582 lines
24 KiB
C++
582 lines
24 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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expected 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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// ?.?.4, Expected for object types
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template <class T, class E>
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class expected;
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// ?.?.5, Expected specialization for void
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template <class E>
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class expected<void,E>;
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// ?.?.6, unexpect tag
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struct unexpect_t {
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unexpect_t() = default;
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};
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inline constexpr unexpect_t unexpect{};
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// ?.?.7, class bad_expected_access
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template <class E>
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class bad_expected_access;
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// ?.?.8, Specialization for void.
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template <>
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class bad_expected_access<void>;
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// ?.?.9, Expected relational operators
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template <class T, class E>
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constexpr bool operator==(const expected<T, E>&, const expected<T, E>&);
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template <class T, class E>
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constexpr bool operator!=(const expected<T, E>&, const expected<T, E>&);
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// ?.?.10, Comparison with T
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template <class T, class E>
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constexpr bool operator==(const expected<T, E>&, const T&);
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template <class T, class E>
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constexpr bool operator==(const T&, const expected<T, E>&);
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template <class T, class E>
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constexpr bool operator!=(const expected<T, E>&, const T&);
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template <class T, class E>
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constexpr bool operator!=(const T&, const expected<T, E>&);
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// ?.?.10, Comparison with unexpected<E>
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template <class T, class E>
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constexpr bool operator==(const expected<T, E>&, const unexpected<E>&);
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template <class T, class E>
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constexpr bool operator==(const unexpected<E>&, const expected<T, E>&);
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template <class T, class E>
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constexpr bool operator!=(const expected<T, E>&, const unexpected<E>&);
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template <class T, class E>
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constexpr bool operator!=(const unexpected<E>&, const expected<T, E>&);
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// ?.?.11, Specialized algorithms
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void swap(expected<T, E>&, expected<T, E>&) noexcept(see below);
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template <class T, class E>
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class expected
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{
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public:
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typedef T value_type;
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typedef E error_type;
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typedef unexpected<E> unexpected_type;
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template <class U>
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struct rebind {
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using type = expected<U, error_type>;
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};
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// ?.?.4.1, constructors
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constexpr expected();
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constexpr expected(const expected&);
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constexpr expected(expected&&) noexcept(see below);
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template <class U, class G>
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EXPLICIT constexpr expected(const expected<U, G>&);
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template <class U, class G>
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EXPLICIT constexpr expected(expected<U, G>&&);
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template <class U = T>
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EXPLICIT constexpr expected(U&& v);
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template <class... Args>
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constexpr explicit expected(in_place_t, Args&&...);
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template <class U, class... Args>
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constexpr explicit expected(in_place_t, initializer_list<U>, Args&&...);
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template <class G = E>
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constexpr expected(unexpected<G> const&);
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template <class G = E>
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constexpr expected(unexpected<G> &&);
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template <class... Args>
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constexpr explicit expected(unexpect_t, Args&&...);
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template <class U, class... Args>
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constexpr explicit expected(unexpect_t, initializer_list<U>, Args&&...);
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// ?.?.4.2, destructor
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~expected();
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// ?.?.4.3, assignment
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expected& operator=(const expected&);
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expected& operator=(expected&&) noexcept(see below);
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template <class U = T> expected& operator=(U&&);
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template <class G = E>
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expected& operator=(const unexpected<G>&);
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template <class G = E>
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expected& operator=(unexpected<G>&&) noexcept(see below);
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template <class... Args>
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void emplace(Args&&...);
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template <class U, class... Args>
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void emplace(initializer_list<U>, Args&&...);
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// ?.?.4.4, swap
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void swap(expected&) noexcept(see below);
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// ?.?.4.5, observers
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constexpr const T* operator ->() const;
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constexpr T* operator ->();
