blob: 9470344e8b831c4dffbb587572c1b3cf47d1fadf [file] [log] [blame]
/*
* Copyright (C) 2019 The Android Open Source Project
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
#pragma once
#include <algorithm>
#include <initializer_list>
#include <type_traits>
#include <utility>
#include <variant>
// android::base::expected is an Android implementation of the std::expected
// proposal.
// http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2018/p0323r7.html
//
// Usage:
// using android::base::expected;
// using android::base::unexpected;
//
// expected<double,std::string> safe_divide(double i, double j) {
// if (j == 0) return unexpected("divide by zero");
// else return i / j;
// }
//
// void test() {
// auto q = safe_divide(10, 0);
// if (q) { printf("%f\n", q.value()); }
// else { printf("%s\n", q.error().c_str()); }
// }
//
// When the proposal becomes part of the standard and is implemented by
// libcxx, this will be removed and android::base::expected will be
// type alias to std::expected.
//
namespace android {
namespace base {
// Synopsis
template<class T, class E>
class expected;
template<class E>
class unexpected;
template<class E>
unexpected(E) -> unexpected<E>;
template<class E>
class bad_expected_access;
template<>
class bad_expected_access<void>;
struct unexpect_t {
explicit unexpect_t() = default;
};
inline constexpr unexpect_t unexpect{};
// macros for SFINAE
#define _ENABLE_IF(...) \
, std::enable_if_t<(__VA_ARGS__)>* = nullptr
// Define NODISCARD_EXPECTED to prevent expected<T,E> from being
// ignored when used as a return value. This is off by default.
#ifdef NODISCARD_EXPECTED
#define _NODISCARD_ [[nodiscard]]
#else
#define _NODISCARD_
#endif
// Class expected
template<class T, class E>
class _NODISCARD_ expected {
public:
using value_type = T;
using error_type = E;
using unexpected_type = unexpected<E>;
template<class U>
using rebind = expected<U, error_type>;
// constructors
constexpr expected() = default;
constexpr expected(const expected& rhs) = default;
constexpr expected(expected&& rhs) noexcept = default;
template<class U, class G _ENABLE_IF(
std::is_constructible_v<T, const U&> &&
std::is_constructible_v<E, const G&> &&
!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> &&
!(!std::is_convertible_v<const U&, T> ||
!std::is_convertible_v<const G&, E>) /* non-explicit */
)>
// NOLINTNEXTLINE(google-explicit-constructor)
constexpr expected(const expected<U, G>& rhs) {
if (rhs.has_value()) var_ = rhs.value();
else var_ = unexpected(rhs.error());
}
template<class U, class G _ENABLE_IF(
std::is_constructible_v<T, const U&> &&
std::is_constructible_v<E, const G&> &&
!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> &&
(!std::is_convertible_v<const U&, T> ||
!std::is_convertible_v<const G&, E>) /* explicit */
)>
constexpr explicit expected(const expected<U, G>& rhs) {
if (rhs.has_value()) var_ = rhs.value();
else var_ = unexpected(rhs.error());
}
template<class U, class G _ENABLE_IF(
std::is_constructible_v<T, const U&> &&
std::is_constructible_v<E, const G&> &&
!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> &&
!(!std::is_convertible_v<const U&, T> ||
!std::is_convertible_v<const G&, E>) /* non-explicit */
)>
// NOLINTNEXTLINE(google-explicit-constructor)
constexpr expected(expected<U, G>&& rhs) {
if (rhs.has_value()) var_ = std::move(rhs.value());
else var_ = unexpected(std::move(rhs.error()));
}
template<class U, class G _ENABLE_IF(
std::is_constructible_v<T, const U&> &&
std::is_constructible_v<E, const G&> &&
!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> &&
(!std::is_convertible_v<const U&, T> ||
