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/*
* Copyright (C) 2016-2017 Apple Inc. All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
*
* THIS SOFTWARE IS PROVIDED BY APPLE INC. AND ITS CONTRIBUTORS ``AS IS''
* AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
* THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
* PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL APPLE INC. OR ITS CONTRIBUTORS
* BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
* CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
* SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
* INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
* CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
* ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF
* THE POSSIBILITY OF SUCH DAMAGE.
*/
// Implementation of Library Fundamentals v3's std::expected, as described here: http://wg21.link/p0323r4
#pragma once
/*
expected synopsis
namespace std {
namespace experimental {
inline namespace fundamentals_v3 {
// ?.?.4, Expected for object types
template <class T, class E>
class expected;
// ?.?.5, Expected specialization for void
template <class E>
class expected<void,E>;
// ?.?.6, unexpect tag
struct unexpect_t {
unexpect_t() = default;
};
inline constexpr unexpect_t unexpect{};
// ?.?.7, class bad_expected_access
template <class E>
class bad_expected_access;
// ?.?.8, Specialization for void.
template <>
class bad_expected_access<void>;
// ?.?.9, Expected relational operators
template <class T, class E>
constexpr bool operator==(const expected<T, E>&, const expected<T, E>&);
template <class T, class E>
constexpr bool operator!=(const expected<T, E>&, const expected<T, E>&);
// ?.?.10, Comparison with T
template <class T, class E>
constexpr bool operator==(const expected<T, E>&, const T&);
template <class T, class E>
constexpr bool operator==(const T&, const expected<T, E>&);
template <class T, class E>
constexpr bool operator!=(const expected<T, E>&, const T&);
template <class T, class E>
constexpr bool operator!=(const T&, const expected<T, E>&);
// ?.?.10, Comparison with unexpected<E>
template <class T, class E>
constexpr bool operator==(const expected<T, E>&, const unexpected<E>&);
template <class T, class E>
constexpr bool operator==(const unexpected<E>&, const expected<T, E>&);
template <class T, class E>
constexpr bool operator!=(const expected<T, E>&, const unexpected<E>&);
template <class T, class E>
constexpr bool operator!=(const unexpected<E>&, const expected<T, E>&);
// ?.?.11, Specialized algorithms
void swap(expected<T, E>&, expected<T, E>&) noexcept(see below);
template <class T, class E>
class expected
{
public:
typedef T value_type;
typedef E error_type;
typedef unexpected<E> unexpected_type;
template <class U>
struct rebind {
using type = expected<U, error_type>;
};
// ?.?.4.1, constructors
constexpr expected();
constexpr expected(const expected&);
constexpr expected(expected&&) noexcept(see below);
template <class U, class G>
EXPLICIT constexpr expected(const expected<U, G>&);
template <class U, class G>
EXPLICIT constexpr expected(expected<U, G>&&);
template <class U = T>
EXPLICIT constexpr expected(U&& v);
template <class... Args>
constexpr explicit expected(in_place_t, Args&&...);
template <class U, class... Args>
constexpr explicit expected(in_place_t, initializer_list<U>, Args&&...);
template <class G = E>
constexpr expected(unexpected<G> const&);
template <class G = E>
constexpr expected(unexpected<G> &&);
template <class... Args>
constexpr explicit expected(unexpect_t, Args&&...);
template <class U, class... Args>
constexpr explicit expected(unexpect_t, initializer_list<U>, Args&&...);
// ?.?.4.2, destructor
~expected();
// ?.?.4.3, assignment
expected& operator=(const expected&);
expected& operator=(expected&&) noexcept(see below);
template <class U = T> expected& operator=(U&&);
template <class G = E>
expected& operator=(const unexpected<G>&);
template <class G = E>
expected& operator=(unexpected<G>&&) noexcept(see below);
template <class... Args>
void emplace(Args&&...);
template <class U, class... Args>
void emplace(initializer_list<U>, Args&&...);
// ?.?.4.4, swap
void swap(expected&) noexcept(see below);
// ?.?.4.5, observers
constexpr const T* operator ->() const;
constexpr T* operator ->();
constexpr const T& operator *() const&;
constexpr T& operator *() &;