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constexpr const T& operator *() const&;
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constexpr T& operator *() &;
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constexpr const T&& operator *() const &&;
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constexpr T&& operator *() &&;
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constexpr explicit operator bool() const noexcept;
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constexpr bool has_value() const noexcept;
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constexpr const T& value() const&;
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constexpr T& value() &;
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constexpr const T&& value() const &&;
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constexpr T&& value() &&;
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constexpr const E& error() const&;
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constexpr E& error() &;
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constexpr const E&& error() const &&;
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constexpr E&& error() &&;
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template <class U>
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constexpr T value_or(U&&) const&;
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template <class U>
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T value_or(U&&) &&;
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private:
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bool has_val; // exposition only
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union
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{
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value_type val; // exposition only
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unexpected_type unexpect; // exposition only
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};
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};
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}}}
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*/
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#include <cstdlib>
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#include <initializer_list>
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#include <type_traits>
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#include <utility>
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#include <wtf/Assertions.h>
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#include <wtf/Compiler.h>
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#include <wtf/StdLibExtras.h>
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#include <wtf/Unexpected.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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struct unexpected_t {
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unexpected_t() = default;
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};
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#if __cplusplus < 201703L
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#define __EXPECTED_INLINE_VARIABLE static const
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#else
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#define __EXPECTED_INLINE_VARIABLE inline
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#endif
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__EXPECTED_INLINE_VARIABLE constexpr unexpected_t unexpect { };
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template<class E> class bad_expected_access;
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template<>
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class bad_expected_access<void> : public std::exception {
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public:
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explicit bad_expected_access() { }
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};
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template<class E>
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class bad_expected_access : public bad_expected_access<void> {
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public:
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explicit bad_expected_access(E val) : val(val) { }
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const char* what() const noexcept override { return std::exception::what(); }
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E& error() & { return val; }
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const E& error() const& { return val; }
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E&& error() && { return std::move(val); }
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const E&& error() const&& { return std::move(val); }
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private:
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E val;
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};
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namespace __expected_detail {
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#if COMPILER_SUPPORTS(EXCEPTIONS)
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#define __EXPECTED_THROW(__exception) (throw __exception)
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#else
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inline NO_RETURN_DUE_TO_CRASH void __expected_terminate() { RELEASE_ASSERT_NOT_REACHED(); }
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#define __EXPECTED_THROW(...) __expected_detail::__expected_terminate()
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#endif
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__EXPECTED_INLINE_VARIABLE constexpr enum class value_tag_t { } value_tag { };
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__EXPECTED_INLINE_VARIABLE constexpr enum class error_tag_t { } error_tag { };
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template<class T, std::enable_if_t<std::is_trivially_destructible<T>::value>* = nullptr> void destroy(T&) { }
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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(); }
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template<class T, class E>
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union constexpr_storage {
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typedef T value_type;
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typedef E error_type;
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typedef unexpected<E> unexpected_type;
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char dummy;
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value_type val;
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error_type err;
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constexpr constexpr_storage() : dummy() { }
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constexpr constexpr_storage(value_tag_t) : val() { }
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constexpr constexpr_storage(error_tag_t) : err() { }
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template<typename U = T>
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constexpr constexpr_storage(value_tag_t, U&& v) : val(std::forward<U>(v)) { }
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template<typename U = E>
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constexpr constexpr_storage(error_tag_t, U&& e) : err(std::forward<U>(e)) { }
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~constexpr_storage() = default;
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};
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template<class T, class E>
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union storage {
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typedef T value_type;
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typedef E error_type;
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typedef unexpected<E> unexpected_type;
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char dummy;
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value_type val;
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error_type err;
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constexpr storage() : dummy() { }
