alias this

[Mf_Gh]

hi, i started to play a round with D and try to do something like:
class A{
        string a = "alias A";
        alias a this;
}

class B:A{
        string b = "alias B";
        alias b this;
}


void main() {
        A b = new B();
        writeln(b); //outputs alias A
}

i thought the output would be "alias B". why isn't the alias 
taken from the runtimetype?