libstdc++-v3/testsuite/20_util/optional/cons/deduction.cc

   1 // Copyright (C) 2017-2022 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-do compile { target c++17 }  }
  19
  20 #include <optional>
  21 #include <type_traits>
  22
  23 struct MoveOnly
  24 {
  25   MoveOnly() = default;
  26   MoveOnly(MoveOnly&&);
  27   MoveOnly& operator=(MoveOnly&&);
  28 };
  29
  30 int main()
  31 {
  32   std::optional x = 5;
  33   static_assert(std::is_same_v<decltype(x), std::optional<int>>);
  34   int y = 42;
  35   std::optional x2 = y;
  36   static_assert(std::is_same_v<decltype(x2), std::optional<int>>);
  37   const int z = 666;
  38   std::optional x3 = z;
  39   static_assert(std::is_same_v<decltype(x3), std::optional<int>>);
  40   std::optional mo = MoveOnly();
  41   static_assert(std::is_same_v<decltype(mo), std::optional<MoveOnly>>);
  42   mo = MoveOnly();
  43
  44   std::optional copy = x;
  45   static_assert(std::is_same_v<decltype(copy), std::optional<int>>);
  46   std::optional move = std::move(mo);
  47   static_assert(std::is_same_v<decltype(move), std::optional<MoveOnly>>);
  48 }