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// { dg-do compile { target c++17 } } // { dg-options "-fconcepts" } template <class...> class tuple {}; tuple<int> t; tuple<auto> y = t; tuple<int,double> t2; tuple<auto...> x = t2; tuple<auto...> x2 = t; tuple<auto> y2 = t2; // { dg-error "" }