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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
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* 1. Redistributions of source code must retain the above copyright
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* 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
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// Implementation of Library Fundamentals v3's std::expected, as described here: http://wg21.link/p0323r4
#pragma once
/*
unexpected synopsis
namespace std {
namespace experimental {
inline namespace fundamentals_v3 {
// ?.?.3, Unexpected object type
template <class E>
class unexpected;
// ?.?.4, Unexpected relational operators
template <class E>
constexpr bool
operator==(const unexpected<E>&, const unexpected<E>&);
template <class E>
constexpr bool
operator!=(const unexpected<E>&, const unexpected<E>&);
template <class E>
class unexpected {
public:
unexpected() = delete;
constexpr explicit unexpected(const E&);
constexpr explicit unexpected(E&&);
constexpr const E& value() const &;
constexpr E& value() &;
constexpr E&& value() &&;
constexpr E const&& value() const&&;
private:
E val; // exposition only
};
}}}
*/
#include <cstdlib>
#include <utility>
#include <wtf/StdLibExtras.h>
namespace std {
namespace experimental {
inline namespace fundamentals_v3 {
template<class E>
class unexpected {
public:
unexpected() = delete;
constexpr explicit unexpected(const E& e) : val(e) { }
constexpr explicit unexpected(E&& e) : val(std::forward<E>(e)) { }
constexpr const E& value() const & { return val; }
constexpr E& value() & { return val; }
constexpr E&& value() && { return WTFMove(val); }
constexpr const E&& value() const && { return WTFMove(val); }
private:
E 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(); }
}}} // namespace std::experimental::fundamentals_v3
template<class E> using Unexpected = std::experimental::unexpected<E>;
// Not in the std::expected spec, but useful to work around lack of C++17 deduction guides.
template<class E> constexpr Unexpected<std::decay_t<E>> makeUnexpected(E&& v) { return Unexpected<typename std::decay<E>::type>(std::forward<E>(v)); }