Diff coverage report for

//

//

// Copyright (c) 2020 Krystian Stasiowski (sdkrystian@gmail.com)

// Copyright (c) 2020 Krystian Stasiowski (sdkrystian@gmail.com)

// Copyright (c) 2022 Dmitry Arkhipov (grisumbras@yandex.ru)

// Copyright (c) 2022 Dmitry Arkhipov (grisumbras@yandex.ru)

//

//

// Distributed under the Boost Software License, Version 1.0. (See accompanying

// 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)

// file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)

//

//

// Official repository: https://github.com/boostorg/json

// Official repository: https://github.com/boostorg/json

//

//

#ifndef BOOST_JSON_IMPL_CONVERSION_HPP

#ifndef BOOST_JSON_IMPL_CONVERSION_HPP

#define BOOST_JSON_IMPL_CONVERSION_HPP

#define BOOST_JSON_IMPL_CONVERSION_HPP

#include <boost/json/fwd.hpp>

#include <boost/json/fwd.hpp>

#include <boost/json/string_view.hpp>

#include <boost/json/string_view.hpp>

#include <boost/describe/enumerators.hpp>

#include <boost/describe/enumerators.hpp>

#include <boost/describe/members.hpp>

#include <boost/describe/members.hpp>

#include <boost/describe/bases.hpp>

#include <boost/describe/bases.hpp>

#include <boost/mp11/algorithm.hpp>

#include <boost/mp11/algorithm.hpp>

#include <boost/mp11/utility.hpp>

#include <boost/mp11/utility.hpp>

#include <boost/system/result.hpp>

#include <boost/system/result.hpp>

#include <iterator>

#include <iterator>

#include <tuple>

#include <tuple>

#include <utility>

#include <utility>

#ifndef BOOST_NO_CXX17_HDR_VARIANT

#ifndef BOOST_NO_CXX17_HDR_VARIANT

# include <variant>

# include <variant>

#endif // BOOST_NO_CXX17_HDR_VARIANT

#endif // BOOST_NO_CXX17_HDR_VARIANT

namespace boost {

namespace boost {

namespace json {

namespace json {

class value_ref;

class value_ref;

namespace detail {

namespace detail {

#ifdef __cpp_lib_nonmember_container_access

#ifdef __cpp_lib_nonmember_container_access

using std::size;

using std::size;

#endif

#endif

template<std::size_t I, class T>

template<std::size_t I, class T>

using tuple_element_t = typename std::tuple_element<I, T>::type;

using tuple_element_t = typename std::tuple_element<I, T>::type;

template<class T>

template<class T>

using iterator_type = decltype(std::begin(std::declval<T&>()));

using iterator_type = decltype(std::begin(std::declval<T&>()));

template<class T>

template<class T>

using iterator_traits = std::iterator_traits< iterator_type<T> >;

using iterator_traits = std::iterator_traits< iterator_type<T> >;

template<class T>

template<class T>

using value_type = typename iterator_traits<T>::value_type;

using value_type = typename iterator_traits<T>::value_type;

template<class T>

template<class T>

using mapped_type = tuple_element_t< 1, value_type<T> >;

using mapped_type = tuple_element_t< 1, value_type<T> >;

// had to make the metafunction always succeeding in order to make it work

// had to make the metafunction always succeeding in order to make it work

// with msvc 14.0

// with msvc 14.0

template<class T>

template<class T>

using key_type_helper = tuple_element_t< 0, value_type<T> >;

using key_type_helper = tuple_element_t< 0, value_type<T> >;

template<class T>

template<class T>

using key_type = mp11::mp_eval_or<

using key_type = mp11::mp_eval_or<

    void,

    void,

    key_type_helper,

    key_type_helper,

    T>;

    T>;

template<class T>

template<class T>

using are_begin_and_end_same = std::is_same<

using are_begin_and_end_same = std::is_same<

    iterator_type<T>,

    iterator_type<T>,

    decltype(std::end(std::declval<T&>()))>;

    decltype(std::end(std::declval<T&>()))>;

