Classes as enums in D?

[Andrew LaChance via Digitalmars-d-learn]

On Monday, 30 November 2015 at 07:54:49 UTC, Rikki Cattermole 
wrote:
> enums don't have to be integral, but for performance reasons it 
> is for the best.
>
> enum Foo : string {
>     A = "a",
>     B = "b",
>     C = "d",
>     ERROR = "What are you talking about?"
> }
>
> void main() {
> 	import std.stdio : writeln;
> 	Foo foo = Foo.ERROR;
> 	writeln(foo, " is: ", cast(string)foo);
> }
>
> Also you are welcome in #d on Freenode (IRC) if you are 
> interesting in talking with the rest of us!
> Btw you probably want tuples (std.typecons : tuple) to emulate 
> those values.

Oh interesting.  So you are saying I could have a struct WhiteKey 
{...} and then an enum that extends WhiteKey?  You also mention 
Tuples, are you recommending the Tuple's type be (WhiteKey, int)? 
  Thanks!