!std::is_convertible_v<const G&, E>) /* explicit */
)>
constexpr explicit expected(expected<U, G>&& rhs) {
if (rhs.has_value()) var_ = std::move(rhs.value());
else var_ = unexpected(std::move(rhs.error()));
}
template <class U = T _ENABLE_IF(
std::is_constructible_v<T, U&&> &&
!std::is_same_v<std::remove_cv_t<std::remove_reference_t<U>>, std::in_place_t> &&
!std::is_same_v<expected<T, E>, std::remove_cv_t<std::remove_reference_t<U>>> &&
!std::is_same_v<unexpected<E>, std::remove_cv_t<std::remove_reference_t<U>>> &&
std::is_convertible_v<U&&, T> /* non-explicit */
)>
// NOLINTNEXTLINE(google-explicit-constructor,bugprone-forwarding-reference-overload)
constexpr expected(U&& v) : var_(std::in_place_index<0>, std::forward<U>(v)) {}
template <class U = T _ENABLE_IF(
std::is_constructible_v<T, U&&> &&
!std::is_same_v<std::remove_cv_t<std::remove_reference_t<U>>, std::in_place_t> &&
!std::is_same_v<expected<T, E>, std::remove_cv_t<std::remove_reference_t<U>>> &&
!std::is_same_v<unexpected<E>, std::remove_cv_t<std::remove_reference_t<U>>> &&
!std::is_convertible_v<U&&, T> /* explicit */
)>
// NOLINTNEXTLINE(bugprone-forwarding-reference-overload)
constexpr explicit expected(U&& v) : var_(std::in_place_index<0>, T(std::forward<U>(v))) {}
template<class G = E _ENABLE_IF(
std::is_constructible_v<E, const G&> &&
std::is_convertible_v<const G&, E> /* non-explicit */
)>
// NOLINTNEXTLINE(google-explicit-constructor)
constexpr expected(const unexpected<G>& e)
: var_(std::in_place_index<1>, e.value()) {}
template<class G = E _ENABLE_IF(
std::is_constructible_v<E, const G&> &&
!std::is_convertible_v<const G&, E> /* explicit */
)>
constexpr explicit expected(const unexpected<G>& e)
: var_(std::in_place_index<1>, E(e.value())) {}
template<class G = E _ENABLE_IF(
std::is_constructible_v<E, G&&> &&
std::is_convertible_v<G&&, E> /* non-explicit */
)>
// NOLINTNEXTLINE(google-explicit-constructor)
constexpr expected(unexpected<G>&& e)
: var_(std::in_place_index<1>, std::move(e.value())) {}
template<class G = E _ENABLE_IF(
std::is_constructible_v<E, G&&> &&
!std::is_convertible_v<G&&, E> /* explicit */
)>
constexpr explicit expected(unexpected<G>&& e)
: var_(std::in_place_index<1>, E(std::move(e.value()))) {}
template<class... Args _ENABLE_IF(
std::is_constructible_v<T, Args&&...>
)>
constexpr explicit expected(std::in_place_t, Args&&... args)
: var_(std::in_place_index<0>, std::forward<Args>(args)...) {}
template<class U, class... Args _ENABLE_IF(
std::is_constructible_v<T, std::initializer_list<U>&, Args...>
)>
constexpr explicit expected(std::in_place_t, std::initializer_list<U> il, Args&&... args)
: var_(std::in_place_index<0>, il, std::forward<Args>(args)...) {}
template<class... Args _ENABLE_IF(
std::is_constructible_v<E, Args...>
)>
constexpr explicit expected(unexpect_t, Args&&... args)
: var_(unexpected_type(std::forward<Args>(args)...)) {}
template<class U, class... Args _ENABLE_IF(
std::is_constructible_v<E, std::initializer_list<U>&, Args...>
)>
constexpr explicit expected(unexpect_t, std::initializer_list<U> il, Args&&... args)
: var_(unexpected_type(il, std::forward<Args>(args)...)) {}
// destructor
~expected() = default;
// assignment
// Note: SFNAIE doesn't work here because assignment operator should be
// non-template. We could workaround this by defining a templated parent class
// having the assignment operator. This incomplete implementation however
// doesn't allow us to copy assign expected<T,E> even when T is non-copy
// assignable. The copy assignment will fail by the underlying std::variant
// anyway though the error message won't be clear.