constexpr const T&& operator *() const &&;
constexpr T&& operator *() &&;
constexpr explicit operator bool() const noexcept;
constexpr bool has_value() const noexcept;
constexpr const T& value() const&;
constexpr T& value() &;
constexpr const T&& value() const &&;
constexpr T&& value() &&;
constexpr const E& error() const&;
constexpr E& error() &;
constexpr const E&& error() const &&;
constexpr E&& error() &&;
template <class U>
constexpr T value_or(U&&) const&;
template <class U>
T value_or(U&&) &&;
private:
bool has_val; // exposition only
union
{
value_type val; // exposition only
unexpected_type unexpect; // exposition only
};
};
}}}
*/
#include <cstdlib>
#include <initializer_list>
#include <type_traits>
#include <utility>
#include <wtf/Assertions.h>
#include <wtf/Compiler.h>
#include <wtf/StdLibExtras.h>
#include <wtf/Unexpected.h>
namespace std {
namespace experimental {
inline namespace fundamentals_v3 {
struct unexpected_t {
unexpected_t() = default;
};
#if __cplusplus < 201703L
#define __EXPECTED_INLINE_VARIABLE static const
#else
#define __EXPECTED_INLINE_VARIABLE inline
#endif
__EXPECTED_INLINE_VARIABLE constexpr unexpected_t unexpect { };
template<class E> class bad_expected_access;
template<>
class bad_expected_access<void> : public std::exception {
public:
explicit bad_expected_access() { }
};
template<class E>
class bad_expected_access : public bad_expected_access<void> {
public:
explicit bad_expected_access(E val) : val(val) { }
virtual const char* what() const noexcept override { return std::exception::what(); }
E& error() & { return val; }
const E& error() const& { return val; }
E&& error() && { return std::move(val); }
const E&& error() const&& { return std::move(val); }
private:
E val;
};
namespace __expected_detail {
#if COMPILER_SUPPORTS(EXCEPTIONS)
#define __EXPECTED_THROW(__exception) (throw __exception)
#else
inline NO_RETURN_DUE_TO_CRASH void __expected_terminate() { RELEASE_ASSERT_NOT_REACHED(); }
#define __EXPECTED_THROW(...) __expected_detail::__expected_terminate()
#endif
__EXPECTED_INLINE_VARIABLE constexpr enum class value_tag_t { } value_tag { };
__EXPECTED_INLINE_VARIABLE constexpr enum class error_tag_t { } error_tag { };
template<class T, std::enable_if_t<std::is_trivially_destructible<T>::value>* = nullptr> void destroy(T&) { }
template<class T, std::enable_if_t<!std::is_trivially_destructible<T>::value && (std::is_class<T>::value || std::is_union<T>::value)>* = nullptr> void destroy(T& t) { t.~T(); }
template<class T, class E>
union constexpr_storage {
typedef T value_type;
typedef E error_type;
typedef unexpected<E> unexpected_type;
char dummy;
value_type val;
error_type err;
constexpr constexpr_storage() : dummy() { }
constexpr constexpr_storage(value_tag_t) : val() { }
constexpr constexpr_storage(error_tag_t) : err() { }
template<typename U = T>
constexpr constexpr_storage(value_tag_t, U&& v) : val(std::forward<U>(v)) { }
template<typename U = E>
constexpr constexpr_storage(error_tag_t, U&& e) : err(std::forward<U>(e)) { }
~constexpr_storage() = default;
};
template<class T, class E>
union storage {
typedef T value_type;
typedef E error_type;
typedef unexpected<E> unexpected_type;
char dummy;
value_type val;
error_type err;
constexpr storage() : dummy() { }
constexpr storage(value_tag_t) : val() { }
constexpr storage(error_tag_t) : err() { }
constexpr storage(value_tag_t, const value_type& val) : val(val) { }
constexpr storage(value_tag_t, value_type&& val) : val(std::forward<value_type>(val)) { }
constexpr storage(error_tag_t, const error_type& err) : err(err) { }
constexpr storage(error_tag_t, error_type&& err) : err(std::forward<error_type>(err)) { }
~storage() { }
};
template<class E>
union constexpr_storage<void, E> {
typedef void value_type;
typedef E error_type;
typedef unexpected<E> unexpected_type;
char dummy;
error_type err;
constexpr constexpr_storage() : dummy() { }
constexpr constexpr_storage(value_tag_t) : dummy() { }
constexpr constexpr_storage(error_tag_t) : err() { }
constexpr constexpr_storage(error_tag_t, const error_type& e) : err(e) { }
~constexpr_storage() = default;
};
template<class E>
union storage<void, E> {
typedef void value_type;
typedef E error_type;
typedef unexpected<E> unexpected_type;
char dummy;
error_type err;
constexpr storage() : dummy() { }
constexpr storage(value_tag_t) : dummy() { }
