We can use std::is_base_of and std::enable_if:
(static_assert can be removed, the above classes can be custom-implemented or used from boost if we cannot reference type_traits)
#include <type_traits>
#include <list>
class Base {};
class Derived: public Base {};
#if 0 // wrapper
template <class T> class MyClass /* where T:Base */ {
private:
static_assert(std::is_base_of<Base, T>::value, "T is not derived from Base");
typename std::enable_if<std::is_base_of<Base, T>::value, T>::type inner;
};
#elif 0 // base class
template <class T> class MyClass: /* where T:Base */
protected std::enable_if<std::is_base_of<Base, T>::value, T>::type {
private:
static_assert(std::is_base_of<Base, T>::value, "T is not derived from Base");
};
#elif 1 // list-of
template <class T> class MyClass /* where T:list<Base> */ {
static_assert(std::is_base_of<Base, typename T::value_type>::value , "T::value_type is not derived from Base");
typedef typename std::enable_if<std::is_base_of<Base, typename T::value_type>::value, T>::type base;
typedef typename std::enable_if<std::is_base_of<Base, typename T::value_type>::value, T>::type::value_type value_type;
};
#endif
int main() {
#if 0 // wrapper or base-class
MyClass<Derived> derived;
MyClass<Base> base;
// error:
MyClass<int> wrong;
#elif 1 // list-of
MyClass<std::list<Derived>> derived;
MyClass<std::list<Base>> base;
// error:
MyClass<std::list<int>> wrong;
#endif
// all of the static_asserts if not commented out
// or "error: no type named ‘type’ in ‘struct std::enable_if<false, ...>’ pointing to:
// 1. inner
// 2. MyClass
// 3. base + value_type
}