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-rw-r--r--src/common/expected.h987
1 files changed, 987 insertions, 0 deletions
diff --git a/src/common/expected.h b/src/common/expected.h
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index 000000000..c8d8579c1
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+++ b/src/common/expected.h
@@ -0,0 +1,987 @@
+// Copyright 2021 yuzu Emulator Project
+// Licensed under GPLv2 or any later version
+// Refer to the license.txt file included.
+
+// This is based on the proposed implementation of std::expected (P0323)
+// https://github.com/TartanLlama/expected/blob/master/include/tl/expected.hpp
+
+#pragma once
+
+#include <type_traits>
+#include <utility>
+
+namespace Common {
+
+template <typename T, typename E>
+class Expected;
+
+template <typename E>
+class Unexpected {
+public:
+ Unexpected() = delete;
+
+ constexpr explicit Unexpected(const E& e) : m_val{e} {}
+
+ constexpr explicit Unexpected(E&& e) : m_val{std::move(e)} {}
+
+ constexpr E& value() & {
+ return m_val;
+ }
+
+ constexpr const E& value() const& {
+ return m_val;
+ }
+
+ constexpr E&& value() && {
+ return std::move(m_val);
+ }
+
+ constexpr const E&& value() const&& {
+ return std::move(m_val);
+ }
+
+private:
+ E m_val;
+};
+
+template <typename E>
+constexpr auto operator<=>(const Unexpected<E>& lhs, const Unexpected<E>& rhs) {
+ return lhs.value() <=> rhs.value();
+}
+
+struct unexpect_t {
+ constexpr explicit unexpect_t() = default;
+};
+
+namespace detail {
+
+struct no_init_t {
+ constexpr explicit no_init_t() = default;
+};
+
+/**
+ * This specialization is for when T is not trivially destructible,
+ * so the destructor must be called on destruction of `expected'
+ * Additionally, this requires E to be trivially destructible
+ */
+template <typename T, typename E, bool = std::is_trivially_destructible_v<T>>
+requires std::is_trivially_destructible_v<E>
+struct expected_storage_base {
+ constexpr expected_storage_base() : m_val{T{}}, m_has_val{true} {}
+
+ constexpr expected_storage_base(no_init_t) : m_has_val{false} {}
+
+ template <typename... Args, std::enable_if_t<std::is_constructible_v<T, Args&&...>>* = nullptr>
+ constexpr expected_storage_base(std::in_place_t, Args&&... args)
+ : m_val{std::forward<Args>(args)...}, m_has_val{true} {}
+
+ template <typename U, typename... Args,
+ std::enable_if_t<std::is_constructible_v<T, std::initializer_list<U>&, Args&&...>>* =
+ nullptr>
+ constexpr expected_storage_base(std::in_place_t, std::initializer_list<U> il, Args&&... args)
+ : m_val{il, std::forward<Args>(args)...}, m_has_val{true} {}
+
+ template <typename... Args, std::enable_if_t<std::is_constructible_v<E, Args&&...>>* = nullptr>
+ constexpr explicit expected_storage_base(unexpect_t, Args&&... args)
+ : m_unexpect{std::forward<Args>(args)...}, m_has_val{false} {}
+
+ template <typename U, typename... Args,
+ std::enable_if_t<std::is_constructible_v<E, std::initializer_list<U>&, Args&&...>>* =
+ 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;
+ };
+
+ bool m_has_val;
+};
+
+/**
+ * This specialization is for when T is trivially destructible,
+ * so the destructor of `expected` can be trivial
+ * Additionally, this requires E to be trivially destructible
+ */
+template <typename T, typename E>
+requires std::is_trivially_destructible_v<E>
+struct expected_storage_base<T, E, true> {
+ constexpr expected_storage_base() : m_val{T{}}, m_has_val{true} {}
+
+ constexpr expected_storage_base(no_init_t) : m_has_val{false} {}
+
+ template <typename... Args, std::enable_if_t<std::is_constructible_v<T, Args&&...>>* = nullptr>
