keyed_element(keyed_element<Key, U, Rst> const& rhs) : Rest(rhs.get_base()), value_(rhs.value_) {}
BOOST_FUSION_GPU_ENABLED keyed_element(keyed_element<Key, U, Rst> const& rhs) : Rest(rhs.get_base()), value_(rhs.value_) {}
keyed_element(keyed_element const& rhs) : Rest(rhs.get_base()), value_(rhs.value_) {}