// msvc 14.0 gets confused when std::is_same is used directly

// msvc 14.0 gets confused when std::is_same is used directly

template<class A, class B>

template<class A, class B>

using is_same_msvc_140 = std::is_same<A, B>;

using is_same_msvc_140 = std::is_same<A, B>;

template<class T>

template<class T>

using is_its_own_value = is_same_msvc_140<value_type<T>, T>;

using is_its_own_value = is_same_msvc_140<value_type<T>, T>;

template<class T>

template<class T>

using not_its_own_value = mp11::mp_not< is_its_own_value<T> >;

using not_its_own_value = mp11::mp_not< is_its_own_value<T> >;

template<class T>

template<class T>

using begin_iterator_category = typename std::iterator_traits<

using begin_iterator_category = typename std::iterator_traits<

    iterator_type<T>>::iterator_category;

    iterator_type<T>>::iterator_category;

template<class T>

template<class T>

using has_positive_tuple_size = mp11::mp_bool<

using has_positive_tuple_size = mp11::mp_bool<

    (std::tuple_size<T>::value > 0) >;

    (std::tuple_size<T>::value > 0) >;

template<class T>

template<class T>

using has_unique_keys = has_positive_tuple_size<decltype(

using has_unique_keys = has_positive_tuple_size<decltype(

    std::declval<T&>().emplace(

    std::declval<T&>().emplace(

        std::declval<value_type<T>>()))>;

        std::declval<value_type<T>>()))>;

template<class T>

template<class T>

using has_string_type = std::is_same<

using has_string_type = std::is_same<

    typename T::string_type, std::basic_string<typename T::value_type> >;

    typename T::string_type, std::basic_string<typename T::value_type> >;

template<class T>

template<class T>

struct is_value_type_pair_helper : std::false_type

struct is_value_type_pair_helper : std::false_type

{ };

{ };

template<class T1, class T2>

template<class T1, class T2>

struct is_value_type_pair_helper<std::pair<T1, T2>> : std::true_type

struct is_value_type_pair_helper<std::pair<T1, T2>> : std::true_type

{ };

{ };

template<class T>

template<class T>

using is_value_type_pair = is_value_type_pair_helper<value_type<T>>;

using is_value_type_pair = is_value_type_pair_helper<value_type<T>>;

template<class T>

template<class T>

using has_size_member_helper

using has_size_member_helper

    = std::is_convertible<decltype(std::declval<T&>().size()), std::size_t>;

    = std::is_convertible<decltype(std::declval<T&>().size()), std::size_t>;

template<class T>

template<class T>

using has_size_member = mp11::mp_valid_and_true<has_size_member_helper, T>;

using has_size_member = mp11::mp_valid_and_true<has_size_member_helper, T>;

template<class T>

template<class T>

using has_free_size_helper

using has_free_size_helper

    = std::is_convertible<

    = std::is_convertible<

        decltype(size(std::declval<T const&>())),

        decltype(size(std::declval<T const&>())),

        std::size_t>;

        std::size_t>;

template<class T>

template<class T>

using has_free_size = mp11::mp_valid_and_true<has_free_size_helper, T>;

using has_free_size = mp11::mp_valid_and_true<has_free_size_helper, T>;

template<class T>

template<class T>

using size_implementation = mp11::mp_cond<

using size_implementation = mp11::mp_cond<

    has_size_member<T>, mp11::mp_int<3>,

    has_size_member<T>, mp11::mp_int<3>,

    has_free_size<T>,   mp11::mp_int<2>,

    has_free_size<T>,   mp11::mp_int<2>,

    std::is_array<T>,   mp11::mp_int<1>,

    std::is_array<T>,   mp11::mp_int<1>,

    mp11::mp_true,      mp11::mp_int<0>>;

    mp11::mp_true,      mp11::mp_int<0>>;

template<class T>

template<class T>

std::size_t

std::size_t

{

{

}

}

template<class T>

template<class T>

std::size_t

std::size_t

{

{

}

}

template<class T, std::size_t N>

template<class T, std::size_t N>

std::size_t

std::size_t

{

{

}

}

template<class T>

template<class T>

std::size_t

std::size_t

{

{

}

}

template<class T>

template<class T>

using has_push_back_helper

using has_push_back_helper

    = decltype(std::declval<T&>().push_back(std::declval<value_type<T>>()));

