ancestors does not include the tag parents of a class' superclasses. It therefore is inconsistent with isa?. Interaction example:

;;;;;;;;;;; user=> (ancestors String)

{java.io.Serializable java.lang.Object java.lang.CharSequence

java.lang.Comparable} user=> (ancestors Object) nil user=> (derive String ::foo) nil user=> (derive Object ::bar) nil user=> (isa? String ::foo) true user=> (isa? String ::bar) true user=> (ancestors Object)

{:user/bar}

user=> (ancestors String) ;; should include ::bar!

{java.io.Serializable java.lang.Object java.lang.CharSequence :user/

foo java.lang.Comparable} ;;;;;;;;;;;

I'd expect that ::bar would be included in the set returned by
(ancestors String). A similar interaction involving only keywords shows that the tag ancestors of a parent are obviously included in the set of ancestors of a child:

;;;;;;;;;; user=> (derive ::p ::gp) nil user=> (derive ::c ::p) nil user=> (ancestors ::c)

{:user/p :user/gp}

;;;;;;;;;;

The fix appears to be relatively simple, assuming I'm fully understanding the problem. Patch attached.

patch applied - r1334 - thanks!