libstdc++-v3/testsuite/20_util/is_constructible/77395.cc

// { dg-do compile { target c++11 } }

// Copyright (C) 2016-2021 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 <type_traits>
#include <utility>

struct derived;
struct base
{
  operator derived & () &;
  operator derived const & () const &;
  operator derived && () &&;
};

struct derived : base {};

base::operator derived & () &
{
  return *static_cast<derived *>(this);
}

base::operator derived const & () const &
{
  return *static_cast<derived const *>(this);
}

base::operator derived && () &&
{
  return std::move(*static_cast<derived *>(this));
}

int main()
{
  base b;
  derived&& d(static_cast<derived&&>(std::move(b)));
  derived&& d2(std::move(b));
  static_assert(std::is_constructible<derived&&, base&&>::value, "");
}