    = decltype(std::declval<T&>().push_back(std::declval<value_type<T>>()));

template<class T>

template<class T>

using has_push_back = mp11::mp_valid<has_push_back_helper, T>;

using has_push_back = mp11::mp_valid<has_push_back_helper, T>;

template<class T>

template<class T>

using inserter_implementation = mp11::mp_cond<

using inserter_implementation = mp11::mp_cond<

    is_tuple_like<T>, mp11::mp_int<2>,

    is_tuple_like<T>, mp11::mp_int<2>,

    has_push_back<T>, mp11::mp_int<1>,

    has_push_back<T>, mp11::mp_int<1>,

    mp11::mp_true,    mp11::mp_int<0>>;

    mp11::mp_true,    mp11::mp_int<0>>;

template<class T>

template<class T>

iterator_type<T>

iterator_type<T>

    T& target,

    T& target,

    mp11::mp_int<2>)

    mp11::mp_int<2>)

{

{

}

}

template<class T>

template<class T>

std::back_insert_iterator<T>

std::back_insert_iterator<T>

    T& target,

    T& target,

    mp11::mp_int<1>)

    mp11::mp_int<1>)

{

{

}

}

template<class T>

template<class T>

std::insert_iterator<T>

std::insert_iterator<T>

    T& target,

    T& target,

    mp11::mp_int<0>)

    mp11::mp_int<0>)

{

{

}

}

using value_from_conversion = mp11::mp_true;

using value_from_conversion = mp11::mp_true;

using value_to_conversion = mp11::mp_false;

using value_to_conversion = mp11::mp_false;

struct user_conversion_tag { };

struct user_conversion_tag { };

struct context_conversion_tag : user_conversion_tag { };

struct context_conversion_tag : user_conversion_tag { };

struct full_context_conversion_tag : context_conversion_tag { };

struct full_context_conversion_tag : context_conversion_tag { };

struct native_conversion_tag { };

struct native_conversion_tag { };

struct value_conversion_tag : native_conversion_tag { };

struct value_conversion_tag : native_conversion_tag { };

struct object_conversion_tag : native_conversion_tag { };

struct object_conversion_tag : native_conversion_tag { };

struct array_conversion_tag : native_conversion_tag { };

struct array_conversion_tag : native_conversion_tag { };

struct string_conversion_tag : native_conversion_tag { };

struct string_conversion_tag : native_conversion_tag { };

struct bool_conversion_tag : native_conversion_tag { };

struct bool_conversion_tag : native_conversion_tag { };

struct value_ref_tag : native_conversion_tag { };

struct value_ref_tag : native_conversion_tag { };

struct number_conversion_tag : native_conversion_tag { };

struct number_conversion_tag : native_conversion_tag { };

struct integral_conversion_tag : number_conversion_tag { };

struct integral_conversion_tag : number_conversion_tag { };

struct floating_point_conversion_tag : number_conversion_tag { };

struct floating_point_conversion_tag : number_conversion_tag { };

struct null_like_conversion_tag { };

struct null_like_conversion_tag { };

struct string_like_conversion_tag { };

struct string_like_conversion_tag { };

struct map_like_conversion_tag { };

struct map_like_conversion_tag { };

struct path_conversion_tag { };

struct path_conversion_tag { };

struct sequence_conversion_tag { };

struct sequence_conversion_tag { };

struct tuple_conversion_tag { };

struct tuple_conversion_tag { };

struct described_class_conversion_tag { };

struct described_class_conversion_tag { };

struct described_enum_conversion_tag { };

struct described_enum_conversion_tag { };

struct variant_conversion_tag { };

struct variant_conversion_tag { };

struct optional_conversion_tag { };

struct optional_conversion_tag { };

struct no_conversion_tag { };

struct no_conversion_tag { };

template<class... Args>

template<class... Args>

using supports_tag_invoke = decltype(tag_invoke( std::declval<Args>()... ));

using supports_tag_invoke = decltype(tag_invoke( std::declval<Args>()... ));

template<class T>

template<class T>

using has_user_conversion_from_impl = supports_tag_invoke<

using has_user_conversion_from_impl = supports_tag_invoke<

    value_from_tag, value&, T&& >;

    value_from_tag, value&, T&& >;

template<class T>

template<class T>

using has_user_conversion_to_impl = supports_tag_invoke<

using has_user_conversion_to_impl = supports_tag_invoke<

    value_to_tag<T>, value const& >;

    value_to_tag<T>, value const& >;

