src/Pure/goal.ML

   | non_atomic (Const ("Pure.all", _) $ _) = true
   | non_atomic _ = false;
 
 fun assume_rule_tac ctxt = norm_hhf_tac ctxt THEN' CSUBGOAL (fn (goal, i) =>
   let
-    val ((_, goal'), ctxt') = Variable.focus_cterm goal ctxt;
+    val ((_, goal'), ctxt') = Variable.focus_cterm NONE goal ctxt;
     val goal'' = Drule.cterm_rule (singleton (Variable.export ctxt' ctxt)) goal';
     val Rs = filter (non_atomic o Thm.term_of) (Drule.strip_imp_prems goal'');
     val tacs = Rs |> map (fn R =>
       eresolve_tac ctxt [Raw_Simplifier.norm_hhf ctxt (Thm.trivial R)] THEN_ALL_NEW assume_tac ctxt);
   in fold_rev (curry op APPEND') tacs (K no_tac) i end);