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145
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1 // Testcase from P0848R0
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2 // { dg-do compile { target concepts } }
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3
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4 #include <type_traits>
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5
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6 template <typename T>
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7 class optional
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8 {
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9 struct empty {};
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10 union {
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11 empty _ = { };
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12 T value;
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13 };
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14 bool engaged = false;
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15
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16 public:
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17 constexpr optional() = default;
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18
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19 constexpr optional(optional const&)
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20 requires std::is_trivially_copy_constructible_v<T>
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21 = default;
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22 constexpr optional(optional const& o)
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23 : engaged (o.engaged)
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24 {
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25 if (engaged)
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26 new (&value) T (o.value);
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27 }
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28
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29 ~optional()
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30 requires std::is_trivially_destructible_v<T>
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31 = default;
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32 ~optional()
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33 {
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34 if (engaged)
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35 value.~T();
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36 }
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37
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38 // ...
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39 };
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40
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41 struct A { A(); A(const A&); ~A(); };
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42
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43 static_assert(std::is_trivially_copy_constructible_v<optional<int>>);
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44 static_assert(!std::is_trivially_copy_constructible_v<optional<A>>);
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45 static_assert(std::is_trivially_destructible_v<optional<int>>);
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46 static_assert(!std::is_trivially_destructible_v<optional<A>>);
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