clang/test/CXX/temp/temp.fct.spec/temp.deduct/temp.deduct.call/p1-0x.cpp

   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
  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
  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 template<typename ...Args1, typename ...Args2>
  57 typename 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
  59 template<typename ...Args1, typename ...Args2>
  60 typename get_nth_type<1, Args1...>::type second_arg_pair(pair<Args1, Args2>...);
  61
  62 void 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 never
  79 // deduced. We interpret this as meaning the types within it are never
  80 // deduced, and thus must match explicitly-specified values.
  81 template<typename ...Types> struct tuple { };
  82
  83 template<typename ...Types>
  84 void pack_not_at_end(tuple<Types...>, Types... values, int); // expected-note {{<int *, double *> vs. <int, int>}}
  85
  86 void 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 parameter
  89   // type" rule apply here?
  90   pack_not_at_end<int*, double*>(t2, 0, 0, 0); // ok
  91 }