[ceph.git] / ceph / src / boost / boost / leaf / handle_errors.hpp

#ifndef BOOST_LEAF_HANDLE_ERRORS_HPP_INCLUDED
#define BOOST_LEAF_HANDLE_ERRORS_HPP_INCLUDED

// Copyright (c) 2018-2020 Emil Dotchevski and Reverge Studios, Inc.

// 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_LEAF_ENABLE_WARNINGS
#   if defined(__clang__)
#       pragma clang system_header
#   elif (__GNUC__*100+__GNUC_MINOR__>301)
#       pragma GCC system_header
#   elif defined(_MSC_VER)
#       pragma warning(push,1)
#   endif
#endif

#include <boost/leaf/context.hpp>
#include <boost/leaf/detail/demangle.hpp>

#ifndef BOOST_LEAF_NO_EXCEPTIONS
#   include <boost/leaf/capture.hpp>
#endif

namespace boost { namespace leaf {

    class error_info
    {
        error_info & operator=( error_info const & ) = delete;

#ifndef BOOST_LEAF_NO_EXCEPTIONS
        static error_id unpack_error_id( std::exception const * ex ) noexcept
        {
            if( std::system_error const * se = dynamic_cast<std::system_error const *>(ex) )
                if( is_error_id(se->code()) )
                    return leaf_detail::make_error_id(se->code().value());
            if( std::error_code const * ec = dynamic_cast<std::error_code const *>(ex) )
                if( is_error_id(*ec) )
                    return leaf_detail::make_error_id(ec->value());
            if( error_id const * err_id = dynamic_cast<error_id const *>(ex) )
                return *err_id;
            return current_error();
        }

        std::exception * const ex_;
#endif

        error_id const err_id_;

    protected:

        error_info( error_info const & ) noexcept = default;

        template <class CharT, class Traits>
        void print( std::basic_ostream<CharT, Traits> & os ) const
        {
            os << "Error ID = " << err_id_.value();
#ifndef BOOST_LEAF_NO_EXCEPTIONS
            if( ex_ )
            {
                os <<
                    "\nException dynamic type: " << leaf_detail::demangle(typeid(*ex_).name()) <<
                    "\nstd::exception::what(): " << ex_->what();
            }
#endif
        }

    public:

        BOOST_LEAF_CONSTEXPR explicit error_info( error_id id ) noexcept:
#ifndef BOOST_LEAF_NO_EXCEPTIONS
            ex_(0),
#endif
            err_id_(id)
        {
        }

#ifndef BOOST_LEAF_NO_EXCEPTIONS
        explicit error_info( std::exception * ex ) noexcept:
            ex_(ex),
            err_id_(unpack_error_id(ex_))
        {
        }
#endif

        BOOST_LEAF_CONSTEXPR error_id error() const noexcept
        {
            return err_id_;
        }

        BOOST_LEAF_CONSTEXPR std::exception * exception() const noexcept
        {
#ifdef BOOST_LEAF_NO_EXCEPTIONS
            return nullptr;
#else
            return ex_;
#endif
        }

        template <class CharT, class Traits>
        friend std::basic_ostream<CharT, Traits> & operator<<( std::basic_ostream<CharT, Traits> & os, error_info const & x )
        {
            os << "leaf::error_info: ";
            x.print(os);
            return os << '\n';
        }
    };

    ////////////////////////////////////////

#if BOOST_LEAF_DIAGNOSTICS

    class diagnostic_info: public error_info
    {
        leaf_detail::e_unexpected_count const * e_uc_;
        void const * tup_;
        void (*print_)( std::ostream &, void const * tup, int key_to_print );

    protected:

        diagnostic_info( diagnostic_info const & ) noexcept = default;

        template <class Tup>
        BOOST_LEAF_CONSTEXPR diagnostic_info( error_info const & ei, leaf_detail::e_unexpected_count const * e_uc, Tup const & tup ) noexcept:
            error_info(ei),
            e_uc_(e_uc),
            tup_(&tup),
            print_(&leaf_detail::tuple_for_each<std::tuple_size<Tup>::value, Tup>::print)
        {
        }

    public:

