variant2/test/variant_visit_cx.cpp

// Copyright 2017, 2024, 2026 Peter Dimov
// Distributed under the Boost Software License, Version 1.0.
// http://www.boost.org/LICENSE_1_0.txt

#include <boost/variant2/variant.hpp>
#include <boost/mp11.hpp>
#include <boost/config.hpp>
#include <boost/config/pragma_message.hpp>

#if defined(BOOST_NO_CXX14_CONSTEXPR)

BOOST_PRAGMA_MESSAGE( "Test skipped because BOOST_NO_CXX14_CONSTEXPR is defined" )
int main() {}

#elif !defined(BOOST_MP11_HAS_CXX14_CONSTEXPR)

BOOST_PRAGMA_MESSAGE("Skipping constexpr visit test because BOOST_MP11_HAS_CXX14_CONSTEXPR is not defined")
int main() {}

#else

using namespace boost::variant2;

struct X
{
    constexpr operator int() const { return 2; }
};

struct F
{
    constexpr int operator()( int x ) const
    {
        return x;
    }
};

#define STATIC_ASSERT(...) static_assert(__VA_ARGS__, #__VA_ARGS__)

int main()
{
    {
        constexpr variant<int> v( 1 );
        STATIC_ASSERT( visit( F(), v ) == 1 );
    }

    {
        constexpr variant<char, int> v( 'a' );
        STATIC_ASSERT( visit( F(), v ) == 'a' );
    }

    {
        constexpr variant<char, int, X> v( X{} );
        STATIC_ASSERT( visit( F(), v ) == 2 );
    }
}

#endif