text: //
  // traits/static_query.hpp
  // ~~~~~~~~~~~~~~~~~~~~~~~
  //
  // Copyright (c) 2003-2021 Christopher M. Kohlhoff (chris at kohlhoff dot com)
  //
  // Distributed under the Boost Software License, Version 1.0. (See accompanying
  // file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
  //
  
  #ifndef ASIO_TRAITS_STATIC_QUERY_HPP
  #define ASIO_TRAITS_STATIC_QUERY_HPP
  
  #if defined(_MSC_VER) && (_MSC_VER >= 1200)
  # pragma once
  #endif // defined(_MSC_VER) && (_MSC_VER >= 1200)
  
  #include "asio/detail/config.hpp"
  #include "asio/detail/type_traits.hpp"
  
  #if defined(ASIO_HAS_DECLTYPE) \
    && defined(ASIO_HAS_NOEXCEPT) \
    && defined(ASIO_HAS_CONSTEXPR) \
    && defined(ASIO_HAS_VARIABLE_TEMPLATES) \
    && defined(ASIO_HAS_WORKING_EXPRESSION_SFINAE)
  # define ASIO_HAS_DEDUCED_STATIC_QUERY_TRAIT 1
  #endif // defined(ASIO_HAS_DECLTYPE)
         //   && defined(ASIO_HAS_NOEXCEPT)
         //   && defined(ASIO_HAS_CONSTEXPR)
         //   && defined(ASIO_HAS_VARIABLE_TEMPLATES)
         //   && defined(ASIO_HAS_WORKING_EXPRESSION_SFINAE)
  
  #include "asio/detail/push_options.hpp"
  
  namespace asio {
  namespace traits {
  
  template <typename T, typename Property, typename = void>
  struct static_query_default;
  
  template <typename T, typename Property, typename = void>
  struct static_query;
  
  } // namespace traits
  namespace detail {
  
  struct no_static_query
  {
    ASIO_STATIC_CONSTEXPR(bool, is_valid = false);
    ASIO_STATIC_CONSTEXPR(bool, is_noexcept = false);
  };
  
  template <typename T, typename Property, typename = void>
  struct static_query_trait :
    conditional<
      is_same<T, typename decay<T>::type>::value
        && is_same<Property, typename decay<Property>::type>::value,
      no_static_query,
      traits::static_query<
        typename decay<T>::type,
        typename decay<Property>::type>
    >::type
  {
  };
  
  #if defined(ASIO_HAS_DEDUCED_STATIC_QUERY_TRAIT)
  
  template <typename T, typename Property>
  struct static_query_trait<T, Property,
    typename void_type<
      decltype(decay<Property>::type::template static_query_v<T>)
    >::type>
  {
    ASIO_STATIC_CONSTEXPR(bool, is_valid = true);
  
    using result_type = decltype(
        decay<Property>::type::template static_query_v<T>);
  
    ASIO_STATIC_CONSTEXPR(bool, is_noexcept =
      noexcept(decay<Property>::type::template static_query_v<T>));
  
    static ASIO_CONSTEXPR result_type value() noexcept(is_noexcept)
    {
      return decay<Property>::type::template static_query_v<T>;
    }
  };
  
  #endif // defined(ASIO_HAS_DEDUCED_STATIC_QUERY_TRAIT)
  
  } // namespace detail
  namespace traits {
  
  template <typename T, typename Property, typename>
  struct static_query_default : detail::static_query_trait<T, Property>
  {
  };
  
  template <typename T, typename Property, typename>
  struct static_query : static_query_default<T, Property>
  {
  };
  
  } // namespace traits
  } // namespace asio
  
  #include "asio/detail/pop_options.hpp"
  
  #endif // ASIO_TRAITS_STATIC_QUERY_HPP
  