c++ - Referencing struct definition inside class in CRTP -

i'm using static polymorphism (crtp method) create class hierarchy. idea use struct defined in derived class in base one. however, vc10 generates following error:

error c2039: 'param_t' : not member of 'd'

and intel c++ generates following error:

error : incomplete type not allowed

it's quite confusing derived::param_t struct type , shall compiled normally. please point out problem in code. thanks.

// base class template<typename derived> struct base {   typedef typename derived::param_t param_t; //error c2039    void setparam(param_t& param);   const param_t& getparam() const;   ...  };  // derived class class d: public base<d> { public:   struct param_t {     double a, b, c;   };    d(param_t& param):param_(param) {}   ...  protected:   param_t param_;     };  int main() {   d::param_t p = {1.0, 0.2, 0.0};   d *pd = new d(p); } 

you can't use types derived class in base class definition. can use inside bodies of member functions. problem typedef typename derived::param_t param_t resolved class d: public base<d> when compiler doesn't know yet nested types of d. member functions compiled after actual instantiation of d when definition of d available.

i think in case can't use crtp method.