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99 lines
3.5 KiB
C++
99 lines
3.5 KiB
C++
/*
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* Copyright (C) 2016-2017 Apple Inc. All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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*
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* THIS SOFTWARE IS PROVIDED BY APPLE INC. AND ITS CONTRIBUTORS ``AS IS''
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* AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
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* THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
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* PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL APPLE INC. OR ITS CONTRIBUTORS
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* BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
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* CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
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* SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
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* INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
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* CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
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* ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF
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* THE POSSIBILITY OF SUCH DAMAGE.
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*/
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// Implementation of Library Fundamentals v3's std::expected, as described here: http://wg21.link/p0323r4
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#pragma once
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/*
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unexpected synopsis
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namespace std {
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namespace experimental {
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inline namespace fundamentals_v3 {
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// ?.?.3, Unexpected object type
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template <class E>
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class unexpected;
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// ?.?.4, Unexpected relational operators
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template <class E>
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constexpr bool
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operator==(const unexpected<E>&, const unexpected<E>&);
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template <class E>
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constexpr bool
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operator!=(const unexpected<E>&, const unexpected<E>&);
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template <class E>
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class unexpected {
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public:
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unexpected() = delete;
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template <class U = E>
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constexpr explicit unexpected(E&&);
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constexpr const E& value() const &;
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constexpr E& value() &;
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constexpr E&& value() &&;
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constexpr E const&& value() const&&;
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private:
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E val; // exposition only
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};
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}}}
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*/
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#include <cstdlib>
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#include <utility>
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#include <wtf/StdLibExtras.h>
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namespace std {
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namespace experimental {
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inline namespace fundamentals_v3 {
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template<class E>
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class unexpected {
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WTF_MAKE_FAST_ALLOCATED;
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public:
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unexpected() = delete;
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template <class U = E>
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constexpr explicit unexpected(U&& u) : val(std::forward<U>(u)) { }
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constexpr const E& value() const & { return val; }
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constexpr E& value() & { return val; }
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constexpr E&& value() && { return WTFMove(val); }
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constexpr const E&& value() const && { return WTFMove(val); }
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private:
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E val;
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};
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template<class E> constexpr bool operator==(const unexpected<E>& lhs, const unexpected<E>& rhs) { return lhs.value() == rhs.value(); }
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template<class E> constexpr bool operator!=(const unexpected<E>& lhs, const unexpected<E>& rhs) { return lhs.value() != rhs.value(); }
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}}} // namespace std::experimental::fundamentals_v3
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template<class E> using Unexpected = std::experimental::unexpected<E>;
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// Not in the std::expected spec, but useful to work around lack of C++17 deduction guides.
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template<class E> constexpr Unexpected<std::decay_t<E>> makeUnexpected(E&& v) { return Unexpected<typename std::decay<E>::type>(std::forward<E>(v)); }
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