https://llvm.org/LICENSE.txt for license information. 5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception 6 // 7 //===----------------------------------------------------------------------===// 8 9 #ifndef _LIBCPP___TYPE_TRAITS_IS_ASSIGNABLE_H 10 #define _LIBCPP___TYPE_TRAITS_IS_ASSIGNABLE_H 11 12 #include <__config> 13 #include <__type_traits/integral_constant.h> 14 15 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER) 16 # pragma GCC system_header 17 #endif 18 19 _LIBCPP_BEGIN_NAMESPACE_STD 20 21 template<typename, typename _Tp> struct __select_2nd { typedef _LIBCPP_NODEBUG _Tp type; }; 22 23 #if __has_builtin(__is_assignable) 24 25 template<class _Tp, class _Up> 26 struct _LIBCPP_TEMPLATE_VIS is_assignable : _BoolConstant<__is_assignable(_Tp, _Up)> { }; 27 28 #if _LIBCPP_STD_VER > 14 29 template <class _Tp, class _Arg> 30 inline constexpr bool is_assignable_v = __is_assignable(_Tp, _Arg); 31 #endif 32 33 #else // __has_builtin(__is_assignable) 34 35 template <class _Tp, class _Arg> 36 typename __select_2nd<decltype((declval<_Tp>() = declval<_Arg>())), true_type>::type 37 __is_assignable_test(int); 38 39 template <class, class> 40 false_type __is_assignable_test(...); 41 42 43 template <class _Tp, class _Arg, bool = is_void<_Tp>::value || is_void<_Arg>::value> 44 struct __is_assignable_imp 45 : public decltype((_VSTD::__is_assignable_test<_Tp, _Arg>(0))) {}; 46 47 template <class _Tp, class _Arg> 48 struct __is_assignable_imp<_Tp, _Arg, true> 49 : public false_type 50 { 51 }; 52 53 template <class _Tp, class _Arg> 54 struct is_assignable 55 : public __is_assignable_imp<_Tp, _Arg> {}; 56 57 #if _LIBCPP_STD_VER > 14 58 template <class _Tp, class _Arg> 59 inline constexpr bool is_assignable_v = is_assignable<_Tp, _Arg>::value; 60 #endif 61 62 #endif // __has_builtin(__is_assignable) 63 64 _LIBCPP_END_NAMESPACE_STD 65 66 #endif // _LIBCPP___TYPE_TRAITS_IS_ASSIGNABLE_H 67