Detecting if a class type (which may or may not have a default constructor) is abstract

[Jarrett Billingsley]

I just don't think it's possible.  If all classes had default ctors,
it'd be easy; is(typeof(new T)) would be false if and only if T were
abstract.  But since that's not the case, I can't think of a way to
generically see if a given class type is abstract.  Any ideas?

It's always a little frustrating when doing type introspection and
having to rely on weird side-effects and properties of types, when the
compiler is just keeping it in some flag or field somewhere.  Sigh.
"is(T == abstract)"?  :P