How can I distinguish an enum constant from an actual enum at compile time?

[Gary Willoughby via Digitalmars-d-learn]

On Friday, 30 October 2015 at 12:18:21 UTC, Gary Willoughby wrote:
> On Friday, 30 October 2015 at 12:03:50 UTC, TheFlyingFiddle 
> wrote:
>> pragma(msg, is(b == enum)); //True
>> pragma(msg, is(a == enum)); //False.
>
> enum isEnum(alias e) = is(e == enum);
>
> isEnum!(a)
> isEnum!(b)
>
> ;)

isEnum!(isEnum)