expected& operator=(const expected& rhs) = default;
// Note for SFNAIE above applies to here as well
expected& operator=(expected&& rhs) noexcept(
std::is_nothrow_move_assignable_v<T>&& std::is_nothrow_move_assignable_v<E>) = default;
template <class U = T _ENABLE_IF(
!std::is_void_v<T> &&
!std::is_same_v<expected<T, E>, std::remove_cv_t<std::remove_reference_t<U>>> &&
!std::conjunction_v<std::is_scalar<T>, std::is_same<T, std::decay_t<U>>> &&
std::is_constructible_v<T, U> && std::is_assignable_v<T&, U> &&
std::is_nothrow_move_constructible_v<E>)>
expected& operator=(U&& rhs) {
var_ = T(std::forward<U>(rhs));
return *this;
}
template<class G = E>
expected& operator=(const unexpected<G>& rhs) {
var_ = rhs;
return *this;
}
template<class G = E _ENABLE_IF(
std::is_nothrow_move_constructible_v<G> &&
std::is_move_assignable_v<G>
)>
expected& operator=(unexpected<G>&& rhs) {
var_ = std::move(rhs);
return *this;
}
// modifiers
template<class... Args _ENABLE_IF(
std::is_nothrow_constructible_v<T, Args...>
)>
T& emplace(Args&&... args) {
expected(std::in_place, std::forward<Args>(args)...).swap(*this);
return value();
}
template<class U, class... Args _ENABLE_IF(
std::is_nothrow_constructible_v<T, std::initializer_list<U>&, Args...>
)>
T& emplace(std::initializer_list<U> il, Args&&... args) {
expected(std::in_place, il, std::forward<Args>(args)...).swap(*this);
return value();
}
// swap
template<typename U = T, typename = std::enable_if_t<(
std::is_swappable_v<U> &&
std::is_swappable_v<E> &&
(std::is_move_constructible_v<U> ||
std::is_move_constructible_v<E>))>>
void swap(expected& rhs) noexcept(
std::is_nothrow_move_constructible_v<T> &&
std::is_nothrow_swappable_v<T> &&
std::is_nothrow_move_constructible_v<E> &&
std::is_nothrow_swappable_v<E>) {
var_.swap(rhs.var_);
}
// observers
constexpr const T* operator->() const { return std::addressof(value()); }
constexpr T* operator->() { return std::addressof(value()); }
constexpr const T& operator*() const& { return value(); }
constexpr T& operator*() & { return value(); }
constexpr const T&& operator*() const&& { return std::move(std::get<T>(var_)); }
constexpr T&& operator*() && { return std::move(std::get<T>(var_)); }
constexpr explicit operator bool() const noexcept { return has_value(); }
constexpr bool has_value() const noexcept { return var_.index() == 0; }
constexpr bool ok() const noexcept { return has_value(); }
constexpr const T& value() const& { return std::get<T>(var_); }
constexpr T& value() & { return std::get<T>(var_); }
constexpr const T&& value() const&& { return std::move(std::get<T>(var_)); }
constexpr T&& value() && { return std::move(std::get<T>(var_)); }
constexpr const E& error() const& { return std::get<unexpected_type>(var_).value(); }
constexpr E& error() & { return std::get<unexpected_type>(var_).value(); }
constexpr const E&& error() const&& { return std::move(std::get<unexpected_type>(var_)).value(); }
constexpr E&& error() && { return std::move(std::get<unexpected_type>(var_)).value(); }
template<class U _ENABLE_IF(
std::is_copy_constructible_v<T> &&
std::is_convertible_v<U, T>
)>
constexpr T value_or(U&& v) const& {
if (has_value()) return value();
else return static_cast<T>(std::forward<U>(v));
}
template<class U _ENABLE_IF(
std::is_move_constructible_v<T> &&
std::is_convertible_v<U, T>
)>
constexpr T value_or(U&& v) && {
if (has_value()) return std::move(value());
else return static_cast<T>(std::forward<U>(v));
}
// expected equality operators
template<class T1, class E1, class T2, class E2>
friend constexpr bool operator==(const expected<T1, E1>& x, const expected<T2, E2>& y);
template<class T1, class E1, class T2, class E2>
friend constexpr bool operator!=(const expected<T1, E1>& x, const expected<T2, E2>& y);
// Comparison with unexpected<E>
template<class T1, class E1, class E2>
friend constexpr bool operator==(const expected<T1, E1>&, const unexpected<E2>&);
template<class T1, class E1, class E2>
friend constexpr bool operator==(const unexpected<E2>&, const expected<T1, E1>&);
template<class T1, class E1, class E2>
friend constexpr bool operator!=(const expected<T1, E1>&, const unexpected<E2>&);
template<class T1, class E1, class E2>
friend constexpr bool operator!=(const unexpected<E2>&, const expected<T1, E1>&);
// Specialized algorithms
template<class T1, class E1>
friend void swap(expected<T1, E1>&, expected<T1, E1>&) noexcept;
private:
std::variant<value_type, unexpected_type> var_;
