1 // RUN: %clang_cc1 -std=c++11 -fsyntax-only -verify %s
2
3 // Metafunction to extract the Nth type from a set of types.
4 template<unsigned N, typename ...Types> struct get_nth_type;
5
6 template<unsigned N, typename Head, typename ...Tail>
7 struct get_nth_type<N, Head, Tail...> : get_nth_type<N-1, Tail...> { };
8
9 template<typename Head, typename ...Tail>
10 struct get_nth_type<0, Head, Tail...> {
11 typedef Head type;
12 };
13
14 // Placeholder type when get_nth_type fails.
15 struct no_type {};
16
17 template<unsigned N>
18 struct get_nth_type<N> {
19 typedef no_type type;
20 };
21
22 template<typename T, typename U> struct pair { };
23 template<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.
29 template<typename ...Args>
30 typename get_nth_type<0, Args...>::type first_arg(Args...);
31
32 template<typename ...Args>
33 typename get_nth_type<1, Args...>::type second_arg(Args...);
34
test_simple_deduction(int * ip,float * fp,double * dp)35 void 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
42 template<typename ...Args>
43 typename get_nth_type<0, Args...>::type first_arg_ref(Args&...);
44
45 template<typename ...Args>
46 typename get_nth_type<1, Args...>::type second_arg_ref(Args&...);
47
test_simple_ref_deduction(int * ip,float * fp,double * dp)48 void 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
56 // FIXME: Use the template parameter names in this diagnostic.
57 template<typename ...Args1, typename ...Args2>
58 typename get_nth_type<0, Args1...>::type first_arg_pair(pair<Args1, Args2>...); // expected-note{{candidate template ignored: could not match 'pair<type-parameter-0-0, type-parameter-0-1>' against 'int'}}
59
60 template<typename ...Args1, typename ...Args2>
61 typename get_nth_type<1, Args1...>::type second_arg_pair(pair<Args1, Args2>...);
62
test_pair_deduction(int * ip,float * fp,double * dp)63 void test_pair_deduction(int *ip, float *fp, double *dp) {
64 int *ip1 = first_arg_pair(make_pair(ip, 17));
65 int *ip2 = first_arg_pair(make_pair(ip, 17), make_pair(fp, 17));
66 int *ip3 = first_arg_pair(make_pair(ip, 17), make_pair(fp, 17),
67 make_pair(dp, 17));
68 float *fp1 = second_arg_pair(make_pair(ip, 17), make_pair(fp, 17));
69 float *fp2 = second_arg_pair(make_pair(ip, 17), make_pair(fp, 17),
70 make_pair(dp, 17));
71 no_type nt1 = first_arg_pair();
72 no_type nt2 = second_arg_pair();
73 no_type nt3 = second_arg_pair(make_pair(ip, 17));
74
75
76 first_arg_pair(make_pair(ip, 17), 16); // expected-error{{no matching function for call to 'first_arg_pair'}}
77 }
78
79 // A function parameter pack not at the end of the parameter list is never
80 // deduced. We interpret this as meaning the types within it are never
81 // deduced, and thus must match explicitly-specified values.
82 template<typename ...Types> struct tuple { };
83
84 template<typename ...Types>
85 void pack_not_at_end(tuple<Types...>, Types... values, int); // expected-note {{<int *, double *> vs. <>}}
86
test_pack_not_at_end(tuple<int *,double * > t2)87 void test_pack_not_at_end(tuple<int*, double*> t2) {
88 pack_not_at_end(t2, 0, 0, 0); // expected-error {{no match}}
89 // FIXME: Should the "original argument type must match deduced parameter
90 // type" rule apply here?
91 pack_not_at_end<int*, double*>(t2, 0, 0, 0); // ok
92 }
93