expected.hpp

 
// expected - An implementation of m5::stl::expected with extensions
// Written in 2017 by Sy Brand (tartanllama@gmail.com, @TartanLlama)
//
// Documentation available at http://tl.tartanllama.xyz/
//
// To the extent possible under law, the author(s) have dedicated all
// copyright and related and neighboring rights to this software to the
// public domain worldwide. This software is distributed without any warranty.
//
// You should have received a copy of the CC0 Public Domain Dedication
// along with this software. If not, see
// <http://creativecommons.org/publicdomain/zero/1.0/>.
//
// Modified for M5 Utility by M5Stack
//
#ifndef M5_UTILITY_STL_EXPECTED_HPP
#define M5_UTILITY_STL_EXPECTED_HPP
 
#define TL_EXPECTED_VERSION_MAJOR 1
#define TL_EXPECTED_VERSION_MINOR 1
#define TL_EXPECTED_VERSION_PATCH 0
 
#include <exception>
#include <functional>
#include <type_traits>
#include <utility>
 
#if defined(__EXCEPTIONS) || defined(_CPPUNWIND)
#define TL_EXPECTED_EXCEPTIONS_ENABLED
#endif
 
#if (defined(_MSC_VER) && _MSC_VER == 1900)
#define TL_EXPECTED_MSVC2015
#define TL_EXPECTED_MSVC2015_CONSTEXPR
#else
#define TL_EXPECTED_MSVC2015_CONSTEXPR constexpr
#endif
 
#if (defined(__GNUC__) && __GNUC__ == 4 && __GNUC_MINOR__ <= 9 && !defined(__clang__))
#define TL_EXPECTED_GCC49
#endif
 
#if (defined(__GNUC__) && __GNUC__ == 5 && __GNUC_MINOR__ <= 4 && !defined(__clang__))
#define TL_EXPECTED_GCC54
#endif
 
#if (defined(__GNUC__) && __GNUC__ == 5 && __GNUC_MINOR__ <= 5 && !defined(__clang__))
#define TL_EXPECTED_GCC55
#endif
 
#if !defined(TL_ASSERT)
// can't have assert in constexpr in C++11 and GCC 4.9 has a compiler bug
// ESP8266's newlib assert() expands PSTR() — a static array declaration
// inside the expression — which is ill-formed in constexpr functions, so
// that toolchain gets the no-op fallback too.
#if (__cplusplus > 201103L) && !defined(TL_EXPECTED_GCC49) && !defined(ESP8266)
#include <cassert>
#define TL_ASSERT(x) assert(x)
#else
#define TL_ASSERT(x)
#endif
#endif
 
#if (defined(__GNUC__) && __GNUC__ == 4 && __GNUC_MINOR__ <= 9 && !defined(__clang__))
// GCC < 5 doesn't support overloading on const&& for member functions
 
#define TL_EXPECTED_NO_CONSTRR
// GCC < 5 doesn't support some standard C++11 type traits
#define TL_EXPECTED_IS_TRIVIALLY_COPY_CONSTRUCTIBLE(T) std::has_trivial_copy_constructor<T>
#define TL_EXPECTED_IS_TRIVIALLY_COPY_ASSIGNABLE(T)    std::has_trivial_copy_assign<T>
 
// This one will be different for GCC 5.7 if it's ever supported
#define TL_EXPECTED_IS_TRIVIALLY_DESTRUCTIBLE(T) std::is_trivially_destructible<T>
 
// GCC 5 < v < 8 has a bug in is_trivially_copy_constructible which breaks
// std::vector for non-copyable types
#elif (defined(__GNUC__) && __GNUC__ < 8 && !defined(__clang__))
#ifndef TL_GCC_LESS_8_TRIVIALLY_COPY_CONSTRUCTIBLE_MUTEX
#define TL_GCC_LESS_8_TRIVIALLY_COPY_CONSTRUCTIBLE_MUTEX
namespace m5 {
namespace stl {
namespace detail {
template <class T>
struct is_trivially_copy_constructible : std::is_trivially_copy_constructible<T> {};
#ifdef _GLIBCXX_VECTOR
template <class T, class A>
struct is_trivially_copy_constructible<std::vector<T, A>> : std::false_type {};
#endif
}  // namespace detail
}  // namespace stl
}  // namespace m5
#endif
 
#define TL_EXPECTED_IS_TRIVIALLY_COPY_CONSTRUCTIBLE(T) stl::detail::is_trivially_copy_constructible<T>
#define TL_EXPECTED_IS_TRIVIALLY_COPY_ASSIGNABLE(T)    std::is_trivially_copy_assignable<T>
#define TL_EXPECTED_IS_TRIVIALLY_DESTRUCTIBLE(T)       std::is_trivially_destructible<T>
#else
#define TL_EXPECTED_IS_TRIVIALLY_COPY_CONSTRUCTIBLE(T) std::is_trivially_copy_constructible<T>
#define TL_EXPECTED_IS_TRIVIALLY_COPY_ASSIGNABLE(T)    std::is_trivially_copy_assignable<T>
#define TL_EXPECTED_IS_TRIVIALLY_DESTRUCTIBLE(T)       std::is_trivially_destructible<T>
#endif
 
#if __cplusplus > 201103L
#define TL_EXPECTED_CXX14
#endif
 
#ifdef TL_EXPECTED_GCC49
#define TL_EXPECTED_GCC49_CONSTEXPR
#else
#define TL_EXPECTED_GCC49_CONSTEXPR constexpr
#endif
 
#if (__cplusplus == 201103L || defined(TL_EXPECTED_MSVC2015) || defined(TL_EXPECTED_GCC49))
#define TL_EXPECTED_11_CONSTEXPR
#else
#define TL_EXPECTED_11_CONSTEXPR constexpr
#endif
 
namespace m5 {
namespace stl {
template <class T, class E>
class expected;
 
#ifndef TL_MONOSTATE_INPLACE_MUTEX
#define TL_MONOSTATE_INPLACE_MUTEX
class monostate {};
 
struct in_place_t {
    explicit in_place_t() = default;
};
static constexpr in_place_t in_place{};
#endif
 
template <class E>
class unexpected {
public:
    static_assert(!std::is_same<E, void>::value, "E must not be void");
 
    unexpected() = delete;
    constexpr explicit unexpected(const E &e) : m_val(e)
    {
    }
 
    constexpr explicit unexpected(E &&e) : m_val(std::move(e))
    {
    }
 
    template <class... Args, typename std::enable_if<std::is_constructible<E, Args &&...>::value>::type * = nullptr>
    constexpr explicit unexpected(Args &&...args) : m_val(std::forward<Args>(args)...)
    {
    }
    template <class U, class... Args,
              typename std::enable_if<std::is_constructible<E, std::initializer_list<U> &, Args &&...>::value>::type * =
                  nullptr>
    constexpr explicit unexpected(std::initializer_list<U> l, Args &&...args) : m_val(l, std::forward<Args>(args)...)
    {
    }
 
    constexpr const E &value() const &
    {
        return m_val;
    }
    TL_EXPECTED_11_CONSTEXPR E &value() &
    {
        return m_val;
    }
    TL_EXPECTED_11_CONSTEXPR E &&value() &&
    {
        return std::move(m_val);
    }
    constexpr const E &&value() const &&
    {
        return std::move(m_val);
    }
 
private:
    E m_val;
};
 
#ifdef __cpp_deduction_guides
template <class E>
unexpected(E) -> unexpected<E>;
#endif
 
template <class E>
constexpr bool operator==(const unexpected<E> &lhs, const unexpected<E> &rhs)
{
    return lhs.value() == rhs.value();
}
template <class E>
constexpr bool operator!=(const unexpected<E> &lhs, const unexpected<E> &rhs)
{
    return lhs.value() != rhs.value();
}
template <class E>
constexpr bool operator<(const unexpected<E> &lhs, const unexpected<E> &rhs)
{
    return lhs.value() < rhs.value();
}
template <class E>
constexpr bool operator<=(const unexpected<E> &lhs, const unexpected<E> &rhs)
{
    return lhs.value() <= rhs.value();
}
template <class E>
constexpr bool operator>(const unexpected<E> &lhs, const unexpected<E> &rhs)
{
    return lhs.value() > rhs.value();
}
template <class E>
constexpr bool operator>=(const unexpected<E> &lhs, const unexpected<E> &rhs)
{
    return lhs.value() >= rhs.value();
}
 
template <class E>
unexpected<typename std::decay<E>::type> make_unexpected(E &&e)
{
    return unexpected<typename std::decay<E>::type>(std::forward<E>(e));
}
 
struct unexpect_t {
    unexpect_t() = default;
};
static constexpr unexpect_t unexpect{};
 
namespace detail {
template <typename E>
[[noreturn]] TL_EXPECTED_11_CONSTEXPR void throw_exception(E &&e)
{
#ifdef TL_EXPECTED_EXCEPTIONS_ENABLED
    throw std::forward<E>(e);
#else
    (void)e;
#ifdef _MSC_VER
    __assume(0);
#else
    __builtin_unreachable();
#endif
#endif
}
 
#ifndef TL_TRAITS_MUTEX
#define TL_TRAITS_MUTEX
// C++14-style aliases for brevity
template <class T>
using remove_const_t = typename std::remove_const<T>::type;
template <class T>
using remove_reference_t = typename std::remove_reference<T>::type;
template <class T>
using decay_t = typename std::decay<T>::type;
template <bool E, class T = void>
using enable_if_t = typename std::enable_if<E, T>::type;
template <bool B, class T, class F>
using conditional_t = typename std::conditional<B, T, F>::type;
 
// std::conjunction from C++17
template <class...>
struct conjunction : std::true_type {};
template <class B>
struct conjunction<B> : B {};
template <class B, class... Bs>
struct conjunction<B, Bs...> : std::conditional<bool(B::value), conjunction<Bs...>, B>::type {};
 
#if defined(_LIBCPP_VERSION) && __cplusplus == 201103L
#define TL_TRAITS_LIBCXX_MEM_FN_WORKAROUND
#endif
 
// In C++11 mode, there's an issue in libc++'s std::mem_fn
// which results in a hard-error when using it in a noexcept expression
// in some cases. This is a check to workaround the common failing case.
#ifdef TL_TRAITS_LIBCXX_MEM_FN_WORKAROUND
template <class T>
struct is_pointer_to_non_const_member_func : std::false_type {};
template <class T, class Ret, class... Args>
struct is_pointer_to_non_const_member_func<Ret (T::*)(Args...)> : std::true_type {};
template <class T, class Ret, class... Args>
struct is_pointer_to_non_const_member_func<Ret (T::*)(Args...) &> : std::true_type {};
template <class T, class Ret, class... Args>
struct is_pointer_to_non_const_member_func<Ret (T::*)(Args...) &&> : std::true_type {};
template <class T, class Ret, class... Args>
struct is_pointer_to_non_const_member_func<Ret (T::*)(Args...) volatile> : std::true_type {};
template <class T, class Ret, class... Args>
struct is_pointer_to_non_const_member_func<Ret (T::*)(Args...) volatile &> : std::true_type {};
template <class T, class Ret, class... Args>
struct is_pointer_to_non_const_member_func<Ret (T::*)(Args...) volatile &&> : std::true_type {};
 
template <class T>
struct is_const_or_const_ref : std::false_type {};
template <class T>
struct is_const_or_const_ref<T const &> : std::true_type {};
template <class T>
struct is_const_or_const_ref<T const> : std::true_type {};
#endif
 
// std::invoke from C++17
// https://stackoverflow.com/questions/38288042/c11-14-invoke-workaround
template <
    typename Fn, typename... Args,
#ifdef TL_TRAITS_LIBCXX_MEM_FN_WORKAROUND
    typename = enable_if_t<!(is_pointer_to_non_const_member_func<Fn>::value && is_const_or_const_ref<Args...>::value)>,
#endif
    typename = enable_if_t<std::is_member_pointer<decay_t<Fn>>::value>, int = 0>
constexpr auto invoke(Fn &&f, Args &&...args) noexcept(noexcept(std::mem_fn(f)(std::forward<Args>(args)...)))
    -> decltype(std::mem_fn(f)(std::forward<Args>(args)...))
{
    return std::mem_fn(f)(std::forward<Args>(args)...);
}
 
template <typename Fn, typename... Args, typename = enable_if_t<!std::is_member_pointer<decay_t<Fn>>::value>>
constexpr auto invoke(Fn &&f, Args &&...args) noexcept(noexcept(std::forward<Fn>(f)(std::forward<Args>(args)...)))
    -> decltype(std::forward<Fn>(f)(std::forward<Args>(args)...))
{
    return std::forward<Fn>(f)(std::forward<Args>(args)...);
}
 