+ constexpr expected_storage_base(std::in_place_t, Args&&... args)
+ : m_val{std::forward<Args>(args)...}, m_has_val{true} {}
+
+ template <typename U, typename... Args,
+ std::enable_if_t<std::is_constructible_v<T, std::initializer_list<U>&, Args&&...>>* =
+ nullptr>
+ constexpr expected_storage_base(std::in_place_t, std::initializer_list<U> il, Args&&... args)
+ : m_val{il, std::forward<Args>(args)...}, m_has_val{true} {}
+
+ template <typename... Args, std::enable_if_t<std::is_constructible_v<E, Args&&...>>* = nullptr>
+ constexpr explicit expected_storage_base(unexpect_t, Args&&... args)
+ : m_unexpect{std::forward<Args>(args)...}, m_has_val{false} {}
+
+ template <typename U, typename... Args,
+ std::enable_if_t<std::is_constructible_v<E, std::initializer_list<U>&, Args&&...>>* =
+ 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;
+ };
+
+ bool m_has_val;
+};
+
+template <typename T, typename E>
+struct expected_operations_base : expected_storage_base<T, E> {
+ using expected_storage_base<T, E>::expected_storage_base;
+
+ template <typename... Args>
+ void construct(Args&&... args) noexcept {
+ new (std::addressof(this->m_val)) T{std::forward<Args>(args)...};
+ this->m_has_val = true;
+ }
+
+ template <typename 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 <typename... Args>
+ void construct_error(Args&&... args) noexcept {
+ new (std::addressof(this->m_unexpect)) Unexpected<E>{std::forward<Args>(args)...};
+ this->m_has_val = false;
+ }
+
+ 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);
+ }
+ }
+
+ template <typename 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;
+ }
+
+ constexpr T& get() & {
+ return this->m_val;
+ }
+
+ constexpr const T& get() const& {
+ return this->m_val;
+ }
+
+ constexpr T&& get() && {
+ return std::move(this->m_val);
+ }
+
+ constexpr const T&& get() const&& {
+ return std::move(this->m_val);
+ }
+
+ constexpr Unexpected<E>& geterr() & {
+ return this->m_unexpect;
+ }
+
+ constexpr const Unexpected<E>& geterr() const& {
+ return this->m_unexpect;
+ }
+
+ constexpr Unexpected<E>&& geterr() && {
+ return std::move(this->m_unexpect);
+ }
+
+ constexpr const Unexpected<E>&& geterr() const&& {
+ return std::move(this->m_unexpect);
+ }
+
+ constexpr void destroy_val() {
+ get().~T();
+ }
+};
+
+/**
+ * This manages conditionally having a trivial copy constructor
+ * This specialization is for when T is trivially copy constructible
+ * Additionally, this requires E to be trivially copy constructible
+ */
+template <typename T, typename E, bool = std::is_trivially_copy_constructible_v<T>>
+requires std::is_trivially_copy_constructible_v<E>
+struct expected_copy_base : expected_operations_base<T, E> {
+ using expected_operations_base<T, E>::expected_operations_base;
+};
+
+/**
+ * This specialization is for when T is not trivially copy constructible
+ * Additionally, this requires E to be trivially copy constructible
+ */
+template <typename T, typename E>
+requires std::is_trivially_copy_constructible_v<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_t{}} {
+ if (rhs.has_value()) {
+ this->construct_with(rhs);
+ } else {
+ this->construct_error(rhs.geterr());
+ }
+ }
+
+ expected_copy_base(expected_copy_base&&) = default;
+
+ expected_copy_base& operator=(const expected_copy_base&) = default;
+
+ expected_copy_base& operator=(expected_copy_base&&) = default;
+};
+
+/**
+ * This manages conditionally having a trivial move constructor
+ * This specialization is for when T is trivially move constructible
+ * Additionally, this requires E to be trivially move constructible
