Boost.TypeErasure docs say template<typename Concept, typename T> const std::type_info & typeid_of(const any< Concept, T > & arg); [...] Requires: Concept includes typeid_<T>. T is a non-reference, CV-unqualified placeholder. which, if my literal reading is right, means that you can't use typeid_of on, say, any<typeid_<>,_self&>, yet the following compiles on GCC #include <boost/type_erasure/any.hpp> #include <boost/type_erasure/builtin.hpp> #include <boost/type_erasure/typeid_of.hpp> #include <iostream> using namespace boost::type_erasure; int main() { int x=0; any<boost::mpl::vector<typeid_<>,relaxed>,_self&> a=x; std::cout<<typeid_of(a).name()<<"\n"; } and correctly outputs the name of the "int" type. Is this a bug in the docs or am I missing something? Thank you, Joaquín M López Muñoz