572 lines
15 KiB
C++
572 lines
15 KiB
C++
//
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// require.hpp
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// ~~~~~~~~~~~
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//
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// Copyright (c) 2003-2023 Christopher M. Kohlhoff (chris at kohlhoff dot com)
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//
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// Distributed under the Boost Software License, Version 1.0. (See accompanying
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// file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
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//
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#ifndef ASIO_REQUIRE_HPP
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#define ASIO_REQUIRE_HPP
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#if defined(_MSC_VER) && (_MSC_VER >= 1200)
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# pragma once
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#endif // defined(_MSC_VER) && (_MSC_VER >= 1200)
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#include "asio/detail/config.hpp"
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#include "asio/detail/type_traits.hpp"
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#include "asio/is_applicable_property.hpp"
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#include "asio/traits/require_member.hpp"
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#include "asio/traits/require_free.hpp"
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#include "asio/traits/static_require.hpp"
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#include "asio/detail/push_options.hpp"
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#if defined(GENERATING_DOCUMENTATION)
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namespace asio {
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/// A customisation point that applies a concept-preserving property to an
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/// object.
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/**
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* The name <tt>require</tt> denotes a customisation point object. The
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* expression <tt>asio::require(E, P0, Pn...)</tt> for some
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* subexpressions <tt>E</tt> and <tt>P0</tt>, and where <tt>Pn...</tt>
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* represents <tt>N</tt> subexpressions (where <tt>N</tt> is 0 or more, and with
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* types <tt>T = decay_t<decltype(E)></tt> and <tt>Prop0 =
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* decay_t<decltype(P0)></tt>) is expression-equivalent to:
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*
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* @li If <tt>is_applicable_property_v<T, Prop0> && Prop0::is_requirable</tt> is
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* not a well-formed constant expression with value <tt>true</tt>,
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* <tt>asio::require(E, P0, Pn...)</tt> is ill-formed.
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*
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* @li Otherwise, <tt>E</tt> if <tt>N == 0</tt> and the expression
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* <tt>Prop0::template static_query_v<T> == Prop0::value()</tt> is a
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* well-formed constant expression with value <tt>true</tt>.
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*
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* @li Otherwise, <tt>(E).require(P0)</tt> if <tt>N == 0</tt> and the expression
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* <tt>(E).require(P0)</tt> is a valid expression.
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*
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* @li Otherwise, <tt>require(E, P0)</tt> if <tt>N == 0</tt> and the expression
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* <tt>require(E, P0)</tt> is a valid expression with overload resolution
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* performed in a context that does not include the declaration of the
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* <tt>require</tt> customization point object.
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*
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* @li Otherwise,
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* <tt>asio::require(asio::require(E, P0), Pn...)</tt>
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* if <tt>N > 0</tt> and the expression
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* <tt>asio::require(asio::require(E, P0), Pn...)</tt>
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* is a valid expression.
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*
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* @li Otherwise, <tt>asio::require(E, P0, Pn...)</tt> is ill-formed.
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*/
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inline constexpr unspecified require = unspecified;
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/// A type trait that determines whether a @c require expression is well-formed.
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/**
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* Class template @c can_require is a trait that is derived from
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* @c true_type if the expression <tt>asio::require(std::declval<T>(),
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* std::declval<Properties>()...)</tt> is well formed; otherwise @c false_type.
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*/
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template <typename T, typename... Properties>
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struct can_require :
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integral_constant<bool, automatically_determined>
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{
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};
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/// A type trait that determines whether a @c require expression will not throw.
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/**
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* Class template @c is_nothrow_require is a trait that is derived from
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* @c true_type if the expression <tt>asio::require(std::declval<T>(),
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* std::declval<Properties>()...)</tt> is @c noexcept; otherwise @c false_type.
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*/
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template <typename T, typename... Properties>
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struct is_nothrow_require :
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integral_constant<bool, automatically_determined>
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{
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};
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/// A type trait that determines the result type of a @c require expression.
