struct my_iter {
    int foo();
};

struct container {
    typedef my_iter iterator;
};

template< typename T > struct exists { typedef void type; };

template< typename C, typename Enable = void> 
struct extract_iterator {
};

template< typename C > 
struct extract_iterator < C, typename exists<typename C::iterator>::type > {
    typedef typename C::iterator type;
};

int main() {   
    extract_iterator<container>::type var; // type is not resolved
    var.foo(); // foo is not resolved
    return 0;
}