+ */
+template <typename T, typename E, bool = std::is_trivially_move_constructible_v<T>>
+requires std::is_trivially_move_constructible_v<E>
+struct expected_move_base : expected_copy_base<T, E> {
+ using expected_copy_base<T, E>::expected_copy_base;
+};
+
+/**
+ * This specialization is for when T is not trivially move constructible
+ * Additionally, this requires E to be trivially move constructible
+ */
+template <typename T, typename E>
+requires std::is_trivially_move_constructible_v<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&) = default;
+
+ expected_move_base(expected_move_base&& rhs) noexcept(std::is_nothrow_move_constructible_v<T>)
+ : expected_copy_base<T, E>{no_init_t{}} {
+ 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&) = default;
+
+ expected_move_base& operator=(expected_move_base&&) = default;
+};
+
+/**
+ * This manages conditionally having a trivial copy assignment operator
+ * This specialization is for when T is trivially copy assignable
+ * Additionally, this requires E to be trivially copy assignable
+ */
+template <typename T, typename E,
+ bool = std::conjunction_v<std::is_trivially_copy_assignable<T>,
+ std::is_trivially_copy_constructible<T>,
+ std::is_trivially_destructible<T>>>
+requires std::conjunction_v<std::is_trivially_copy_assignable<E>,
+ std::is_trivially_copy_constructible<E>,
+ std::is_trivially_destructible<E>>
+struct expected_copy_assign_base : expected_move_base<T, E> {
+ using expected_move_base<T, E>::expected_move_base;
+};
+
+/**
+ * This specialization is for when T is not trivially copy assignable
+ * Additionally, this requires E to be trivially copy assignable
+ */
+template <typename T, typename E>
+requires std::conjunction_v<std::is_trivially_copy_assignable<E>,
+ std::is_trivially_copy_constructible<E>,
+ std::is_trivially_destructible<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&) = default;
+
+ expected_copy_assign_base(expected_copy_assign_base&&) = 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&&) = default;
+};
+
+/**
+ * This manages conditionally having a trivial move assignment operator
+ * This specialization is for when T is trivially move assignable
+ * Additionally, this requires E to be trivially move assignable
+ */
+template <typename T, typename E,
+ bool = std::conjunction_v<std::is_trivially_move_assignable<T>,
+ std::is_trivially_move_constructible<T>,
+ std::is_trivially_destructible<T>>>
+requires std::conjunction_v<std::is_trivially_move_assignable<E>,
+ std::is_trivially_move_constructible<E>,
+ std::is_trivially_destructible<E>>
+struct expected_move_assign_base : expected_copy_assign_base<T, E> {
+ using expected_copy_assign_base<T, E>::expected_copy_assign_base;
+};
+
+/**
+ * This specialization is for when T is not trivially move assignable
+ * Additionally, this requires E to be trivially move assignable
+ */
+template <typename T, typename E>
+requires std::conjunction_v<std::is_trivially_move_assignable<E>,
+ std::is_trivially_move_constructible<E>,
+ std::is_trivially_destructible<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&) = default;
+
+ expected_move_assign_base(expected_move_assign_base&&) = default;
+
+ expected_move_assign_base& operator=(const expected_move_assign_base&) = default;
+
+ expected_move_assign_base& operator=(expected_move_assign_base&& rhs) noexcept(
+ std::conjunction_v<std::is_nothrow_move_constructible<T>,
+ std::is_nothrow_move_assignable<T>>) {
+ 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
+ * Additionally, this requires E to be copy/move constructible
+ */