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constexpr storage(value_tag_t) : val() { }
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constexpr storage(error_tag_t) : err() { }
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constexpr storage(value_tag_t, const value_type& val) : val(val) { }
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constexpr storage(value_tag_t, value_type&& val) : val(std::forward<value_type>(val)) { }
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constexpr storage(error_tag_t, const error_type& err) : err(err) { }
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constexpr storage(error_tag_t, error_type&& err) : err(std::forward<error_type>(err)) { }
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~storage() { }
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};
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template<class E>
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union constexpr_storage<void, E> {
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typedef void value_type;
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typedef E error_type;
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typedef unexpected<E> unexpected_type;
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char dummy;
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error_type err;
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constexpr constexpr_storage() : dummy() { }
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constexpr constexpr_storage(value_tag_t) : dummy() { }
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constexpr constexpr_storage(error_tag_t) : err() { }
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constexpr constexpr_storage(error_tag_t, const error_type& e) : err(e) { }
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~constexpr_storage() = default;
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};
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template<class E>
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union storage<void, E> {
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typedef void value_type;
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typedef E error_type;
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typedef unexpected<E> unexpected_type;
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char dummy;
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error_type err;
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constexpr storage() : dummy() { }
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constexpr storage(value_tag_t) : dummy() { }
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constexpr storage(error_tag_t) : err() { }
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constexpr storage(error_tag_t, const error_type& err) : err(err) { }
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constexpr storage(error_tag_t, error_type&& err) : err(std::forward<error_type>(err)) { }
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~storage() { }
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};
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template<class T, class E>
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struct constexpr_base {
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typedef T value_type;
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typedef E error_type;
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typedef unexpected<E> unexpected_type;
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constexpr_storage<value_type, error_type> s;
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bool has;
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constexpr constexpr_base() : s(), has(true) { }
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constexpr constexpr_base(value_tag_t tag) : s(tag), has(true) { }
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constexpr constexpr_base(error_tag_t tag) : s(tag), has(false) { }
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template<typename U = T>
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constexpr constexpr_base(value_tag_t tag, U&& val) : s(tag, std::forward<U>(val)), has(true) { }
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template<typename U = E>
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constexpr constexpr_base(error_tag_t tag, U&& err) : s(tag, std::forward<U>(err)), has(false) { }
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~constexpr_base() = default;
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};
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template<class T, class E>
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struct base {
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typedef T value_type;
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typedef E error_type;
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typedef unexpected<E> unexpected_type;
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storage<value_type, error_type> s;
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bool has;
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constexpr base() : s(), has(true) { }
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constexpr base(value_tag_t tag) : s(tag), has(true) { }
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constexpr base(error_tag_t tag) : s(tag), has(false) { }
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constexpr base(value_tag_t tag, const value_type& val) : s(tag, val), has(true) { }
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constexpr base(value_tag_t tag, value_type&& val) : s(tag, std::forward<value_type>(val)), has(true) { }
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constexpr base(error_tag_t tag, const error_type& err) : s(tag, err), has(false) { }
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constexpr base(error_tag_t tag, error_type&& err) : s(tag, std::forward<error_type>(err)), has(false) { }
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base(const base& o)
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: has(o.has)
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{
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if (has)
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::new (std::addressof(s.val)) value_type(o.s.val);
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else
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::new (std::addressof(s.err)) error_type(o.s.err);
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}
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base(base&& o)
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: has(o.has)
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{
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if (has)
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::new (std::addressof(s.val)) value_type(std::move(o.s.val));
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else
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::new (std::addressof(s.err)) error_type(std::move(o.s.err));
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}
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~base()
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{
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if (has)
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destroy(s.val);
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else
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destroy(s.err);
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}
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};
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template<class E>
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struct constexpr_base<void, E> {
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typedef void value_type;
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typedef E error_type;
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typedef unexpected<E> unexpected_type;
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constexpr_storage<value_type, error_type> s;
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bool has;
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constexpr constexpr_base() : s(), has(true) { }
