enum with classes/structs

[useo]

Hey guys,

is it possible to declare a enum where all entries are instances of a
class (or struct), like the following:

class a {
   ...
   public this(uint i) {
     ...
   }
   ...
}

enum myEnum : a {
   entry1 = new a(0);
   entry2 = new a(1);
}

... or does enumerations only support constant-expressions? Thanks!