// std::invoke_result from C++17
template <class F, class, class... Us>
struct invoke_result_impl;
 
template <class F, class... Us>
struct invoke_result_impl<F, decltype(detail::invoke(std::declval<F>(), std::declval<Us>()...), void()), Us...> {
    using type = decltype(detail::invoke(std::declval<F>(), std::declval<Us>()...));
};
 
template <class F, class... Us>
using invoke_result = invoke_result_impl<F, void, Us...>;
 
template <class F, class... Us>
using invoke_result_t = typename invoke_result<F, Us...>::type;
 
#if defined(_MSC_VER) && _MSC_VER <= 1900
// TODO make a version which works with MSVC 2015
template <class T, class U = T>
struct is_swappable : std::true_type {};
 
template <class T, class U = T>
struct is_nothrow_swappable : std::true_type {};
#else
// https://stackoverflow.com/questions/26744589/what-is-a-proper-way-to-implement-is-swappable-to-test-for-the-swappable-concept
namespace swap_adl_tests {
// if swap ADL finds this then it would call std::swap otherwise (same
// signature)
struct tag {};
 
template <class T>
tag swap(T &, T &);
template <class T, std::size_t N>
tag swap(T (&a)[N], T (&b)[N]);
 
// helper functions to test if an unqualified swap is possible, and if it
// becomes std::swap
template <class, class>
std::false_type can_swap(...) noexcept(false);
template <class T, class U, class = decltype(swap(std::declval<T &>(), std::declval<U &>()))>
std::true_type can_swap(int) noexcept(noexcept(swap(std::declval<T &>(), std::declval<U &>())));
 
template <class, class>
std::false_type uses_std(...);
template <class T, class U>
std::is_same<decltype(swap(std::declval<T &>(), std::declval<U &>())), tag> uses_std(int);
 
template <class T>
struct is_std_swap_noexcept : std::integral_constant<bool, std::is_nothrow_move_constructible<T>::value &&
                                                               std::is_nothrow_move_assignable<T>::value> {};
 
template <class T, std::size_t N>
struct is_std_swap_noexcept<T[N]> : is_std_swap_noexcept<T> {};
 
template <class T, class U>
struct is_adl_swap_noexcept : std::integral_constant<bool, noexcept(can_swap<T, U>(0))> {};
}  // namespace swap_adl_tests
 
template <class T, class U = T>
struct is_swappable
    : std::integral_constant<bool, decltype(detail::swap_adl_tests::can_swap<T, U>(0))::value &&
                                       (!decltype(detail::swap_adl_tests::uses_std<T, U>(0))::value ||
                                        (std::is_move_assignable<T>::value && std::is_move_constructible<T>::value))> {
};
 
template <class T, std::size_t N>
struct is_swappable<T[N], T[N]>
    : std::integral_constant<bool, decltype(detail::swap_adl_tests::can_swap<T[N], T[N]>(0))::value &&
                                       (!decltype(detail::swap_adl_tests::uses_std<T[N], T[N]>(0))::value ||
                                        is_swappable<T, T>::value)> {};
 
template <class T, class U = T>
struct is_nothrow_swappable
    : std::integral_constant<bool, is_swappable<T, U>::value &&
                                       ((decltype(detail::swap_adl_tests::uses_std<T, U>(0))::value &&
                                         detail::swap_adl_tests::is_std_swap_noexcept<T>::value) ||
                                        (!decltype(detail::swap_adl_tests::uses_std<T, U>(0))::value &&
                                         detail::swap_adl_tests::is_adl_swap_noexcept<T, U>::value))> {};
#endif
#endif
 
// Trait for checking if a type is a tl::expected
template <class T>
struct is_expected_impl : std::false_type {};
template <class T, class E>
struct is_expected_impl<expected<T, E>> : std::true_type {};
template <class T>
using is_expected = is_expected_impl<decay_t<T>>;
 
template <class T, class E, class U>
using expected_enable_forward_value =
    detail::enable_if_t<std::is_constructible<T, U &&>::value && !std::is_same<detail::decay_t<U>, in_place_t>::value &&
                        !std::is_same<expected<T, E>, detail::decay_t<U>>::value &&
                        !std::is_same<unexpected<E>, detail::decay_t<U>>::value>;
 
template <class T, class E, class U, class G, class UR, class GR>
using expected_enable_from_other = detail::enable_if_t<
    std::is_constructible<T, UR>::value && std::is_constructible<E, GR>::value &&
    !std::is_constructible<T, expected<U, G> &>::value && !std::is_constructible<T, expected<U, G> &&>::value &&
    !std::is_constructible<T, const expected<U, G> &>::value &&
    !std::is_constructible<T, const expected<U, G> &&>::value && !std::is_convertible<expected<U, G> &, T>::value &&
    !std::is_convertible<expected<U, G> &&, T>::value && !std::is_convertible<const expected<U, G> &, T>::value &&
    !std::is_convertible<const expected<U, G> &&, T>::value>;
 
template <class T, class U>
using is_void_or = conditional_t<std::is_void<T>::value, std::true_type, U>;
 
template <class T>
using is_copy_constructible_or_void = is_void_or<T, std::is_copy_constructible<T>>;
 
template <class T>
using is_move_constructible_or_void = is_void_or<T, std::is_move_constructible<T>>;
 
template <class T>
using is_copy_assignable_or_void = is_void_or<T, std::is_copy_assignable<T>>;
 
template <class T>
using is_move_assignable_or_void = is_void_or<T, std::is_move_assignable<T>>;
 
}  // namespace detail
 
namespace detail {
struct no_init_t {};
static constexpr no_init_t no_init{};
 
// Implements the storage of the values, and ensures that the destructor is
// trivial if it can be.
//
// This specialization is for where neither `T` or `E` is trivially
// destructible, so the destructors must be called on destruction of the
// `expected`
template <class T, class E, bool = std::is_trivially_destructible<T>::value,
          bool = std::is_trivially_destructible<E>::value>
struct expected_storage_base {
    constexpr expected_storage_base() : m_val(T{}), m_has_val(true)
    {
    }
    constexpr expected_storage_base(no_init_t) : m_no_init(), m_has_val(false)
    {
    }
 
    template <class... Args, detail::enable_if_t<std::is_constructible<T, Args &&...>::value> * = nullptr>
    constexpr expected_storage_base(in_place_t, Args &&...args) : m_val(std::forward<Args>(args)...), m_has_val(true)
    {
    }
 
    template <class U, class... Args,
              detail::enable_if_t<std::is_constructible<T, std::initializer_list<U> &, Args &&...>::value> * = nullptr>
    constexpr expected_storage_base(in_place_t, std::initializer_list<U> il, Args &&...args)
        : m_val(il, std::forward<Args>(args)...), m_has_val(true)
    {
    }
    template <class... Args, detail::enable_if_t<std::is_constructible<E, Args &&...>::value> * = nullptr>
    constexpr explicit expected_storage_base(unexpect_t, Args &&...args)
        : m_unexpect(std::forward<Args>(args)...), m_has_val(false)
    {
    }
 
    template <class U, class... Args,
              detail::enable_if_t<std::is_constructible<E, std::initializer_list<U> &, Args &&...>::value> * = nullptr>
    constexpr explicit expected_storage_base(unexpect_t, std::initializer_list<U> il, Args &&...args)
        : m_unexpect(il, std::forward<Args>(args)...), m_has_val(false)
    {
    }
 
    ~expected_storage_base()
    {
        if (m_has_val) {
            m_val.~T();
        } else {
            m_unexpect.~unexpected<E>();
        }
    }
    union {
        T m_val;
        unexpected<E> m_unexpect;
        char m_no_init;
    };
    bool m_has_val;
};
 
// This specialization is for when both `T` and `E` are trivially-destructible,
// so the destructor of the `expected` can be trivial.
template <class T, class E>
struct expected_storage_base<T, E, true, true> {
    constexpr expected_storage_base() : m_val(T{}), m_has_val(true)
    {
    }
    constexpr expected_storage_base(no_init_t) : m_no_init(), m_has_val(false)
    {
    }
 
    template <class... Args, detail::enable_if_t<std::is_constructible<T, Args &&...>::value> * = nullptr>
    constexpr expected_storage_base(in_place_t, Args &&...args) : m_val(std::forward<Args>(args)...), m_has_val(true)
    {
    }
 
    template <class U, class... Args,
              detail::enable_if_t<std::is_constructible<T, std::initializer_list<U> &, Args &&...>::value> * = nullptr>
    constexpr expected_storage_base(in_place_t, std::initializer_list<U> il, Args &&...args)
        : m_val(il, std::forward<Args>(args)...), m_has_val(true)
    {
    }
    template <class... Args, detail::enable_if_t<std::is_constructible<E, Args &&...>::value> * = nullptr>
    constexpr explicit expected_storage_base(unexpect_t, Args &&...args)
        : m_unexpect(std::forward<Args>(args)...), m_has_val(false)
    {
    }
 
    template <class U, class... Args,
              detail::enable_if_t<std::is_constructible<E, std::initializer_list<U> &, Args &&...>::value> * = nullptr>
    constexpr explicit expected_storage_base(unexpect_t, std::initializer_list<U> il, Args &&...args)
        : m_unexpect(il, std::forward<Args>(args)...), m_has_val(false)
    {
    }
 
    ~expected_storage_base() = default;
    union {
        T m_val;
        unexpected<E> m_unexpect;
        char m_no_init;
    };
    bool m_has_val;
};
 
// T is trivial, E is not.
template <class T, class E>
struct expected_storage_base<T, E, true, false> {
    constexpr expected_storage_base() : m_val(T{}), m_has_val(true)
    {
    }
    TL_EXPECTED_MSVC2015_CONSTEXPR expected_storage_base(no_init_t) : m_no_init(), m_has_val(false)
    {
    }
 
    template <class... Args, detail::enable_if_t<std::is_constructible<T, Args &&...>::value> * = nullptr>
    constexpr expected_storage_base(in_place_t, Args &&...args) : m_val(std::forward<Args>(args)...), m_has_val(true)
    {
    }
 
    template <class U, class... Args,
              detail::enable_if_t<std::is_constructible<T, std::initializer_list<U> &, Args &&...>::value> * = nullptr>
    constexpr expected_storage_base(in_place_t, std::initializer_list<U> il, Args &&...args)
        : m_val(il, std::forward<Args>(args)...), m_has_val(true)
    {
    }
    template <class... Args, detail::enable_if_t<std::is_constructible<E, Args &&...>::value> * = nullptr>
    constexpr explicit expected_storage_base(unexpect_t, Args &&...args)
        : m_unexpect(std::forward<Args>(args)...), m_has_val(false)
    {
    }
 
    template <class U, class... Args,
              detail::enable_if_t<std::is_constructible<E, std::initializer_list<U> &, Args &&...>::value> * = nullptr>
    constexpr explicit expected_storage_base(unexpect_t, std::initializer_list<U> il, Args &&...args)
        : m_unexpect(il, std::forward<Args>(args)...), m_has_val(false)
    {
    }
 
    ~expected_storage_base()
    {
        if (!m_has_val) {
            m_unexpect.~unexpected<E>();
        }
    }
 
    union {
        T m_val;
        unexpected<E> m_unexpect;
        char m_no_init;
    };
    bool m_has_val;
};
 
// E is trivial, T is not.
template <class T, class E>
struct expected_storage_base<T, E, false, true> {
    constexpr expected_storage_base() : m_val(T{}), m_has_val(true)
    {
    }
    constexpr expected_storage_base(no_init_t) : m_no_init(), m_has_val(false)
    {
    }
 
    template <class... Args, detail::enable_if_t<std::is_constructible<T, Args &&...>::value> * = nullptr>
    constexpr expected_storage_base(in_place_t, Args &&...args) : m_val(std::forward<Args>(args)...), m_has_val(true)
    {
    }
 
    template <class U, class... Args,
              detail::enable_if_t<std::is_constructible<T, std::initializer_list<U> &, Args &&...>::value> * = nullptr>
    constexpr expected_storage_base(in_place_t, std::initializer_list<U> il, Args &&...args)
        : m_val(il, std::forward<Args>(args)...), m_has_val(true)
    {
    }
    template <class... Args, detail::enable_if_t<std::is_constructible<E, Args &&...>::value> * = nullptr>
    constexpr explicit expected_storage_base(unexpect_t, Args &&...args)
        : m_unexpect(std::forward<Args>(args)...), m_has_val(false)
    {
    }
 
    template <class U, class... Args,
              detail::enable_if_t<std::is_constructible<E, std::initializer_list<U> &, Args &&...>::value> * = nullptr>
    constexpr explicit expected_storage_base(unexpect_t, std::initializer_list<U> il, Args &&...args)
        : m_unexpect(il, std::forward<Args>(args)...), m_has_val(false)
    {
    }
 