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constexpr constexpr_base(value_tag_t tag) : s(tag), has(true) { }
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constexpr constexpr_base(error_tag_t tag) : s(tag), has(false) { }
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constexpr constexpr_base(error_tag_t tag, const error_type& err) : s(tag, err), has(false) { }
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constexpr constexpr_base(error_tag_t tag, error_type&& err) : s(tag, std::forward<error_type>(err)), has(false) { }
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~constexpr_base() = default;
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};
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template<class E>
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struct base<void, E> {
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typedef void value_type;
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typedef E error_type;
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typedef unexpected<E> unexpected_type;
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storage<value_type, error_type> s;
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bool has;
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constexpr base() : s(), has(true) { }
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constexpr base(value_tag_t tag) : s(tag), has(true) { }
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constexpr base(error_tag_t tag) : s(tag), has(false) { }
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constexpr base(error_tag_t tag, const error_type& err) : s(tag, err), has(false) { }
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constexpr base(error_tag_t tag, error_type&& err) : s(tag, std::forward<error_type>(err)), has(false) { }
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base(const base& o)
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: has(o.has)
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{
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if (!has)
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::new (std::addressof(s.err)) error_type(o.s.err);
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}
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base(base&& o)
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: has(o.has)
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{
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if (!has)
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::new (std::addressof(s.err)) error_type(std::move(o.s.err));
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}
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~base()
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{
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if (!has)
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destroy(s.err);
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}
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};
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template<class T, class E>
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using base_select = typename std::conditional<
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((std::is_void<T>::value || std::is_trivially_destructible<T>::value)
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&& std::is_trivially_destructible<E>::value),
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constexpr_base<typename std::remove_const<T>::type, typename std::remove_const<E>::type>,
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base<typename std::remove_const<T>::type, typename std::remove_const<E>::type>
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>::type;
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} // namespace __expected_detail
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template<class T, class E>
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class expected : private __expected_detail::base_select<T, E> {
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WTF_MAKE_FAST_ALLOCATED;
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typedef __expected_detail::base_select<T, E> base;
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public:
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typedef typename base::value_type value_type;
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typedef typename base::error_type error_type;
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typedef typename base::unexpected_type unexpected_type;
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private:
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typedef expected<value_type, error_type> type;
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public:
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template<class U> struct rebind {
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using type = expected<U, error_type>;
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};
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constexpr expected() : base(__expected_detail::value_tag) { }
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expected(const expected&) = default;
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expected(expected&&) = default;
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constexpr expected(const value_type& e) : base(__expected_detail::value_tag, e) { }
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constexpr expected(value_type&& e) : base(__expected_detail::value_tag, std::forward<value_type>(e)) { }
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template<class... Args> constexpr explicit expected(std::in_place_t, Args&&... args) : base(__expected_detail::value_tag, value_type(std::forward<Args>(args)...)) { }
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// template<class U, class... Args> constexpr explicit expected(in_place_t, std::initializer_list<U>, Args&&...);
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constexpr expected(const unexpected_type& u) : base(__expected_detail::error_tag, u.value()) { }
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constexpr expected(unexpected_type&& u) : base(__expected_detail::error_tag, std::forward<unexpected_type>(u).value()) { }
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template<class Err> constexpr expected(const unexpected<Err>& u) : base(__expected_detail::error_tag, u.value()) { }
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template<class Err> constexpr expected(unexpected<Err>&& u) : base(__expected_detail::error_tag, std::forward<Err>(u.value())) { }
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template<class... Args> constexpr explicit expected(unexpected_t, Args&&... args) : base(__expected_detail::value_tag, unexpected_type(std::forward<Args>(args)...)) { }
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// template<class U, class... Args> constexpr explicit expected(unexpected_t, std::initializer_list<U>, Args&&...);
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~expected() = default;
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expected& operator=(const expected& e) { type(e).swap(*this); return *this; }
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expected& operator=(expected&& e) { type(std::move(e)).swap(*this); return *this; }
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template<class U> expected& operator=(U&& u) { type(std::forward<U>(u)).swap(*this); return *this; }
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expected& operator=(const unexpected_type& u) { type(u).swap(*this); return *this; }
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expected& operator=(unexpected_type&& u) { type(std::move(u)).swap(*this); return *this; }
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// template<class... Args> void emplace(Args&&...);
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// template<class U, class... Args> void emplace(std::initializer_list<U>, Args&&...);
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void swap(expected& o)
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{
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using std::swap;
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if (base::has && o.has)
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swap(base::s.val, o.s.val);
