[boost] Phoenix: is there a Phoenix expression trait?

Hi, I'm adding a convert_to Phoenix like functor to Boost.Conversion. I would like to use the same name, i.e. convert_to, but the overloads conflict. I would like to use sfinae to choose the correct overloading between template inline typename expression::convert_to, U>::type const convert_to(U const& u); template Target convert_to(Source const& from, boost::dummy::base_tag const& p=boost::dummy::base_tag()) Is there a trait that can be used to detect if the parameter is a Phoenix expression? BTW, I have just based my implementation on the one for static_cast, that uses the detail boost::phoenix::detail::target Could someone explain me why this is needed? Could this detail be moved to the user interface? Best, Vicente