    ~expected_storage_base()
    {
        if (m_has_val) {
            m_val.~T();
        }
    }
    union {
        T m_val;
        unexpected<E> m_unexpect;
        char m_no_init;
    };
    bool m_has_val;
};
 
// `T` is `void`, `E` is trivially-destructible
template <class E>
struct expected_storage_base<void, E, false, true> {
#if __GNUC__ <= 5
// no constexpr for GCC 4/5 bug
#else
    TL_EXPECTED_MSVC2015_CONSTEXPR
#endif
    expected_storage_base() : m_has_val(true)
    {
    }
 
    constexpr expected_storage_base(no_init_t) : m_val(), m_has_val(false)
    {
    }
 
    constexpr expected_storage_base(in_place_t) : m_has_val(true)
    {
    }
 
    template <class... Args, detail::enable_if_t<std::is_constructible<E, Args &&...>::value> * = nullptr>
    constexpr explicit expected_storage_base(unexpect_t, Args &&...args)
        : m_unexpect(std::forward<Args>(args)...), m_has_val(false)
    {
    }
 
    template <class U, class... Args,
              detail::enable_if_t<std::is_constructible<E, std::initializer_list<U> &, Args &&...>::value> * = nullptr>
    constexpr explicit expected_storage_base(unexpect_t, std::initializer_list<U> il, Args &&...args)
        : m_unexpect(il, std::forward<Args>(args)...), m_has_val(false)
    {
    }
 
    ~expected_storage_base() = default;
    struct dummy {};
    union {
        unexpected<E> m_unexpect;
        dummy m_val;
    };
    bool m_has_val;
};
 
// `T` is `void`, `E` is not trivially-destructible
template <class E>
struct expected_storage_base<void, E, false, false> {
    constexpr expected_storage_base() : m_dummy(), m_has_val(true)
    {
    }
    constexpr expected_storage_base(no_init_t) : m_dummy(), m_has_val(false)
    {
    }
 
    constexpr expected_storage_base(in_place_t) : m_dummy(), m_has_val(true)
    {
    }
 
    template <class... Args, detail::enable_if_t<std::is_constructible<E, Args &&...>::value> * = nullptr>
    constexpr explicit expected_storage_base(unexpect_t, Args &&...args)
        : m_unexpect(std::forward<Args>(args)...), m_has_val(false)
    {
    }
 
    template <class U, class... Args,
              detail::enable_if_t<std::is_constructible<E, std::initializer_list<U> &, Args &&...>::value> * = nullptr>
    constexpr explicit expected_storage_base(unexpect_t, std::initializer_list<U> il, Args &&...args)
        : m_unexpect(il, std::forward<Args>(args)...), m_has_val(false)
    {
    }
 
    ~expected_storage_base()
    {
        if (!m_has_val) {
            m_unexpect.~unexpected<E>();
        }
    }
 
    union {
        unexpected<E> m_unexpect;
        char m_dummy;
    };
    bool m_has_val;
};
 
// This base class provides some handy member functions which can be used in
// further derived classes
template <class T, class E>
struct expected_operations_base : expected_storage_base<T, E> {
    using expected_storage_base<T, E>::expected_storage_base;
 
    template <class... Args>
    void construct(Args &&...args) noexcept
    {
        new (std::addressof(this->m_val)) T(std::forward<Args>(args)...);
        this->m_has_val = true;
    }
 
    template <class Rhs>
    void construct_with(Rhs &&rhs) noexcept
    {
        new (std::addressof(this->m_val)) T(std::forward<Rhs>(rhs).get());
        this->m_has_val = true;
    }
 
    template <class... Args>
    void construct_error(Args &&...args) noexcept
    {
        new (std::addressof(this->m_unexpect)) unexpected<E>(std::forward<Args>(args)...);
        this->m_has_val = false;
    }
 
#ifdef TL_EXPECTED_EXCEPTIONS_ENABLED
 
    // These assign overloads ensure that the most efficient assignment
    // implementation is used while maintaining the strong exception guarantee.
    // The problematic case is where rhs has a value, but *this does not.
    //
    // This overload handles the case where we can just copy-construct `T`
    // directly into place without throwing.
    template <class U = T, detail::enable_if_t<std::is_nothrow_copy_constructible<U>::value> * = nullptr>
    void assign(const expected_operations_base &rhs) noexcept
    {
        if (!this->m_has_val && rhs.m_has_val) {
            geterr().~unexpected<E>();
            construct(rhs.get());
        } else {
            assign_common(rhs);
        }
    }
 
    // This overload handles the case where we can attempt to create a copy of
    // `T`, then no-throw move it into place if the copy was successful.
    template <class U = T, detail::enable_if_t<!std::is_nothrow_copy_constructible<U>::value &&
                                               std::is_nothrow_move_constructible<U>::value> * = nullptr>
    void assign(const expected_operations_base &rhs) noexcept
    {
        if (!this->m_has_val && rhs.m_has_val) {
            T tmp = rhs.get();
            geterr().~unexpected<E>();
            construct(std::move(tmp));
        } else {
            assign_common(rhs);
        }
    }
 
    // This overload is the worst-case, where we have to move-construct the
    // unexpected value into temporary storage, then try to copy the T into place.
    // If the construction succeeds, then everything is fine, but if it throws,
    // then we move the old unexpected value back into place before rethrowing the
    // exception.
    template <class U = T, detail::enable_if_t<!std::is_nothrow_copy_constructible<U>::value &&
                                               !std::is_nothrow_move_constructible<U>::value> * = nullptr>
    void assign(const expected_operations_base &rhs)
    {
        if (!this->m_has_val && rhs.m_has_val) {
            auto tmp = std::move(geterr());
            geterr().~unexpected<E>();
 
#ifdef TL_EXPECTED_EXCEPTIONS_ENABLED
            try {
                construct(rhs.get());
            } catch (...) {
                geterr() = std::move(tmp);
                throw;
            }
#else
            construct(rhs.get());
#endif
        } else {
            assign_common(rhs);
        }
    }
 
    // These overloads do the same as above, but for rvalues
    template <class U = T, detail::enable_if_t<std::is_nothrow_move_constructible<U>::value> * = nullptr>
    void assign(expected_operations_base &&rhs) noexcept
    {
        if (!this->m_has_val && rhs.m_has_val) {
            geterr().~unexpected<E>();
            construct(std::move(rhs).get());
        } else {
            assign_common(std::move(rhs));
        }
    }
 
    template <class U = T, detail::enable_if_t<!std::is_nothrow_move_constructible<U>::value> * = nullptr>
    void assign(expected_operations_base &&rhs)
    {
        if (!this->m_has_val && rhs.m_has_val) {
            auto tmp = std::move(geterr());
            geterr().~unexpected<E>();
#ifdef TL_EXPECTED_EXCEPTIONS_ENABLED
            try {
                construct(std::move(rhs).get());
            } catch (...) {
                geterr() = std::move(tmp);
                throw;
            }
#else
            construct(std::move(rhs).get());
#endif
        } else {
            assign_common(std::move(rhs));
        }
    }
 
#else
 
    // If exceptions are disabled then we can just copy-construct
    void assign(const expected_operations_base &rhs) noexcept
    {
        if (!this->m_has_val && rhs.m_has_val) {
            geterr().~unexpected<E>();
            construct(rhs.get());
        } else {
            assign_common(rhs);
        }
    }
 
    void assign(expected_operations_base &&rhs) noexcept
    {
        if (!this->m_has_val && rhs.m_has_val) {
            geterr().~unexpected<E>();
            construct(std::move(rhs).get());
        } else {
            assign_common(std::move(rhs));
        }
    }
 
#endif
 
    // The common part of move/copy assigning
    template <class Rhs>
    void assign_common(Rhs &&rhs)
    {
        if (this->m_has_val) {
            if (rhs.m_has_val) {
                get() = std::forward<Rhs>(rhs).get();
            } else {
                destroy_val();
                construct_error(std::forward<Rhs>(rhs).geterr());
            }
        } else {
            if (!rhs.m_has_val) {
                geterr() = std::forward<Rhs>(rhs).geterr();
            }
        }
    }
 
    bool has_value() const
    {
        return this->m_has_val;
    }
 
    TL_EXPECTED_11_CONSTEXPR T &get() &
    {
        return this->m_val;
    }
    constexpr const T &get() const &
    {
        return this->m_val;
    }
    TL_EXPECTED_11_CONSTEXPR T &&get() &&
    {
        return std::move(this->m_val);
    }
#ifndef TL_EXPECTED_NO_CONSTRR
    constexpr const T &&get() const &&
    {
        return std::move(this->m_val);
    }
#endif
 
    TL_EXPECTED_11_CONSTEXPR unexpected<E> &geterr() &
    {
        return this->m_unexpect;
    }
    constexpr const unexpected<E> &geterr() const &
    {
        return this->m_unexpect;
    }
    TL_EXPECTED_11_CONSTEXPR unexpected<E> &&geterr() &&
    {
        return std::move(this->m_unexpect);
    }
#ifndef TL_EXPECTED_NO_CONSTRR
    constexpr const unexpected<E> &&geterr() const &&
    {
        return std::move(this->m_unexpect);
    }
#endif
 
    TL_EXPECTED_11_CONSTEXPR void destroy_val()
    {
        get().~T();
    }
};
 
// This base class provides some handy member functions which can be used in
// further derived classes
template <class E>
struct expected_operations_base<void, E> : expected_storage_base<void, E> {
    using expected_storage_base<void, E>::expected_storage_base;
 
    template <class... Args>
    void construct() noexcept
    {
        this->m_has_val = true;
    }
 
    // This function doesn't use its argument, but needs it so that code in
    // levels above this can work independently of whether T is void
    template <class Rhs>
    void construct_with(Rhs &&) noexcept
    {
        this->m_has_val = true;
    }
 
    template <class... Args>
    void construct_error(Args &&...args) noexcept
    {
        new (std::addressof(this->m_unexpect)) unexpected<E>(std::forward<Args>(args)...);
        this->m_has_val = false;
    }
 
    template <class Rhs>
    void assign(Rhs &&rhs) noexcept
    {
        if (!this->m_has_val) {
            if (rhs.m_has_val) {
                geterr().~unexpected<E>();
                construct();
            } else {
                geterr() = std::forward<Rhs>(rhs).geterr();
            }
        } else {
            if (!rhs.m_has_val) {
                construct_error(std::forward<Rhs>(rhs).geterr());
            }
        }
    }
 
    bool has_value() const
    {
        return this->m_has_val;
    }
 
    TL_EXPECTED_11_CONSTEXPR unexpected<E> &geterr() &
    {
        return this->m_unexpect;
    }
    constexpr const unexpected<E> &geterr() const &
    {
        return this->m_unexpect;
    }
    TL_EXPECTED_11_CONSTEXPR unexpected<E> &&geterr() &&
    {
        return std::move(this->m_unexpect);
    }
#ifndef TL_EXPECTED_NO_CONSTRR
    constexpr const unexpected<E> &&geterr() const &&
    {
        return std::move(this->m_unexpect);
    }
#endif
 
    TL_EXPECTED_11_CONSTEXPR void destroy_val()
    {
        // no-op
    }
};
 
// This class manages conditionally having a trivial copy constructor
// This specialization is for when T and E are trivially copy constructible
template <class T, class E,
          bool = is_void_or<T, TL_EXPECTED_IS_TRIVIALLY_COPY_CONSTRUCTIBLE(T)>::value &&
                 TL_EXPECTED_IS_TRIVIALLY_COPY_CONSTRUCTIBLE(E)::value>
struct expected_copy_base : expected_operations_base<T, E> {
    using expected_operations_base<T, E>::expected_operations_base;
};
 
