libstdc++-v3/testsuite/20_util/optional/constexpr/nullopt.cc

   1 // { dg-options "-std=gnu++17" }
   2 // { dg-do compile }
   3
   4 // Copyright (C) 2013-2017 Free Software Foundation, Inc.
   5 //
   6 // This file is part of the GNU ISO C++ Library.  This library is free
   7 // software; you can redistribute it and/or modify it under the
   8 // terms of the GNU General Public License as published by the
   9 // Free Software Foundation; either version 3, or (at your option)
  10 // any later version.
  11
  12 // This library is distributed in the hope that it will be useful,
  13 // but WITHOUT ANY WARRANTY; without even the implied warranty of
  14 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  15 // GNU General Public License for more details.
  16
  17 // You should have received a copy of the GNU General Public License along
  18 // with this library; see the file COPYING3.  If not see
  19 // <http://www.gnu.org/licenses/>.
  20
  21 #include <optional>
  22 #include <testsuite_hooks.h>
  23
  24 int main()
  25 {
  26   // [20.5.6] Disengaged state indicator
  27   static_assert( std::is_same<decltype(std::nullopt), const std::nullopt_t>(), "" );
  28   static_assert( std::is_empty<std::nullopt_t>(), "" );
  29   static_assert( std::is_literal_type<std::nullopt_t>(), "" );
  30   static_assert( !std::is_default_constructible<std::nullopt_t>(), "" );
  31
  32   {
  33     constexpr std::optional<int> o = std::nullopt;
  34     static_assert( !o, "" );
  35   }
  36
  37   {
  38     constexpr std::optional<int> o = { std::nullopt };
  39     static_assert( !o, "" );
  40   }
  41
  42   {
  43     constexpr std::optional<int> o { std::nullopt };
  44     static_assert( !o, "" );
  45   }
  46 }