src/HOL/Tools/Nitpick/nitpick_hol.ML

         SOME s' =>
         do_const (depth + 1) Ts (list_comb (Const (s', T), ts)) (s', T) ts
       | NONE =>
         let
           fun def_inline_threshold () =
-            if is_boolean_type (nth_range_type (length ts) T) andalso
+            if is_boolean_type (body_type T) andalso
                total_consts <> SOME true then
               def_inline_threshold_for_booleans
             else
               def_inline_threshold_for_non_booleans
           val (const, ts) =