+template <typename T, typename E, bool EnableCopy = std::is_copy_constructible_v<T>,
+ bool EnableMove = std::is_move_constructible_v<T>>
+requires std::conjunction_v<std::is_copy_constructible<E>, std::is_move_constructible<E>>
+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 <typename T, typename E>
+requires std::conjunction_v<std::is_copy_constructible<E>, std::is_move_constructible<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 <typename T, typename E>
+requires std::conjunction_v<std::is_copy_constructible<E>, std::is_move_constructible<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 <typename T, typename E>
+requires std::conjunction_v<std::is_copy_constructible<E>, std::is_move_constructible<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 assignment operators
+ * depending on whether T is copy/move constructible + assignable
+ * Additionally, this requires E to be copy/move constructible + assignable
+ */
+template <
+ typename T, typename E,
+ bool EnableCopy = std::conjunction_v<std::is_copy_constructible<T>, std::is_copy_assignable<T>>,
+ bool EnableMove = std::conjunction_v<std::is_move_constructible<T>, std::is_move_assignable<T>>>
+requires std::conjunction_v<std::is_copy_constructible<E>, std::is_move_constructible<E>,
+ std::is_copy_assignable<E>, std::is_move_assignable<E>>
+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 <typename T, typename E>
+requires std::conjunction_v<std::is_copy_constructible<E>, std::is_move_constructible<E>,
+ std::is_copy_assignable<E>, std::is_move_assignable<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 <typename T, typename E>
+requires std::conjunction_v<std::is_copy_constructible<E>, std::is_move_constructible<E>,
+ std::is_copy_assignable<E>, std::is_move_assignable<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 <typename T, typename E>
+requires std::conjunction_v<std::is_copy_constructible<E>, std::is_move_constructible<E>,
+ std::is_copy_assignable<E>, std::is_move_assignable<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 {
+ constexpr explicit default_constructor_tag() = default;
+};
+
+/**
+ * expected_default_ctor_base will ensure that expected
+ * has a deleted default constructor if T is not default constructible
+ * This specialization is for when T is default constructible
+ */
+template <typename T, typename E, bool Enable = std::is_default_constructible_v<T>>
+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) {}
+};
+
+template <typename T, typename 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) {}
+};
+
+template <typename T, typename E, typename U>
+using expected_enable_forward_value =
+ std::enable_if_t<std::is_constructible_v<T, U&&> &&
+ !std::is_same_v<std::remove_cvref_t<U>, std::in_place_t> &&
+ !std::is_same_v<Expected<T, E>, std::remove_cvref_t<U>> &&
+ !std::is_same_v<Unexpected<E>, std::remove_cvref_t<U>>>;
+
+template <typename T, typename E, typename U, typename G, typename UR, typename GR>
+using expected_enable_from_other = std::enable_if_t<
+ std::is_constructible_v<T, UR> && std::is_constructible_v<E, GR> &&
+ !std::is_constructible_v<T, Expected<U, G>&> && !std::is_constructible_v<T, Expected<U, G>&&> &&
+ !std::is_constructible_v<T, const Expected<U, G>&> &&
+ !std::is_constructible_v<T, const Expected<U, G>&&> &&
+ !std::is_convertible_v<Expected<U, G>&, T> && !std::is_convertible_v<Expected<U, G>&&, T> &&
+ !std::is_convertible_v<const Expected<U, G>&, T> &&
+ !std::is_convertible_v<const Expected<U, G>&&, T>>;
+
+} // namespace detail
+
+template <typename T, typename 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> {
