Determining whether something is an interface?

[Christopher Wright]

You can determine whether a type is a class:
is (T : Object)

There's no equivalent for interfaces. You can use the compiles trait:
__traits(compiles, class Something : T {})
Except you can't -- it only takes expressions, not declarations.

There are traits for abstract classes (interfaces aren't) and final 
classes; how about something for interfaces? Or should I just start 
using abstract classes instead?