In C++ 20 mode the variadic data can be empty and the result will be an empty list of the form 'BOOST_PP_NIL'.
#include <boost/preprocessor/variadic/to_list.hpp>
BOOST_PP_VARIADIC_TO_LIST(x, y, z)
// expands to (x, (y, (z, BOOST_PP_NIL)))
Distributed under the Boost Software License, Version 1.0. (See accompanying file LICENSE_1_0.txt or copy at www.boost.org/LICENSE_1_0.txt)