libcxx/test/std/utilities/meta/meta.trans/meta.trans.other/common_reference.compile.pass.cpp

   1 //===----------------------------------------------------------------------===//
   2 //
   3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
   4 // See https://llvm.org/LICENSE.txt for license information.
   5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
   6 //
   7 //===----------------------------------------------------------------------===//
   8
   9 // UNSUPPORTED: c++03, c++11, c++14, c++17
  10
  11 // type_traits
  12 // common_reference
  13
  14 #include <tuple>
  15 #include <type_traits>
  16 #include <utility>
  17
  18 #include "test_macros.h"
  19
  20 template <class T>
  21 constexpr bool has_type = requires {
  22   typename T::type;
  23 };
  24
  25 // A slightly simplified variation of std::tuple
  26 template <class...>
  27 struct UserTuple {};
  28
  29 template <class, class, class>
  30 struct Tuple_helper {};
  31 template <class... Ts, class... Us>
  32 struct Tuple_helper<std::void_t<std::common_reference_t<Ts, Us>...>, UserTuple<Ts...>, UserTuple<Us...> > {
  33   using type = UserTuple<std::common_reference_t<Ts, Us>...>;
  34 };
  35
  36 template <class... Ts, class... Us, template <class> class TQual, template <class> class UQual>
  37 struct std::basic_common_reference< ::UserTuple<Ts...>, ::UserTuple<Us...>, TQual, UQual>
  38     : ::Tuple_helper<void, UserTuple<TQual<Ts>...>, UserTuple<UQual<Us>...> > {};
  39
  40 struct X2 {};
  41 struct Y2 {};
  42 struct Z2 {};
  43
  44 template <>
  45 struct std::common_type<X2, Y2> {
  46   using type = Z2;
  47 };
  48 template <>
  49 struct std::common_type<Y2, X2> {
  50   using type = Z2;
  51 };
  52
  53 // (6.1)
  54 //  -- If sizeof...(T) is zero, there shall be no member type.
  55 static_assert(!has_type<std::common_reference<> >);
  56
  57 // (6.2)
  58 //  -- Otherwise, if sizeof...(T) is one, let T0 denote the sole type in the
  59 //     pack T. The member typedef type shall denote the same type as T0.
  60 static_assert(std::is_same_v<std::common_reference_t<void>, void>);
  61 static_assert(std::is_same_v<std::common_reference_t<int>, int>);
  62 static_assert(std::is_same_v<std::common_reference_t<int&>, int&>);
  63 static_assert(std::is_same_v<std::common_reference_t<int&&>, int&&>);
  64 static_assert(std::is_same_v<std::common_reference_t<int const>, int const>);
  65 static_assert(std::is_same_v<std::common_reference_t<int const&>, int const&>);
  66 static_assert(std::is_same_v<std::common_reference_t<int const&&>, int const&&>);
  67 static_assert(std::is_same_v<std::common_reference_t<int volatile[]>, int volatile[]>);
  68 static_assert(std::is_same_v<std::common_reference_t<int volatile (&)[]>, int volatile (&)[]>);
  69 static_assert(std::is_same_v<std::common_reference_t<int volatile (&&)[]>, int volatile (&&)[]>);
  70 static_assert(std::is_same_v<std::common_reference_t<void (&)()>, void (&)()>);
  71 static_assert(std::is_same_v<std::common_reference_t<void (&&)()>, void (&&)()>);
  72
  73 // (6.3)
  74 //  -- Otherwise, if sizeof...(T) is two, let T1 and T2 denote the two types in
  75 //     the pack T. Then
  76 // (6.3.1)
  77 //    -- If T1 and T2 are reference types and COMMON_REF(T1, T2) is well-formed,
  78 //       then the member typedef type denotes that type.