        template <class CharT, class Traits>
        friend std::basic_ostream<CharT, Traits> & operator<<( std::basic_ostream<CharT, Traits> & os, diagnostic_info const & x )
        {
            os << "leaf::diagnostic_info for ";
            x.print(os);
            os << ":\n";
            x.print_(os, x.tup_, x.error().value());
            if( x.e_uc_  )
                x.e_uc_->print(os);
            return os;
        }
    };

    namespace leaf_detail
    {
        struct diagnostic_info_: diagnostic_info
        {
            template <class Tup>
            BOOST_LEAF_CONSTEXPR diagnostic_info_( error_info const & ei, leaf_detail::e_unexpected_count const * e_uc, Tup const & tup ) noexcept:
                diagnostic_info(ei, e_uc, tup)
            {
            }
        };

        template <>
        struct handler_argument_traits<diagnostic_info const &>: handler_argument_always_available<e_unexpected_count>
        {
            template <class Tup>
            BOOST_LEAF_CONSTEXPR static diagnostic_info_ get( Tup const & tup, error_info const & ei ) noexcept
            {
                return diagnostic_info_(ei, handler_argument_traits_defaults<e_unexpected_count>::check(tup, ei), tup);
            }
        };
    }

#else

    class diagnostic_info: public error_info
    {
    protected:

        diagnostic_info( diagnostic_info const & ) noexcept = default;

        BOOST_LEAF_CONSTEXPR diagnostic_info( error_info const & ei ) noexcept:
            error_info(ei)
        {
        }

    public:

        template <class CharT, class Traits>
        friend std::basic_ostream<CharT, Traits> & operator<<( std::basic_ostream<CharT, Traits> & os, diagnostic_info const & x )
        {
            os <<
                "leaf::diagnostic_info requires #define BOOST_LEAF_DIAGNOSTICS 1\n"
                "leaf::error_info: ";
            x.print(os);
            return os << '\n';
        }
    };

    namespace leaf_detail
    {
        struct diagnostic_info_: diagnostic_info
        {
            BOOST_LEAF_CONSTEXPR diagnostic_info_( error_info const & ei ) noexcept:
                diagnostic_info(ei)
            {
            }
        };

        template <>
        struct handler_argument_traits<diagnostic_info const &>: handler_argument_always_available<void>
        {
            template <class Tup>
            BOOST_LEAF_CONSTEXPR static diagnostic_info_ get( Tup const & tup, error_info const & ei ) noexcept
            {
                return diagnostic_info_(ei);
            }
        };
    }

#endif

    ////////////////////////////////////////

#if BOOST_LEAF_DIAGNOSTICS

    class verbose_diagnostic_info: public error_info
    {
        leaf_detail::e_unexpected_info const * e_ui_;
        void const * tup_;
        void (*print_)( std::ostream &, void const * tup, int key_to_print );

    protected:

        verbose_diagnostic_info( verbose_diagnostic_info const & ) noexcept = default;

        template <class Tup>
        BOOST_LEAF_CONSTEXPR verbose_diagnostic_info( error_info const & ei, leaf_detail::e_unexpected_info const * e_ui, Tup const & tup ) noexcept:
            error_info(ei),
            e_ui_(e_ui),
            tup_(&tup),
            print_(&leaf_detail::tuple_for_each<std::tuple_size<Tup>::value, Tup>::print)
        {
        }

    public:

        template <class CharT, class Traits>
        friend std::basic_ostream<CharT, Traits> & operator<<( std::basic_ostream<CharT, Traits> & os, verbose_diagnostic_info const & x )
        {
            os << "leaf::verbose_diagnostic_info for ";
            x.print(os);
            os << ":\n";
            x.print_(os, x.tup_, x.error().value());
            if( x.e_ui_ )
                x.e_ui_->print(os);
            return os;
        }
    };

    namespace leaf_detail
    {
        struct verbose_diagnostic_info_: verbose_diagnostic_info
        {
            template <class Tup>
            BOOST_LEAF_CONSTEXPR verbose_diagnostic_info_( error_info const & ei, leaf_detail::e_unexpected_info const * e_ui, Tup const & tup ) noexcept:
                verbose_diagnostic_info(ei, e_ui, tup)
            {
            }
        };

        template <>
        struct handler_argument_traits<verbose_diagnostic_info const &>: handler_argument_always_available<e_unexpected_info>
        {
            template <class Tup>
            BOOST_LEAF_CONSTEXPR static verbose_diagnostic_info_ get( Tup const & tup, error_info const & ei ) noexcept
            {
                return verbose_diagnostic_info_(ei, handler_argument_traits_defaults<e_unexpected_info>::check(tup, ei), tup);
            }
        };
    }

