libstdc++-v3/testsuite/20_util/optional/observers/6.cc

   1 // { dg-options "-std=gnu++17" }
   2 // { dg-do compile }
   3
   4 // Copyright (C) 2016 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 moved_to 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 struct Y
  25 {
  26   constexpr int test() & {return 7;}
  27 };
  28
  29 constexpr int
  30 test()
  31 {
  32   std::optional<Y> opt{Y{}};
  33   return opt.value().test();
  34 }
  35
  36 int main()
  37 {
  38   static_assert(test());
  39 }