(use coops)

(module
 m1
 *
 (import chicken scheme)
 (use coops)
 (define-class a1)
 (define-method (foo (o a1))
   (print "1")))

(module
 m2
 *
 (import chicken scheme)
 (use coops)
 (define-class a2)
 (define-method (foo (o a2))
   (print "2")))

(import m1 m2)

(print (foo (make a2)))
(print (foo (make a1)))

;; 2
;; #<unspecified>

;; Error: (foo) no method defined for given argument classes: (#<coops standard-class `a1'>)