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else if (base::has && !o.has) {
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error_type e(std::move(o.s.err));
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__expected_detail::destroy(o.s.err);
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::new (std::addressof(o.s.val)) value_type(std::move(base::s.val));
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__expected_detail::destroy(base::s.val);
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::new (std::addressof(base::s.err)) error_type(std::move(e));
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swap(base::has, o.has);
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} else if (!base::has && o.has) {
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value_type v(std::move(o.s.val));
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__expected_detail::destroy(o.s.val);
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::new (std::addressof(o.s.err)) error_type(std::move(base::s.err));
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__expected_detail::destroy(base::s.err);
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::new (std::addressof(base::s.val)) value_type(std::move(v));
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swap(base::has, o.has);
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} else
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swap(base::s.err, o.s.err);
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}
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constexpr const value_type* operator->() const { return &base::s.val; }
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value_type* operator->() { return &base::s.val; }
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constexpr const value_type& operator*() const & { return base::s.val; }
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value_type& operator*() & { return base::s.val; }
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constexpr const value_type&& operator*() const && { return std::move(base::s.val); }
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constexpr value_type&& operator*() && { return std::move(base::s.val); }
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constexpr explicit operator bool() const { return base::has; }
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constexpr bool has_value() const { return base::has; }
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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); }
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constexpr value_type& value() & { return base::has ? base::s.val : (__EXPECTED_THROW(bad_expected_access<error_type>(base::s.err)), base::s.val); }
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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)); }
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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)); }
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constexpr const error_type& error() const & { return !base::has ? base::s.err : (__EXPECTED_THROW(bad_expected_access<void>()), base::s.err); }
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error_type& error() & { return !base::has ? base::s.err : (__EXPECTED_THROW(bad_expected_access<void>()), base::s.err); }
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constexpr error_type&& error() && { return std::move(!base::has ? base::s.err : (__EXPECTED_THROW(bad_expected_access<void>()), base::s.err)); }
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constexpr const error_type&& error() const && { return std::move(!base::has ? base::s.err : (__EXPECTED_THROW(bad_expected_access<void>()), base::s.err)); }
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template<class U> constexpr value_type value_or(U&& u) const & { return base::has ? **this : static_cast<value_type>(std::forward<U>(u)); }
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template<class U> value_type value_or(U&& u) && { return base::has ? std::move(**this) : static_cast<value_type>(std::forward<U>(u)); }
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};
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template<class E>
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class expected<void, E> : private __expected_detail::base_select<void, E> {
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typedef __expected_detail::base_select<void, E> base;
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public:
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typedef typename base::value_type value_type;
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typedef typename base::error_type error_type;
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typedef typename base::unexpected_type unexpected_type;
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private:
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typedef expected<value_type, error_type> type;
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public:
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template<class U> struct rebind {
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using type = expected<U, error_type>;
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};
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constexpr expected() : base(__expected_detail::value_tag) { }
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expected(const expected&) = default;
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expected(expected&&) = default;
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// constexpr explicit expected(in_place_t);
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constexpr expected(unexpected_type const& u) : base(__expected_detail::error_tag, u.value()) { }
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constexpr expected(unexpected_type&& u) : base(__expected_detail::error_tag, std::forward<unexpected_type>(u).value()) { }
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template<class Err> constexpr expected(unexpected<Err> const& u) : base(__expected_detail::error_tag, u.value()) { }
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~expected() = default;
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expected& operator=(const expected& e) { type(e).swap(*this); return *this; }
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expected& operator=(expected&& e) { type(std::move(e)).swap(*this); return *this; }
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expected& operator=(const unexpected_type& u) { type(u).swap(*this); return *this; } // Not in the current paper.
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expected& operator=(unexpected_type&& u) { type(std::move(u)).swap(*this); return *this; } // Not in the current paper.
|
|
// void emplace();
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|
|
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);
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|
} 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; }
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|
constexpr bool has_value() const { return base::has; }
|
|
void value() const { !base::has ? __EXPECTED_THROW(bad_expected_access<void>()) : void(); }
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|
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)); }
|
|
};
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|
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|
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()); }
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template<class T, class E> constexpr bool operator!=(const expected<T, E>& x, const expected<T, E>& y) { return !(x == y); }
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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()); }
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|
|
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; }
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|
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; }
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|
|
|
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(); }
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|
|
|
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>;
|