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131
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1 // { dg-do compile { target c++17 } }
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111
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2
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3 template <class T> struct A {
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4 using value_type = T;
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5 A(value_type); // #1
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6 A(const A&); // #2
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7 A(T, T, int); // #3
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8 template<class U> A(int, T, U); // #4
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9 }; // A(A); #5, the copy deduction candidate
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10
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11 A x (1, 2, 3); // uses #3, generated from a non-template constructor
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12
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13 template <class T> A(T) -> A<T>; // #6, less specialized than #5
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14
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15 A a (42); // uses #6 to deduce A<int> and #1 to initialize
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16 A b = a; // uses #5 to deduce A<int> and #2 to initialize
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17
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18 template <class T> A(A<T>) -> A<A<T>>; // #7, as specialized as #5
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19
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20 A b2 = a; // uses #7 to deduce A<A<int>> and #1 to initialize
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21
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22 template <class,class> struct same;
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23 template <class T> struct same<T,T> {};
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24
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25 same<decltype(a),A<int>> s1;
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26 same<decltype(b),A<int>> s2;
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27 same<decltype(b2),A<A<int>>> s3;
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