// This specialization is for when T or E are not trivially copy constructible
template <class T, class E>
struct expected_copy_base<T, E, false> : expected_operations_base<T, E> {
    using expected_operations_base<T, E>::expected_operations_base;
 
    expected_copy_base() = default;
    expected_copy_base(const expected_copy_base &rhs) : expected_operations_base<T, E>(no_init)
    {
        if (rhs.has_value()) {
            this->construct_with(rhs);
        } else {
            this->construct_error(rhs.geterr());
        }
    }
 
    expected_copy_base(expected_copy_base &&rhs)                 = default;
    expected_copy_base &operator=(const expected_copy_base &rhs) = default;
    expected_copy_base &operator=(expected_copy_base &&rhs)      = default;
};
 
// This class manages conditionally having a trivial move constructor
// Unfortunately there's no way to achieve this in GCC < 5 AFAIK, since it
// doesn't implement an analogue to std::is_trivially_move_constructible. We
// have to make do with a non-trivial move constructor even if T is trivially
// move constructible
#ifndef TL_EXPECTED_GCC49
template <class T, class E,
          bool = is_void_or<T, std::is_trivially_move_constructible<T>>::value &&
                 std::is_trivially_move_constructible<E>::value>
struct expected_move_base : expected_copy_base<T, E> {
    using expected_copy_base<T, E>::expected_copy_base;
};
#else
template <class T, class E, bool = false>
struct expected_move_base;
#endif
template <class T, class E>
struct expected_move_base<T, E, false> : expected_copy_base<T, E> {
    using expected_copy_base<T, E>::expected_copy_base;
 
    expected_move_base()                              = default;
    expected_move_base(const expected_move_base &rhs) = default;
 
    expected_move_base(expected_move_base &&rhs) noexcept(std::is_nothrow_move_constructible<T>::value)
        : expected_copy_base<T, E>(no_init)
    {
        if (rhs.has_value()) {
            this->construct_with(std::move(rhs));
        } else {
            this->construct_error(std::move(rhs.geterr()));
        }
    }
    expected_move_base &operator=(const expected_move_base &rhs) = default;
    expected_move_base &operator=(expected_move_base &&rhs)      = default;
};
 
// This class manages conditionally having a trivial copy assignment operator
template <class T, class E,
          bool = is_void_or<T, conjunction<TL_EXPECTED_IS_TRIVIALLY_COPY_ASSIGNABLE(T),
                                           TL_EXPECTED_IS_TRIVIALLY_COPY_CONSTRUCTIBLE(T),
                                           TL_EXPECTED_IS_TRIVIALLY_DESTRUCTIBLE(T)>>::value &&
                 TL_EXPECTED_IS_TRIVIALLY_COPY_ASSIGNABLE(E)::value &&
                 TL_EXPECTED_IS_TRIVIALLY_COPY_CONSTRUCTIBLE(E)::value &&
                 TL_EXPECTED_IS_TRIVIALLY_DESTRUCTIBLE(E)::value>
struct expected_copy_assign_base : expected_move_base<T, E> {
    using expected_move_base<T, E>::expected_move_base;
};
 
template <class T, class E>
struct expected_copy_assign_base<T, E, false> : expected_move_base<T, E> {
    using expected_move_base<T, E>::expected_move_base;
 
    expected_copy_assign_base()                                     = default;
    expected_copy_assign_base(const expected_copy_assign_base &rhs) = default;
 
    expected_copy_assign_base(expected_copy_assign_base &&rhs) = default;
    expected_copy_assign_base &operator=(const expected_copy_assign_base &rhs)
    {
        this->assign(rhs);
        return *this;
    }
    expected_copy_assign_base &operator=(expected_copy_assign_base &&rhs) = default;
};
 
// This class manages conditionally having a trivial move assignment operator
// Unfortunately there's no way to achieve this in GCC < 5 AFAIK, since it
// doesn't implement an analogue to std::is_trivially_move_assignable. We have
// to make do with a non-trivial move assignment operator even if T is trivially
// move assignable
#ifndef TL_EXPECTED_GCC49
template <class T, class E,
          bool = is_void_or<T, conjunction<std::is_trivially_destructible<T>, std::is_trivially_move_constructible<T>,
                                           std::is_trivially_move_assignable<T>>>::value &&
                 std::is_trivially_destructible<E>::value && std::is_trivially_move_constructible<E>::value &&
                 std::is_trivially_move_assignable<E>::value>
struct expected_move_assign_base : expected_copy_assign_base<T, E> {
    using expected_copy_assign_base<T, E>::expected_copy_assign_base;
};
#else
template <class T, class E, bool = false>
struct expected_move_assign_base;
#endif
 
template <class T, class E>
struct expected_move_assign_base<T, E, false> : expected_copy_assign_base<T, E> {
    using expected_copy_assign_base<T, E>::expected_copy_assign_base;
 
    expected_move_assign_base()                                     = default;
    expected_move_assign_base(const expected_move_assign_base &rhs) = default;
 
    expected_move_assign_base(expected_move_assign_base &&rhs) = default;
 
    expected_move_assign_base &operator=(const expected_move_assign_base &rhs) = default;
 
    expected_move_assign_base &operator=(expected_move_assign_base &&rhs) noexcept(
        std::is_nothrow_move_constructible<T>::value && std::is_nothrow_move_assignable<T>::value)
    {
        this->assign(std::move(rhs));
        return *this;
    }
};
 
// expected_delete_ctor_base will conditionally delete copy and move
// constructors depending on whether T is copy/move constructible
template <class T, class E,
          bool EnableCopy = (is_copy_constructible_or_void<T>::value && std::is_copy_constructible<E>::value),
          bool EnableMove = (is_move_constructible_or_void<T>::value && std::is_move_constructible<E>::value)>
struct expected_delete_ctor_base {
    expected_delete_ctor_base()                                                 = default;
    expected_delete_ctor_base(const expected_delete_ctor_base &)                = default;
    expected_delete_ctor_base(expected_delete_ctor_base &&) noexcept            = default;
    expected_delete_ctor_base &operator=(const expected_delete_ctor_base &)     = default;
    expected_delete_ctor_base &operator=(expected_delete_ctor_base &&) noexcept = default;
};
 
template <class T, class E>
struct expected_delete_ctor_base<T, E, true, false> {
    expected_delete_ctor_base()                                                 = default;
    expected_delete_ctor_base(const expected_delete_ctor_base &)                = default;
    expected_delete_ctor_base(expected_delete_ctor_base &&) noexcept            = delete;
    expected_delete_ctor_base &operator=(const expected_delete_ctor_base &)     = default;
    expected_delete_ctor_base &operator=(expected_delete_ctor_base &&) noexcept = default;
};
 
template <class T, class E>
struct expected_delete_ctor_base<T, E, false, true> {
    expected_delete_ctor_base()                                                 = default;
    expected_delete_ctor_base(const expected_delete_ctor_base &)                = delete;
    expected_delete_ctor_base(expected_delete_ctor_base &&) noexcept            = default;
    expected_delete_ctor_base &operator=(const expected_delete_ctor_base &)     = default;
    expected_delete_ctor_base &operator=(expected_delete_ctor_base &&) noexcept = default;
};
 
template <class T, class E>
struct expected_delete_ctor_base<T, E, false, false> {
    expected_delete_ctor_base()                                                 = default;
    expected_delete_ctor_base(const expected_delete_ctor_base &)                = delete;
    expected_delete_ctor_base(expected_delete_ctor_base &&) noexcept            = delete;
    expected_delete_ctor_base &operator=(const expected_delete_ctor_base &)     = default;
    expected_delete_ctor_base &operator=(expected_delete_ctor_base &&) noexcept = default;
};
 
// expected_delete_assign_base will conditionally delete copy and move
// constructors depending on whether T and E are copy/move constructible +
// assignable
template <class T, class E,
          bool EnableCopy = (is_copy_constructible_or_void<T>::value && std::is_copy_constructible<E>::value &&
                             is_copy_assignable_or_void<T>::value && std::is_copy_assignable<E>::value),
          bool EnableMove = (is_move_constructible_or_void<T>::value && std::is_move_constructible<E>::value &&
                             is_move_assignable_or_void<T>::value && std::is_move_assignable<E>::value)>
struct expected_delete_assign_base {
    expected_delete_assign_base()                                                   = default;
    expected_delete_assign_base(const expected_delete_assign_base &)                = default;
    expected_delete_assign_base(expected_delete_assign_base &&) noexcept            = default;
    expected_delete_assign_base &operator=(const expected_delete_assign_base &)     = default;
    expected_delete_assign_base &operator=(expected_delete_assign_base &&) noexcept = default;
};
 
template <class T, class E>
struct expected_delete_assign_base<T, E, true, false> {
    expected_delete_assign_base()                                                   = default;
    expected_delete_assign_base(const expected_delete_assign_base &)                = default;
    expected_delete_assign_base(expected_delete_assign_base &&) noexcept            = default;
    expected_delete_assign_base &operator=(const expected_delete_assign_base &)     = default;
    expected_delete_assign_base &operator=(expected_delete_assign_base &&) noexcept = delete;
};
 
template <class T, class E>
struct expected_delete_assign_base<T, E, false, true> {
    expected_delete_assign_base()                                                   = default;
    expected_delete_assign_base(const expected_delete_assign_base &)                = default;
    expected_delete_assign_base(expected_delete_assign_base &&) noexcept            = default;
    expected_delete_assign_base &operator=(const expected_delete_assign_base &)     = delete;
    expected_delete_assign_base &operator=(expected_delete_assign_base &&) noexcept = default;
};
 
template <class T, class E>
struct expected_delete_assign_base<T, E, false, false> {
    expected_delete_assign_base()                                                   = default;
    expected_delete_assign_base(const expected_delete_assign_base &)                = default;
    expected_delete_assign_base(expected_delete_assign_base &&) noexcept            = default;
    expected_delete_assign_base &operator=(const expected_delete_assign_base &)     = delete;
    expected_delete_assign_base &operator=(expected_delete_assign_base &&) noexcept = delete;
};
 
// This is needed to be able to construct the expected_default_ctor_base which
// follows, while still conditionally deleting the default constructor.
struct default_constructor_tag {
    explicit constexpr default_constructor_tag() = default;
};
 
// expected_default_ctor_base will ensure that expected has a deleted default
// consturctor if T is not default constructible.
// This specialization is for when T is default constructible
template <class T, class E, bool Enable = std::is_default_constructible<T>::value || std::is_void<T>::value>
struct expected_default_ctor_base {
    constexpr expected_default_ctor_base() noexcept                                    = default;
    constexpr expected_default_ctor_base(expected_default_ctor_base const &) noexcept  = default;
    constexpr expected_default_ctor_base(expected_default_ctor_base &&) noexcept       = default;
    expected_default_ctor_base &operator=(expected_default_ctor_base const &) noexcept = default;
    expected_default_ctor_base &operator=(expected_default_ctor_base &&) noexcept      = default;
 
    constexpr explicit expected_default_ctor_base(default_constructor_tag)
    {
    }
};
 
// This specialization is for when T is not default constructible
template <class T, class E>
struct expected_default_ctor_base<T, E, false> {
    constexpr expected_default_ctor_base() noexcept                                    = delete;
    constexpr expected_default_ctor_base(expected_default_ctor_base const &) noexcept  = default;
    constexpr expected_default_ctor_base(expected_default_ctor_base &&) noexcept       = default;
    expected_default_ctor_base &operator=(expected_default_ctor_base const &) noexcept = default;
    expected_default_ctor_base &operator=(expected_default_ctor_base &&) noexcept      = default;
 
    constexpr explicit expected_default_ctor_base(default_constructor_tag)
    {
    }
};
}  // namespace detail
 
template <class E>
class bad_expected_access : public std::exception {
public:
    explicit bad_expected_access(E e) : m_val(std::move(e))
    {
    }
 
    virtual const char *what() const noexcept override
    {
        return "Bad expected access";
    }
 
    const E &error() const &
    {
        return m_val;
    }
    E &error() &
    {
        return m_val;
    }
    const E &&error() const &&
    {
        return std::move(m_val);
    }
    E &&error() &&
    {
        return std::move(m_val);
    }
 
private:
    E m_val;
};
 
template <class T, class E>
class expected : private detail::expected_move_assign_base<T, E>,
                 private detail::expected_delete_ctor_base<T, E>,
                 private detail::expected_delete_assign_base<T, E>,
                 private detail::expected_default_ctor_base<T, E> {
    static_assert(!std::is_reference<T>::value, "T must not be a reference");
    static_assert(!std::is_same<T, std::remove_cv<in_place_t>::type>::value, "T must not be in_place_t");
    static_assert(!std::is_same<T, std::remove_cv<unexpect_t>::type>::value, "T must not be unexpect_t");
    static_assert(!std::is_same<T, typename std::remove_cv<unexpected<E>>::type>::value, "T must not be unexpected<E>");
    static_assert(!std::is_reference<E>::value, "E must not be a reference");
 
