src/HOL/Tools/Quickcheck/quickcheck_common.ML

     val vs = (map o apsnd) (curry (Sorts.inter_sort algebra) sort_vs) raw_vs
     fun insts_of sort constr  = (map (rpair sort) o flat o maps snd o maps snd)
       (Datatype_Aux.interpret_construction descr vs constr)
     val insts = insts_of sort  { atyp = single, dtyp = (K o K o K) [] }
       @ insts_of aux_sort { atyp = K [], dtyp = K o K }
-    val has_inst = exists (fn tyco => can (Sorts.mg_domain algebra tyco) sort) tycos;
+    val has_inst = exists (fn tyco => Sorts.has_instance algebra tyco sort) tycos;
   in if has_inst then thy
     else case perhaps_constrain thy insts vs
      of SOME constrain => instantiate config descr
           (map constrain vs) tycos prfx (names, auxnames)
             ((pairself o map o map_atyps) (fn TFree v => TFree (constrain v)) raw_TUs) thy