libstdc++-v3/testsuite/20_util/optional/assignment/9.cc

// { dg-do compile { target c++17 } }

// Copyright (C) 2018-2022 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 <optional>

constexpr bool f()
{
  std::optional<int> o1{42};
  std::optional<int> o2;
  o2 = o1;
  return (o1 == o2);
}

constexpr bool f2()
{
  std::optional<int> o1{42};
  std::optional<int> o2;
  std::optional<int> o3;
  o2 = o1;
  o3 = std::move(o2);
  return (o1 == o3);
}

void g()
{
  constexpr bool b = f();
  static_assert(b);
  constexpr bool b2 = f2();
  static_assert(b2);
}

struct NonTrivialButConstexpr
{
  int dummy;
  NonTrivialButConstexpr() = default;
  constexpr NonTrivialButConstexpr(int val) : dummy(val) {}
  NonTrivialButConstexpr(const NonTrivialButConstexpr&) = default;
  NonTrivialButConstexpr(NonTrivialButConstexpr&&) = default;
  constexpr NonTrivialButConstexpr&
  operator=(const NonTrivialButConstexpr& other)
  {
    dummy = other.dummy;
    return *this;
  }
  constexpr NonTrivialButConstexpr&
  operator=(NonTrivialButConstexpr&& other)
  {
    dummy = other.dummy;
    return *this;
  }
};

constexpr bool f3()
{
  std::optional<NonTrivialButConstexpr> d1, d2;
  d1 = d2;
  std::optional<NonTrivialButConstexpr> o1{42};
  std::optional<NonTrivialButConstexpr> o2{22};
  o2 = o1;
  return ((*o1).dummy == (*o2).dummy && o1->dummy == o2->dummy);
}

constexpr bool f4()
{
  std::optional<NonTrivialButConstexpr> d1, d2;
  d1 = std::move(d2);
  std::optional<NonTrivialButConstexpr> o1{42};
  std::optional<NonTrivialButConstexpr> o2{22};
  std::optional<NonTrivialButConstexpr> o3{33};
  o2 = o1;
  o3 = std::move(o2);
  return ((*o1).dummy == (*o3).dummy && o1->dummy == o3->dummy);
}

void g2()
{
  constexpr bool b = f3();
  static_assert(b);
  constexpr bool b2 = f4();
  static_assert(b2);
}