libstdc++-v3/testsuite/20_util/common_reference/requirements/typedefs.cc

   1 // Copyright (C) 2019-2020 Free Software Foundation, Inc.
   2 //
   3 // This file is part of the GNU ISO C++ Library.  This library is free
   4 // software; you can redistribute it and/or modify it under the
   5 // terms of the GNU General Public License as published by the
   6 // Free Software Foundation; either version 3, or (at your option)
   7 // any later version.
   8 //
   9 // This library is distributed in the hope that it will be useful,
  10 // but WITHOUT ANY WARRANTY; without even the implied warranty of
  11 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  12 // GNU General Public License for more details.
  13 //
  14 // You should have received a copy of the GNU General Public License along
  15 // with this library; see the file COPYING3.  If not see
  16 // <http://www.gnu.org/licenses/>.
  17
  18 // { dg-options "-std=gnu++2a" }
  19 // { dg-do compile { target c++2a } }
  20
  21 #include <type_traits>
  22
  23 template<typename T, typename = void>
  24   struct has_type : std::false_type { };
  25
  26 template<typename T>
  27   struct has_type<T, std::void_t<typename T::type>> : std::true_type { };
  28
  29 template<typename... T>
  30 constexpr bool
  31 has_common_ref()
  32 {
  33   return has_type<std::common_reference<T...>>::value;
  34 }
  35
  36 using std::is_same_v;
  37 using std::common_reference_t;
  38
  39 void test01()
  40 {
  41
  42   static_assert( !has_common_ref<>() );
  43   static_assert( !has_common_ref<char(*)(), int(*)()>() );
  44   static_assert( !has_common_ref<void*, int>() );
  45
  46   static_assert( is_same_v<common_reference_t<int>, int> );
  47   static_assert( is_same_v<common_reference_t<int&>, int&> );
  48   static_assert( is_same_v<common_reference_t<void>, void> );
  49   static_assert( is_same_v<common_reference_t<const void>, const void> );
  50   static_assert( is_same_v<common_reference_t<const void, void>, void> );
  51   static_assert( is_same_v<common_reference_t<void(*const)(), void(*)()>, void(*)()> );
  52   static_assert( is_same_v<common_reference_t<int, int>, int> );
  53   static_assert( is_same_v<common_reference_t<int&, int>, int> );
  54   static_assert( is_same_v<common_reference_t<int, int&>, int> );
  55   static_assert( is_same_v<common_reference_t<int&&, int>, int> );
  56   static_assert( is_same_v<common_reference_t<int&, int&>, int&> );
  57   static_assert( is_same_v<common_reference_t<int&, int&&>, const int&> );
  58   static_assert( is_same_v<common_reference_t<int&&, int&>, const int&> );
  59   static_assert( is_same_v<common_reference_t<int&&, int&&>, int&&> );
  60   static_assert( is_same_v<common_reference_t<int&&, const int&&>, const int&&> );
  61   static_assert( is_same_v<common_reference_t<int&, int&, int&&>, const int&> );
  62   static_assert( is_same_v<common_reference_t<int&&, int&, int&>, const int&> );
  63   static_assert( is_same_v<common_reference_t<char&, int&>, int> );
  64   static_assert( is_same_v<common_reference_t<long&, int&>, long> );
  65 }
  66
  67 struct A { };
  68 struct B { };
  69 struct C { };
  70
  71 template<template<typename> class AQual, template<typename> class BQual>
  72 struct std::basic_common_reference<A, B, AQual, BQual>
  73 {
  74   using type = BQual<AQual<C>>;
  75 };
  76
  77 static_assert( is_same_v<common_reference_t<A, B>, C> );
  78 static_assert( is_same_v<common_reference_t<A&, B>, C&> );
  79 static_assert( is_same_v<common_reference_t<A&, const B>, C&> );
  80 static_assert( is_same_v<common_reference_t<const A, B&>, const C&> );
  81 static_assert( is_same_v<common_reference_t<const A&, B&&>, const C&> );
  82 static_assert( is_same_v<common_reference_t<const A, B&&>, const C&&> );
  83
  84 struct D { };
  85 struct E { };
  86 struct F { };
  87
  88 template<> struct std::common_type<D, E> { using type = F; };
  89
  90 static_assert( is_same_v<common_reference_t<D, E>, F> );
  91 static_assert( is_same_v<common_reference_t<D&, E>, F> );
  92 static_assert( is_same_v<common_reference_t<D&, E&&>, F> );