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/**
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* Class template @c require_result is a trait that determines the result
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* type of the expression <tt>asio::require(std::declval<T>(),
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* std::declval<Properties>()...)</tt>.
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*/
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template <typename T, typename... Properties>
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struct require_result
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{
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/// The result of the @c require expression.
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typedef automatically_determined type;
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};
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} // namespace asio
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#else // defined(GENERATING_DOCUMENTATION)
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namespace asio_require_fn {
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using asio::conditional;
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using asio::decay;
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using asio::declval;
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using asio::enable_if;
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using asio::is_applicable_property;
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using asio::traits::require_free;
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using asio::traits::require_member;
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using asio::traits::static_require;
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void require();
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enum overload_type
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{
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identity,
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call_member,
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call_free,
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two_props,
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n_props,
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ill_formed
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};
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template <typename Impl, typename T, typename Properties, typename = void,
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typename = void, typename = void, typename = void, typename = void>
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struct call_traits
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{
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ASIO_STATIC_CONSTEXPR(overload_type, overload = ill_formed);
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ASIO_STATIC_CONSTEXPR(bool, is_noexcept = false);
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typedef void result_type;
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};
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template <typename Impl, typename T, typename Property>
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struct call_traits<Impl, T, void(Property),
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typename enable_if<
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is_applicable_property<
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typename decay<T>::type,
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typename decay<Property>::type
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>::value
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>::type,
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typename enable_if<
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decay<Property>::type::is_requirable
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>::type,
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typename enable_if<
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static_require<T, Property>::is_valid
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>::type>
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{
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ASIO_STATIC_CONSTEXPR(overload_type, overload = identity);
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ASIO_STATIC_CONSTEXPR(bool, is_noexcept = true);
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#if defined(ASIO_HAS_MOVE)
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typedef ASIO_MOVE_ARG(T) result_type;
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#else // defined(ASIO_HAS_MOVE)
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typedef ASIO_MOVE_ARG(typename decay<T>::type) result_type;
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#endif // defined(ASIO_HAS_MOVE)
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};
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template <typename Impl, typename T, typename Property>
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struct call_traits<Impl, T, void(Property),
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typename enable_if<
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is_applicable_property<
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typename decay<T>::type,
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typename decay<Property>::type
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>::value
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>::type,
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typename enable_if<
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decay<Property>::type::is_requirable
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>::type,
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typename enable_if<
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!static_require<T, Property>::is_valid
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>::type,
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typename enable_if<
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require_member<typename Impl::template proxy<T>::type, Property>::is_valid
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>::type> :
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require_member<typename Impl::template proxy<T>::type, Property>
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{
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ASIO_STATIC_CONSTEXPR(overload_type, overload = call_member);
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};
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template <typename Impl, typename T, typename Property>
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struct call_traits<Impl, T, void(Property),
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typename enable_if<
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is_applicable_property<
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typename decay<T>::type,
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typename decay<Property>::type
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>::value
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>::type,
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typename enable_if<
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decay<Property>::type::is_requirable
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>::type,
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typename enable_if<
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!static_require<T, Property>::is_valid
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>::type,
