Enum of types

[Diggory]

I want to create an enum of some number of types, eg. { ubyte, 
ushort, uint, float }

It should be straightforward to get a member of the enum from the 
type itself. Basically I have an object that stores some typed 
data, but the type may not be known at compile time, only the set 
of possible types. When constructing the object the user should 
be able to tell it what type of data it will hold. Also the 
underlying type of the enum should be efficient to store and 
compare.

So far the best I can come up with is using a mixin and CTFE to 
generate the code for an enum plus a template function to convert 
from a type to a member of the enum, but it seems like there 
might be a better way?