+public:
+ using value_type = T;
+ using error_type = E;
+ using unexpected_type = Unexpected<E>;
+
+ constexpr Expected() = default;
+ constexpr Expected(const Expected&) = default;
+ constexpr Expected(Expected&&) = default;
+ Expected& operator=(const Expected&) = default;
+ Expected& operator=(Expected&&) = default;
+
+ template <typename... Args, std::enable_if_t<std::is_constructible_v<T, Args&&...>>* = nullptr>
+ constexpr Expected(std::in_place_t, Args&&... args)
+ : impl_base{std::in_place, std::forward<Args>(args)...},
+ ctor_base{detail::default_constructor_tag{}} {}
+
+ template <typename U, typename... Args,
+ std::enable_if_t<std::is_constructible_v<T, std::initializer_list<U>&, Args&&...>>* =
+ nullptr>
+ constexpr Expected(std::in_place_t, std::initializer_list<U> il, Args&&... args)
+ : impl_base{std::in_place, il, std::forward<Args>(args)...},
+ ctor_base{detail::default_constructor_tag{}} {}
+
+ template <typename G = E, std::enable_if_t<std::is_constructible_v<E, const G&>>* = nullptr,
+ std::enable_if_t<!std::is_convertible_v<const G&, E>>* = nullptr>
+ constexpr explicit Expected(const Unexpected<G>& e)
+ : impl_base{unexpect_t{}, e.value()}, ctor_base{detail::default_constructor_tag{}} {}
+
+ template <typename G = E, std::enable_if_t<std::is_constructible_v<E, const G&>>* = nullptr,
+ std::enable_if_t<std::is_convertible_v<const G&, E>>* = nullptr>
+ constexpr Expected(Unexpected<G> const& e)
+ : impl_base{unexpect_t{}, e.value()}, ctor_base{detail::default_constructor_tag{}} {}
+
+ template <typename G = E, std::enable_if_t<std::is_constructible_v<E, G&&>>* = nullptr,
+ std::enable_if_t<!std::is_convertible_v<G&&, E>>* = nullptr>
+ constexpr explicit Expected(Unexpected<G>&& e) noexcept(std::is_nothrow_constructible_v<E, G&&>)
+ : impl_base{unexpect_t{}, std::move(e.value())}, ctor_base{
+ detail::default_constructor_tag{}} {}
+
+ template <typename G = E, std::enable_if_t<std::is_constructible_v<E, G&&>>* = nullptr,
+ std::enable_if_t<std::is_convertible_v<G&&, E>>* = nullptr>
+ constexpr Expected(Unexpected<G>&& e) noexcept(std::is_nothrow_constructible_v<E, G&&>)
+ : impl_base{unexpect_t{}, std::move(e.value())}, ctor_base{
+ detail::default_constructor_tag{}} {}
+
+ template <typename... Args, std::enable_if_t<std::is_constructible_v<E, Args&&...>>* = nullptr>
+ constexpr explicit Expected(unexpect_t, Args&&... args)
+ : impl_base{unexpect_t{}, std::forward<Args>(args)...},
+ ctor_base{detail::default_constructor_tag{}} {}
+
+ template <typename U, typename... Args,
+ std::enable_if_t<std::is_constructible_v<E, std::initializer_list<U>&, Args&&...>>* =
+ nullptr>
+ constexpr explicit Expected(unexpect_t, std::initializer_list<U> il, Args&&... args)
+ : impl_base{unexpect_t{}, il, std::forward<Args>(args)...},
+ ctor_base{detail::default_constructor_tag{}} {}
+
+ template <typename U, typename G,
+ std::enable_if_t<!(std::is_convertible_v<U const&, T> &&
+ std::is_convertible_v<G const&, E>)>* = nullptr,
+ detail::expected_enable_from_other<T, E, U, G, const U&, const G&>* = nullptr>
+ constexpr explicit 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 <typename U, typename G,
+ std::enable_if_t<(std::is_convertible_v<U const&, T> &&
+ std::is_convertible_v<G const&, E>)>* = nullptr,
+ detail::expected_enable_from_other<T, E, U, G, const U&, const G&>* = nullptr>
+ 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 <typename U, typename G,
+ std::enable_if_t<!(std::is_convertible_v<U&&, T> && std::is_convertible_v<G&&, E>)>* =
+ nullptr,
+ detail::expected_enable_from_other<T, E, U, G, U&&, G&&>* = nullptr>