constexpr storage(error_tag_t) : err() { }
constexpr storage(error_tag_t, const error_type& err) : err(err) { }
constexpr storage(error_tag_t, error_type&& err) : err(std::forward<error_type>(err)) { }
~storage() { }
};
template<class T, class E>
struct constexpr_base {
typedef T value_type;
typedef E error_type;
typedef unexpected<E> unexpected_type;
constexpr_storage<value_type, error_type> s;
bool has;
constexpr constexpr_base() : s(), has(true) { }
constexpr constexpr_base(value_tag_t tag) : s(tag), has(true) { }
constexpr constexpr_base(error_tag_t tag) : s(tag), has(false) { }
template<typename U = T>
constexpr constexpr_base(value_tag_t tag, U&& val) : s(tag, std::forward<U>(val)), has(true) { }
template<typename U = E>
constexpr constexpr_base(error_tag_t tag, U&& err) : s(tag, std::forward<U>(err)), has(false) { }
~constexpr_base() = default;
};
template<class T, class E>
struct base {
typedef T value_type;
typedef E error_type;
typedef unexpected<E> unexpected_type;
storage<value_type, error_type> s;
bool has;
constexpr base() : s(), has(true) { }
constexpr base(value_tag_t tag) : s(tag), has(true) { }
constexpr base(error_tag_t tag) : s(tag), has(false) { }
constexpr base(value_tag_t tag, const value_type& val) : s(tag, val), has(true) { }
constexpr base(value_tag_t tag, value_type&& val) : s(tag, std::forward<value_type>(val)), has(true) { }
constexpr base(error_tag_t tag, const error_type& err) : s(tag, err), has(false) { }
constexpr base(error_tag_t tag, error_type&& err) : s(tag, std::forward<error_type>(err)), has(false) { }
base(const base& o)
: has(o.has)
{
if (has)
::new (std::addressof(s.val)) value_type(o.s.val);
else
::new (std::addressof(s.err)) error_type(o.s.err);
}
base(base&& o)
: has(o.has)
{
if (has)
::new (std::addressof(s.val)) value_type(std::move(o.s.val));
else
::new (std::addressof(s.err)) error_type(std::move(o.s.err));
}
~base()
{
if (has)
destroy(s.val);
else
destroy(s.err);
}
};
template<class E>
struct constexpr_base<void, E> {
typedef void value_type;
typedef E error_type;
typedef unexpected<E> unexpected_type;
constexpr_storage<value_type, error_type> s;
bool has;
constexpr constexpr_base() : s(), has(true) { }
constexpr constexpr_base(value_tag_t tag) : s(tag), has(true) { }
constexpr constexpr_base(error_tag_t tag) : s(tag), has(false) { }
constexpr constexpr_base(error_tag_t tag, const error_type& err) : s(tag, err), has(false) { }
constexpr constexpr_base(error_tag_t tag, error_type&& err) : s(tag, std::forward<error_type>(err)), has(false) { }
~constexpr_base() = default;
};
template<class E>
struct base<void, E> {
typedef void value_type;
typedef E error_type;
typedef unexpected<E> unexpected_type;
storage<value_type, error_type> s;
bool has;
constexpr base() : s(), has(true) { }
constexpr base(value_tag_t tag) : s(tag), has(true) { }
constexpr base(error_tag_t tag) : s(tag), has(false) { }
constexpr base(error_tag_t tag, const error_type& err) : s(tag, err), has(false) { }
constexpr base(error_tag_t tag, error_type&& err) : s(tag, std::forward<error_type>(err)), has(false) { }
base(const base& o)
: has(o.has)
{
if (!has)
::new (std::addressof(s.err)) error_type(o.s.err);
}
base(base&& o)
: has(o.has)
{
if (!has)
::new (std::addressof(s.err)) error_type(std::move(o.s.err));
}
~base()
{
if (!has)
destroy(s.err);
}
};
template<class T, class E>
using base_select = typename std::conditional<
((std::is_void<T>::value || std::is_trivially_destructible<T>::value)
&& std::is_trivially_destructible<E>::value),
constexpr_base<typename std::remove_const<T>::type, typename std::remove_const<E>::type>,
base<typename std::remove_const<T>::type, typename std::remove_const<E>::type>
>::type;
} // namespace __expected_detail
template<class T, class E>
class expected : private __expected_detail::base_select<T, E> {
typedef __expected_detail::base_select<T, E> base;
public:
typedef typename base::value_type value_type;
typedef typename base::error_type error_type;
typedef typename base::unexpected_type unexpected_type;
private:
typedef expected<value_type, error_type> type;
public:
template<class U> struct rebind {
using type = expected<U, error_type>;
};
constexpr expected() : base(__expected_detail::value_tag) { }
expected(const expected&) = default;
expected(expected&&) = default;
constexpr expected(const value_type& e) : base(__expected_detail::value_tag, e) { }