};
template<class T1, class E1, class T2, class E2>
constexpr bool operator==(const expected<T1, E1>& x, const expected<T2, E2>& y) {
if (x.has_value() != y.has_value()) return false;
if (!x.has_value()) return x.error() == y.error();
return *x == *y;
}
template<class T1, class E1, class T2, class E2>
constexpr bool operator!=(const expected<T1, E1>& x, const expected<T2, E2>& y) {
return !(x == y);
}
// Comparison with unexpected<E>
template<class T1, class E1, class E2>
constexpr bool operator==(const expected<T1, E1>& x, const unexpected<E2>& y) {
return !x.has_value() && (x.error() == y.value());
}
template<class T1, class E1, class E2>
constexpr bool operator==(const unexpected<E2>& x, const expected<T1, E1>& y) {
return !y.has_value() && (x.value() == y.error());
}
template<class T1, class E1, class E2>
constexpr bool operator!=(const expected<T1, E1>& x, const unexpected<E2>& y) {
return x.has_value() || (x.error() != y.value());
}
template<class T1, class E1, class E2>
constexpr bool operator!=(const unexpected<E2>& x, const expected<T1, E1>& y) {
return y.has_value() || (x.value() != y.error());
}
template<class E>
class _NODISCARD_ expected<void, E> {
public:
using value_type = void;
using error_type = E;
using unexpected_type = unexpected<E>;
// constructors
constexpr expected() = default;
constexpr expected(const expected& rhs) = default;
constexpr expected(expected&& rhs) noexcept = default;
template<class U, class G _ENABLE_IF(
std::is_void_v<U> &&
std::is_convertible_v<const G&, E> /* non-explicit */
)>
// NOLINTNEXTLINE(google-explicit-constructor)
constexpr expected(const expected<U, G>& rhs) {
if (!rhs.has_value()) var_ = unexpected(rhs.error());
}
template<class U, class G _ENABLE_IF(
std::is_void_v<U> &&
!std::is_convertible_v<const G&, E> /* explicit */
)>
constexpr explicit expected(const expected<U, G>& rhs) {
if (!rhs.has_value()) var_ = unexpected(rhs.error());
}
template<class U, class G _ENABLE_IF(
std::is_void_v<U> &&
std::is_convertible_v<const G&&, E> /* non-explicit */
)>
// NOLINTNEXTLINE(google-explicit-constructor)
constexpr expected(expected<U, G>&& rhs) {
if (!rhs.has_value()) var_ = unexpected(std::move(rhs.error()));
}
template<class U, class G _ENABLE_IF(
std::is_void_v<U> &&
!std::is_convertible_v<const G&&, E> /* explicit */
)>
constexpr explicit expected(expected<U, G>&& rhs) {
if (!rhs.has_value()) var_ = unexpected(std::move(rhs.error()));
}
template<class G = E _ENABLE_IF(
std::is_constructible_v<E, const G&> &&
std::is_convertible_v<const G&, E> /* non-explicit */
)>
// NOLINTNEXTLINE(google-explicit-constructor)
constexpr expected(const unexpected<G>& e)
: var_(std::in_place_index<1>, e.value()) {}
template<class G = E _ENABLE_IF(
std::is_constructible_v<E, const G&> &&
!std::is_convertible_v<const G&, E> /* explicit */
)>
constexpr explicit expected(const unexpected<G>& e)
: var_(std::in_place_index<1>, E(e.value())) {}
template<class G = E _ENABLE_IF(
std::is_constructible_v<E, G&&> &&
std::is_convertible_v<G&&, E> /* non-explicit */
)>
// NOLINTNEXTLINE(google-explicit-constructor)
constexpr expected(unexpected<G>&& e)
: var_(std::in_place_index<1>, std::move(e.value())) {}
template<class G = E _ENABLE_IF(
std::is_constructible_v<E, G&&> &&
!std::is_convertible_v<G&&, E> /* explicit */
)>
constexpr explicit expected(unexpected<G>&& e)
: var_(std::in_place_index<1>, E(std::move(e.value()))) {}
template<class... Args _ENABLE_IF(
sizeof...(Args) == 0
)>
constexpr explicit expected(std::in_place_t, Args&&...) {}
template<class... Args _ENABLE_IF(
std::is_constructible_v<E, Args...>
)>
constexpr explicit expected(unexpect_t, Args&&... args)
: var_(unexpected_type(std::forward<Args>(args)...)) {}
template<class U, class... Args _ENABLE_IF(
std::is_constructible_v<E, std::initializer_list<U>&, Args...>
)>
constexpr explicit expected(unexpect_t, std::initializer_list<U> il, Args&&... args)
: var_(unexpected_type(il, std::forward<Args>(args)...)) {}
// destructor
~expected() = default;
// assignment
// Note: SFNAIE doesn't work here because assignment operator should be
// non-template. We could workaround this by defining a templated parent class
// having the assignment operator. This incomplete implementation however
// doesn't allow us to copy assign expected<T,E> even when T is non-copy
// assignable. The copy assignment will fail by the underlying std::variant
// anyway though the error message won't be clear.
