src/HOL/Tools/Quickcheck/narrowing_generators.ML

 val active = Attrib.setup_config_bool @{binding quickcheck_narrowing_active} (K true);
 
 val setup =
   Code.datatype_interpretation ensure_partial_term_of
   #> Code.datatype_interpretation ensure_partial_term_of_code
-  #> Datatype.interpretation (Quickcheck_Common.ensure_sort_datatype
-    (((@{sort typerep}, @{sort term_of}), @{sort narrowing}), instantiate_narrowing_datatype))
+  #> Quickcheck_Common.datatype_interpretation (@{sort narrowing}, instantiate_narrowing_datatype)
   #> Context.theory_map (Quickcheck.add_tester ("narrowing", (active, test_goals)))
     
 end;