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typename enable_if<
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!require_member<typename Impl::template proxy<T>::type, Property>::is_valid
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>::type,
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typename enable_if<
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require_free<T, Property>::is_valid
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>::type> :
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require_free<T, Property>
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{
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ASIO_STATIC_CONSTEXPR(overload_type, overload = call_free);
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};
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template <typename Impl, typename T, typename P0, typename P1>
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struct call_traits<Impl, T, void(P0, P1),
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typename enable_if<
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call_traits<Impl, T, void(P0)>::overload != ill_formed
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>::type,
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typename enable_if<
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call_traits<
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Impl,
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typename call_traits<Impl, T, void(P0)>::result_type,
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void(P1)
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>::overload != ill_formed
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>::type>
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{
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ASIO_STATIC_CONSTEXPR(overload_type, overload = two_props);
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ASIO_STATIC_CONSTEXPR(bool, is_noexcept =
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(
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call_traits<Impl, T, void(P0)>::is_noexcept
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&&
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call_traits<
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Impl,
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typename call_traits<Impl, T, void(P0)>::result_type,
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void(P1)
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>::is_noexcept
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));
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typedef typename decay<
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typename call_traits<
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Impl,
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typename call_traits<Impl, T, void(P0)>::result_type,
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void(P1)
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>::result_type
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>::type result_type;
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};
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template <typename Impl, typename T, typename P0,
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typename P1, typename ASIO_ELLIPSIS PN>
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struct call_traits<Impl, T, void(P0, P1, PN ASIO_ELLIPSIS),
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typename enable_if<
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call_traits<Impl, T, void(P0)>::overload != ill_formed
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>::type,
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typename enable_if<
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call_traits<
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Impl,
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typename call_traits<Impl, T, void(P0)>::result_type,
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void(P1, PN ASIO_ELLIPSIS)
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>::overload != ill_formed
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>::type>
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{
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ASIO_STATIC_CONSTEXPR(overload_type, overload = n_props);
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ASIO_STATIC_CONSTEXPR(bool, is_noexcept =
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(
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call_traits<Impl, T, void(P0)>::is_noexcept
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&&
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call_traits<
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Impl,
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typename call_traits<Impl, T, void(P0)>::result_type,
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void(P1, PN ASIO_ELLIPSIS)
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>::is_noexcept
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));
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typedef typename decay<
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typename call_traits<
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Impl,
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typename call_traits<Impl, T, void(P0)>::result_type,
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void(P1, PN ASIO_ELLIPSIS)
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>::result_type
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>::type result_type;
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};
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struct impl
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{
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template <typename T>
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struct proxy
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{
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#if defined(ASIO_HAS_DEDUCED_REQUIRE_MEMBER_TRAIT)
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struct type
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{
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template <typename P>
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auto require(ASIO_MOVE_ARG(P) p)
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noexcept(
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noexcept(
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declval<typename conditional<true, T, P>::type>().require(
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ASIO_MOVE_CAST(P)(p))
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)
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)
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-> decltype(
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declval<typename conditional<true, T, P>::type>().require(
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ASIO_MOVE_CAST(P)(p))
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);
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};
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#else // defined(ASIO_HAS_DEDUCED_REQUIRE_MEMBER_TRAIT)
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typedef T type;
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#endif // defined(ASIO_HAS_DEDUCED_REQUIRE_MEMBER_TRAIT)
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};
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template <typename T, typename Property>
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ASIO_NODISCARD ASIO_CONSTEXPR typename enable_if<
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call_traits<impl, T, void(Property)>::overload == identity,