  79 struct B {};
  80 struct D : B {};
  81 static_assert(std::is_same_v<std::common_reference_t<B&, D&>, B&>);
  82 static_assert(std::is_same_v<std::common_reference_t<B const&, D&>, B const&>);
  83 static_assert(std::is_same_v<std::common_reference_t<B&, D const&>, B const&>);
  84 static_assert(std::is_same_v<std::common_reference_t<B&, D const&, D&>, B const&>);
  85 static_assert(std::is_same_v<std::common_reference_t<B&, D&, B&, D&>, B&>);
  86
  87 static_assert(std::is_same_v<std::common_reference_t<B&&, D&&>, B&&>);
  88 static_assert(std::is_same_v<std::common_reference_t<B const&&, D&&>, B const&&>);
  89 static_assert(std::is_same_v<std::common_reference_t<B&&, D const&&>, B const&&>);
  90 static_assert(std::is_same_v<std::common_reference_t<B&, D&&>, B const&>);
  91 static_assert(std::is_same_v<std::common_reference_t<B&, D const&&>, B const&>);
  92 static_assert(std::is_same_v<std::common_reference_t<B const&, D&&>, B const&>);
  93
  94 static_assert(std::is_same_v<std::common_reference_t<B&&, D&>, B const&>);
  95 static_assert(std::is_same_v<std::common_reference_t<B&&, D const&>, B const&>);
  96 static_assert(std::is_same_v<std::common_reference_t<B const&&, D&>, B const&>);
  97
  98 static_assert(std::is_same_v<std::common_reference_t<int const&, int volatile&>, int const volatile&>);
  99 static_assert(std::is_same_v<std::common_reference_t<int const volatile&&, int volatile&&>, int const volatile&&>);
 100
 101 static_assert(std::is_same_v<std::common_reference_t<int (&)[10], int (&&)[10]>, int const (&)[10]>);
 102 static_assert(std::is_same_v<std::common_reference_t<int const (&)[10], int volatile (&)[10]>, int const volatile (&)[10]>);
 103
 104 // (6.3.2)
 105 //    -- Otherwise, if basic_common_reference<remove_cvref_t<T1>,
 106 //       remove_cvref_t<T2>, XREF(T1), XREF(T2)>::type is well-formed, then the
 107 //       member typedef type denotes that type.
 108 static_assert(std::is_same_v<std::common_reference_t<const UserTuple<int, short>&, UserTuple<int&, short volatile&>>,
 109                              UserTuple<const int&, const volatile short&>>);
 110
 111 static_assert(std::is_same_v<std::common_reference_t<volatile UserTuple<int, short>&, const UserTuple<int, short>&>,
 112                              const volatile UserTuple<int, short>&>);
 113
 114 // (6.3.3)
 115 //    -- Otherwise, if COND_RES(T1, T2) is well-formed, then the member typedef
 116 //       type denotes that type.
 117 static_assert(std::is_same_v<std::common_reference_t<void, void>, void>);
 118 static_assert(std::is_same_v<std::common_reference_t<int, short>, int>);
 119 static_assert(std::is_same_v<std::common_reference_t<int, short&>, int>);
 120 static_assert(std::is_same_v<std::common_reference_t<int&, short&>, int>);
 121 static_assert(std::is_same_v<std::common_reference_t<int&, short>, int>);
 122
 123 // tricky volatile reference case
 124 static_assert(std::is_same_v<std::common_reference_t<int&&, int volatile&>, int>);
 125 static_assert(std::is_same_v<std::common_reference_t<int volatile&, int&&>, int>);
 126
 127 static_assert(std::is_same_v<std::common_reference_t<int (&)[10], int (&)[11]>, int*>);
 128
 129 // https://github.com/ericniebler/stl2/issues/338
 130 struct MyIntRef {
 131   MyIntRef(int&);
 132 };
 133 static_assert(std::is_same_v<std::common_reference_t<int&, MyIntRef>, MyIntRef>);
 134
 135 // (6.3.4)
 136 //    -- Otherwise, if common_type_t<T1, T2> is well-formed, then the member
 137 //       typedef type denotes that type.
 138 struct moveonly {
 139   moveonly() = default;
 140   moveonly(moveonly&&) = default;
 141   moveonly& operator=(moveonly&&) = default;
 142 };
 143 struct moveonly2 : moveonly {};
 144
 145 static_assert(std::is_same_v<std::common_reference_t<moveonly const&, moveonly>, moveonly>);
 146 static_assert(std::is_same_v<std::common_reference_t<moveonly2 const&, moveonly>, moveonly>);
 147 static_assert(std::is_same_v<std::common_reference_t<moveonly const&, moveonly2>, moveonly>);
 148
 149 static_assert(std::is_same_v<std::common_reference_t<X2&, Y2 const&>, Z2>);
 150
 151 // (6.3.5)
 152 //    -- Otherwise, there shall be no member type.
 153 static_assert(!has_type<std::common_reference<volatile UserTuple<short>&, const UserTuple<int, short>&> >);
 154
 155 // (6.4)
 156 //  -- Otherwise, if sizeof...(T) is greater than two, let T1, T2, and Rest,
 157 //     respectively, denote the first, second, and (pack of) remaining types
 158 //     comprising T. Let C be the type common_reference_t<T1, T2>. Then:
 159 // (6.4.1)
 160 //    -- If there is such a type C, the member typedef type shall denote the
 161 //       same type, if any, as common_reference_t<C, Rest...>.
