text: //
  // traits/set_error_free.hpp
  // ~~~~~~~~~~~~~~~~~~~~~~~~~
  //
  // Copyright (c) 2003-2020 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 BOOST_ASIO_TRAITS_SET_ERROR_FREE_HPP
  #define BOOST_ASIO_TRAITS_SET_ERROR_FREE_HPP
  
  #if defined(_MSC_VER) && (_MSC_VER >= 1200)
  # pragma once
  #endif // defined(_MSC_VER) && (_MSC_VER >= 1200)
  
  #include <boost/asio/detail/config.hpp>
  #include <boost/asio/detail/type_traits.hpp>
  
  #if defined(BOOST_ASIO_HAS_DECLTYPE) \
    && defined(BOOST_ASIO_HAS_NOEXCEPT) \
    && defined(BOOST_ASIO_HAS_WORKING_EXPRESSION_SFINAE)
  # define BOOST_ASIO_HAS_DEDUCED_SET_ERROR_FREE_TRAIT 1
  #endif // defined(BOOST_ASIO_HAS_DECLTYPE)
         //   && defined(BOOST_ASIO_HAS_NOEXCEPT)
         //   && defined(BOOST_ASIO_HAS_WORKING_EXPRESSION_SFINAE)
  
  #include <boost/asio/detail/push_options.hpp>
  
  namespace boost {
  namespace asio {
  namespace traits {
  
  template <typename T, typename E, typename = void>
  struct set_error_free_default;
  
  template <typename T, typename E, typename = void>
  struct set_error_free;
  
  } // namespace traits
  namespace detail {
  
  struct no_set_error_free
  {
    BOOST_ASIO_STATIC_CONSTEXPR(bool, is_valid = false);
    BOOST_ASIO_STATIC_CONSTEXPR(bool, is_noexcept = false);
  };
  
  #if defined(BOOST_ASIO_HAS_DEDUCED_SET_ERROR_FREE_TRAIT)
  
  template <typename T, typename E, typename = void>
  struct set_error_free_trait : no_set_error_free
  {
  };
  
  template <typename T, typename E>
  struct set_error_free_trait<T, E,
    typename void_type<
      decltype(set_error(declval<T>(), declval<E>()))
    >::type>
  {
    BOOST_ASIO_STATIC_CONSTEXPR(bool, is_valid = true);
  
    using result_type = decltype(
      set_error(declval<T>(), declval<E>()));
  
    BOOST_ASIO_STATIC_CONSTEXPR(bool, is_noexcept = noexcept(
      set_error(declval<T>(), declval<E>())));
  };
  
  #else // defined(BOOST_ASIO_HAS_DEDUCED_SET_ERROR_FREE_TRAIT)
  
  template <typename T, typename E, typename = void>
  struct set_error_free_trait :
    conditional<
      is_same<T, typename remove_reference<T>::type>::value
        && is_same<E, typename decay<E>::type>::value,
      typename conditional<
        is_same<T, typename add_const<T>::type>::value,
        no_set_error_free,
        traits::set_error_free<typename add_const<T>::type, E>
      >::type,
      traits::set_error_free<
        typename remove_reference<T>::type,
        typename decay<E>::type>
    >::type
  {
  };
  
  #endif // defined(BOOST_ASIO_HAS_DEDUCED_SET_ERROR_FREE_TRAIT)
  
  } // namespace detail
  namespace traits {
  
  template <typename T, typename E, typename>
  struct set_error_free_default :
    detail::set_error_free_trait<T, E>
  {
  };
  
  template <typename T, typename E, typename>
  struct set_error_free :
    set_error_free_default<T, E>
  {
  };
  
  } // namespace traits
  } // namespace asio
  } // namespace boost
  
  #include <boost/asio/detail/pop_options.hpp>
  
  #endif // BOOST_ASIO_TRAITS_SET_ERROR_FREE_HPP
  