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typename call_traits<impl, T, void(Property)>::result_type
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>::type
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operator()(
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ASIO_MOVE_ARG(T) t,
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ASIO_MOVE_ARG(Property)) const
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ASIO_NOEXCEPT_IF((
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call_traits<impl, T, void(Property)>::is_noexcept))
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{
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return ASIO_MOVE_CAST(T)(t);
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}
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template <typename T, typename Property>
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ASIO_NODISCARD ASIO_CONSTEXPR typename enable_if<
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call_traits<impl, T, void(Property)>::overload == call_member,
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typename call_traits<impl, T, void(Property)>::result_type
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>::type
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operator()(
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ASIO_MOVE_ARG(T) t,
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ASIO_MOVE_ARG(Property) p) const
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ASIO_NOEXCEPT_IF((
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call_traits<impl, T, void(Property)>::is_noexcept))
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{
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return ASIO_MOVE_CAST(T)(t).require(
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ASIO_MOVE_CAST(Property)(p));
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}
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template <typename T, typename Property>
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ASIO_NODISCARD ASIO_CONSTEXPR typename enable_if<
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call_traits<impl, T, void(Property)>::overload == call_free,
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typename call_traits<impl, T, void(Property)>::result_type
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>::type
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operator()(
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ASIO_MOVE_ARG(T) t,
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ASIO_MOVE_ARG(Property) p) const
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ASIO_NOEXCEPT_IF((
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call_traits<impl, T, void(Property)>::is_noexcept))
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{
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return require(
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ASIO_MOVE_CAST(T)(t),
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ASIO_MOVE_CAST(Property)(p));
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}
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template <typename T, typename P0, typename P1>
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ASIO_NODISCARD ASIO_CONSTEXPR typename enable_if<
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call_traits<impl, T, void(P0, P1)>::overload == two_props,
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typename call_traits<impl, T, void(P0, P1)>::result_type
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>::type
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operator()(
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ASIO_MOVE_ARG(T) t,
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ASIO_MOVE_ARG(P0) p0,
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ASIO_MOVE_ARG(P1) p1) const
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ASIO_NOEXCEPT_IF((
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call_traits<impl, T, void(P0, P1)>::is_noexcept))
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{
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return (*this)(
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(*this)(
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ASIO_MOVE_CAST(T)(t),
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ASIO_MOVE_CAST(P0)(p0)),
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ASIO_MOVE_CAST(P1)(p1));
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}
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template <typename T, typename P0, typename P1,
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typename ASIO_ELLIPSIS PN>
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ASIO_NODISCARD ASIO_CONSTEXPR typename enable_if<
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call_traits<impl, T,
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void(P0, P1, PN ASIO_ELLIPSIS)>::overload == n_props,
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typename call_traits<impl, T,
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void(P0, P1, PN ASIO_ELLIPSIS)>::result_type
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>::type
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operator()(
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ASIO_MOVE_ARG(T) t,
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ASIO_MOVE_ARG(P0) p0,
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ASIO_MOVE_ARG(P1) p1,
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ASIO_MOVE_ARG(PN) ASIO_ELLIPSIS pn) const
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ASIO_NOEXCEPT_IF((
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call_traits<impl, T, void(P0, P1, PN ASIO_ELLIPSIS)>::is_noexcept))
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{
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return (*this)(
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(*this)(
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ASIO_MOVE_CAST(T)(t),
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ASIO_MOVE_CAST(P0)(p0)),
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ASIO_MOVE_CAST(P1)(p1),
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ASIO_MOVE_CAST(PN)(pn) ASIO_ELLIPSIS);
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}
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};
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template <typename T = impl>
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struct static_instance
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{
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static const T instance;
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};
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template <typename T>
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const T static_instance<T>::instance = {};
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} // namespace asio_require_fn
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namespace asio {
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namespace {
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static ASIO_CONSTEXPR const asio_require_fn::impl&
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require = asio_require_fn::static_instance<>::instance;
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} // namespace
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typedef asio_require_fn::impl require_t;
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#if defined(ASIO_HAS_VARIADIC_TEMPLATES)
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template <typename T, typename... Properties>
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struct can_require :
