libcxx/test/std/utilities/utility/pairs/pairs.pair/assign_const_copy_pair.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, c++20
  10
  11 // <utility>
  12
  13 // template <class T1, class T2> struct pair
  14 // constexpr const pair& operator=(const pair& p) const;
  15
  16 #include <cassert>
  17 #include <utility>
  18
  19 #include "test_macros.h"
  20 #include "copy_move_types.h"
  21
  22 // Constraints:
  23 // is_copy_assignable<const first_type> is true and
  24 // is_copy_assignable<const second_type> is true.
  25
  26 // clang-format off
  27 static_assert(std::is_assignable_v<const std::pair<int&, int&>&,
  28                                    const std::pair<int&, int&>&>);
  29 static_assert(!std::is_assignable_v<const std::pair<int, int>&,
  30                                     const std::pair<int, int>&>);
  31 static_assert(!std::is_assignable_v<const std::pair<int, int&>&,
  32                                     const std::pair<int, int&>&>);
  33 static_assert(!std::is_assignable_v<const std::pair<int&, int>&,
  34                                     const std::pair<int&, int>&>);
  35
  36 static_assert(std::is_assignable_v<const std::pair<ConstCopyAssign, ConstCopyAssign>&,
  37                                    const std::pair<ConstCopyAssign, ConstCopyAssign>&>);
  38 static_assert(!std::is_assignable_v<const std::pair<CopyAssign, CopyAssign>&,
  39                                    const std::pair<CopyAssign, CopyAssign>&>);
  40
  41 // clang-format on
  42
  43 constexpr bool test() {
  44   // reference types
  45   {
  46     int i1    = 1;
  47     int i2    = 2;
  48     double d1 = 3.0;
  49     double d2 = 5.0;
  50     const std::pair<int&, double&> p1{i1, d1};
  51     const std::pair<int&, double&> p2{i2, d2};
  52     p2 = p1;
  53     assert(p2.first == 1);
  54     assert(p2.second == 3.0);
  55   }
  56
  57   // user defined const copy assignment
  58   {
  59     const std::pair<ConstCopyAssign, ConstCopyAssign> p1{1, 2};
  60     const std::pair<ConstCopyAssign, ConstCopyAssign> p2{3, 4};
  61     p2 = p1;
  62     assert(p2.first.val == 1);
  63     assert(p2.second.val == 2);
  64   }
  65
  66   // The correct assignment operator of the underlying type is used
  67   {
  68     std::pair<TracedAssignment, const TracedAssignment> t1{};
  69     const std::pair<TracedAssignment, const TracedAssignment> t2{};
  70     t2 = t1;
  71     assert(t2.first.constCopyAssign == 1);
  72     assert(t2.second.constCopyAssign == 1);
  73   }
  74
  75   return true;
  76 }
  77
  78 int main(int, char**) {
  79   test();
  80 // gcc cannot have mutable member in constant expression
  81 #if !defined(TEST_COMPILER_GCC)
  82   static_assert(test());
  83 #endif
  84   return 0;
  85 }