variant2/test/variant_emplace_index_cx.cpp

// Copyright 2017 Peter Dimov.
//
// Distributed under the Boost Software License, Version 1.0.
//
// See accompanying file LICENSE_1_0.txt or copy at
// http://www.boost.org/LICENSE_1_0.txt

#include <boost/variant2/variant.hpp>

using namespace boost::variant2;

struct X
{
    int v;
    constexpr X(): v( 0 ) {}
    constexpr explicit X( int v ): v( v ) {}
	constexpr operator int() const { return v; }
};

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

template<class V, std::size_t I, class A> constexpr A test( A const& a )
{
    V v;

    v.template emplace<I>( a );

    return get<I>(v);
}

int main()
{
    {
        constexpr auto w = test<variant<int>, 0>( 1 );
        STATIC_ASSERT( w == 1 );
    }

    {
        constexpr auto w = test<variant<X>, 0>( 1 );
        STATIC_ASSERT( w == 1 );
    }

    {
        constexpr auto w = test<variant<int, float>, 0>( 1 );
        STATIC_ASSERT( w == 1 );
    }

    {
        constexpr auto w = test<variant<int, float>, 1>( 3.0f );
        STATIC_ASSERT( w == 3.0f );
    }

    {
        constexpr auto w = test<variant<int, int, float, float, X, X>, 0>( 1 );
        STATIC_ASSERT( w == 1 );
    }

    {
        constexpr auto w = test<variant<int, int, float, float, X, X>, 1>( 1 );
        STATIC_ASSERT( w == 1 );
    }

    {
        constexpr auto w = test<variant<int, int, float, float, X, X>, 2>( 2.0f );
        STATIC_ASSERT( w == 2.0f );
    }

    {
        constexpr auto w = test<variant<int, int, float, float, X, X>, 3>( 3.0f );
        STATIC_ASSERT( w == 3.0f );
    }

    {
        constexpr auto w = test<variant<int, int, float, float, X, X>, 4>( 4 );
        STATIC_ASSERT( w == 4 );
    }

    {
        constexpr auto w = test<variant<int, int, float, float, X, X>, 5>( 5 );
        STATIC_ASSERT( w == 5 );
    }
}