    T *valptr()
    {
        return std::addressof(this->m_val);
    }
    const T *valptr() const
    {
        return std::addressof(this->m_val);
    }
    unexpected<E> *errptr()
    {
        return std::addressof(this->m_unexpect);
    }
    const unexpected<E> *errptr() const
    {
        return std::addressof(this->m_unexpect);
    }
 
    template <class U = T, detail::enable_if_t<!std::is_void<U>::value> * = nullptr>
    TL_EXPECTED_11_CONSTEXPR U &val()
    {
        return this->m_val;
    }
    TL_EXPECTED_11_CONSTEXPR unexpected<E> &err()
    {
        return this->m_unexpect;
    }
 
    template <class U = T, detail::enable_if_t<!std::is_void<U>::value> * = nullptr>
    constexpr const U &val() const
    {
        return this->m_val;
    }
    constexpr const unexpected<E> &err() const
    {
        return this->m_unexpect;
    }
 
    using impl_base = detail::expected_move_assign_base<T, E>;
    using ctor_base = detail::expected_default_ctor_base<T, E>;
 
public:
    typedef T value_type;
    typedef E error_type;
    typedef unexpected<E> unexpected_type;
 
#if defined(TL_EXPECTED_CXX14) && !defined(TL_EXPECTED_GCC49) && !defined(TL_EXPECTED_GCC54) && \
    !defined(TL_EXPECTED_GCC55)
    template <class F>
    TL_EXPECTED_11_CONSTEXPR auto and_then(F &&f) &
    {
        return and_then_impl(*this, std::forward<F>(f));
    }
    template <class F>
    TL_EXPECTED_11_CONSTEXPR auto and_then(F &&f) &&
    {
        return and_then_impl(std::move(*this), std::forward<F>(f));
    }
    template <class F>
    constexpr auto and_then(F &&f) const &
    {
        return and_then_impl(*this, std::forward<F>(f));
    }
 
#ifndef TL_EXPECTED_NO_CONSTRR
    template <class F>
    constexpr auto and_then(F &&f) const &&
    {
        return and_then_impl(std::move(*this), std::forward<F>(f));
    }
#endif
 
#else
    template <class F>
    TL_EXPECTED_11_CONSTEXPR auto and_then(F &&f) & -> decltype(and_then_impl(std::declval<expected &>(),
                                                                              std::forward<F>(f)))
    {
        return and_then_impl(*this, std::forward<F>(f));
    }
    template <class F>
    TL_EXPECTED_11_CONSTEXPR auto and_then(F &&f) && -> decltype(and_then_impl(std::declval<expected &&>(),
                                                                               std::forward<F>(f)))
    {
        return and_then_impl(std::move(*this), std::forward<F>(f));
    }
    template <class F>
    constexpr auto and_then(F &&f) const & -> decltype(and_then_impl(std::declval<expected const &>(),
                                                                     std::forward<F>(f)))
    {
        return and_then_impl(*this, std::forward<F>(f));
    }
 
#ifndef TL_EXPECTED_NO_CONSTRR
    template <class F>
    constexpr auto and_then(F &&f) const && -> decltype(and_then_impl(std::declval<expected const &&>(),
                                                                      std::forward<F>(f)))
    {
        return and_then_impl(std::move(*this), std::forward<F>(f));
    }
#endif
#endif
 
#if defined(TL_EXPECTED_CXX14) && !defined(TL_EXPECTED_GCC49) && !defined(TL_EXPECTED_GCC54) && \
    !defined(TL_EXPECTED_GCC55)
    template <class F>
    TL_EXPECTED_11_CONSTEXPR auto map(F &&f) &
    {
        return expected_map_impl(*this, std::forward<F>(f));
    }
    template <class F>
    TL_EXPECTED_11_CONSTEXPR auto map(F &&f) &&
    {
        return expected_map_impl(std::move(*this), std::forward<F>(f));
    }
    template <class F>
    constexpr auto map(F &&f) const &
    {
        return expected_map_impl(*this, std::forward<F>(f));
    }
    template <class F>
    constexpr auto map(F &&f) const &&
    {
        return expected_map_impl(std::move(*this), std::forward<F>(f));
    }
#else
    template <class F>
    TL_EXPECTED_11_CONSTEXPR decltype(expected_map_impl(std::declval<expected &>(), std::declval<F &&>())) map(F &&f) &
    {
        return expected_map_impl(*this, std::forward<F>(f));
    }
    template <class F>
    TL_EXPECTED_11_CONSTEXPR decltype(expected_map_impl(std::declval<expected>(), std::declval<F &&>())) map(F &&f) &&
    {
        return expected_map_impl(std::move(*this), std::forward<F>(f));
    }
    template <class F>
    constexpr decltype(expected_map_impl(std::declval<const expected &>(), std::declval<F &&>())) map(F &&f) const &
    {
        return expected_map_impl(*this, std::forward<F>(f));
    }
 
#ifndef TL_EXPECTED_NO_CONSTRR
    template <class F>
    constexpr decltype(expected_map_impl(std::declval<const expected &&>(), std::declval<F &&>())) map(F &&f) const &&
    {
        return expected_map_impl(std::move(*this), std::forward<F>(f));
    }
#endif
#endif
 
#if defined(TL_EXPECTED_CXX14) && !defined(TL_EXPECTED_GCC49) && !defined(TL_EXPECTED_GCC54) && \
    !defined(TL_EXPECTED_GCC55)
    template <class F>
    TL_EXPECTED_11_CONSTEXPR auto transform(F &&f) &
    {
        return expected_map_impl(*this, std::forward<F>(f));
    }
    template <class F>
    TL_EXPECTED_11_CONSTEXPR auto transform(F &&f) &&
    {
        return expected_map_impl(std::move(*this), std::forward<F>(f));
    }
    template <class F>
    constexpr auto transform(F &&f) const &
    {
        return expected_map_impl(*this, std::forward<F>(f));
    }
    template <class F>
    constexpr auto transform(F &&f) const &&
    {
        return expected_map_impl(std::move(*this), std::forward<F>(f));
    }
#else
    template <class F>
    TL_EXPECTED_11_CONSTEXPR decltype(expected_map_impl(std::declval<expected &>(), std::declval<F &&>())) transform(
        F &&f) &
    {
        return expected_map_impl(*this, std::forward<F>(f));
    }
    template <class F>
    TL_EXPECTED_11_CONSTEXPR decltype(expected_map_impl(std::declval<expected>(), std::declval<F &&>())) transform(
        F &&f) &&
    {
        return expected_map_impl(std::move(*this), std::forward<F>(f));
    }
    template <class F>
    constexpr decltype(expected_map_impl(std::declval<const expected &>(), std::declval<F &&>())) transform(
        F &&f) const &
    {
        return expected_map_impl(*this, std::forward<F>(f));
    }
 
#ifndef TL_EXPECTED_NO_CONSTRR
    template <class F>
    constexpr decltype(expected_map_impl(std::declval<const expected &&>(), std::declval<F &&>())) transform(
        F &&f) const &&
    {
        return expected_map_impl(std::move(*this), std::forward<F>(f));
    }
#endif
#endif
 
#if defined(TL_EXPECTED_CXX14) && !defined(TL_EXPECTED_GCC49) && !defined(TL_EXPECTED_GCC54) && \
    !defined(TL_EXPECTED_GCC55)
    template <class F>
    TL_EXPECTED_11_CONSTEXPR auto map_error(F &&f) &
    {
        return map_error_impl(*this, std::forward<F>(f));
    }
    template <class F>
    TL_EXPECTED_11_CONSTEXPR auto map_error(F &&f) &&
    {
        return map_error_impl(std::move(*this), std::forward<F>(f));
    }
    template <class F>
    constexpr auto map_error(F &&f) const &
    {
        return map_error_impl(*this, std::forward<F>(f));
    }
    template <class F>
    constexpr auto map_error(F &&f) const &&
    {
        return map_error_impl(std::move(*this), std::forward<F>(f));
    }
#else
    template <class F>
    TL_EXPECTED_11_CONSTEXPR decltype(map_error_impl(std::declval<expected &>(), std::declval<F &&>())) map_error(
        F &&f) &
    {
        return map_error_impl(*this, std::forward<F>(f));
    }
    template <class F>
    TL_EXPECTED_11_CONSTEXPR decltype(map_error_impl(std::declval<expected &&>(), std::declval<F &&>())) map_error(
        F &&f) &&
    {
        return map_error_impl(std::move(*this), std::forward<F>(f));
    }
    template <class F>
    constexpr decltype(map_error_impl(std::declval<const expected &>(), std::declval<F &&>())) map_error(F &&f) const &
    {
        return map_error_impl(*this, std::forward<F>(f));
    }
 
#ifndef TL_EXPECTED_NO_CONSTRR
    template <class F>
    constexpr decltype(map_error_impl(std::declval<const expected &&>(), std::declval<F &&>())) map_error(
        F &&f) const &&
    {
        return map_error_impl(std::move(*this), std::forward<F>(f));
    }
#endif
#endif
#if defined(TL_EXPECTED_CXX14) && !defined(TL_EXPECTED_GCC49) && !defined(TL_EXPECTED_GCC54) && \
    !defined(TL_EXPECTED_GCC55)
    template <class F>
    TL_EXPECTED_11_CONSTEXPR auto transform_error(F &&f) &
    {
        return map_error_impl(*this, std::forward<F>(f));
    }
    template <class F>
    TL_EXPECTED_11_CONSTEXPR auto transform_error(F &&f) &&
    {
        return map_error_impl(std::move(*this), std::forward<F>(f));
    }
    template <class F>
    constexpr auto transform_error(F &&f) const &
    {
        return map_error_impl(*this, std::forward<F>(f));
    }
    template <class F>
    constexpr auto transform_error(F &&f) const &&
    {
        return map_error_impl(std::move(*this), std::forward<F>(f));
    }
#else
    template <class F>
    TL_EXPECTED_11_CONSTEXPR decltype(map_error_impl(std::declval<expected &>(), std::declval<F &&>())) transform_error(
        F &&f) &
    {
        return map_error_impl(*this, std::forward<F>(f));
    }
    template <class F>
    TL_EXPECTED_11_CONSTEXPR decltype(map_error_impl(std::declval<expected &&>(), std::declval<F &&>()))
    transform_error(F &&f) &&
    {
        return map_error_impl(std::move(*this), std::forward<F>(f));
    }
    template <class F>
    constexpr decltype(map_error_impl(std::declval<const expected &>(), std::declval<F &&>())) transform_error(
        F &&f) const &
    {
        return map_error_impl(*this, std::forward<F>(f));
    }
 
#ifndef TL_EXPECTED_NO_CONSTRR
    template <class F>
    constexpr decltype(map_error_impl(std::declval<const expected &&>(), std::declval<F &&>())) transform_error(
        F &&f) const &&
    {
        return map_error_impl(std::move(*this), std::forward<F>(f));
    }
#endif
#endif
    template <class F>
    expected TL_EXPECTED_11_CONSTEXPR or_else(F &&f) &
    {
        return or_else_impl(*this, std::forward<F>(f));
    }
 
    template <class F>
    expected TL_EXPECTED_11_CONSTEXPR or_else(F &&f) &&
    {
        return or_else_impl(std::move(*this), std::forward<F>(f));
    }
 
    template <class F>
    expected constexpr or_else(F &&f) const &
    {
        return or_else_impl(*this, std::forward<F>(f));
    }
 
