// Copyright (C) 2019-2023 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/>.

// { dg-options "-std=gnu++2a" }
// { dg-do compile { target c++2a } }

#include <functional>

#ifndef __cpp_lib_constexpr_functional
# error "Feature test macro for constexpr invoke is missing"
#elif __cpp_lib_constexpr_functional < 201907L
# error "Feature test macro for constexpr invoke has wrong value"
#endif

constexpr int inc(int i) { return i + 1; }
constexpr auto inc_f = &inc;
static_assert( std::invoke(inc_f, 2) == 3);

struct Dec
{
  constexpr int operator()(int i) const { return i - 1; }
};

static_assert( std::invoke(Dec{}, 5) == 4 );