How to add const qualifiers in template

I want to `const_value_type` be const even if `T` is a pointer, which is not possible with `std::add_const<>` So I tried something like this: ``` template<typename value_type, bool is_pointer> struct add_const_pointer{ typedef const value_type type; }; template<typename value_type> struct add_const_pointer<value_type, true>{ typedef const value_type *type; }; template<typename T> class Foo { public: typedef T value_type; typedef add_const_pointer<std::remove_pointer<T>, std::is_pointer<T>::value>::type const_value_type; // here I get compiler error: missing type specifier - int assumed. } ``` but I get compiler error: missing type specifier - int assumed.