BOOST_HANA_CONSTANT_CHECK(evaluate<'?', '+', '2'> == hana::nothing);
BOOST_HANA_CONSTANT_CHECK(evaluate<'1', '?', '2'> == hana::nothing);
BOOST_HANA_CONSTANT_CHECK(evaluate<'?', '+', '2'> == hana::nothing);
BOOST_HANA_CONSTANT_CHECK(evaluate<'1', '?', '2'> == hana::nothing);