How is std::shared_ptr polymorphic?

I'm developing some container class, which has similar idea: holding pointer inside.

#include <iostream>

template<class T>
class Container
{
public:
    Container ( )
    {
         pointer = new T ( );
    }

    ~Container ( )
    {
        delete pointer;
    }

    T* operator->( )
    {
        return pointer;
    }
private:
     T* pointer;
};

struct Base
{
    virtual void who ( )
    {
        std::cout << "Base" << std::endl;
    }
};


struct Child : public Base
{
    virtual void who ( ) override
    {
        std::cout << "Child" << std::endl;
    }
};


void test ( Container<Base>& c )
{
    c->who ( );
}

int main ( )
{
    Container<Child> child;
    test ( child );
}

This code fails to compile: error C2664: 'void test(Container &)' : cannot convert argument 1 from 'Container' to 'Container &'

However if I use std::shared_ptr, instead of Container, everything works fine. So question is:

Is std::shared_ptr-like polymorphysm implementable? Or is this feature, which was somehow harcoded in C++? Sorry for my primitive language.

Thank you!