template<class T>

template<class T>

using has_nonthrowing_user_conversion_to_impl = supports_tag_invoke<

using has_nonthrowing_user_conversion_to_impl = supports_tag_invoke<

    try_value_to_tag<T>, value const& >;

    try_value_to_tag<T>, value const& >;

template< class T, class Dir >

template< class T, class Dir >

using has_user_conversion1 = mp11::mp_if<

using has_user_conversion1 = mp11::mp_if<

    std::is_same<Dir, value_from_conversion>,

    std::is_same<Dir, value_from_conversion>,

    mp11::mp_valid<has_user_conversion_from_impl, T>,

    mp11::mp_valid<has_user_conversion_from_impl, T>,

    mp11::mp_or<

    mp11::mp_or<

        mp11::mp_valid<has_user_conversion_to_impl, T>,

        mp11::mp_valid<has_user_conversion_to_impl, T>,

        mp11::mp_valid<has_nonthrowing_user_conversion_to_impl, T>>>;

        mp11::mp_valid<has_nonthrowing_user_conversion_to_impl, T>>>;

template< class Ctx, class T >

template< class Ctx, class T >

using has_context_conversion_from_impl = supports_tag_invoke<

using has_context_conversion_from_impl = supports_tag_invoke<

    value_from_tag, value&, T&&, Ctx const& >;

    value_from_tag, value&, T&&, Ctx const& >;

template< class Ctx, class T >

template< class Ctx, class T >

using has_context_conversion_to_impl = supports_tag_invoke<

using has_context_conversion_to_impl = supports_tag_invoke<

    value_to_tag<T>, value const&, Ctx const& >;

    value_to_tag<T>, value const&, Ctx const& >;

template< class Ctx, class T >

template< class Ctx, class T >

using has_nonthrowing_context_conversion_to_impl = supports_tag_invoke<

using has_nonthrowing_context_conversion_to_impl = supports_tag_invoke<

    try_value_to_tag<T>, value const&, Ctx const& >;

    try_value_to_tag<T>, value const&, Ctx const& >;

template< class Ctx, class T, class Dir >

template< class Ctx, class T, class Dir >

using has_user_conversion2 = mp11::mp_if<

using has_user_conversion2 = mp11::mp_if<

    std::is_same<Dir, value_from_conversion>,

    std::is_same<Dir, value_from_conversion>,

    mp11::mp_valid<has_context_conversion_from_impl, Ctx, T>,

    mp11::mp_valid<has_context_conversion_from_impl, Ctx, T>,

    mp11::mp_or<

    mp11::mp_or<

        mp11::mp_valid<has_context_conversion_to_impl, Ctx, T>,

        mp11::mp_valid<has_context_conversion_to_impl, Ctx, T>,

        mp11::mp_valid<has_nonthrowing_context_conversion_to_impl, Ctx, T>>>;

        mp11::mp_valid<has_nonthrowing_context_conversion_to_impl, Ctx, T>>>;

template< class Ctx, class T >

template< class Ctx, class T >

using has_full_context_conversion_from_impl = supports_tag_invoke<

using has_full_context_conversion_from_impl = supports_tag_invoke<

    value_from_tag, value&, T&&, Ctx const&, Ctx const& >;

    value_from_tag, value&, T&&, Ctx const&, Ctx const& >;

template< class Ctx, class T >

template< class Ctx, class T >

using has_full_context_conversion_to_impl = supports_tag_invoke<

using has_full_context_conversion_to_impl = supports_tag_invoke<

    value_to_tag<T>, value const&, Ctx const&,  Ctx const& >;

    value_to_tag<T>, value const&, Ctx const&,  Ctx const& >;

template< class Ctx, class T >

template< class Ctx, class T >

using has_nonthrowing_full_context_conversion_to_impl = supports_tag_invoke<

using has_nonthrowing_full_context_conversion_to_impl = supports_tag_invoke<

    try_value_to_tag<T>, value const&, Ctx const&, Ctx const& >;

    try_value_to_tag<T>, value const&, Ctx const&, Ctx const& >;

