Looping over all enum values

[Mark Isaacson via Digitalmars-d-learn]

Is there a mechanism that allows you to loop over all of an
enum's values? I've wanted to do so a couple times now for
CTFE/mixin templates.

I was able to loop over the underlying type when my enum was
integer-based, but I can't do that if the values are strings
(also that solution is quite hacky).

Perhaps there's a pattern involving __traits?