#else

    class verbose_diagnostic_info: public error_info
    {
    protected:

        verbose_diagnostic_info( verbose_diagnostic_info const & ) noexcept = default;

        BOOST_LEAF_CONSTEXPR verbose_diagnostic_info( error_info const & ei ) noexcept:
            error_info(ei)
        {
        }

    public:

        template <class CharT, class Traits>
        friend std::basic_ostream<CharT, Traits> & operator<<( std::basic_ostream<CharT, Traits> & os, verbose_diagnostic_info const & x )
        {
            os <<
                "leaf::verbose_diagnostic_info requires #define BOOST_LEAF_DIAGNOSTICS 1\n"
                "leaf::error_info: ";
            x.print(os);
            return os << '\n';
        }
    };

    namespace leaf_detail
    {
        struct verbose_diagnostic_info_: verbose_diagnostic_info
        {
            BOOST_LEAF_CONSTEXPR verbose_diagnostic_info_( error_info const & ei ) noexcept:
                verbose_diagnostic_info(ei)
            {
            }
        };


        template <>
        struct handler_argument_traits<verbose_diagnostic_info const &>: handler_argument_always_available<void>
        {
            template <class Tup>
            BOOST_LEAF_CONSTEXPR static verbose_diagnostic_info_ get( Tup const & tup, error_info const & ei ) noexcept
            {
                return verbose_diagnostic_info_(ei);
            }
        };
    }

#endif

    ////////////////////////////////////////

    namespace leaf_detail
    {
        template <class T, class... List>
        struct type_index;

        template <class T, class... Cdr>
        struct type_index<T, T, Cdr...>
        {
            constexpr static int value = 0;
        };

        template <class T, class Car, class... Cdr>
        struct type_index<T, Car, Cdr...>
        {
            constexpr static int value = 1 + type_index<T,Cdr...>::value;
        };

        template <class T, class Tuple>
        struct tuple_type_index;

        template <class T, class... TupleTypes>
        struct tuple_type_index<T,std::tuple<TupleTypes...>>
        {
            constexpr static int value = type_index<T,TupleTypes...>::value;
        };

#ifndef BOOST_LEAF_NO_EXCEPTIONS

        template <class E, bool = std::is_class<E>::value>
        struct peek_exception;

        template <>
        struct peek_exception<std::exception const, true>
        {
            BOOST_LEAF_CONSTEXPR static std::exception const * peek( error_info const & ei ) noexcept
            {
                return ei.exception();
            }
        };

        template <>
        struct peek_exception<std::exception, true>
        {
            BOOST_LEAF_CONSTEXPR static std::exception * peek( error_info const & ei ) noexcept
            {
                return ei.exception();
            }
        };

        template <>
        struct peek_exception<std::error_code const, true>
        {
            static std::error_code const * peek( error_info const & ei ) noexcept
            {
                auto const ex = ei.exception();
                if( std::system_error * se = dynamic_cast<std::system_error *>(ex) )
                    return &se->code();
                else if( std::error_code * ec = dynamic_cast<std::error_code *>(ex) )
                    return ec;
                else
                    return 0;
            }
        };

        template <>
        struct peek_exception<std::error_code, true>
        {
            static std::error_code * peek( error_info const & ei ) noexcept
            {
                auto const ex = ei.exception();
                if( std::system_error * se = dynamic_cast<std::system_error *>(ex) )
                    return const_cast<std::error_code *>(&se->code());
                else if( std::error_code * ec = dynamic_cast<std::error_code *>(ex) )
                    return ec;
                else
                    return 0;
            }
        };

        template <class E>
        struct peek_exception<E, true>
        {
            static E * peek( error_info const & ei ) noexcept
            {
                return dynamic_cast<E *>(ei.exception());
            }
        };

        template <class E>
        struct peek_exception<E, false>
        {
            BOOST_LEAF_CONSTEXPR static E * peek( error_info const & ) noexcept
            {
                return 0;
            }
        };