+ constexpr explicit 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 <typename U, typename G,
+ std::enable_if_t<(std::is_convertible_v<U&&, T> && std::is_convertible_v<G&&, E>)>* =
+ nullptr,
+ detail::expected_enable_from_other<T, E, U, G, U&&, G&&>* = nullptr>
+ 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 <typename U = T, std::enable_if_t<!std::is_convertible_v<U&&, T>>* = nullptr,
+ detail::expected_enable_forward_value<T, E, U>* = nullptr>
+ constexpr explicit Expected(U&& v) : Expected{std::in_place, std::forward<U>(v)} {}
+
+ template <typename U = T, std::enable_if_t<std::is_convertible_v<U&&, T>>* = nullptr,
+ detail::expected_enable_forward_value<T, E, U>* = nullptr>
+ constexpr Expected(U&& v) : Expected{std::in_place, std::forward<U>(v)} {}
+
+ template <typename U = T, typename G = T,
+ std::enable_if_t<std::is_nothrow_constructible_v<T, U&&>>* = nullptr,
+ std::enable_if_t<(
+ !std::is_same_v<Expected<T, E>, std::remove_cvref_t<U>> &&
+ !std::conjunction_v<std::is_scalar<T>, std::is_same<T, std::remove_cvref_t<U>>> &&
+ std::is_constructible_v<T, U> && std::is_assignable_v<G&, U> &&
+ std::is_nothrow_move_constructible_v<E>)>* = 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 <typename U = T, typename G = T,
+ std::enable_if_t<!std::is_nothrow_constructible_v<T, U&&>>* = nullptr,
+ std::enable_if_t<(
+ !std::is_same_v<Expected<T, E>, std::remove_cvref_t<U>> &&
+ !std::conjunction_v<std::is_scalar<T>, std::is_same<T, std::remove_cvref_t<U>>> &&
+ std::is_constructible_v<T, U> && std::is_assignable_v<G&, U> &&
+ std::is_nothrow_move_constructible_v<E>)>* = nullptr>
+ Expected& operator=(U&& v) {
+ if (has_value()) {
+ val() = std::forward<U>(v);
+ } else {
+ auto tmp = std::move(err());
+ err().~Unexpected<E>();
+ new (valptr()) T{std::forward<U>(v)};
+ this->m_has_val = true;
+ }
+
+ return *this;
+ }
+
+ template <typename G = E, std::enable_if_t<std::is_nothrow_copy_constructible_v<G> &&
+ std::is_assignable_v<G&, G>>* = 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 <typename G = E, std::enable_if_t<std::is_nothrow_move_constructible_v<G> &&
+ std::is_move_assignable_v<G>>* = 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 <typename... Args,
+ std::enable_if_t<std::is_nothrow_constructible_v<T, Args&&...>>* = 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 <typename... Args,
+ std::enable_if_t<!std::is_nothrow_constructible_v<T, Args&&...>>* = nullptr>
+ void emplace(Args&&... args) {
+ if (has_value()) {
+ val() = T{std::forward<Args>(args)...};
+ } else {
+ auto tmp = std::move(err());
+ err().~Unexpected<E>();
+ new (valptr()) T{std::forward<Args>(args)...};
+ this->m_has_val = true;
+ }
+ }
+
+ template <typename U, typename... Args,
+ std::enable_if_t<std::is_nothrow_constructible_v<T, std::initializer_list<U>&,
+ Args&&...>>* = 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 <typename U, typename... Args,
+ std::enable_if_t<!std::is_nothrow_constructible_v<T, std::initializer_list<U>&,
+ Args&&...>>* = 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>();
+ new (valptr()) T{il, std::forward<Args>(args)...};
+ this->m_has_val = true;
+ }
+ }
+
+ constexpr T* operator->() {
+ return valptr();
+ }
+
+ constexpr const T* operator->() const {
+ return valptr();
+ }
+
+ template <typename U = T>
+ constexpr U& operator*() & {
+ return val();
+ }
+
+ template <typename U = T>
+ constexpr const U& operator*() const& {
+ return val();
+ }
+
+ template <typename U = T>
+ constexpr U&& operator*() && {
+ return std::move(val());
+ }
+
+ template <typename U = T>