#ifndef TL_EXPECTED_NO_CONSTRR
    template <class F>
    expected constexpr or_else(F &&f) const &&
    {
        return or_else_impl(std::move(*this), std::forward<F>(f));
    }
#endif
    constexpr expected()                     = default;
    constexpr expected(const expected &rhs)  = default;
    constexpr expected(expected &&rhs)       = default;
    expected &operator=(const expected &rhs) = default;
    expected &operator=(expected &&rhs)      = default;
 
    template <class... Args, detail::enable_if_t<std::is_constructible<T, Args &&...>::value> * = nullptr>
    constexpr expected(in_place_t, Args &&...args)
        : impl_base(in_place, std::forward<Args>(args)...), ctor_base(detail::default_constructor_tag{})
    {
    }
 
    template <class U, class... Args,
              detail::enable_if_t<std::is_constructible<T, std::initializer_list<U> &, Args &&...>::value> * = nullptr>
    constexpr expected(in_place_t, std::initializer_list<U> il, Args &&...args)
        : impl_base(in_place, il, std::forward<Args>(args)...), ctor_base(detail::default_constructor_tag{})
    {
    }
 
    template <class G = E, detail::enable_if_t<std::is_constructible<E, const G &>::value> * = nullptr,
              detail::enable_if_t<!std::is_convertible<const G &, E>::value> * = nullptr>
    explicit constexpr expected(const unexpected<G> &e)
        : impl_base(unexpect, e.value()), ctor_base(detail::default_constructor_tag{})
    {
    }
 
    template <class G = E, detail::enable_if_t<std::is_constructible<E, const G &>::value> * = nullptr,
              detail::enable_if_t<std::is_convertible<const G &, E>::value> * = nullptr>
    constexpr expected(unexpected<G> const &e)
        : impl_base(unexpect, e.value()), ctor_base(detail::default_constructor_tag{})
    {
    }
 
    template <class G = E, detail::enable_if_t<std::is_constructible<E, G &&>::value> * = nullptr,
              detail::enable_if_t<!std::is_convertible<G &&, E>::value> * = nullptr>
    explicit constexpr expected(unexpected<G> &&e) noexcept(std::is_nothrow_constructible<E, G &&>::value)
        : impl_base(unexpect, std::move(e.value())), ctor_base(detail::default_constructor_tag{})
    {
    }
 
    template <class G = E, detail::enable_if_t<std::is_constructible<E, G &&>::value> * = nullptr,
              detail::enable_if_t<std::is_convertible<G &&, E>::value> * = nullptr>
    constexpr expected(unexpected<G> &&e) noexcept(std::is_nothrow_constructible<E, G &&>::value)
        : impl_base(unexpect, std::move(e.value())), ctor_base(detail::default_constructor_tag{})
    {
    }
 
    template <class... Args, detail::enable_if_t<std::is_constructible<E, Args &&...>::value> * = nullptr>
    constexpr explicit expected(unexpect_t, Args &&...args)
        : impl_base(unexpect, std::forward<Args>(args)...), ctor_base(detail::default_constructor_tag{})
    {
    }
 
    template <class U, class... Args,
              detail::enable_if_t<std::is_constructible<E, std::initializer_list<U> &, Args &&...>::value> * = nullptr>
    constexpr explicit expected(unexpect_t, std::initializer_list<U> il, Args &&...args)
        : impl_base(unexpect, il, std::forward<Args>(args)...), ctor_base(detail::default_constructor_tag{})
    {
    }
 
    template <class U, class G,
              detail::enable_if_t<!(std::is_convertible<U const &, T>::value &&
                                    std::is_convertible<G const &, E>::value)> *     = nullptr,
              detail::expected_enable_from_other<T, E, U, G, const U &, const G &> * = nullptr>
    explicit TL_EXPECTED_11_CONSTEXPR expected(const expected<U, G> &rhs) : ctor_base(detail::default_constructor_tag{})
    {
        if (rhs.has_value()) {
            this->construct(*rhs);
        } else {
            this->construct_error(rhs.error());
        }
    }
 
    template <class U, class G,
              detail::enable_if_t<(std::is_convertible<U const &, T>::value &&
                                   std::is_convertible<G const &, E>::value)> *      = nullptr,
              detail::expected_enable_from_other<T, E, U, G, const U &, const G &> * = nullptr>
    TL_EXPECTED_11_CONSTEXPR expected(const expected<U, G> &rhs) : ctor_base(detail::default_constructor_tag{})
    {
        if (rhs.has_value()) {
            this->construct(*rhs);
        } else {
            this->construct_error(rhs.error());
        }
    }
 
    template <
        class U, class G,
        detail::enable_if_t<!(std::is_convertible<U &&, T>::value && std::is_convertible<G &&, E>::value)> * = nullptr,
        detail::expected_enable_from_other<T, E, U, G, U &&, G &&> *                                         = nullptr>
    explicit TL_EXPECTED_11_CONSTEXPR expected(expected<U, G> &&rhs) : ctor_base(detail::default_constructor_tag{})
    {
        if (rhs.has_value()) {
            this->construct(std::move(*rhs));
        } else {
            this->construct_error(std::move(rhs.error()));
        }
    }
 
    template <
        class U, class G,
        detail::enable_if_t<(std::is_convertible<U &&, T>::value && std::is_convertible<G &&, E>::value)> * = nullptr,
        detail::expected_enable_from_other<T, E, U, G, U &&, G &&> *                                        = nullptr>
    TL_EXPECTED_11_CONSTEXPR expected(expected<U, G> &&rhs) : ctor_base(detail::default_constructor_tag{})
    {
        if (rhs.has_value()) {
            this->construct(std::move(*rhs));
        } else {
            this->construct_error(std::move(rhs.error()));
        }
    }
 
    template <class U = T, detail::enable_if_t<!std::is_convertible<U &&, T>::value> * = nullptr,
              detail::expected_enable_forward_value<T, E, U> * = nullptr>
    explicit TL_EXPECTED_MSVC2015_CONSTEXPR expected(U &&v) : expected(in_place, std::forward<U>(v))
    {
    }
 
    template <class U = T, detail::enable_if_t<std::is_convertible<U &&, T>::value> * = nullptr,
              detail::expected_enable_forward_value<T, E, U> * = nullptr>
    TL_EXPECTED_MSVC2015_CONSTEXPR expected(U &&v) : expected(in_place, std::forward<U>(v))
    {
    }
 
    template <
        class U = T, class G = T, detail::enable_if_t<std::is_nothrow_constructible<T, U &&>::value> * = nullptr,
        detail::enable_if_t<!std::is_void<G>::value> *                        = nullptr,
        detail::enable_if_t<(!std::is_same<expected<T, E>, detail::decay_t<U>>::value &&
                             !detail::conjunction<std::is_scalar<T>, std::is_same<T, detail::decay_t<U>>>::value &&
                             std::is_constructible<T, U>::value && std::is_assignable<G &, U>::value &&
                             std::is_nothrow_move_constructible<E>::value)> * = nullptr>
    expected &operator=(U &&v)
    {
        if (has_value()) {
            val() = std::forward<U>(v);
        } else {
            err().~unexpected<E>();
            ::new (valptr()) T(std::forward<U>(v));
            this->m_has_val = true;
        }
 
        return *this;
    }
 
    template <
        class U = T, class G = T, detail::enable_if_t<!std::is_nothrow_constructible<T, U &&>::value> * = nullptr,
        detail::enable_if_t<!std::is_void<U>::value> *                        = nullptr,
        detail::enable_if_t<(!std::is_same<expected<T, E>, detail::decay_t<U>>::value &&
                             !detail::conjunction<std::is_scalar<T>, std::is_same<T, detail::decay_t<U>>>::value &&
                             std::is_constructible<T, U>::value && std::is_assignable<G &, U>::value &&
                             std::is_nothrow_move_constructible<E>::value)> * = nullptr>
    expected &operator=(U &&v)
    {
        if (has_value()) {
            val() = std::forward<U>(v);
        } else {
            auto tmp = std::move(err());
            err().~unexpected<E>();
 
#ifdef TL_EXPECTED_EXCEPTIONS_ENABLED
            try {
                ::new (valptr()) T(std::forward<U>(v));
                this->m_has_val = true;
            } catch (...) {
                err() = std::move(tmp);
                throw;
            }
#else
            ::new (valptr()) T(std::forward<U>(v));
            this->m_has_val = true;
#endif
        }
 
        return *this;
    }
 
    template <class G = E, detail::enable_if_t<std::is_nothrow_copy_constructible<G>::value &&
                                               std::is_assignable<G &, G>::value> * = nullptr>
    expected &operator=(const unexpected<G> &rhs)
    {
        if (!has_value()) {
            err() = rhs;
        } else {
            this->destroy_val();
            ::new (errptr()) unexpected<E>(rhs);
            this->m_has_val = false;
        }
 
        return *this;
    }
 
    template <class G = E, detail::enable_if_t<std::is_nothrow_move_constructible<G>::value &&
                                               std::is_move_assignable<G>::value> * = nullptr>
    expected &operator=(unexpected<G> &&rhs) noexcept
    {
        if (!has_value()) {
            err() = std::move(rhs);
        } else {
            this->destroy_val();
            ::new (errptr()) unexpected<E>(std::move(rhs));
            this->m_has_val = false;
        }
 
        return *this;
    }
 
    template <class... Args, detail::enable_if_t<std::is_nothrow_constructible<T, Args &&...>::value> * = nullptr>
    void emplace(Args &&...args)
    {
        if (has_value()) {
            val().~T();
        } else {
            err().~unexpected<E>();
            this->m_has_val = true;
        }
        ::new (valptr()) T(std::forward<Args>(args)...);
    }
 
    template <class... Args, detail::enable_if_t<!std::is_nothrow_constructible<T, Args &&...>::value> * = nullptr>
    void emplace(Args &&...args)
    {
        if (has_value()) {
            val().~T();
            ::new (valptr()) T(std::forward<Args>(args)...);
        } else {
            auto tmp = std::move(err());
            err().~unexpected<E>();
 
#ifdef TL_EXPECTED_EXCEPTIONS_ENABLED
            try {
                ::new (valptr()) T(std::forward<Args>(args)...);
                this->m_has_val = true;
            } catch (...) {
                err() = std::move(tmp);
                throw;
            }
#else
            ::new (valptr()) T(std::forward<Args>(args)...);
            this->m_has_val = true;
#endif
        }
    }
 
    template <class U, class... Args,
              detail::enable_if_t<std::is_nothrow_constructible<T, std::initializer_list<U> &, Args &&...>::value> * =
                  nullptr>
    void emplace(std::initializer_list<U> il, Args &&...args)
    {
        if (has_value()) {
            T t(il, std::forward<Args>(args)...);
            val() = std::move(t);
        } else {
            err().~unexpected<E>();
            ::new (valptr()) T(il, std::forward<Args>(args)...);
            this->m_has_val = true;
        }
    }
 
    template <class U, class... Args,
              detail::enable_if_t<!std::is_nothrow_constructible<T, std::initializer_list<U> &, Args &&...>::value> * =
                  nullptr>
    void emplace(std::initializer_list<U> il, Args &&...args)
    {
        if (has_value()) {
            T t(il, std::forward<Args>(args)...);
            val() = std::move(t);
        } else {
            auto tmp = std::move(err());
            err().~unexpected<E>();
 
#ifdef TL_EXPECTED_EXCEPTIONS_ENABLED
            try {
                ::new (valptr()) T(il, std::forward<Args>(args)...);
                this->m_has_val = true;
            } catch (...) {
                err() = std::move(tmp);
                throw;
            }
#else
            ::new (valptr()) T(il, std::forward<Args>(args)...);
            this->m_has_val = true;
#endif
        }
    }
 
private:
    using t_is_void                       = std::true_type;
    using t_is_not_void                   = std::false_type;
    using t_is_nothrow_move_constructible = std::true_type;
    using move_constructing_t_can_throw   = std::false_type;
    using e_is_nothrow_move_constructible = std::true_type;
    using move_constructing_e_can_throw   = std::false_type;
 
    void swap_where_both_have_value(expected & /*rhs*/, t_is_void) noexcept
    {
        // swapping void is a no-op
    }
 
    void swap_where_both_have_value(expected &rhs, t_is_not_void)
    {
        using std::swap;
        swap(val(), rhs.val());
    }
 
    void swap_where_only_one_has_value(expected &rhs, t_is_void) noexcept(std::is_nothrow_move_constructible<E>::value)
    {
        ::new (errptr()) unexpected_type(std::move(rhs.err()));
        rhs.err().~unexpected_type();
        std::swap(this->m_has_val, rhs.m_has_val);
    }
 
    void swap_where_only_one_has_value(expected &rhs, t_is_not_void)
    {
        swap_where_only_one_has_value_and_t_is_not_void(rhs, typename std::is_nothrow_move_constructible<T>::type{},
                                                        typename std::is_nothrow_move_constructible<E>::type{});
    }
 
    void swap_where_only_one_has_value_and_t_is_not_void(expected &rhs, t_is_nothrow_move_constructible,
                                                         e_is_nothrow_move_constructible) noexcept
    {
        auto temp = std::move(val());
        val().~T();
        ::new (errptr()) unexpected_type(std::move(rhs.err()));
        rhs.err().~unexpected_type();
        ::new (rhs.valptr()) T(std::move(temp));
        std::swap(this->m_has_val, rhs.m_has_val);
    }
 
