alias this & cast

[andre via Digitalmars-d-learn]

Hi,

I am 80% sure, the failing assertion is correct but please have a 
look.
Second assertion fails.
Kind regards
André

class A{}

class B{}

class C : B
{
        A a;
        alias a this;
        
        this()
        {
                a = new A();
        }
}

void main()
{
        B b = new C();

        // OK
        assert(cast(C)b);
        
        // fails
        assert(cast(A)b);       
}