This is a small excerpt from the Boost Concepts library, there's various rather unusual techniques employed in it, with preprocessor tricks and various compiler specific tweeks, but this one has defeated me! What is the purpose of "*********** Model:: ***********" ? Maybe it's just to generate a distinctive diagnostic, but it's very sensitive to exact numbers of asterisks! In general what's going on here is the compiler is checking that the destructor of the Model (which is a concept instantiated with a particular type), can be instantiated, but without ever running the destructor or creating an instance of the Model. struct failed {}; template <class Model> struct requirement<failed ************ Model::************> { static void failed() { ((Model*)0)->~Model(); } }; Any insight appreciated. Kind Regards Rob.