text: // { dg-do run { target c++14 } }
  
  // Copyright (C) 2013-2017 Free Software Foundation, Inc.
  //
  // This file is part of the GNU ISO C++ Library.  This library is free
  // software; you can redistribute it and/or modify it under the
  // terms of the GNU General Public License as published by the
  // Free Software Foundation; either version 3, or (at your option)
  // any later version.
  
  // This library is distributed in the hope that it will be useful,
  // but WITHOUT ANY WARRANTY; without even the implied warranty of
  // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  // GNU General Public License for more details.
  
  // You should have received a copy of the GNU General Public License along
  // with this library; see the file COPYING3.  If not see
  // <http://www.gnu.org/licenses/>.
  
  #include <experimental/optional>
  #include <testsuite_hooks.h>
  
  struct exception {};
  
  int counter = 0;
  
  struct mixin_counter
  {
    mixin_counter() { ++counter; }
    mixin_counter(mixin_counter const&) { ++counter; }
    ~mixin_counter() { --counter; }
  };
  
  struct value_type : private mixin_counter
  {
    enum state_type
    {
      zero,
      moved_from,
      throwing_construction,
      throwing_copy,
      throwing_copy_assignment,
      throwing_move,
      throwing_move_assignment,
      threw,
    };
  
    value_type() = default;
  
    explicit value_type(state_type state_)
    : state(state_)
    {
      throw_if(throwing_construction);
    }
  
    value_type(value_type const& other)
    : state(other.state)
    {
      throw_if(throwing_copy);
    }
  
    value_type&
    operator=(value_type const& other)
    {
      state = other.state;
      throw_if(throwing_copy_assignment);
      return *this;
    }
  
    value_type(value_type&& other)
    : state(other.state)
    {
      other.state = moved_from;
      throw_if(throwing_move);
    }
  
    value_type&
    operator=(value_type&& other)
    {
      state = other.state;
      other.state = moved_from;
      throw_if(throwing_move_assignment);
      return *this;
    }
  
    void throw_if(state_type match)
    {
      if(state == match)
      {
        state = threw;
        throw exception {};
      }
    }
  
    state_type state = zero;
  };
  
  int main()
  {
    using O = std::experimental::optional<value_type>;
    using S = value_type::state_type;
    auto const make = [](S s = S::zero) { return O { std::experimental::in_place, s }; };
  
    enum outcome_type { nothrow, caught, bad_catch };
  
    // Check copy/move assignment for disengaged optional
  
    // From disengaged optional
    {
      O o;
      VERIFY( !o );
      O p;
      o = p;
      VERIFY( !o );
      VERIFY( !p );
    }
  
    {
      O o;
      VERIFY( !o );
      O p;
      o = std::move(p);
      VERIFY( !o );
      VERIFY( !p );
    }
  
    {
      O o;
      VERIFY( !o );
      o = {};
      VERIFY( !o );
    }
  
    // From engaged optional
    {
      O o;
      VERIFY( !o );
      O p = make(S::throwing_copy_assignment);
      o = p;
      VERIFY( o && o->state == S::throwing_copy_assignment );
      VERIFY( p && p->state == S::throwing_copy_assignment );
    }
  
    {
      O o;
      VERIFY( !o );
      O p = make(S::throwing_move_assignment);
      o = std::move(p);
      VERIFY( o && o->state == S::throwing_move_assignment );
      VERIFY( p && p->state == S::moved_from );
    }
  
    {
      outcome_type outcome {};
      O o;
      VERIFY( !o );
      O p = make(S::throwing_copy);
  
      try
      {
        o = p;
      }
      catch(exception const&)
      { outcome = caught; }
      catch(...)
      { outcome = bad_catch; }
  
      VERIFY( outcome == caught );
      VERIFY( !o );
      VERIFY( p && p->state == S::throwing_copy );
    }
  
    {
      outcome_type outcome {};
      O o;
      VERIFY( !o );
      O p = make(S::throwing_move);
  
      try
      {
        o = std::move(p);
      }
      catch(exception const&)
      { outcome = caught; }
      catch(...)
      { outcome = bad_catch; }
  
      VERIFY( outcome == caught );
      VERIFY( !o );
      VERIFY( p && p->state == S::moved_from );
    }
  
    VERIFY( counter == 0 );
  }
  