353 lines
9.9 KiB
C++
353 lines
9.9 KiB
C++
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//
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// require_concept.hpp
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// ~~~~~~~~~~~~~~~~~~~
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//
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// Copyright (c) 2003-2021 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_CONCEPT_HPP
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#define ASIO_REQUIRE_CONCEPT_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_concept_member.hpp"
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#include "asio/traits/require_concept_free.hpp"
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#include "asio/traits/static_require_concept.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-enforcing property to an
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/// object.
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/**
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* The name <tt>require_concept</tt> denotes a customization point object. The
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* expression <tt>asio::require_concept(E, P)</tt> for some
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* subexpressions <tt>E</tt> and <tt>P</tt> (with types <tt>T =
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* decay_t<decltype(E)></tt> and <tt>Prop = decay_t<decltype(P)></tt>) is
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* expression-equivalent to:
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*
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* @li If <tt>is_applicable_property_v<T, Prop> &&
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* Prop::is_requirable_concept</tt> is not a well-formed constant expression
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* with value <tt>true</tt>, <tt>asio::require_concept(E, P)</tt> is
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* ill-formed.
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*
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* @li Otherwise, <tt>E</tt> if the expression <tt>Prop::template
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* static_query_v<T> == Prop::value()</tt> is a well-formed constant
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* expression with value <tt>true</tt>.
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*
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* @li Otherwise, <tt>(E).require_concept(P)</tt> if the expression
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* <tt>(E).require_concept(P)</tt> is well-formed.
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*
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* @li Otherwise, <tt>require_concept(E, P)</tt> if the expression
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* <tt>require_concept(E, P)</tt> is a valid expression with overload
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* resolution performed in a context that does not include the declaration
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* of the <tt>require_concept</tt> customization point object.
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*
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* @li Otherwise, <tt>asio::require_concept(E, P)</tt> is ill-formed.
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*/
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inline constexpr unspecified require_concept = unspecified;
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/// A type trait that determines whether a @c require_concept expression is
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/// well-formed.
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/**
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* Class template @c can_require_concept is a trait that is derived from
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* @c true_type if the expression
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* <tt>asio::require_concept(std::declval<T>(),
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* std::declval<Property>())</tt> is well formed; otherwise @c false_type.
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*/
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template <typename T, typename Property>
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struct can_require_concept :
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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_concept expression will
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/// not throw.
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/**
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* Class template @c is_nothrow_require_concept is a trait that is derived from
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* @c true_type if the expression
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* <tt>asio::require_concept(std::declval<T>(),
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* std::declval<Property>())</tt> is @c noexcept; otherwise @c false_type.
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*/
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template <typename T, typename Property>
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struct is_nothrow_require_concept :
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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_concept
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/// expression.
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/**
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* Class template @c require_concept_result is a trait that determines the
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* result type of the expression
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* <tt>asio::require_concept(std::declval<T>(),
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* std::declval<Property>())</tt>.
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*/
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template <typename T, typename Property>
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struct require_concept_result
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{
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/// The result of the @c require_concept 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_concept_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_concept_free;
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using asio::traits::require_concept_member;
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using asio::traits::static_require_concept;
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void require_concept();
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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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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_concept
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>::type,
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typename enable_if<
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static_require_concept<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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typedef ASIO_MOVE_ARG(T) 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_concept
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>::type,
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typename enable_if<
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!static_require_concept<T, Property>::is_valid
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>::type,
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typename enable_if<
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require_concept_member<
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typename Impl::template proxy<T>::type,
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Property
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>::is_valid
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>::type> :
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require_concept_member<
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typename Impl::template proxy<T>::type,
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Property
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>
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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_concept
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>::type,
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typename enable_if<
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!static_require_concept<T, Property>::is_valid
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>::type,
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typename enable_if<
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!require_concept_member<
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typename Impl::template proxy<T>::type,
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Property
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>::is_valid
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>::type,
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typename enable_if<
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require_concept_free<T, Property>::is_valid
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>::type> :
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require_concept_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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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_CONCEPT_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_concept(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_concept(
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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_concept(
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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_CONCEPT_MEMBER_TRAIT)
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typedef T type;
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#endif // defined(ASIO_HAS_DEDUCED_REQUIRE_CONCEPT_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_concept(
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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_concept(
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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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};
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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_concept_fn
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namespace asio {
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namespace {
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static ASIO_CONSTEXPR const asio_require_concept_fn::impl&
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require_concept = asio_require_concept_fn::static_instance<>::instance;
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} // namespace
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typedef asio_require_concept_fn::impl require_concept_t;
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template <typename T, typename Property>
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struct can_require_concept :
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integral_constant<bool,
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asio_require_concept_fn::call_traits<
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require_concept_t, T, void(Property)>::overload !=
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asio_require_concept_fn::ill_formed>
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{
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};
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#if defined(ASIO_HAS_VARIABLE_TEMPLATES)
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template <typename T, typename Property>
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constexpr bool can_require_concept_v
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= can_require_concept<T, Property>::value;
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#endif // defined(ASIO_HAS_VARIABLE_TEMPLATES)
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template <typename T, typename Property>
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struct is_nothrow_require_concept :
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integral_constant<bool,
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asio_require_concept_fn::call_traits<
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require_concept_t, T, void(Property)>::is_noexcept>
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{
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};
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#if defined(ASIO_HAS_VARIABLE_TEMPLATES)
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template <typename T, typename Property>
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constexpr bool is_nothrow_require_concept_v
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= is_nothrow_require_concept<T, Property>::value;
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#endif // defined(ASIO_HAS_VARIABLE_TEMPLATES)
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template <typename T, typename Property>
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struct require_concept_result
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{
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typedef typename asio_require_concept_fn::call_traits<
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require_concept_t, T, void(Property)>::result_type type;
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};
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} // namespace asio
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#endif // defined(GENERATING_DOCUMENTATION)
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#include "asio/detail/pop_options.hpp"
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#endif // ASIO_REQUIRE_CONCEPT_HPP
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