#endif

        template <class E, class SlotsTuple>
        BOOST_LEAF_CONSTEXPR inline
        E const *
        peek( SlotsTuple const & tup, error_info const & ei ) noexcept
        {
            if( error_id err = ei.error() )
                if( E const * e = std::get<tuple_type_index<slot<E>,SlotsTuple>::value>(tup).has_value(err.value()) )
                    return e;
#ifndef BOOST_LEAF_NO_EXCEPTIONS
                else
                    return peek_exception<E const>::peek(ei);
#endif
            return 0;
        }

        template <class E, class SlotsTuple>
        BOOST_LEAF_CONSTEXPR inline
        E *
        peek( SlotsTuple & tup, error_info const & ei ) noexcept
        {
            if( error_id err = ei.error() )
                if( E * e = std::get<tuple_type_index<slot<E>,SlotsTuple>::value>(tup).has_value(err.value()) )
                    return e;
#ifndef BOOST_LEAF_NO_EXCEPTIONS
                else
                    return peek_exception<E>::peek(ei);
#endif
            return 0;
        }
    }

    ////////////////////////////////////////

    namespace leaf_detail
    {
        template <class A>
        template <class Tup>
        BOOST_LEAF_CONSTEXPR inline
        typename handler_argument_traits_defaults<A, false>::error_type const *
        handler_argument_traits_defaults<A, false>::
        check( Tup const & tup, error_info const & ei ) noexcept
        {
            return peek<typename std::decay<A>::type>(tup, ei);
        }

        template <class A>
        template <class Tup>
        BOOST_LEAF_CONSTEXPR inline
        typename handler_argument_traits_defaults<A, false>::error_type *
        handler_argument_traits_defaults<A, false>::
        check( Tup & tup, error_info const & ei ) noexcept
        {
            return peek<typename std::decay<A>::type>(tup, ei);
        }

        template <class Tup>
        BOOST_LEAF_CONSTEXPR inline
        std::exception const *
        handler_argument_traits<void>::
        check( Tup const &, error_info const & ei ) noexcept
        {
            return ei.exception();
        }

        template <class Tup, class... List>
        struct check_arguments;

        template <class Tup>
        struct check_arguments<Tup>
        {
            BOOST_LEAF_CONSTEXPR static bool check( Tup const &, error_info const & )
            {
                return true;
            }
        };

        template <class Tup, class Car, class... Cdr>
        struct check_arguments<Tup, Car, Cdr...>
        {
            BOOST_LEAF_CONSTEXPR static bool check( Tup & tup, error_info const & ei ) noexcept
            {
                return handler_argument_traits<Car>::check(tup, ei) && check_arguments<Tup, Cdr...>::check(tup, ei);
            }
        };
    }

    ////////////////////////////////////////

    namespace leaf_detail
    {
        template <class>
        struct handler_matches_any_error: std::false_type
        {
        };

        template <template<class...> class L>
        struct handler_matches_any_error<L<>>: std::true_type
        {
        };

        template <template<class...> class L, class Car, class... Cdr>
        struct handler_matches_any_error<L<Car, Cdr...>>
        {
            constexpr static bool value = handler_argument_traits<Car>::always_available && handler_matches_any_error<L<Cdr...>>::value;
        };
    }

    ////////////////////////////////////////

    namespace leaf_detail
    {
        template <class Tup, class... A>
        BOOST_LEAF_CONSTEXPR inline bool check_handler_( Tup & tup, error_info const & ei, leaf_detail_mp11::mp_list<A...> ) noexcept
        {
            return check_arguments<Tup, A...>::check(tup, ei);
        }

        template <class R, class F, bool IsResult = is_result_type<R>::value, class FReturnType = fn_return_type<F>>
        struct handler_caller
        {
            template <class Tup, class... A>
            BOOST_LEAF_CONSTEXPR static R call( Tup & tup, error_info const & ei, F && f, leaf_detail_mp11::mp_list<A...> )
            {
                return std::forward<F>(f)( handler_argument_traits<A>::get(tup, ei)... );
            }
        };

        template <template <class...> class Result, class... E, class F>
        struct handler_caller<Result<void, E...>, F, true, void>
        {
            using R = Result<void, E...>;

            template <class Tup, class... A>
            BOOST_LEAF_CONSTEXPR static R call( Tup & tup, error_info const & ei, F && f, leaf_detail_mp11::mp_list<A...> )
            {
                std::forward<F>(f)( handler_argument_traits<A>::get(tup, ei)... );
                return { };
            }
        };