    void swap_where_only_one_has_value_and_t_is_not_void(expected &rhs, t_is_nothrow_move_constructible,
                                                         move_constructing_e_can_throw)
    {
        auto temp = std::move(val());
        val().~T();
#ifdef TL_EXPECTED_EXCEPTIONS_ENABLED
        try {
            ::new (errptr()) unexpected_type(std::move(rhs.err()));
            rhs.err().~unexpected_type();
            ::new (rhs.valptr()) T(std::move(temp));
            std::swap(this->m_has_val, rhs.m_has_val);
        } catch (...) {
            val() = std::move(temp);
            throw;
        }
#else
        ::new (errptr()) unexpected_type(std::move(rhs.err()));
        rhs.err().~unexpected_type();
        ::new (rhs.valptr()) T(std::move(temp));
        std::swap(this->m_has_val, rhs.m_has_val);
#endif
    }
 
    void swap_where_only_one_has_value_and_t_is_not_void(expected &rhs, move_constructing_t_can_throw,
                                                         e_is_nothrow_move_constructible)
    {
        auto temp = std::move(rhs.err());
        rhs.err().~unexpected_type();
#ifdef TL_EXPECTED_EXCEPTIONS_ENABLED
        try {
            ::new (rhs.valptr()) T(std::move(val()));
            val().~T();
            ::new (errptr()) unexpected_type(std::move(temp));
            std::swap(this->m_has_val, rhs.m_has_val);
        } catch (...) {
            rhs.err() = std::move(temp);
            throw;
        }
#else
        ::new (rhs.valptr()) T(std::move(val()));
        val().~T();
        ::new (errptr()) unexpected_type(std::move(temp));
        std::swap(this->m_has_val, rhs.m_has_val);
#endif
    }
 
public:
    template <class OT = T, class OE = E>
    detail::enable_if_t<detail::is_swappable<OT>::value && detail::is_swappable<OE>::value &&
                        (std::is_nothrow_move_constructible<OT>::value ||
                         std::is_nothrow_move_constructible<OE>::value)>
    swap(expected &rhs) noexcept(std::is_nothrow_move_constructible<T>::value &&
                                 detail::is_nothrow_swappable<T>::value &&
                                 std::is_nothrow_move_constructible<E>::value && detail::is_nothrow_swappable<E>::value)
    {
        if (has_value() && rhs.has_value()) {
            swap_where_both_have_value(rhs, typename std::is_void<T>::type{});
        } else if (!has_value() && rhs.has_value()) {
            rhs.swap(*this);
        } else if (has_value()) {
            swap_where_only_one_has_value(rhs, typename std::is_void<T>::type{});
        } else {
            using std::swap;
            swap(err(), rhs.err());
        }
    }
 
    constexpr const T *operator->() const
    {
        TL_ASSERT(has_value());
        return valptr();
    }
    TL_EXPECTED_11_CONSTEXPR T *operator->()
    {
        TL_ASSERT(has_value());
        return valptr();
    }
 
    template <class U = T, detail::enable_if_t<!std::is_void<U>::value> * = nullptr>
    constexpr const U &operator*() const &
    {
        TL_ASSERT(has_value());
        return val();
    }
    template <class U = T, detail::enable_if_t<!std::is_void<U>::value> * = nullptr>
    TL_EXPECTED_11_CONSTEXPR U &operator*() &
    {
        TL_ASSERT(has_value());
        return val();
    }
    template <class U = T, detail::enable_if_t<!std::is_void<U>::value> * = nullptr>
    constexpr const U &&operator*() const &&
    {
        TL_ASSERT(has_value());
        return std::move(val());
    }
    template <class U = T, detail::enable_if_t<!std::is_void<U>::value> * = nullptr>
    TL_EXPECTED_11_CONSTEXPR U &&operator*() &&
    {
        TL_ASSERT(has_value());
        return std::move(val());
    }
    constexpr bool has_value() const noexcept
    {
        return this->m_has_val;
    }
    constexpr bool has_error() const noexcept
    {
        return !(this->has_value());
    }  // Add by M5Stack
    constexpr explicit operator bool() const noexcept
    {
        return this->m_has_val;
    }
 
    template <class U = T, detail::enable_if_t<!std::is_void<U>::value> * = nullptr>
    TL_EXPECTED_11_CONSTEXPR const U &value() const &
    {
        if (!has_value()) detail::throw_exception(bad_expected_access<E>(err().value()));
        return val();
    }
    template <class U = T, detail::enable_if_t<!std::is_void<U>::value> * = nullptr>
    TL_EXPECTED_11_CONSTEXPR U &value() &
    {
        if (!has_value()) detail::throw_exception(bad_expected_access<E>(err().value()));
        return val();
    }
    template <class U = T, detail::enable_if_t<!std::is_void<U>::value> * = nullptr>
    TL_EXPECTED_11_CONSTEXPR const U &&value() const &&
    {
        if (!has_value()) detail::throw_exception(bad_expected_access<E>(std::move(err()).value()));
        return std::move(val());
    }
    template <class U = T, detail::enable_if_t<!std::is_void<U>::value> * = nullptr>
    TL_EXPECTED_11_CONSTEXPR U &&value() &&
    {
        if (!has_value()) detail::throw_exception(bad_expected_access<E>(std::move(err()).value()));
        return std::move(val());
    }
 
    constexpr const E &error() const &
    {
        TL_ASSERT(!has_value());
        return err().value();
    }
    TL_EXPECTED_11_CONSTEXPR E &error() &
    {
        TL_ASSERT(!has_value());
        return err().value();
    }
    constexpr const E &&error() const &&
    {
        TL_ASSERT(!has_value());
        return std::move(err().value());
    }
    TL_EXPECTED_11_CONSTEXPR E &&error() &&
    {
        TL_ASSERT(!has_value());
        return std::move(err().value());
    }
 
    template <class U>
    constexpr T value_or(U &&v) const &
    {
        static_assert(std::is_copy_constructible<T>::value && std::is_convertible<U &&, T>::value,
                      "T must be copy-constructible and convertible to from U&&");
        return bool(*this) ? **this : static_cast<T>(std::forward<U>(v));
    }
    template <class U>
    TL_EXPECTED_11_CONSTEXPR T value_or(U &&v) &&
    {
        static_assert(std::is_move_constructible<T>::value && std::is_convertible<U &&, T>::value,
                      "T must be move-constructible and convertible to from U&&");
        return bool(*this) ? std::move(**this) : static_cast<T>(std::forward<U>(v));
    }
 
    // Add by M5Stack
    template <class G = E>
    constexpr E error_or(G &&e) const &
    {
        static_assert(std::is_copy_constructible<E>::value && std::is_convertible<G, E>::value,
                      "E must be copy-constructible and convertible to from G&&");
        return has_value() ? std::forward<G>(e) : error();
    }
    template <class G = E>
    TL_EXPECTED_11_CONSTEXPR E error_or(G &&e) &&
    {
        static_assert(std::is_move_constructible<E>::value && std::is_convertible<G, E>::value,
                      "E must be move-constructible and convertible to from G&&");
        return has_value() ? std::forward<G>(e) : std::move(error());
    }
};
 
namespace detail {
template <class Exp>
using exp_t = typename detail::decay_t<Exp>::value_type;
template <class Exp>
using err_t = typename detail::decay_t<Exp>::error_type;
template <class Exp, class Ret>
using ret_t = expected<Ret, err_t<Exp>>;
 
#ifdef TL_EXPECTED_CXX14
template <class Exp, class F, detail::enable_if_t<!std::is_void<exp_t<Exp>>::value> * = nullptr,
          class Ret = decltype(detail::invoke(std::declval<F>(), *std::declval<Exp>()))>
constexpr auto and_then_impl(Exp &&exp, F &&f)
{
    static_assert(detail::is_expected<Ret>::value, "F must return an expected");
 
    return exp.has_value() ? detail::invoke(std::forward<F>(f), *std::forward<Exp>(exp))
                           : Ret(unexpect, std::forward<Exp>(exp).error());
}
 
template <class Exp, class F, detail::enable_if_t<std::is_void<exp_t<Exp>>::value> * = nullptr,
          class Ret = decltype(detail::invoke(std::declval<F>()))>
constexpr auto and_then_impl(Exp &&exp, F &&f)
{
    static_assert(detail::is_expected<Ret>::value, "F must return an expected");
 
    return exp.has_value() ? detail::invoke(std::forward<F>(f)) : Ret(unexpect, std::forward<Exp>(exp).error());
}
#else
template <class>
struct TC;
template <class Exp, class F, class Ret = decltype(detail::invoke(std::declval<F>(), *std::declval<Exp>())),
          detail::enable_if_t<!std::is_void<exp_t<Exp>>::value> * = nullptr>
auto and_then_impl(Exp &&exp, F &&f) -> Ret
{
    static_assert(detail::is_expected<Ret>::value, "F must return an expected");
 
    return exp.has_value() ? detail::invoke(std::forward<F>(f), *std::forward<Exp>(exp))
                           : Ret(unexpect, std::forward<Exp>(exp).error());
}
 
template <class Exp, class F, class Ret = decltype(detail::invoke(std::declval<F>())),
          detail::enable_if_t<std::is_void<exp_t<Exp>>::value> * = nullptr>
constexpr auto and_then_impl(Exp &&exp, F &&f) -> Ret
{
    static_assert(detail::is_expected<Ret>::value, "F must return an expected");
 
    return exp.has_value() ? detail::invoke(std::forward<F>(f)) : Ret(unexpect, std::forward<Exp>(exp).error());
}
#endif
 
#ifdef TL_EXPECTED_CXX14
template <class Exp, class F, detail::enable_if_t<!std::is_void<exp_t<Exp>>::value> * = nullptr,
          class Ret = decltype(detail::invoke(std::declval<F>(), *std::declval<Exp>())),
          detail::enable_if_t<!std::is_void<Ret>::value> * = nullptr>
constexpr auto expected_map_impl(Exp &&exp, F &&f)
{
    using result = ret_t<Exp, detail::decay_t<Ret>>;
    return exp.has_value() ? result(detail::invoke(std::forward<F>(f), *std::forward<Exp>(exp)))
                           : result(unexpect, std::forward<Exp>(exp).error());
}
 
template <class Exp, class F, detail::enable_if_t<!std::is_void<exp_t<Exp>>::value> * = nullptr,
          class Ret = decltype(detail::invoke(std::declval<F>(), *std::declval<Exp>())),
          detail::enable_if_t<std::is_void<Ret>::value> * = nullptr>
auto expected_map_impl(Exp &&exp, F &&f)
{
    using result = expected<void, err_t<Exp>>;
    if (exp.has_value()) {
        detail::invoke(std::forward<F>(f), *std::forward<Exp>(exp));
        return result();
    }
 
    return result(unexpect, std::forward<Exp>(exp).error());
}
 
template <class Exp, class F, detail::enable_if_t<std::is_void<exp_t<Exp>>::value> * = nullptr,
          class Ret                                        = decltype(detail::invoke(std::declval<F>())),
          detail::enable_if_t<!std::is_void<Ret>::value> * = nullptr>
constexpr auto expected_map_impl(Exp &&exp, F &&f)
{
    using result = ret_t<Exp, detail::decay_t<Ret>>;
    return exp.has_value() ? result(detail::invoke(std::forward<F>(f)))
                           : result(unexpect, std::forward<Exp>(exp).error());
}
 
template <class Exp, class F, detail::enable_if_t<std::is_void<exp_t<Exp>>::value> * = nullptr,
          class Ret                                       = decltype(detail::invoke(std::declval<F>())),
          detail::enable_if_t<std::is_void<Ret>::value> * = nullptr>
auto expected_map_impl(Exp &&exp, F &&f)
{
    using result = expected<void, err_t<Exp>>;
    if (exp.has_value()) {
        detail::invoke(std::forward<F>(f));
        return result();
    }
 
    return result(unexpect, std::forward<Exp>(exp).error());
}
#else
template <class Exp, class F, detail::enable_if_t<!std::is_void<exp_t<Exp>>::value> * = nullptr,
          class Ret = decltype(detail::invoke(std::declval<F>(), *std::declval<Exp>())),
          detail::enable_if_t<!std::is_void<Ret>::value> * = nullptr>
 
constexpr auto expected_map_impl(Exp &&exp, F &&f) -> ret_t<Exp, detail::decay_t<Ret>>
{
    using result = ret_t<Exp, detail::decay_t<Ret>>;
 