template< class Ctx, class T, class Dir >

template< class Ctx, class T, class Dir >

using has_user_conversion3 = mp11::mp_if<

using has_user_conversion3 = mp11::mp_if<

    std::is_same<Dir, value_from_conversion>,

    std::is_same<Dir, value_from_conversion>,

    mp11::mp_valid<has_full_context_conversion_from_impl, Ctx, T>,

    mp11::mp_valid<has_full_context_conversion_from_impl, Ctx, T>,

    mp11::mp_or<

    mp11::mp_or<

        mp11::mp_valid<has_full_context_conversion_to_impl, Ctx, T>,

        mp11::mp_valid<has_full_context_conversion_to_impl, Ctx, T>,

        mp11::mp_valid<

        mp11::mp_valid<

            has_nonthrowing_full_context_conversion_to_impl, Ctx, T>>>;

            has_nonthrowing_full_context_conversion_to_impl, Ctx, T>>>;

template< class T >

template< class T >

using described_non_public_members = describe::describe_members<

using described_non_public_members = describe::describe_members<

    T,

    T,

    describe::mod_private

    describe::mod_private

        | describe::mod_protected

        | describe::mod_protected

        | boost::describe::mod_inherited>;

        | boost::describe::mod_inherited>;

#if defined(BOOST_MSVC) && BOOST_MSVC < 1920

#if defined(BOOST_MSVC) && BOOST_MSVC < 1920

template< class T >

template< class T >

struct described_member_t_impl;

struct described_member_t_impl;

template< class T, class C >

template< class T, class C >

struct described_member_t_impl<T C::*>

struct described_member_t_impl<T C::*>

{

{

    using type = T;

    using type = T;

};

};

template< class T, class D >

template< class T, class D >

using described_member_t = remove_cvref<

using described_member_t = remove_cvref<

    typename described_member_t_impl<

    typename described_member_t_impl<

        remove_cvref<decltype(D::pointer)> >::type>;

        remove_cvref<decltype(D::pointer)> >::type>;

#else

#else

template< class T, class D >

template< class T, class D >

using described_member_t = remove_cvref<decltype(

using described_member_t = remove_cvref<decltype(

    std::declval<T&>().* D::pointer )>;

    std::declval<T&>().* D::pointer )>;

#endif

#endif

template< class T >

template< class T >

using described_members = describe::describe_members<

using described_members = describe::describe_members<

    T, describe::mod_any_access | describe::mod_inherited>;

    T, describe::mod_any_access | describe::mod_inherited>;

#ifdef BOOST_DESCRIBE_CXX14

#ifdef BOOST_DESCRIBE_CXX14

constexpr

constexpr

bool

bool

compare_strings(char const* l, char const* r)

compare_strings(char const* l, char const* r)

{

{

#if defined(_MSC_VER) && (_MSC_VER <= 1900) && !defined(__clang__)

#if defined(_MSC_VER) && (_MSC_VER <= 1900) && !defined(__clang__)

    return *l == *r && ( (*l == 0) | compare_strings(l + 1, r + 1) );

    return *l == *r && ( (*l == 0) | compare_strings(l + 1, r + 1) );

#else

#else

    do

    do

    {

    {

        if( *l != *r )

        if( *l != *r )

            return false;

            return false;

        if( *l == 0 )

        if( *l == 0 )

            return true;

            return true;

        ++l;

        ++l;

        ++r;

        ++r;

    } while(true);

    } while(true);

#endif

#endif

}

}

template< class L, class R >

template< class L, class R >

struct equal_member_names

struct equal_member_names

    : mp11::mp_bool< compare_strings(L::name, R::name) >

    : mp11::mp_bool< compare_strings(L::name, R::name) >

{};

{};

template< class T >

template< class T >

using uniquely_named_members = mp11::mp_same<

using uniquely_named_members = mp11::mp_same<

    mp11::mp_unique_if< described_members<T>, equal_member_names >,

    mp11::mp_unique_if< described_members<T>, equal_member_names >,

    described_members<T> >;

    described_members<T> >;

#else

#else

// we only check this in C++14, but the template should exist nevertheless

// we only check this in C++14, but the template should exist nevertheless

template< class T >

template< class T >

using uniquely_named_members = std::true_type;

using uniquely_named_members = std::true_type;

#endif // BOOST_DESCRIBE_CXX14

#endif // BOOST_DESCRIBE_CXX14

// user conversion (via tag_invoke)