+ constexpr const U&& operator*() const&& {
+ 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 <typename U = T>
+ constexpr U& value() & {
+ return val();
+ }
+
+ template <typename U = T>
+ constexpr const U& value() const& {
+ return val();
+ }
+
+ template <typename U = T>
+ constexpr U&& value() && {
+ return std::move(val());
+ }
+
+ template <typename U = T>
+ constexpr const U&& value() const&& {
+ return std::move(val());
+ }
+
+ constexpr E& error() & {
+ return err().value();
+ }
+
+ constexpr const E& error() const& {
+ return err().value();
+ }
+
+ constexpr E&& error() && {
+ return std::move(err().value());
+ }
+
+ constexpr const E&& error() const&& {
+ return std::move(err().value());
+ }
+
+ template <typename U>
+ constexpr T value_or(U&& v) const& {
+ static_assert(std::is_copy_constructible_v<T> && std::is_convertible_v<U&&, T>,
+ "T must be copy-constructible and convertible from U&&");
+ return bool(*this) ? **this : static_cast<T>(std::forward<U>(v));
+ }
+
+ template <typename U>
+ constexpr T value_or(U&& v) && {
+ static_assert(std::is_move_constructible_v<T> && std::is_convertible_v<U&&, T>,
+ "T must be move-constructible and convertible from U&&");
+ return bool(*this) ? std::move(**this) : static_cast<T>(std::forward<U>(v));
+ }
+
+private:
+ static_assert(!std::is_reference_v<T>, "T must not be a reference");
+ static_assert(!std::is_same_v<T, std::remove_cv_t<std::in_place_t>>,
+ "T must not be std::in_place_t");
+ static_assert(!std::is_same_v<T, std::remove_cv_t<unexpect_t>>, "T must not be unexpect_t");
+ static_assert(!std::is_same_v<T, std::remove_cv_t<Unexpected<E>>>,
+ "T must not be Unexpected<E>");
+ static_assert(!std::is_reference_v<E>, "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 <typename U = T>
+ constexpr U& val() {
+ return this->m_val;
+ }
+
+ template <typename U = T>
+ constexpr const U& val() const {
+ return this->m_val;
+ }
+
+ constexpr Unexpected<E>& err() {
+ return this->m_unexpect;
+ }
+
+ 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>;
+};
+
+template <typename T, typename E, typename U, typename 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 <typename T, typename E, typename U, typename F>
+constexpr bool operator!=(const Expected<T, E>& lhs, const Expected<U, F>& rhs) {
+ return !operator==(lhs, rhs);
+}
+
+template <typename T, typename E, typename U>
+constexpr bool operator==(const Expected<T, E>& x, const U& v) {
+ return x.has_value() ? *x == v : false;
+}
+
+template <typename T, typename E, typename U>
+constexpr bool operator==(const U& v, const Expected<T, E>& x) {
+ return x.has_value() ? *x == v : false;
+}
+
+template <typename T, typename E, typename U>
+constexpr bool operator!=(const Expected<T, E>& x, const U& v) {
+ return !operator==(x, v);
+}
+
+template <typename T, typename E, typename U>
+constexpr bool operator!=(const U& v, const Expected<T, E>& x) {
+ return !operator==(v, x);
+}
+
+template <typename T, typename E>
+constexpr bool operator==(const Expected<T, E>& x, const Unexpected<E>& e) {
+ return x.has_value() ? false : x.error() == e.value();
+}
+
+template <typename T, typename E>
+constexpr bool operator==(const Unexpected<E>& e, const Expected<T, E>& x) {
+ return x.has_value() ? false : x.error() == e.value();
+}
+
+template <typename T, typename E>
+constexpr bool operator!=(const Expected<T, E>& x, const Unexpected<E>& e) {
+ return !operator==(x, e);
+}
+
+template <typename T, typename E>
+constexpr bool operator!=(const Unexpected<E>& e, const Expected<T, E>& x) {
+ return !operator==(e, x);
+}
+
+} // namespace Common