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131
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1 // { dg-do compile { target c++17 } }
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2 // { dg-options "-fconcepts" }
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111
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3
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4 template<typename T>
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5 concept bool Eq() { return requires(T t) { t == t; }; }
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6
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7 struct Nt {
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8 template<Eq T> friend void f(T) { }
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9 } nt;
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10
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11 template<typename T> struct S;
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12
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13 template<Eq T>
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14 void proc(S<T>*);
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15
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16 template<typename T>
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17 struct S {
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18 friend bool operator==(S, S) requires Eq<T>() { return true; }
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19
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20 friend void proc<>(S*); // { dg-error "does not match any template declaration" }
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21 };
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22
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23 struct X { } x;
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24
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25 int main() {
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26 // f(0); // OK
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27 f(nt); // { dg-error "cannot call" }
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28 f(x); // { dg-error "3:'f' was not declared" }
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29
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30 S<int> si;
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31 si == si; // OK
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32
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33 S<X> sx;
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34 sx == sx; // { dg-error "no match" }
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35 }
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