// user conversion (via tag_invoke)

template< class Ctx, class T, class Dir >

template< class Ctx, class T, class Dir >

using user_conversion_category = mp11::mp_cond<

using user_conversion_category = mp11::mp_cond<

    has_user_conversion3<Ctx, T, Dir>, full_context_conversion_tag,

    has_user_conversion3<Ctx, T, Dir>, full_context_conversion_tag,

    has_user_conversion2<Ctx, T, Dir>, context_conversion_tag,

    has_user_conversion2<Ctx, T, Dir>, context_conversion_tag,

    has_user_conversion1<T, Dir>,      user_conversion_tag>;

    has_user_conversion1<T, Dir>,      user_conversion_tag>;

// native conversions (constructors and member functions of value)

// native conversions (constructors and member functions of value)

template< class T >

template< class T >

using native_conversion_category = mp11::mp_cond<

using native_conversion_category = mp11::mp_cond<

    std::is_same<T, value>,  value_conversion_tag,

    std::is_same<T, value>,  value_conversion_tag,

    std::is_same<T, array>,  array_conversion_tag,

    std::is_same<T, array>,  array_conversion_tag,

    std::is_same<T, object>, object_conversion_tag,

    std::is_same<T, object>, object_conversion_tag,

    std::is_same<T, string>, string_conversion_tag>;

    std::is_same<T, string>, string_conversion_tag>;

// generic conversions

// generic conversions

template< class T >

template< class T >

using generic_conversion_category = mp11::mp_cond<

using generic_conversion_category = mp11::mp_cond<

    // std::is_same<T,std::initializer_list<value_ref>>, init_list_tag,

    // std::is_same<T,std::initializer_list<value_ref>>, init_list_tag,

    std::is_same<T, value_ref>, value_ref_tag,

    std::is_same<T, value_ref>, value_ref_tag,

    std::is_same<T, bool>,     bool_conversion_tag,

    std::is_same<T, bool>,     bool_conversion_tag,

    std::is_integral<T>,       integral_conversion_tag,

    std::is_integral<T>,       integral_conversion_tag,

    std::is_floating_point<T>, floating_point_conversion_tag,

    std::is_floating_point<T>, floating_point_conversion_tag,

    is_null_like<T>,           null_like_conversion_tag,

    is_null_like<T>,           null_like_conversion_tag,

    is_string_like<T>,         string_like_conversion_tag,

    is_string_like<T>,         string_like_conversion_tag,

    is_variant_like<T>,        variant_conversion_tag,

    is_variant_like<T>,        variant_conversion_tag,

    is_optional_like<T>,       optional_conversion_tag,

    is_optional_like<T>,       optional_conversion_tag,

    is_map_like<T>,            map_like_conversion_tag,

    is_map_like<T>,            map_like_conversion_tag,

    is_sequence_like<T>,       sequence_conversion_tag,

    is_sequence_like<T>,       sequence_conversion_tag,

    is_tuple_like<T>,          tuple_conversion_tag,

    is_tuple_like<T>,          tuple_conversion_tag,

    is_described_class<T>,     described_class_conversion_tag,

    is_described_class<T>,     described_class_conversion_tag,

    is_described_enum<T>,      described_enum_conversion_tag,

    is_described_enum<T>,      described_enum_conversion_tag,

    is_path_like<T>,           path_conversion_tag,

    is_path_like<T>,           path_conversion_tag,

    // failed to find a suitable implementation

    // failed to find a suitable implementation

    mp11::mp_true,             no_conversion_tag>;

    mp11::mp_true,             no_conversion_tag>;

template< class T >

template< class T >

using nested_type = typename T::type;

using nested_type = typename T::type;

template< class T1, class T2 >

template< class T1, class T2 >

using conversion_category_impl_helper = mp11::mp_eval_if_not<

using conversion_category_impl_helper = mp11::mp_eval_if_not<

    std::is_same<detail::no_conversion_tag, T1>,

    std::is_same<detail::no_conversion_tag, T1>,

    T1,

    T1,

    mp11::mp_eval_or_q, T1, mp11::mp_quote<nested_type>, T2>;

    mp11::mp_eval_or_q, T1, mp11::mp_quote<nested_type>, T2>;

