92 lines · cpp
1// RUN: %clang_cc1 -std=c++11 -fsyntax-only -verify %s2 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 the26// parameter-declaration-list, the type A of each remaining argument27// of the call is compared with the type P of the declarator-id of the28// 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: could not match 'pair<Args1, Args2>' against 'int'}}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// A function parameter pack not at the end of the parameter list is never79// deduced. We interpret this as meaning the types within it are never80// deduced, and thus must match explicitly-specified values.81template<typename ...Types> struct tuple { };82 83template<typename ...Types>84void pack_not_at_end(tuple<Types...>, Types... values, int); // expected-note {{<int *, double *> vs. <int, int>}}85 86void test_pack_not_at_end(tuple<int*, double*> t2) {87 pack_not_at_end(t2, 0, 0, 0); // expected-error {{no match}}88 // FIXME: Should the "original argument type must match deduced parameter89 // type" rule apply here?90 pack_not_at_end<int*, double*>(t2, 0, 0, 0); // ok91}92