>
> This is almost the same code as written initially,
> let somone explain why the hell this is working:
>
> ---
> module test;
> import std.conv;
>
> class Parent {
>   @property final string typeName() {
>     return to!string(this);
>   }
> }
>
> class Child : Parent {
> }
>
> void main() {
>   auto p = new Parent;
>   auto c = new Child;
>   assert(p.typeName == __MODULE__ ~ ".Parent");
>   assert(c.typeName == __MODULE__ ~ ".Child");
> }
> ---

Because to!string calls toString, which is a virtual function. It's the same as the NVI-Idiom in C++.