template< class Ctx, class T, class Dir >

template< class Ctx, class T, class Dir >

struct conversion_category_impl

struct conversion_category_impl

{

{

    using type = mp11::mp_fold<

    using type = mp11::mp_fold<

        mp11::mp_list<

        mp11::mp_list<

            mp11::mp_defer<user_conversion_category, Ctx, T, Dir>,

            mp11::mp_defer<user_conversion_category, Ctx, T, Dir>,

            mp11::mp_defer<native_conversion_category, T>,

            mp11::mp_defer<native_conversion_category, T>,

            mp11::mp_defer<generic_conversion_category, T>>,

            mp11::mp_defer<generic_conversion_category, T>>,

        no_conversion_tag,

        no_conversion_tag,

        conversion_category_impl_helper>;

        conversion_category_impl_helper>;

};

};

template< class Ctx, class T, class Dir >

template< class Ctx, class T, class Dir >

using conversion_category =

using conversion_category =

    typename conversion_category_impl< Ctx, T, Dir >::type;

    typename conversion_category_impl< Ctx, T, Dir >::type;

template< class T >

template< class T >

using any_conversion_tag = mp11::mp_not<

using any_conversion_tag = mp11::mp_not<

    std::is_same< T, no_conversion_tag > >;

    std::is_same< T, no_conversion_tag > >;

template< class T, class Dir, class... Ctxs >

template< class T, class Dir, class... Ctxs >

struct conversion_category_impl< std::tuple<Ctxs...>, T, Dir >

struct conversion_category_impl< std::tuple<Ctxs...>, T, Dir >

{

{

    using ctxs = mp11::mp_list< remove_cvref<Ctxs>... >;

    using ctxs = mp11::mp_list< remove_cvref<Ctxs>... >;

    using cats = mp11::mp_list<

    using cats = mp11::mp_list<

        conversion_category<remove_cvref<Ctxs>, T, Dir>... >;

        conversion_category<remove_cvref<Ctxs>, T, Dir>... >;

    template< class I >

    template< class I >

    using exists = mp11::mp_less< I, mp11::mp_size<cats> >;

    using exists = mp11::mp_less< I, mp11::mp_size<cats> >;

    using context2 = mp11::mp_find< cats, full_context_conversion_tag >;

    using context2 = mp11::mp_find< cats, full_context_conversion_tag >;

    using context1 = mp11::mp_find< cats, context_conversion_tag >;

    using context1 = mp11::mp_find< cats, context_conversion_tag >;

    using context0 = mp11::mp_find< cats, user_conversion_tag >;

    using context0 = mp11::mp_find< cats, user_conversion_tag >;

    using index = mp11::mp_cond<

    using index = mp11::mp_cond<

        exists<context2>, context2,

        exists<context2>, context2,

        exists<context1>, context1,

        exists<context1>, context1,

        exists<context0>, context0,

        exists<context0>, context0,

        mp11::mp_true, mp11::mp_find_if< cats, any_conversion_tag > >;

        mp11::mp_true, mp11::mp_find_if< cats, any_conversion_tag > >;

    using type = mp11::mp_eval_or<

    using type = mp11::mp_eval_or<

        no_conversion_tag,

        no_conversion_tag,

        mp11::mp_at, cats, index >;

        mp11::mp_at, cats, index >;

};

};

struct no_context

struct no_context

{};

{};

template <class T, class Dir>

template <class T, class Dir>

using can_convert = mp11::mp_not<

using can_convert = mp11::mp_not<

    std::is_same<

    std::is_same<

        detail::conversion_category<no_context, T, Dir>,

        detail::conversion_category<no_context, T, Dir>,

        detail::no_conversion_tag>>;

        detail::no_conversion_tag>>;

template<class Impl1, class Impl2>

template<class Impl1, class Impl2>

using conversion_round_trips_helper = mp11::mp_or<

using conversion_round_trips_helper = mp11::mp_or<

    std::is_same<Impl1, Impl2>,

    std::is_same<Impl1, Impl2>,

    std::is_base_of<user_conversion_tag, Impl1>,

    std::is_base_of<user_conversion_tag, Impl1>,

    std::is_base_of<user_conversion_tag, Impl2>>;

    std::is_base_of<user_conversion_tag, Impl2>>;

template< class Ctx, class T, class Dir >

template< class Ctx, class T, class Dir >

using conversion_round_trips  = conversion_round_trips_helper<

using conversion_round_trips  = conversion_round_trips_helper<

    conversion_category<Ctx, T, Dir>,

    conversion_category<Ctx, T, Dir>,

    conversion_category<Ctx, T, mp11::mp_not<Dir>>>;

    conversion_category<Ctx, T, mp11::mp_not<Dir>>>;

template< class T1, class T2 >

template< class T1, class T2 >

struct copy_cref_helper

struct copy_cref_helper

{

{

    using type = remove_cvref<T2>;

    using type = remove_cvref<T2>;