constexpr expected(value_type&& e) : base(__expected_detail::value_tag, std::forward<value_type>(e)) { }
template<class... Args> constexpr explicit expected(std::in_place_t, Args&&... args) : base(__expected_detail::value_tag, value_type(std::forward<Args>(args)...)) { }
// template<class U, class... Args> constexpr explicit expected(in_place_t, std::initializer_list<U>, Args&&...);
constexpr expected(const unexpected_type& u) : base(__expected_detail::error_tag, u.value()) { }
constexpr expected(unexpected_type&& u) : base(__expected_detail::error_tag, std::forward<unexpected_type>(u).value()) { }
template<class Err> constexpr expected(const unexpected<Err>& u) : base(__expected_detail::error_tag, u.value()) { }
template<class Err> constexpr expected(unexpected<Err>&& u) : base(__expected_detail::error_tag, std::forward<Err>(u.value())) { }
template<class... Args> constexpr explicit expected(unexpected_t, Args&&... args) : base(__expected_detail::value_tag, unexpected_type(std::forward<Args>(args)...)) { }
// template<class U, class... Args> constexpr explicit expected(unexpected_t, std::initializer_list<U>, Args&&...);
~expected() = default;
expected& operator=(const expected& e) { type(e).swap(*this); return *this; }
expected& operator=(expected&& e) { type(std::move(e)).swap(*this); return *this; }
template<class U> expected& operator=(U&& u) { type(std::move(u)).swap(*this); return *this; }
expected& operator=(const unexpected_type& u) { type(u).swap(*this); return *this; }
expected& operator=(unexpected_type&& u) { type(std::move(u)).swap(*this); return *this; }
// template<class... Args> void emplace(Args&&...);
// template<class U, class... Args> void emplace(std::initializer_list<U>, Args&&...);
void swap(expected& o)
{
using std::swap;
if (base::has && o.has)
swap(base::s.val, o.s.val);
else if (base::has && !o.has) {
error_type e(std::move(o.s.err));
__expected_detail::destroy(o.s.err);
::new (std::addressof(o.s.val)) value_type(std::move(base::s.val));
__expected_detail::destroy(base::s.val);
::new (std::addressof(base::s.err)) error_type(std::move(e));
swap(base::has, o.has);
} else if (!base::has && o.has) {
value_type v(std::move(o.s.val));
__expected_detail::destroy(o.s.val);
::new (std::addressof(o.s.err)) error_type(std::move(base::s.err));
__expected_detail::destroy(base::s.err);
::new (std::addressof(base::s.val)) value_type(std::move(v));
swap(base::has, o.has);
} else
swap(base::s.err, o.s.err);
}
constexpr const value_type* operator->() const { return &base::s.val; }
value_type* operator->() { return &base::s.val; }
constexpr const value_type& operator*() const & { return base::s.val; }
value_type& operator*() & { return base::s.val; }
constexpr const value_type&& operator*() const && { return std::move(base::s.val); }
constexpr value_type&& operator*() && { return std::move(base::s.val); }
constexpr explicit operator bool() const { return base::has; }
constexpr bool has_value() const { return base::has; }
constexpr const value_type& value() const & { return base::has ? base::s.val : (__EXPECTED_THROW(bad_expected_access<error_type>(base::s.err)), base::s.val); }
constexpr value_type& value() & { return base::has ? base::s.val : (__EXPECTED_THROW(bad_expected_access<error_type>(base::s.err)), base::s.val); }
constexpr const value_type&& value() const && { return std::move(base::has ? base::s.val : (__EXPECTED_THROW(bad_expected_access<error_type>(base::s.err)), base::s.val)); }
constexpr value_type&& value() && { return std::move(base::has ? base::s.val : (__EXPECTED_THROW(bad_expected_access<error_type>(base::s.err)), base::s.val)); }
constexpr const error_type& error() const & { return !base::has ? base::s.err : (__EXPECTED_THROW(bad_expected_access<void>()), base::s.err); }
error_type& error() & { return !base::has ? base::s.err : (__EXPECTED_THROW(bad_expected_access<void>()), base::s.err); }
constexpr error_type&& error() && { return std::move(!base::has ? base::s.err : (__EXPECTED_THROW(bad_expected_access<void>()), base::s.err)); }
constexpr const error_type&& error() const && { return std::move(!base::has ? base::s.err : (__EXPECTED_THROW(bad_expected_access<void>()), base::s.err)); }
template<class U> constexpr value_type value_or(U&& u) const & { return base::has ? **this : static_cast<value_type>(std::forward<U>(u)); }