    return exp.has_value() ? result(detail::invoke(std::forward<F>(f), *std::forward<Exp>(exp)))
                           : result(unexpect, std::forward<Exp>(exp).error());
}
 
template <class Exp, class F, detail::enable_if_t<!std::is_void<exp_t<Exp>>::value> * = nullptr,
          class Ret = decltype(detail::invoke(std::declval<F>(), *std::declval<Exp>())),
          detail::enable_if_t<std::is_void<Ret>::value> * = nullptr>
 
auto expected_map_impl(Exp &&exp, F &&f) -> expected<void, err_t<Exp>>
{
    if (exp.has_value()) {
        detail::invoke(std::forward<F>(f), *std::forward<Exp>(exp));
        return {};
    }
 
    return unexpected<err_t<Exp>>(std::forward<Exp>(exp).error());
}
 
template <class Exp, class F, detail::enable_if_t<std::is_void<exp_t<Exp>>::value> * = nullptr,
          class Ret                                        = decltype(detail::invoke(std::declval<F>())),
          detail::enable_if_t<!std::is_void<Ret>::value> * = nullptr>
 
constexpr auto expected_map_impl(Exp &&exp, F &&f) -> ret_t<Exp, detail::decay_t<Ret>>
{
    using result = ret_t<Exp, detail::decay_t<Ret>>;
 
    return exp.has_value() ? result(detail::invoke(std::forward<F>(f)))
                           : result(unexpect, std::forward<Exp>(exp).error());
}
 
template <class Exp, class F, detail::enable_if_t<std::is_void<exp_t<Exp>>::value> * = nullptr,
          class Ret                                       = decltype(detail::invoke(std::declval<F>())),
          detail::enable_if_t<std::is_void<Ret>::value> * = nullptr>
 
auto expected_map_impl(Exp &&exp, F &&f) -> expected<void, err_t<Exp>>
{
    if (exp.has_value()) {
        detail::invoke(std::forward<F>(f));
        return {};
    }
 
    return unexpected<err_t<Exp>>(std::forward<Exp>(exp).error());
}
#endif
 
#if defined(TL_EXPECTED_CXX14) && !defined(TL_EXPECTED_GCC49) && !defined(TL_EXPECTED_GCC54) && \
    !defined(TL_EXPECTED_GCC55)
template <class Exp, class F, detail::enable_if_t<!std::is_void<exp_t<Exp>>::value> * = nullptr,
          class Ret = decltype(detail::invoke(std::declval<F>(), std::declval<Exp>().error())),
          detail::enable_if_t<!std::is_void<Ret>::value> * = nullptr>
constexpr auto map_error_impl(Exp &&exp, F &&f)
{
    using result = expected<exp_t<Exp>, detail::decay_t<Ret>>;
    return exp.has_value() ? result(*std::forward<Exp>(exp))
                           : result(unexpect, detail::invoke(std::forward<F>(f), std::forward<Exp>(exp).error()));
}
template <class Exp, class F, detail::enable_if_t<!std::is_void<exp_t<Exp>>::value> * = nullptr,
          class Ret = decltype(detail::invoke(std::declval<F>(), std::declval<Exp>().error())),
          detail::enable_if_t<std::is_void<Ret>::value> * = nullptr>
auto map_error_impl(Exp &&exp, F &&f)
{
    using result = expected<exp_t<Exp>, monostate>;
    if (exp.has_value()) {
        return result(*std::forward<Exp>(exp));
    }
 
    detail::invoke(std::forward<F>(f), std::forward<Exp>(exp).error());
    return result(unexpect, monostate{});
}
template <class Exp, class F, detail::enable_if_t<std::is_void<exp_t<Exp>>::value> * = nullptr,
          class Ret = decltype(detail::invoke(std::declval<F>(), std::declval<Exp>().error())),
          detail::enable_if_t<!std::is_void<Ret>::value> * = nullptr>
constexpr auto map_error_impl(Exp &&exp, F &&f)
{
    using result = expected<exp_t<Exp>, detail::decay_t<Ret>>;
    return exp.has_value() ? result()
                           : result(unexpect, detail::invoke(std::forward<F>(f), std::forward<Exp>(exp).error()));
}
template <class Exp, class F, detail::enable_if_t<std::is_void<exp_t<Exp>>::value> * = nullptr,
          class Ret = decltype(detail::invoke(std::declval<F>(), std::declval<Exp>().error())),
          detail::enable_if_t<std::is_void<Ret>::value> * = nullptr>
auto map_error_impl(Exp &&exp, F &&f)
{
    using result = expected<exp_t<Exp>, monostate>;
    if (exp.has_value()) {
        return result();
    }
 
    detail::invoke(std::forward<F>(f), std::forward<Exp>(exp).error());
    return result(unexpect, monostate{});
}
#else
template <class Exp, class F, detail::enable_if_t<!std::is_void<exp_t<Exp>>::value> * = nullptr,
          class Ret = decltype(detail::invoke(std::declval<F>(), std::declval<Exp>().error())),
          detail::enable_if_t<!std::is_void<Ret>::value> * = nullptr>
constexpr auto map_error_impl(Exp &&exp, F &&f) -> expected<exp_t<Exp>, detail::decay_t<Ret>>
{
    using result = expected<exp_t<Exp>, detail::decay_t<Ret>>;
 
    return exp.has_value() ? result(*std::forward<Exp>(exp))
                           : result(unexpect, detail::invoke(std::forward<F>(f), std::forward<Exp>(exp).error()));
}
 
template <class Exp, class F, detail::enable_if_t<!std::is_void<exp_t<Exp>>::value> * = nullptr,
          class Ret = decltype(detail::invoke(std::declval<F>(), std::declval<Exp>().error())),
          detail::enable_if_t<std::is_void<Ret>::value> * = nullptr>
auto map_error_impl(Exp &&exp, F &&f) -> expected<exp_t<Exp>, monostate>
{
    using result = expected<exp_t<Exp>, monostate>;
    if (exp.has_value()) {
        return result(*std::forward<Exp>(exp));
    }
 
    detail::invoke(std::forward<F>(f), std::forward<Exp>(exp).error());
    return result(unexpect, monostate{});
}
 
template <class Exp, class F, detail::enable_if_t<std::is_void<exp_t<Exp>>::value> * = nullptr,
          class Ret = decltype(detail::invoke(std::declval<F>(), std::declval<Exp>().error())),
          detail::enable_if_t<!std::is_void<Ret>::value> * = nullptr>
constexpr auto map_error_impl(Exp &&exp, F &&f) -> expected<exp_t<Exp>, detail::decay_t<Ret>>
{
    using result = expected<exp_t<Exp>, detail::decay_t<Ret>>;
 
    return exp.has_value() ? result()
                           : result(unexpect, detail::invoke(std::forward<F>(f), std::forward<Exp>(exp).error()));
}
 
template <class Exp, class F, detail::enable_if_t<std::is_void<exp_t<Exp>>::value> * = nullptr,
          class Ret = decltype(detail::invoke(std::declval<F>(), std::declval<Exp>().error())),
          detail::enable_if_t<std::is_void<Ret>::value> * = nullptr>
auto map_error_impl(Exp &&exp, F &&f) -> expected<exp_t<Exp>, monostate>
{
    using result = expected<exp_t<Exp>, monostate>;
    if (exp.has_value()) {
        return result();
    }
 
    detail::invoke(std::forward<F>(f), std::forward<Exp>(exp).error());
    return result(unexpect, monostate{});
}
#endif
 
#ifdef TL_EXPECTED_CXX14
template <class Exp, class F, class Ret = decltype(detail::invoke(std::declval<F>(), std::declval<Exp>().error())),
          detail::enable_if_t<!std::is_void<Ret>::value> * = nullptr>
constexpr auto or_else_impl(Exp &&exp, F &&f)
{
    static_assert(detail::is_expected<Ret>::value, "F must return an expected");
    return exp.has_value() ? std::forward<Exp>(exp)
                           : detail::invoke(std::forward<F>(f), std::forward<Exp>(exp).error());
}
 
template <class Exp, class F, class Ret = decltype(detail::invoke(std::declval<F>(), std::declval<Exp>().error())),
          detail::enable_if_t<std::is_void<Ret>::value> * = nullptr>
detail::decay_t<Exp> or_else_impl(Exp &&exp, F &&f)
{
    return exp.has_value()
               ? std::forward<Exp>(exp)
               : (detail::invoke(std::forward<F>(f), std::forward<Exp>(exp).error()), std::forward<Exp>(exp));
}
#else
template <class Exp, class F, class Ret = decltype(detail::invoke(std::declval<F>(), std::declval<Exp>().error())),
          detail::enable_if_t<!std::is_void<Ret>::value> * = nullptr>
auto or_else_impl(Exp &&exp, F &&f) -> Ret
{
    static_assert(detail::is_expected<Ret>::value, "F must return an expected");
    return exp.has_value() ? std::forward<Exp>(exp)
                           : detail::invoke(std::forward<F>(f), std::forward<Exp>(exp).error());
}
 
template <class Exp, class F, class Ret = decltype(detail::invoke(std::declval<F>(), std::declval<Exp>().error())),
          detail::enable_if_t<std::is_void<Ret>::value> * = nullptr>
detail::decay_t<Exp> or_else_impl(Exp &&exp, F &&f)
{
    return exp.has_value()
               ? std::forward<Exp>(exp)
               : (detail::invoke(std::forward<F>(f), std::forward<Exp>(exp).error()), std::forward<Exp>(exp));
}
#endif
}  // namespace detail
 
template <class T, class E, class U, class F>
constexpr bool operator==(const expected<T, E> &lhs, const expected<U, F> &rhs)
{
    return (lhs.has_value() != rhs.has_value()) ? false
                                                : (!lhs.has_value() ? lhs.error() == rhs.error() : *lhs == *rhs);
}
template <class T, class E, class U, class F>
constexpr bool operator!=(const expected<T, E> &lhs, const expected<U, F> &rhs)
{
    return (lhs.has_value() != rhs.has_value()) ? true : (!lhs.has_value() ? lhs.error() != rhs.error() : *lhs != *rhs);
}
template <class E, class F>
constexpr bool operator==(const expected<void, E> &lhs, const expected<void, F> &rhs)
{
    return (lhs.has_value() != rhs.has_value()) ? false : (!lhs.has_value() ? lhs.error() == rhs.error() : true);
}
template <class E, class F>
constexpr bool operator!=(const expected<void, E> &lhs, const expected<void, F> &rhs)
{
    return (lhs.has_value() != rhs.has_value()) ? true : (!lhs.has_value() ? lhs.error() == rhs.error() : false);
}
 
template <class T, class E, class U>
constexpr bool operator==(const expected<T, E> &x, const U &v)
{
    return x.has_value() ? *x == v : false;
}
template <class T, class E, class U>
constexpr bool operator==(const U &v, const expected<T, E> &x)
{
    return x.has_value() ? *x == v : false;
}
template <class T, class E, class U>
constexpr bool operator!=(const expected<T, E> &x, const U &v)
{
    return x.has_value() ? *x != v : true;
}
template <class T, class E, class U>
constexpr bool operator!=(const U &v, const expected<T, E> &x)
{
    return x.has_value() ? *x != v : true;
}
 
template <class T, class E>
constexpr bool operator==(const expected<T, E> &x, const unexpected<E> &e)
{
    return x.has_value() ? false : x.error() == e.value();
}
template <class T, class E>
constexpr bool operator==(const unexpected<E> &e, const expected<T, E> &x)
{
    return x.has_value() ? false : x.error() == e.value();
}
template <class T, class E>
constexpr bool operator!=(const expected<T, E> &x, const unexpected<E> &e)
{
    return x.has_value() ? true : x.error() != e.value();
}
template <class T, class E>
constexpr bool operator!=(const unexpected<E> &e, const expected<T, E> &x)
{
    return x.has_value() ? true : x.error() != e.value();
}
 
template <class T, class E,
          detail::enable_if_t<(std::is_void<T>::value || std::is_move_constructible<T>::value) &&
                              detail::is_swappable<T>::value && std::is_move_constructible<E>::value &&
                              detail::is_swappable<E>::value> * = nullptr>
void swap(expected<T, E> &lhs, expected<T, E> &rhs) noexcept(noexcept(lhs.swap(rhs)))
{
    lhs.swap(rhs);
}
}  // namespace stl
}  // namespace m5
 
#endif