        template <class T>
        struct is_tuple: std::false_type { };

        template <class... T>
        struct is_tuple<std::tuple<T...>>: std::true_type { };

        template <class... T>
        struct is_tuple<std::tuple<T...> &>: std::true_type { };

        template <class R, class Tup, class H>
        BOOST_LEAF_CONSTEXPR
        inline
        typename std::enable_if<!is_tuple<H>::value, R>::type
        handle_error_( Tup & tup, error_info const & ei, H && h )
        {
            static_assert( handler_matches_any_error<fn_mp_args<H>>::value, "The last handler passed to handle_all must match any error." );
            return handler_caller<R, H>::call( tup, ei, std::forward<H>(h), fn_mp_args<H>{ } );
        }

        template <class R, class Tup, class Car, class... Cdr>
        BOOST_LEAF_CONSTEXPR inline
        typename std::enable_if<!is_tuple<Car>::value, R>::type
        handle_error_( Tup & tup, error_info const & ei, Car && car, Cdr && ... cdr )
        {
            if( handler_matches_any_error<fn_mp_args<Car>>::value || check_handler_( tup, ei, fn_mp_args<Car>{ } ) )
                return handler_caller<R, Car>::call( tup, ei, std::forward<Car>(car), fn_mp_args<Car>{ } );
            else
                return handle_error_<R>( tup, ei, std::forward<Cdr>(cdr)...);
        }

        template <class R, class Tup, class HTup, size_t ... I>
        BOOST_LEAF_CONSTEXPR inline
        R
        handle_error_tuple_( Tup & tup, error_info const & ei, leaf_detail_mp11::index_sequence<I...>, HTup && htup )
        {
            return handle_error_<R>(tup, ei, std::get<I>(std::forward<HTup>(htup))...);
        }

        template <class R, class Tup, class HTup, class... Cdr, size_t ... I>
        BOOST_LEAF_CONSTEXPR inline
        R
        handle_error_tuple_( Tup & tup, error_info const & ei, leaf_detail_mp11::index_sequence<I...>, HTup && htup, Cdr && ... cdr )
        {
            return handle_error_<R>(tup, ei, std::get<I>(std::forward<HTup>(htup))..., std::forward<Cdr>(cdr)...);
        }

        template <class R, class Tup, class H>
        BOOST_LEAF_CONSTEXPR inline
        typename std::enable_if<is_tuple<H>::value, R>::type
        handle_error_( Tup & tup, error_info const & ei, H && h )
        {
            return handle_error_tuple_<R>(
                tup,
                ei,
                leaf_detail_mp11::make_index_sequence<std::tuple_size<typename std::decay<H>::type>::value>(),
                std::forward<H>(h));
        }

        template <class R, class Tup, class Car, class... Cdr>
        BOOST_LEAF_CONSTEXPR inline
        typename std::enable_if<is_tuple<Car>::value, R>::type
        handle_error_( Tup & tup, error_info const & ei, Car && car, Cdr && ... cdr )
        {
            return handle_error_tuple_<R>(
                tup,
                ei,
                leaf_detail_mp11::make_index_sequence<std::tuple_size<typename std::decay<Car>::type>::value>(),
                std::forward<Car>(car),
                std::forward<Cdr>(cdr)...);
        }
    }

    ////////////////////////////////////////

    template <class... E>
    template <class R, class... H>
    BOOST_LEAF_CONSTEXPR BOOST_LEAF_ALWAYS_INLINE
    R
    context<E...>::
    handle_error( error_id id, H && ... h ) const
    {
        BOOST_LEAF_ASSERT(!is_active());
        return leaf_detail::handle_error_<R>(tup(), error_info(id), std::forward<H>(h)...);
    }

    template <class... E>
    template <class R, class... H>
    BOOST_LEAF_CONSTEXPR BOOST_LEAF_ALWAYS_INLINE
    R
    context<E...>::
    handle_error( error_id id, H && ... h )
    {
        BOOST_LEAF_ASSERT(!is_active());
        return leaf_detail::handle_error_<R>(tup(), error_info(id), std::forward<H>(h)...);
    }

