Virtual functions and inheritance

[Baz via Digitalmars-d-learn]

On Tuesday, 27 January 2015 at 04:38:59 UTC, David Monagle wrote:
> Hi guys,
>
> I'm a former C++ developer and really enjoying working with D 
> now. I have a question that I hope some of you may be able to 
> answer.
>
> class Parent {
>   @property string typeName() {
>     return typeof(this).stringof;
>   }
> }
>
> class Child : Parent {
> }
>
> void main() {
>   auto p = new Parent;
>   auto c = new Child;
>   assert(p.typeName == "Parent");
>   assert(p.typeName == "Child");
> }
>
>
> I'm looking for an explanation as to why this doesn't work, 
> then a suggestion for how I may achieve child classes being 
> able to generate a string description of their own type, 
> without redefining the typeName property on each child. (I'm 
> currently solving this with a mixin, but I was hoping for a 
> better solution.
>
> I'm assuming it doesn't work because either typeof(this) or 
> .stringof is evaluated at compile time?

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");
}
---