 162 static_assert(std::is_same_v<std::common_reference_t<int, int, int>, int>);
 163 static_assert(std::is_same_v<std::common_reference_t<int&&, int const&, int volatile&>, int const volatile&>);
 164 static_assert(std::is_same_v<std::common_reference_t<int&&, int const&, float&>, float>);
 165
 166 // (6.4.2)
 167 //    -- Otherwise, there shall be no member type.
 168 static_assert(!has_type<std::common_reference<int, short, int, char*> >);
 169
 170 #if TEST_STD_VER > 20
 171 static_assert(std::is_same_v<std::common_reference_t<std::tuple<int, int>>, std::tuple<int, int>>);
 172 static_assert(std::is_same_v<std::common_reference_t<std::tuple<int, long>, std::tuple<long, int>>, std::tuple<long, long>>);
 173 static_assert(std::is_same_v<std::common_reference_t<std::tuple<int&, const int&>, std::tuple<const int&, int>>,
 174                              std::tuple<const int&, int>>);
 175 static_assert(std::is_same_v<std::common_reference_t<std::tuple<int&, volatile int&>, std::tuple<volatile int&, int>>,
 176                              std::tuple<volatile int&, int>>);
 177 static_assert(std::is_same_v<std::common_reference_t<std::tuple<int&, const volatile int&>, std::tuple<const volatile int&, int>>,
 178                              std::tuple<const volatile int&, int>>);
 179 static_assert(!has_type<std::common_reference_t<std::tuple<const int&, volatile int&>, std::tuple<volatile int&, const int&>>>);
 180
 181 static_assert(std::is_same_v<std::common_reference_t<std::tuple<int, X2>, std::tuple<int, Y2>>, std::tuple<int, Z2>>);
 182 static_assert(std::is_same_v<std::common_reference_t<std::tuple<int, X2>, std::tuple<int, Y2>>, std::tuple<int, Z2>>);
 183 static_assert(!has_type<std::common_reference<std::tuple<int, const X2>, std::tuple<float, const Z2>>>);
 184 static_assert(!has_type<std::common_reference<std::tuple<int, X2>, std::tuple<float, Z2>>>);
 185 static_assert(!has_type<std::common_reference<std::tuple<int, X2>, int, X2>>);
 186
 187 struct A {};
 188 template <template<class> class TQual, template<class> class UQual>
 189 struct std::basic_common_reference<A, std::tuple<B>, TQual, UQual> {
 190   using type = tuple<UQual<B>>;
 191 };
 192
 193 static_assert(std::is_same_v<std::common_reference_t<A, std::tuple<B>, std::tuple<D>>, std::tuple<B>>);
 194
 195
 196 static_assert(std::is_same_v<std::common_reference_t<std::pair<int, int>>,
 197                              std::pair<int, int>>);
 198 static_assert(std::is_same_v<std::common_reference_t<std::pair<int, long>, std::pair<long, int>>,
 199                              std::pair<long, long>>);
 200 static_assert(std::is_same_v<std::common_reference_t<std::pair<int&, const int&>, std::pair<const int&, int>>,
 201                              std::pair<const int&, int>>);
 202 static_assert(std::is_same_v<std::common_reference_t<std::pair<int&, volatile int&>, std::pair<volatile int&, int>>,
 203                              std::pair<volatile int&, int>>);
 204 static_assert(std::is_same_v<std::common_reference_t<std::pair<int&, const volatile int&>, std::pair<const volatile int&, int>>,
 205                              std::pair<const volatile int&, int>>);
 206 static_assert(!has_type<std::common_reference_t<std::pair<const int&, volatile int&>,
 207                         std::pair<volatile int&, const int&>>>);
 208
 209 static_assert(std::is_same_v<std::common_reference_t<std::pair<int, X2>, std::pair<int, Y2>>, std::pair<int, Z2>>);
 210 static_assert(std::is_same_v<std::common_reference_t<std::pair<int, X2>, std::pair<int, Y2>>, std::pair<int, Z2>>);
 211 static_assert(!has_type<std::common_reference<std::pair<int, const X2>, std::pair<float, const Z2>>>);
 212 static_assert(!has_type<std::common_reference<std::pair<int, X2>, std::pair<float, Z2>>>);
 213 static_assert(!has_type<std::common_reference<std::pair<int, X2>, int, X2>>);
 214 #endif