| 1 | // Copyright (C) 2020 Klarälvdalens Datakonsult AB, a KDAB Group company, info@kdab.com, author Marc Mutz <marc.mutz@kdab.com> |
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| 2 | // Copyright (C) 2022 The Qt Company Ltd. |
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| 3 | // SPDX-License-Identifier: LicenseRef-Qt-Commercial OR LGPL-3.0-only OR GPL-2.0-only OR GPL-3.0-only |
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| 4 | |
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| 5 | #ifndef QXPTYPE_TRAITS_H |
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| 6 | #define QXPTYPE_TRAITS_H |
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| 7 | |
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| 8 | #include <QtCore/qtconfigmacros.h> |
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| 9 | |
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| 10 | #include <type_traits> |
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| 11 | |
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| 12 | // |
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| 13 | // W A R N I N G |
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| 14 | // ------------- |
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| 15 | // |
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| 16 | // This file is not part of the Qt API. Types and functions defined in this |
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| 17 | // file can reliably be replaced by their std counterparts, once available. |
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| 18 | // You may use these definitions in your own code, but be aware that we |
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| 19 | // will remove them once Qt depends on the C++ version that supports |
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| 20 | // them in namespace std. There will be NO deprecation warning, the |
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| 21 | // definitions will JUST go away. |
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| 22 | // |
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| 23 | // If you can't agree to these terms, don't use these definitions! |
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| 24 | // |
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| 25 | // We mean it. |
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| 26 | // |
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| 27 | |
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| 28 | QT_BEGIN_NAMESPACE |
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| 29 | |
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| 30 | // like std::experimental::{nonesuch,is_detected/_v}(LFTSv2) |
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| 31 | namespace qxp { |
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| 32 | |
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| 33 | struct nonesuch { |
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| 34 | ~nonesuch() = delete; |
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| 35 | nonesuch(const nonesuch&) = delete; |
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| 36 | void operator=(const nonesuch&) = delete; |
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| 37 | }; |
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| 38 | |
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| 39 | namespace _detail { |
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| 40 | template <typename T, typename Void, template <typename...> class Op, typename...Args> |
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| 41 | struct detector { |
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| 42 | using value_t = std::false_type; |
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| 43 | using type = T; |
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| 44 | }; |
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| 45 | template <typename T, template <typename...> class Op, typename...Args> |
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| 46 | struct detector<T, std::void_t<Op<Args...>>, Op, Args...> { |
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| 47 | using value_t = std::true_type; |
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| 48 | using type = Op<Args...>; |
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| 49 | }; |
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| 50 | } // namespace _detail |
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| 51 | |
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| 52 | template <template <typename...> class Op, typename...Args> |
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| 53 | using is_detected = typename _detail::detector<qxp::nonesuch, void, Op, Args...>::value_t; |
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| 54 | |
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| 55 | template <template <typename...> class Op, typename...Args> |
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| 56 | constexpr inline bool is_detected_v = is_detected<Op, Args...>::value; |
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| 57 | |
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| 58 | } // namespace qxp |
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| 59 | |
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| 60 | QT_END_NAMESPACE |
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| 61 | |
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| 62 | #endif // QXPTYPE_TRAITS_H |
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| 63 | |
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| 64 | |
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