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1 // { dg-do compile { target c++17 } }
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2
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3 #include <memory>
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4 #include <tuple>
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5 #include <string>
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6
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7 struct X : private std::shared_ptr<int>
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8 {
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9 std::string fun_payload;
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10 };
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11
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12 template<int N> std::string& get(X& x)
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13 {
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14 if constexpr(N==0) return x.fun_payload;
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15 }
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16
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17 namespace std {
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18 template<> class tuple_size<X> : public std::integral_constant<int, 1> {};
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19 template<> class tuple_element<0, X> {public: using type = std::string;};
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20 }
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21
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22 struct X2 : private std::shared_ptr<int>
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23 {
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24 int fun_payload;
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25 template <class T> void get();
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26 };
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27
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28 template<int N> int& get(X2& x)
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29 {
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30 if constexpr(N==0) return x.fun_payload;
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31 }
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32
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33 namespace std {
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34 template<> class tuple_size<X2> : public std::integral_constant<int, 1> {};
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35 template<> class tuple_element<0, X2> {public: using type = int;};
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36 }
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37
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38 class X3
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39 {
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40 double fun_payload;
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41 public:
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42 template <int N> double& get()
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43 {
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44 if constexpr(N==0) return fun_payload;
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45 }
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46 };
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47
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48 namespace std {
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49 template<> class tuple_size<X3> : public std::integral_constant<int, 1> {};
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50 template<> class tuple_element<0, X3> {public: using type = double;};
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51 }
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52
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53 int main()
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54 {
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55 X x;
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56 auto& [b1] = x;
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57 X2 x2;
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58 auto& [b2] = x2;
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59 X3 x3;
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60 auto& [b3] = x3;
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61 }
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