    ////////////////////////////////////////

#ifdef BOOST_LEAF_NO_EXCEPTIONS

    template <class TryBlock, class... H>
    BOOST_LEAF_CONSTEXPR inline
    typename std::decay<decltype(std::declval<TryBlock>()().value())>::type
    try_handle_all( TryBlock && try_block, H && ... h ) noexcept
    {
        static_assert(is_result_type<decltype(std::declval<TryBlock>()())>::value, "The return type of the try_block passed to a try_handle_all function must be registered with leaf::is_result_type");
        context_type_from_handlers<H...> ctx;
        auto active_context = activate_context(ctx);
        if( auto r = std::forward<TryBlock>(try_block)() )
            return r.value();
        else
        {
            error_id id = r.error();
            ctx.deactivate();
            using R = typename std::decay<decltype(std::declval<TryBlock>()().value())>::type;
            return ctx.template handle_error<R>(std::move(id), std::forward<H>(h)...);
        }
    }

    template <class TryBlock, class... H>
    BOOST_LEAF_NODISCARD BOOST_LEAF_CONSTEXPR inline
    typename std::decay<decltype(std::declval<TryBlock>()())>::type
    try_handle_some( TryBlock && try_block, H && ... h ) noexcept
    {
        static_assert(is_result_type<decltype(std::declval<TryBlock>()())>::value, "The return type of the try_block passed to a try_handle_some function must be registered with leaf::is_result_type");
        context_type_from_handlers<H...> ctx;
        auto active_context = activate_context(ctx);
        if( auto r = std::forward<TryBlock>(try_block)() )
            return r;
        else
        {
            error_id id = r.error();
            ctx.deactivate();
            using R = typename std::decay<decltype(std::declval<TryBlock>()())>::type;
            auto rr = ctx.template handle_error<R>(std::move(id), std::forward<H>(h)..., [&r]()->R { return std::move(r); });
            if( !rr )
                ctx.propagate();
            return rr;
        }
    }

    template <class TryBlock, class... H>
    BOOST_LEAF_CONSTEXPR inline
    decltype(std::declval<TryBlock>()())
    try_catch( TryBlock && try_block, H && ... ) noexcept
    {
        static_assert(sizeof(context_type_from_handlers<H...>) > 0,
            "When exceptions are disabled, try_catch can't fail and has no use for the handlers, but this ensures that the supplied H... types are compatible.");
        return std::forward<TryBlock>(try_block)();
    }

#else

    namespace leaf_detail
    {
        template <class Ctx, class TryBlock, class... H>
        decltype(std::declval<TryBlock>()())
        try_catch_( Ctx & ctx, TryBlock && try_block, H && ... h )
        {
            using namespace leaf_detail;
            BOOST_LEAF_ASSERT(ctx.is_active());
            using R = decltype(std::declval<TryBlock>()());
            try
            {
                return std::forward<TryBlock>(try_block)();
            }
            catch( capturing_exception const & cap )
            {
                try
                {
                    cap.unload_and_rethrow_original_exception();
                }
                catch( std::exception & ex )
                {
                    ctx.deactivate();
                    return handle_error_<R>(ctx.tup(), error_info(&ex), std::forward<H>(h)...,
                        []() -> R { throw; } );
                }
                catch(...)
                {
                    ctx.deactivate();
                    return handle_error_<R>(ctx.tup(), error_info(nullptr), std::forward<H>(h)...,
                        []() -> R { throw; } );
                }
            }
            catch( std::exception & ex )
            {
                ctx.deactivate();
                return handle_error_<R>(ctx.tup(), error_info(&ex), std::forward<H>(h)...,
                    []() -> R { throw; } );
            }
            catch(...)
            {
                ctx.deactivate();
                return handle_error_<R>(ctx.tup(), error_info(nullptr), std::forward<H>(h)...,
                    []() -> R { throw; } );
            }
        }
    }

    template <class TryBlock, class... H>
    BOOST_LEAF_CONSTEXPR inline
    typename std::decay<decltype(std::declval<TryBlock>()().value())>::type
    try_handle_all( TryBlock && try_block, H && ... h )
    {
        static_assert(is_result_type<decltype(std::declval<TryBlock>()())>::value, "The return type of the try_block passed to a try_handle_all function must be registered with leaf::is_result_type");
        context_type_from_handlers<H...> ctx;
        auto active_context = activate_context(ctx);
        if( auto r = leaf_detail::try_catch_(
                ctx,
                [&]
                {
                    return std::forward<TryBlock>(try_block)();
                },
                std::forward<H>(h)...) )
            return r.value();
        else
        {
            error_id id = r.error();
            if( ctx.is_active() )
                ctx.deactivate();
            using R = typename std::decay<decltype(std::declval<TryBlock>()().value())>::type;
            return ctx.template handle_error<R>(std::move(id), std::forward<H>(h)...);
        }
    }