expected& operator=(const expected& rhs) = default;
// Note for SFNAIE above applies to here as well
expected& operator=(expected&& rhs) noexcept(std::is_nothrow_move_assignable_v<E>) = default;
template<class G = E>
expected& operator=(const unexpected<G>& rhs) {
var_ = rhs;
return *this;
}
template<class G = E _ENABLE_IF(
std::is_nothrow_move_constructible_v<G> &&
std::is_move_assignable_v<G>
)>
expected& operator=(unexpected<G>&& rhs) {
var_ = std::move(rhs);
return *this;
}
// modifiers
void emplace() {
var_ = std::monostate();
}
// swap
template<typename = std::enable_if_t<
std::is_swappable_v<E>>
>
void swap(expected& rhs) noexcept(std::is_nothrow_move_constructible_v<E>) {
var_.swap(rhs.var_);
}
// observers
constexpr explicit operator bool() const noexcept { return has_value(); }
constexpr bool has_value() const noexcept { return var_.index() == 0; }
constexpr bool ok() const noexcept { return has_value(); }
constexpr void value() const& { if (!has_value()) std::get<0>(var_); }
constexpr const E& error() const& { return std::get<unexpected_type>(var_).value(); }
constexpr E& error() & { return std::get<unexpected_type>(var_).value(); }
constexpr const E&& error() const&& { return std::move(std::get<unexpected_type>(var_)).value(); }
constexpr E&& error() && { return std::move(std::get<unexpected_type>(var_)).value(); }
// expected equality operators
template<class E1, class E2>
friend constexpr bool operator==(const expected<void, E1>& x, const expected<void, E2>& y);
// Specialized algorithms
template<class T1, class E1>
friend void swap(expected<T1, E1>&, expected<T1, E1>&) noexcept;
private:
std::variant<std::monostate, unexpected_type> var_;
};
template<class E1, class E2>
constexpr bool operator==(const expected<void, E1>& x, const expected<void, E2>& y) {
if (x.has_value() != y.has_value()) return false;
if (!x.has_value()) return x.error() == y.error();
return true;
}
template<class T1, class E1, class E2>
constexpr bool operator==(const expected<T1, E1>& x, const expected<void, E2>& y) {
if (x.has_value() != y.has_value()) return false;
if (!x.has_value()) return x.error() == y.error();
return false;
}
template<class E1, class T2, class E2>
constexpr bool operator==(const expected<void, E1>& x, const expected<T2, E2>& y) {
if (x.has_value() != y.has_value()) return false;
if (!x.has_value()) return x.error() == y.error();
return false;
}
template<class E>
class unexpected {
public:
// constructors
constexpr unexpected(const unexpected&) = default;
constexpr unexpected(unexpected&&) noexcept(std::is_nothrow_move_constructible_v<E>) = default;
template <class Err = E _ENABLE_IF(
std::is_constructible_v<E, Err> &&
!std::is_same_v<std::remove_cv_t<std::remove_reference_t<E>>, std::in_place_t> &&
!std::is_same_v<std::remove_cv_t<std::remove_reference_t<E>>, unexpected>)>
// NOLINTNEXTLINE(google-explicit-constructor,bugprone-forwarding-reference-overload)
constexpr unexpected(Err&& e) : val_(std::forward<Err>(e)) {}
template<class U, class... Args _ENABLE_IF(
std::is_constructible_v<E, std::initializer_list<U>&, Args...>
)>
constexpr explicit unexpected(std::in_place_t, std::initializer_list<U> il, Args&&... args)
: val_(il, std::forward<Args>(args)...) {}
template<class Err _ENABLE_IF(
std::is_constructible_v<E, Err> &&
!std::is_constructible_v<E, unexpected<Err>&> &&
!std::is_constructible_v<E, unexpected<Err>> &&
!std::is_constructible_v<E, const unexpected<Err>&> &&
!std::is_constructible_v<E, const unexpected<Err>> &&
!std::is_convertible_v<unexpected<Err>&, E> &&
!std::is_convertible_v<unexpected<Err>, E> &&
!std::is_convertible_v<const unexpected<Err>&, E> &&
!std::is_convertible_v<const unexpected<Err>, E> &&
