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1 // PR c++/69995
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2 // { dg-do compile { target c++14 } }
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3
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4 #define assert(X) static_assert((X),#X)
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5
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6 #define CONSTEXPR constexpr
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7
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8 template <typename T, unsigned long Size>
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9 struct array {
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10 T elems_[Size];
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11
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12 constexpr T const& operator[](unsigned long n) const
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13 { return elems_[n]; }
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14
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15 constexpr T& operator[](unsigned long n)
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16 { return elems_[n]; }
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17 };
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18
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19 template <typename T>
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20 CONSTEXPR void my_swap(T& a, T& b) {
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21 T tmp = a;
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22 a = b;
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23 b = tmp;
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24 }
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25
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26 CONSTEXPR auto rotate2() {
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27 array<array<int, 2>, 2> result{};
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28 array<int, 2> a{{0, 1}};
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29
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30 result[0] = a;
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31 my_swap(a[0], a[1]);
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32 result[1] = a;
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33
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34 return result;
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35 }
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36
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37 int main() {
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38 CONSTEXPR auto indices = rotate2();
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39 assert(indices[0][0] == 0);
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40 assert(indices[0][1] == 1);
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41 assert(indices[1][0] == 1);
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42 assert(indices[1][1] == 0);
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43 }
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