src/Pure/Tools/codegen_thingol.ML

             ([], transform_itype ty)))
       | elim_sorts (Fun (eqs, (sortctxt, ty))) =
           let
             val _ = writeln "TRANSFORMING FUN (1)";
             val varnames_ctxt =
-              dig
+              burrow
                 (Term.invent_names ((vars_of_iexprs o map snd) eqs @
                   (vars_of_ipats o Library.flat o map fst) eqs) "d" o length)
                 (map snd sortctxt);
             val _ = writeln "TRANSFORMING FUN (2)";
             val vname_alist = map2 (fn (vt, sort) => fn vs => (vt, vs ~~ sort))