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integral_constant<bool,
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asio_require_fn::call_traits<
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require_t, T, void(Properties...)>::overload
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!= asio_require_fn::ill_formed>
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{
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};
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#else // defined(ASIO_HAS_VARIADIC_TEMPLATES)
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template <typename T, typename P0 = void,
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typename P1 = void, typename P2 = void>
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struct can_require :
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integral_constant<bool,
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asio_require_fn::call_traits<require_t, T, void(P0, P1, P2)>::overload
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!= asio_require_fn::ill_formed>
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{
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};
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template <typename T, typename P0, typename P1>
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struct can_require<T, P0, P1> :
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integral_constant<bool,
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asio_require_fn::call_traits<require_t, T, void(P0, P1)>::overload
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!= asio_require_fn::ill_formed>
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{
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};
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template <typename T, typename P0>
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struct can_require<T, P0> :
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integral_constant<bool,
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asio_require_fn::call_traits<require_t, T, void(P0)>::overload
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!= asio_require_fn::ill_formed>
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{
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};
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template <typename T>
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struct can_require<T> :
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false_type
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{
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};
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#endif // defined(ASIO_HAS_VARIADIC_TEMPLATES)
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#if defined(ASIO_HAS_VARIABLE_TEMPLATES)
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template <typename T, typename ASIO_ELLIPSIS Properties>
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constexpr bool can_require_v
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= can_require<T, Properties ASIO_ELLIPSIS>::value;
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#endif // defined(ASIO_HAS_VARIABLE_TEMPLATES)
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#if defined(ASIO_HAS_VARIADIC_TEMPLATES)
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template <typename T, typename... Properties>
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struct is_nothrow_require :
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integral_constant<bool,
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asio_require_fn::call_traits<
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require_t, T, void(Properties...)>::is_noexcept>
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{
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};
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#else // defined(ASIO_HAS_VARIADIC_TEMPLATES)
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template <typename T, typename P0 = void,
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typename P1 = void, typename P2 = void>
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struct is_nothrow_require :
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integral_constant<bool,
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asio_require_fn::call_traits<
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require_t, T, void(P0, P1, P2)>::is_noexcept>
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{
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};
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template <typename T, typename P0, typename P1>
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struct is_nothrow_require<T, P0, P1> :
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integral_constant<bool,
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asio_require_fn::call_traits<
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require_t, T, void(P0, P1)>::is_noexcept>
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{
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};
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template <typename T, typename P0>
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struct is_nothrow_require<T, P0> :
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integral_constant<bool,
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|
asio_require_fn::call_traits<
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require_t, T, void(P0)>::is_noexcept>
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|
{
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|
};
|
|
|
|
template <typename T>
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struct is_nothrow_require<T> :
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|
false_type
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|
{
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|
};
|
|
|
|
#endif // defined(ASIO_HAS_VARIADIC_TEMPLATES)
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|
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|
#if defined(ASIO_HAS_VARIABLE_TEMPLATES)
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|
|
|
template <typename T, typename ASIO_ELLIPSIS Properties>
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constexpr bool is_nothrow_require_v
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|
= is_nothrow_require<T, Properties ASIO_ELLIPSIS>::value;
|
|
|
|
#endif // defined(ASIO_HAS_VARIABLE_TEMPLATES)
|
|
|
|
#if defined(ASIO_HAS_VARIADIC_TEMPLATES)
|
|
|
|
template <typename T, typename... Properties>
|
|
struct require_result
|
|
{
|
|
typedef typename asio_require_fn::call_traits<
|
|
require_t, T, void(Properties...)>::result_type type;
|
|
};
|
|
|
|
#else // defined(ASIO_HAS_VARIADIC_TEMPLATES)
|
|
|
|
template <typename T, typename P0 = void,
|
|
typename P1 = void, typename P2 = void>
|
|
struct require_result
|
|
{
|
|
typedef typename asio_require_fn::call_traits<
|
|
require_t, T, void(P0, P1, P2)>::result_type type;
|
|
};
|
|
|
|
template <typename T, typename P0, typename P1>
|
|
struct require_result<T, P0, P1>
|
|
{
|
|
typedef typename asio_require_fn::call_traits<
|
|
require_t, T, void(P0, P1)>::result_type type;
|
|
};
|
|
|
|
template <typename T, typename P0>
|
|
struct require_result<T, P0>
|
|
{
|
|
typedef typename asio_require_fn::call_traits<
|
|
require_t, T, void(P0)>::result_type type;
|
|
};
|
|
|
|
template <typename T>
|
|
struct require_result<T>
|
|
{
|
|
};
|
|
|
|
#endif // defined(ASIO_HAS_VARIADIC_TEMPLATES)
|
|
|
|
} // namespace asio
|
|
|
|
#endif // defined(GENERATING_DOCUMENTATION)
|
|
|
|
#include "asio/detail/pop_options.hpp"
|
|
|
|
#endif // ASIO_REQUIRE_HPP
|