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/* Copyright (C) 2017-2024 Free Software Foundation, Inc.
This file is part of GDB.
This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 3 of the License, or
(at your option) any later version.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program. If not, see <http://www.gnu.org/licenses/>. */
#ifndef COMMON_TRAITS_H
#define COMMON_TRAITS_H
#include <type_traits>
namespace gdb {
/* Implementation of the detection idiom:
- http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2015/n4502.pdf
- http://en.cppreference.com/w/cpp/experimental/is_detected
*/
struct nonesuch
{
nonesuch () = delete;
~nonesuch () = delete;
nonesuch (const nonesuch &) = delete;
void operator= (const nonesuch &) = delete;
};
namespace detection_detail {
/* Implementation of the detection idiom (negative case). */
template<typename Default, typename AlwaysVoid,
template<typename...> class Op, typename... Args>
struct detector
{
using value_t = std::false_type;
using type = Default;
};
/* Implementation of the detection idiom (positive case). */
template<typename Default, template<typename...> class Op, typename... Args>
struct detector<Default, std::void_t<Op<Args...>>, Op, Args...>
{
using value_t = std::true_type;
using type = Op<Args...>;
};
/* Detect whether Op<Args...> is a valid type, use Default if not. */
template<typename Default, template<typename...> class Op,
typename... Args>
using detected_or = detector<Default, void, Op, Args...>;
/* Op<Args...> if that is a valid type, otherwise Default. */
template<typename Default, template<typename...> class Op,
typename... Args>
using detected_or_t
= typename detected_or<Default, Op, Args...>::type;
} /* detection_detail */
template<template<typename...> class Op, typename... Args>
using is_detected
= typename detection_detail::detector<nonesuch, void, Op, Args...>::value_t;
template<template<typename...> class Op, typename... Args>
using detected_t
= typename detection_detail::detector<nonesuch, void, Op, Args...>::type;
template<typename Default, template<typename...> class Op, typename... Args>
using detected_or = detection_detail::detected_or<Default, Op, Args...>;
template<typename Default, template<typename...> class Op, typename... Args>
using detected_or_t = typename detected_or<Default, Op, Args...>::type;
template<typename Expected, template<typename...> class Op, typename... Args>
using is_detected_exact = std::is_same<Expected, detected_t<Op, Args...>>;
template<typename To, template<typename...> class Op, typename... Args>
using is_detected_convertible
= std::is_convertible<detected_t<Op, Args...>, To>;
/* A few trait helpers, mainly stolen from libstdc++. Uppercase
because "and/or", etc. are reserved keywords. */
template<typename Predicate>
struct Not : public std::integral_constant<bool, !Predicate::value>
{};
template<typename...>
struct Or;
template<>
struct Or<> : public std::false_type
{};
template<typename B1>
struct Or<B1> : public B1
{};
template<typename B1, typename B2>
struct Or<B1, B2>
: public std::conditional<B1::value, B1, B2>::type
{};
template<typename B1,typename B2,typename B3, typename... Bn>
struct Or<B1, B2, B3, Bn...>
: public std::conditional<B1::value, B1, Or<B2, B3, Bn...>>::type
{};
template<typename...>
struct And;
template<>
struct And<> : public std::true_type
{};
template<typename B1>
struct And<B1> : public B1
{};
template<typename B1, typename B2>
struct And<B1, B2>
: public std::conditional<B1::value, B2, B1>::type
{};
template<typename B1, typename B2, typename B3, typename... Bn>
struct And<B1, B2, B3, Bn...>
: public std::conditional<B1::value, And<B2, B3, Bn...>, B1>::type
{};
/* Concepts-light-like helper to make SFINAE logic easier to read. */
template<typename Condition>
using Requires = typename std::enable_if<Condition::value, void>::type;
}
#endif /* COMMON_TRAITS_H */
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