src/HOL/Decision_Procs/approximation.ML

   in
     fold prepend_prem order all_tac
   end
 
 fun approximation_conv ctxt ct =
-  approximation_oracle (Proof_Context.theory_of ctxt, Thm.term_of ct |> tap (tracing o Syntax.string_of_term ctxt));
+  approximation_oracle (Proof_Context.theory_of ctxt, Thm.term_of ct);
 
 fun approximate ctxt t =
   approximation_oracle (Proof_Context.theory_of ctxt, t)
   |> Thm.prop_of |> Logic.dest_equals |> snd;