--- /dev/null
+///
+// expected - An implementation of std::expected with extensions
+// Written in 2017 by Simon Brand (simonrbrand@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/>.
+///
+
+#ifndef TL_EXPECTED_HPP
+#define TL_EXPECTED_HPP
+
+#define TL_EXPECTED_VERSION_MAJOR 1
+#define TL_EXPECTED_VERSION_MINOR 0
+#define TL_EXPECTED_VERSION_PATCH 1
+
+#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(__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 tl {
+ 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
+ }
+}
+#endif
+
+#define TL_EXPECTED_IS_TRIVIALLY_COPY_CONSTRUCTIBLE(T) \
+ tl::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 tl {
+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)) {}
+
+ 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;
+};
+
+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
+ #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> {
+ TL_EXPECTED_MSVC2015_CONSTEXPR 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(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;
+};
+
+/// An `expected<T, E>` object is an object that contains the storage for
+/// another object and manages the lifetime of this contained object `T`.
+/// Alternatively it could contain the storage for another unexpected object
+/// `E`. The contained object may not be initialized after the expected object
+/// has been initialized, and may not be destroyed before the expected object
+/// has been destroyed. The initialization state of the contained object is
+/// tracked by the expected object.
+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>>::value,
+ "T must not be in_place_t");
+ static_assert(!std::is_same<T, std::remove_cv<unexpect_t>>::value,
+ "T must not be unexpect_t");
+ static_assert(!std::is_same<T, std::remove_cv<unexpected<E>>>::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
+ 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(std::forward<Args>(args)...);
+ } else {
+ err().~unexpected<E>();
+ ::new (valptr()) T(std::forward<Args>(args)...);
+ this->m_has_val = true;
+ }
+ }
+
+ template <class... Args, detail::enable_if_t<!std::is_nothrow_constructible<
+ T, Args &&...>::value> * = nullptr>
+ void emplace(Args &&... args) {
+ if (has_value()) {
+ val() = 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,
+ t_is_nothrow_move_constructible) {
+ auto temp = std::move(rhs.err());
+ rhs.err().~unexpected_type();
+#ifdef TL_EXPECTED_EXCEPTIONS_ENABLED
+ try {
+ ::new (rhs.valptr()) T(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(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 { return valptr(); }
+ TL_EXPECTED_11_CONSTEXPR T *operator->() { return valptr(); }
+
+ template <class U = T,
+ detail::enable_if_t<!std::is_void<U>::value> * = nullptr>
+ constexpr const U &operator*() const & {
+ return val();
+ }
+ template <class U = T,
+ detail::enable_if_t<!std::is_void<U>::value> * = nullptr>
+ TL_EXPECTED_11_CONSTEXPR U &operator*() & {
+ return val();
+ }
+ template <class U = T,
+ detail::enable_if_t<!std::is_void<U>::value> * = nullptr>
+ constexpr const U &&operator*() const && {
+ return std::move(val());
+ }
+ template <class U = T,
+ detail::enable_if_t<!std::is_void<U>::value> * = nullptr>
+ TL_EXPECTED_11_CONSTEXPR U &&operator*() && {
+ return std::move(val());
+ }
+
+ constexpr bool has_value() const noexcept { return this->m_has_val; }
+ 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 & { return err().value(); }
+ TL_EXPECTED_11_CONSTEXPR E &error() & { return err().value(); }
+ constexpr const E &&error() const && { return std::move(err().value()); }
+ TL_EXPECTED_11_CONSTEXPR E &&error() && { 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));
+ }
+};
+
+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 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 tl
+
+#endif
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