    template <class TryBlock, class... H>
    BOOST_LEAF_NODISCARD BOOST_LEAF_CONSTEXPR inline
    typename std::decay<decltype(std::declval<TryBlock>()())>::type
    try_handle_some( TryBlock && try_block, H && ... h )
    {
        static_assert(is_result_type<decltype(std::declval<TryBlock>()())>::value, "The return type of the try_block passed to a try_handle_some function must be registered with leaf::is_result_type");
        context_type_from_handlers<H...> ctx;
        auto active_context = activate_context(ctx);
        if( auto r = leaf_detail::try_catch_(
                ctx,
                [&]
                {
                    return std::forward<TryBlock>(try_block)();
                },
                std::forward<H>(h)...) )
            return r;
        else
        {
            error_id id = r.error();
            if( ctx.is_active() )
                ctx.deactivate();
            using R = typename std::decay<decltype(std::declval<TryBlock>()())>::type;
            auto rr = ctx.template handle_error<R>(std::move(id), std::forward<H>(h)..., [&r]()->R { return std::move(r); });
            if( !rr )
                ctx.propagate();
            return rr;
        }
    }

    template <class TryBlock, class... H>
    BOOST_LEAF_CONSTEXPR inline
    decltype(std::declval<TryBlock>()())
    try_catch( TryBlock && try_block, H && ... h )
    {
        context_type_from_handlers<H...> ctx;
        auto active_context = activate_context(ctx);
        return leaf_detail::try_catch_(
            ctx,
            [&]
            {
                return std::forward<TryBlock>(try_block)();
            },
            std::forward<H>(h)...);
    }

#endif

} }

// Boost Exception Integration

namespace boost { class exception; }
namespace boost { template <class Tag,class T> class error_info; }
namespace boost { namespace exception_detail { template <class ErrorInfo> struct get_info; } }

namespace boost { namespace leaf {

    namespace leaf_detail
    {
        template <class T>
        struct match_enum_type;

        template <class Tag, class T>
        struct match_enum_type<boost::error_info<Tag, T>>
        {
            using type = T;
        };

        template <class Ex>
        BOOST_LEAF_CONSTEXPR inline Ex * get_exception( error_info const & ei )
        {
            return dynamic_cast<Ex *>(ei.exception());
        }

        template <class, class T>
        struct dependent_type { using type = T; };

        template <class Dep, class T>
        using dependent_type_t = typename dependent_type<Dep, T>::type;

        template <class Tag, class T>
        struct handler_argument_traits<boost::error_info<Tag, T>>
        {
            using error_type = void;
            constexpr static bool always_available = false;

            template <class Tup>
            BOOST_LEAF_CONSTEXPR static T * check( Tup & tup, error_info const & ei ) noexcept
            {
                using boost_exception = dependent_type_t<T, boost::exception>;
                if( auto * be = get_exception<boost_exception>(ei) )
                    return exception_detail::get_info<boost::error_info<Tag, T>>::get(*be);
                else
                    return 0;
            }

            template <class Tup>
            BOOST_LEAF_CONSTEXPR static boost::error_info<Tag, T> get( Tup const & tup, error_info const & ei ) noexcept
            {
                return boost::error_info<Tag, T>(*check(tup, ei));
            }
        };

        template <class Tag, class T> struct handler_argument_traits<boost::error_info<Tag, T> const &>: handler_argument_traits_require_by_value<boost::error_info<Tag, T>> { };
        template <class Tag, class T> struct handler_argument_traits<boost::error_info<Tag, T> const *>: handler_argument_traits_require_by_value<boost::error_info<Tag, T>> { };
        template <class Tag, class T> struct handler_argument_traits<boost::error_info<Tag, T> &>: handler_argument_traits_require_by_value<boost::error_info<Tag, T>> { };
        template <class Tag, class T> struct handler_argument_traits<boost::error_info<Tag, T> *>: handler_argument_traits_require_by_value<boost::error_info<Tag, T>> { };
    }

} }

#endif