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_UNDERLYING_TYPE_H
10 #define _LIBCPP___TYPE_TRAITS_UNDERLYING_TYPE_H
11 
12 #include <__config>
13 #include <__type_traits/is_enum.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 <class _Tp, bool = is_enum<_Tp>::value> struct __underlying_type_impl;
22 
23 template <class _Tp>
24 struct __underlying_type_impl<_Tp, false> {};
25 
26 template <class _Tp>
27 struct __underlying_type_impl<_Tp, true>
28 {
29     typedef __underlying_type(_Tp) type;
30 };
31 
32 template <class _Tp>
33 struct underlying_type : __underlying_type_impl<_Tp, is_enum<_Tp>::value> {};
34 
35 #if _LIBCPP_STD_VER > 11
36 template <class _Tp> using underlying_type_t = typename underlying_type<_Tp>::type;
37 #endif
38 
39 _LIBCPP_END_NAMESPACE_STD
40 
41 #endif // _LIBCPP___TYPE_TRAITS_UNDERLYING_TYPE_H
42