std::is_convertible_v<Err, E> /* non-explicit */
)>
// NOLINTNEXTLINE(google-explicit-constructor)
constexpr unexpected(const unexpected<Err>& rhs)
: val_(rhs.value()) {}
template<class Err _ENABLE_IF(
std::is_constructible_v<E, Err> &&
!std::is_constructible_v<E, unexpected<Err>&> &&
!std::is_constructible_v<E, unexpected<Err>> &&
!std::is_constructible_v<E, const unexpected<Err>&> &&
!std::is_constructible_v<E, const unexpected<Err>> &&
!std::is_convertible_v<unexpected<Err>&, E> &&
!std::is_convertible_v<unexpected<Err>, E> &&
!std::is_convertible_v<const unexpected<Err>&, E> &&
!std::is_convertible_v<const unexpected<Err>, E> &&
!std::is_convertible_v<Err, E> /* explicit */
)>
constexpr explicit unexpected(const unexpected<Err>& rhs)
: val_(E(rhs.value())) {}
template<class Err _ENABLE_IF(
std::is_constructible_v<E, Err> &&
!std::is_constructible_v<E, unexpected<Err>&> &&
!std::is_constructible_v<E, unexpected<Err>> &&
!std::is_constructible_v<E, const unexpected<Err>&> &&
!std::is_constructible_v<E, const unexpected<Err>> &&
!std::is_convertible_v<unexpected<Err>&, E> &&
!std::is_convertible_v<unexpected<Err>, E> &&
!std::is_convertible_v<const unexpected<Err>&, E> &&
!std::is_convertible_v<const unexpected<Err>, E> &&
std::is_convertible_v<Err, E> /* non-explicit */
)>
// NOLINTNEXTLINE(google-explicit-constructor)
constexpr unexpected(unexpected<Err>&& rhs)
: val_(std::move(rhs.value())) {}
template<class Err _ENABLE_IF(
std::is_constructible_v<E, Err> &&
!std::is_constructible_v<E, unexpected<Err>&> &&
!std::is_constructible_v<E, unexpected<Err>> &&
!std::is_constructible_v<E, const unexpected<Err>&> &&
!std::is_constructible_v<E, const unexpected<Err>> &&
!std::is_convertible_v<unexpected<Err>&, E> &&
!std::is_convertible_v<unexpected<Err>, E> &&
!std::is_convertible_v<const unexpected<Err>&, E> &&
!std::is_convertible_v<const unexpected<Err>, E> &&
!std::is_convertible_v<Err, E> /* explicit */
)>
constexpr explicit unexpected(unexpected<Err>&& rhs)
: val_(E(std::move(rhs.value()))) {}
// assignment
constexpr unexpected& operator=(const unexpected&) = default;
constexpr unexpected& operator=(unexpected&&) noexcept(std::is_nothrow_move_assignable_v<E>) =
default;
template<class Err = E>
constexpr unexpected& operator=(const unexpected<Err>& rhs) {
val_ = rhs.value();
return *this;
}
template<class Err = E>
constexpr unexpected& operator=(unexpected<Err>&& rhs) {
val_ = std::forward<E>(rhs.value());
return *this;
}
// observer
constexpr const E& value() const& noexcept { return val_; }
constexpr E& value() & noexcept { return val_; }
constexpr const E&& value() const&& noexcept { return std::move(val_); }
constexpr E&& value() && noexcept { return std::move(val_); }
void swap(unexpected& other) noexcept(std::is_nothrow_swappable_v<E>) {
std::swap(val_, other.val_);
}
template<class E1, class E2>
friend constexpr bool
operator==(const unexpected<E1>& e1, const unexpected<E2>& e2);
template<class E1, class E2>
friend constexpr bool
operator!=(const unexpected<E1>& e1, const unexpected<E2>& e2);
template<class E1>
friend void swap(unexpected<E1>& x, unexpected<E1>& y) noexcept(noexcept(x.swap(y)));
private:
E val_;
};
template<class E1, class E2>
constexpr bool
operator==(const unexpected<E1>& e1, const unexpected<E2>& e2) {
return e1.value() == e2.value();
}
template<class E1, class E2>
constexpr bool
operator!=(const unexpected<E1>& e1, const unexpected<E2>& e2) {
return e1.value() != e2.value();
}
template<class E1>
void swap(unexpected<E1>& x, unexpected<E1>& y) noexcept(noexcept(x.swap(y))) {
x.swap(y);
}
// TODO: bad_expected_access class
#undef _ENABLE_IF
#undef _NODISCARD_
} // namespace base
} // namespace android