1// RUN: %clang_cc1 -std=c++11 -fsyntax-only -verify %s 2 3// Metafunction to extract the Nth type from a set of types. 4template<unsigned N, typename ...Types> struct get_nth_type; 5 6template<unsigned N, typename Head, typename ...Tail> 7struct get_nth_type<N, Head, Tail...> : get_nth_type<N-1, Tail...> { }; 8 9template<typename Head, typename ...Tail> 10struct get_nth_type<0, Head, Tail...> { 11 typedef Head type; 12}; 13 14// Placeholder type when get_nth_type fails. 15struct no_type {}; 16 17template<unsigned N> 18struct get_nth_type<N> { 19 typedef no_type type; 20}; 21 22template<typename T, typename U> struct pair { }; 23template<typename T, typename U> pair<T, U> make_pair(T, U); 24 25// For a function parameter pack that occurs at the end of the 26// parameter-declaration-list, the type A of each remaining argument 27// of the call is compared with the type P of the declarator-id of the 28// function parameter pack. 29template<typename ...Args> 30typename get_nth_type<0, Args...>::type first_arg(Args...); 31 32template<typename ...Args> 33typename get_nth_type<1, Args...>::type second_arg(Args...); 34 35void test_simple_deduction(int *ip, float *fp, double *dp) { 36 int *ip1 = first_arg(ip); 37 int *ip2 = first_arg(ip, fp); 38 int *ip3 = first_arg(ip, fp, dp); 39 no_type nt1 = first_arg(); 40} 41 42template<typename ...Args> 43typename get_nth_type<0, Args...>::type first_arg_ref(Args&...); 44 45template<typename ...Args> 46typename get_nth_type<1, Args...>::type second_arg_ref(Args&...); 47 48void test_simple_ref_deduction(int *ip, float *fp, double *dp) { 49 int *ip1 = first_arg_ref(ip); 50 int *ip2 = first_arg_ref(ip, fp); 51 int *ip3 = first_arg_ref(ip, fp, dp); 52 no_type nt1 = first_arg_ref(); 53} 54 55 56template<typename ...Args1, typename ...Args2> 57typename get_nth_type<0, Args1...>::type first_arg_pair(pair<Args1, Args2>...); // expected-note{{candidate template ignored: failed template argument deduction}} 58 59template<typename ...Args1, typename ...Args2> 60typename get_nth_type<1, Args1...>::type second_arg_pair(pair<Args1, Args2>...); 61 62void test_pair_deduction(int *ip, float *fp, double *dp) { 63 int *ip1 = first_arg_pair(make_pair(ip, 17)); 64 int *ip2 = first_arg_pair(make_pair(ip, 17), make_pair(fp, 17)); 65 int *ip3 = first_arg_pair(make_pair(ip, 17), make_pair(fp, 17), 66 make_pair(dp, 17)); 67 float *fp1 = second_arg_pair(make_pair(ip, 17), make_pair(fp, 17)); 68 float *fp2 = second_arg_pair(make_pair(ip, 17), make_pair(fp, 17), 69 make_pair(dp, 17)); 70 no_type nt1 = first_arg_pair(); 71 no_type nt2 = second_arg_pair(); 72 no_type nt3 = second_arg_pair(make_pair(ip, 17)); 73 74 75 first_arg_pair(make_pair(ip, 17), 16); // expected-error{{no matching function for call to 'first_arg_pair'}} 76} 77 78// For a function parameter pack that does not occur at the end of the 79// parameter-declaration-list, the type of the parameter pack is a 80// non-deduced context. 81template<typename ...Types> struct tuple { }; 82 83template<typename ...Types> 84void pack_not_at_end(tuple<Types...>, Types... values, int); 85 86void test_pack_not_at_end(tuple<int*, double*> t2) { 87 pack_not_at_end(t2, 0, 0, 0); 88} 89