};

};

template< class T1, class T2 >

template< class T1, class T2 >

using copy_cref = typename copy_cref_helper< T1, T2 >::type;

using copy_cref = typename copy_cref_helper< T1, T2 >::type;

template< class T1, class T2 >

template< class T1, class T2 >

struct copy_cref_helper<T1 const, T2>

struct copy_cref_helper<T1 const, T2>

{

{

    using type = remove_cvref<T2> const;

    using type = remove_cvref<T2> const;

};

};

template< class T1, class T2 >

template< class T1, class T2 >

struct copy_cref_helper<T1&, T2>

struct copy_cref_helper<T1&, T2>

{

{

    using type = copy_cref<T1, T2>&;

    using type = copy_cref<T1, T2>&;

};

};

template< class T1, class T2 >

template< class T1, class T2 >

struct copy_cref_helper<T1&&, T2>

struct copy_cref_helper<T1&&, T2>

{

{

    using type = copy_cref<T1, T2>&&;

    using type = copy_cref<T1, T2>&&;

};

};

template< class Rng, class Traits >

template< class Rng, class Traits >

using forwarded_value_helper = mp11::mp_if<

using forwarded_value_helper = mp11::mp_if<

    std::is_convertible<

    std::is_convertible<

        typename Traits::reference,

        typename Traits::reference,

        copy_cref<Rng, typename Traits::value_type> >,

        copy_cref<Rng, typename Traits::value_type> >,

    copy_cref<Rng, typename Traits::value_type>,

    copy_cref<Rng, typename Traits::value_type>,

    typename Traits::value_type >;

    typename Traits::value_type >;

template< class Rng >

template< class Rng >

using forwarded_value = forwarded_value_helper<

using forwarded_value = forwarded_value_helper<

    Rng, iterator_traits< Rng > >;

    Rng, iterator_traits< Rng > >;

template< class Ctx, class T, class Dir >

template< class Ctx, class T, class Dir >

struct supported_context

struct supported_context

{

{

    using type = Ctx;

    using type = Ctx;

    static

    static

    type const&

    type const&

    {

    {

    }

    }

};

};

template< class T, class Dir, class... Ctxs >

template< class T, class Dir, class... Ctxs >

struct supported_context< std::tuple<Ctxs...>, T, Dir >

struct supported_context< std::tuple<Ctxs...>, T, Dir >

{

{

    using Ctx = std::tuple<Ctxs...>;

    using Ctx = std::tuple<Ctxs...>;

    using impl = conversion_category_impl<Ctx, T, Dir>;

    using impl = conversion_category_impl<Ctx, T, Dir>;

    using index = typename impl::index;

    using index = typename impl::index;

    using next_supported = supported_context<

    using next_supported = supported_context<

        mp11::mp_at< typename impl::ctxs, index >, T, Dir >;

        mp11::mp_at< typename impl::ctxs, index >, T, Dir >;

    using type = typename next_supported::type;

    using type = typename next_supported::type;

    static

    static

    type const&

    type const&

    {

    {

    }

    }

};

};

template< class T >

template< class T >

using value_result_type = typename std::decay<

using value_result_type = typename std::decay<

    decltype( std::declval<T&>().value() )>::type;

    decltype( std::declval<T&>().value() )>::type;

template< class T >

template< class T >

using can_reset = decltype( std::declval<T&>().reset() );

using can_reset = decltype( std::declval<T&>().reset() );

template< class T >

template< class T >

using has_valueless_by_exception =

using has_valueless_by_exception =

    decltype( std::declval<T const&>().valueless_by_exception() );

    decltype( std::declval<T const&>().valueless_by_exception() );

} // namespace detail

} // namespace detail

template <class T>

template <class T>

struct result_for<T, value>

struct result_for<T, value>

{

{