template<class U> value_type value_or(U&& u) && { return base::has ? std::move(**this) : static_cast<value_type>(std::forward<U>(u)); }
};
template<class E>
class expected<void, E> : private __expected_detail::base_select<void, E> {
typedef __expected_detail::base_select<void, E> base;
public:
typedef typename base::value_type value_type;
typedef typename base::error_type error_type;
typedef typename base::unexpected_type unexpected_type;
private:
typedef expected<value_type, error_type> type;
public:
template<class U> struct rebind {
using type = expected<U, error_type>;
};
constexpr expected() : base(__expected_detail::value_tag) { }
expected(const expected&) = default;
expected(expected&&) = default;
// constexpr explicit expected(in_place_t);
constexpr expected(unexpected_type const& u) : base(__expected_detail::error_tag, u.value()) { }
constexpr expected(unexpected_type&& u) : base(__expected_detail::error_tag, std::forward<unexpected_type>(u).value()) { }
template<class Err> constexpr expected(unexpected<Err> const& u) : base(__expected_detail::error_tag, u.value()) { }
~expected() = default;
expected& operator=(const expected& e) { type(e).swap(*this); return *this; }
expected& operator=(expected&& e) { type(std::move(e)).swap(*this); return *this; }
expected& operator=(const unexpected_type& u) { type(u).swap(*this); return *this; } // Not in the current paper.
expected& operator=(unexpected_type&& u) { type(std::move(u)).swap(*this); return *this; } // Not in the current paper.
// void emplace();
void swap(expected& o)
{
using std::swap;
if (base::has && o.has) {
// Do nothing.
} else if (base::has && !o.has) {
error_type e(std::move(o.s.err));
::new (std::addressof(base::s.err)) error_type(e);
swap(base::has, o.has);
} else if (!base::has && o.has) {
::new (std::addressof(o.s.err)) error_type(std::move(base::s.err));
swap(base::has, o.has);
} else
swap(base::s.err, o.s.err);
}
constexpr explicit operator bool() const { return base::has; }
constexpr bool has_value() const { return base::has; }
void value() const { !base::has ? __EXPECTED_THROW(bad_expected_access<void>()) : void(); }
constexpr const E& error() const & { return !base::has ? base::s.err : (__EXPECTED_THROW(bad_expected_access<void>()), base::s.err); }
E& error() & { return !base::has ? base::s.err : (__EXPECTED_THROW(bad_expected_access<void>()), base::s.err); }
constexpr E&& error() && { return std::move(!base::has ? base::s.err : (__EXPECTED_THROW(bad_expected_access<void>()), base::s.err)); }
};
template<class T, class E> constexpr bool operator==(const expected<T, E>& x, const expected<T, E>& y) { return bool(x) == bool(y) && (x ? x.value() == y.value() : x.error() == y.error()); }
template<class T, class E> constexpr bool operator!=(const expected<T, E>& x, const expected<T, E>& y) { return !(x == y); }
template<class E> constexpr bool operator==(const expected<void, E>& x, const expected<void, E>& y) { return bool(x) == bool(y) && (x ? true : x.error() == y.error()); }
template<class T, class E> constexpr bool operator==(const expected<T, E>& x, const T& y) { return x ? *x == y : false; }
template<class T, class E> constexpr bool operator==(const T& x, const expected<T, E>& y) { return y ? x == *y : false; }
template<class T, class E> constexpr bool operator!=(const expected<T, E>& x, const T& y) { return x ? *x != y : true; }
template<class T, class E> constexpr bool operator!=(const T& x, const expected<T, E>& y) { return y ? x != *y : true; }
template<class T, class E> constexpr bool operator==(const expected<T, E>& x, const unexpected<E>& y) { return x ? false : x.error() == y.value(); }
template<class T, class E> constexpr bool operator==(const unexpected<E>& x, const expected<T, E>& y) { return y ? false : x.value() == y.error(); }
template<class T, class E> constexpr bool operator!=(const expected<T, E>& x, const unexpected<E>& y) { return x ? true : x.error() != y.value(); }
template<class T, class E> constexpr bool operator!=(const unexpected<E>& x, const expected<T, E>& y) { return y ? true : x.value() != y.error(); }
template<typename T, typename E> void swap(expected<T, E>& x, expected<T, E>& y) { x.swap(y); }
}}} // namespace std::experimental::fundamentals_v3
__EXPECTED_INLINE_VARIABLE constexpr auto& unexpect = std::experimental::unexpect;
template<class T, class E> using Expected = std::experimental::expected<T, E>;