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1 // Testcase from P0512R0 for C++17 NB comment US 19
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2 // { dg-do compile { target c++17 } }
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3
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4 template<typename> struct remove_ref;
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5 template<typename _Tp> struct remove_ref { typedef _Tp type; };
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6 template<typename _Tp> struct remove_ref<_Tp&> { typedef _Tp type; };
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7 template<typename _Tp> struct remove_ref<_Tp&&> { typedef _Tp type; };
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8 template<typename _Tp> using remove_ref_t = typename remove_ref<_Tp>::type;
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9
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10 template<class T> struct A {
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11 A(T, int*); // #1
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12 A(A<T>&, int*); // #2
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13 enum { value };
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14 };
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15 template<class T, int N = remove_ref_t<T>::value> A(T&&, int*) -> A<T>; //#3
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16
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17 A a{1,0}; // uses #1 to deduce A<int> and initializes with #1
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18 A b{a,0}; // uses #2 to deduce A<int> and initializes with #2
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19
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20 template <class,class> struct same;
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21 template <class T> struct same<T,T> {};
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22
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23 same<decltype(a),A<int>> s1;
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24 same<decltype(b),A<int>> s2;
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