I hesitate to mark this as [Polygon] because the error message is in a different part of Boost. However, I have little idea what the actual cause of the problem is or what any of the relevant stuff even means, so I figure [Polygon] is as good as anything at the moment... As before, this is a custom version of CodeWarrior an embedded ARM system, so I have no idea how well it corresponds with other versions of CodeWarrior. Here is a trivial program that illustrates the problem, using the BOOST_VERY_LITTLE_SFINAE patch from the last discussion here: #include <iostream> #define BOOST_VERY_LITTLE_SFINAE #include <boost/polygon/polygon.hpp> using namespace boost::polygon; using namespace boost::polygon::operators; int main() { polygon_set_data<int> ps; ps += rectangle_data<int>(0, 0, 1, 1); return 0; } This results in the following error message : Error : illegal use of template argument dependent type 'T::type' The error occurs in this part of boost/mpl/aux_/preprocessed/plain/and.hpp: template< typename T1, typename T2, typename T3, typename T4 > struct and_impl< true,T1,T2,T3,T4 > : and_impl< BOOST_MPL_AUX_NESTED_TYPE_WKND(T1)::value , T2, T3, T4 , true_ > { }; Any ideas about what's wrong or how to fix it? - Kef