diff --git a/src/HOL/Analysis/metric_arith.ML b/src/HOL/Analysis/metric_arith.ML
--- a/src/HOL/Analysis/metric_arith.ML
+++ b/src/HOL/Analysis/metric_arith.ML
@@ -1,330 +1,329 @@
 (*  Title:      HOL/Analysis/metric_arith.ML
     Author:     Maximilian Schäffeler (port from HOL Light)
 
 A decision procedure for metric spaces.
 *)
 
 signature METRIC_ARITH =
 sig
   val trace: bool Config.T
   val metric_arith_tac : Proof.context -> int -> tactic
 end
 
 structure Metric_Arith : METRIC_ARITH =
 struct
 
 fun default d x = case x of SOME y => SOME y | NONE => d
 
 (* apply f to both cterms in ct_pair, merge results *)
 fun app_union_ct_pair f ct_pair = uncurry (union (op aconvc)) (apply2 f ct_pair)
 
 val trace = Attrib.setup_config_bool \<^binding>\<open>metric_trace\<close> (K false)
 
 fun trace_tac ctxt msg =
   if Config.get ctxt trace then print_tac ctxt msg
   else all_tac
 
 fun argo_trace_ctxt ctxt =
   if Config.get ctxt trace
   then Config.map (Argo_Tactic.trace) (K "basic") ctxt
   else ctxt
 
 fun IF_UNSOLVED' tac i = IF_UNSOLVED (tac i)
 fun REPEAT' tac i = REPEAT (tac i)
 
 fun free_in v ct = Cterms.defined (Cterms.build (Drule.add_frees_cterm ct)) v
 
 (* build a cterm set with elements cts of type ty *)
 fun mk_ct_set ctxt ty =
   map Thm.term_of #>
   HOLogic.mk_set ty #>
   Thm.cterm_of ctxt
 
 fun prenex_tac ctxt =
   let
     val prenex_simps = Proof_Context.get_thms ctxt @{named_theorems metric_prenex}
     val prenex_ctxt = put_simpset HOL_basic_ss ctxt addsimps prenex_simps
   in
     simp_tac prenex_ctxt THEN'
     K (trace_tac ctxt "Prenex form")
   end
 
 fun nnf_tac ctxt =
   let
     val nnf_simps = Proof_Context.get_thms ctxt @{named_theorems metric_nnf}
     val nnf_ctxt = put_simpset HOL_basic_ss ctxt addsimps nnf_simps
   in
     simp_tac nnf_ctxt THEN'
     K (trace_tac ctxt "NNF form")
   end
 
 fun unfold_tac ctxt =
   asm_full_simp_tac (put_simpset HOL_basic_ss ctxt addsimps (
     Proof_Context.get_thms ctxt @{named_theorems metric_unfold}))
 
 fun pre_arith_tac ctxt =
   simp_tac (put_simpset HOL_basic_ss ctxt addsimps (
     Proof_Context.get_thms ctxt @{named_theorems metric_pre_arith})) THEN'
     K (trace_tac ctxt "Prepared for decision procedure")
 
 fun dist_refl_sym_tac ctxt =
   let
     val refl_sym_simps = @{thms dist_self dist_commute add_0_right add_0_left simp_thms}
     val refl_sym_ctxt = put_simpset HOL_basic_ss ctxt addsimps refl_sym_simps
   in
     simp_tac refl_sym_ctxt THEN'
     K (trace_tac ctxt ("Simplified using " ^ @{make_string} refl_sym_simps))
   end
 
 fun is_exists ct =
   case Thm.term_of ct of
     Const (\<^const_name>\<open>HOL.Ex\<close>,_)$_ => true
   | Const (\<^const_name>\<open>Trueprop\<close>,_)$_ => is_exists (Thm.dest_arg ct)
   | _ => false
 
 fun is_forall ct =
   case Thm.term_of ct of
     Const (\<^const_name>\<open>HOL.All\<close>,_)$_ => true
   | Const (\<^const_name>\<open>Trueprop\<close>,_)$_ => is_forall (Thm.dest_arg ct)
   | _ => false
 
 fun dist_ty mty = mty --> mty --> \<^typ>\<open>real\<close>
 
 (* find all free points in ct of type metric_ty *)
 fun find_points ctxt metric_ty ct =
   let
     fun find ct =
       (if Thm.typ_of_cterm ct = metric_ty then [ct] else []) @ (
         case Thm.term_of ct of
           _ $ _ =>
           app_union_ct_pair find (Thm.dest_comb ct)
         | Abs (_, _, _) =>
           (* ensure the point doesn't contain the bound variable *)
           let val (var, bod) = Thm.dest_abs_global ct in
             filter (free_in var #> not) (find bod)
           end
         | _ => [])
     val points = find ct
   in
     case points of
       [] =>
       (* if no point can be found, invent one *)
       let
         val free_name = Term.variant_frees (Thm.term_of ct) [("x", metric_ty)]
       in
         map (Free #> Thm.cterm_of ctxt) free_name
       end
     | _ => points
   end
 
 (* find all cterms "dist x y" in ct, where x and y have type metric_ty *)
 fun find_dist metric_ty ct =
   let
     val dty = dist_ty metric_ty
     fun find ct =
       case Thm.term_of ct of
         Const (\<^const_name>\<open>dist\<close>, ty) $ _ $ _ =>
         if ty = dty then [ct] else []
       | _ $ _ =>
         app_union_ct_pair find (Thm.dest_comb ct)
       | Abs (_, _, _) =>
         let val (var, bod) = Thm.dest_abs_global ct in
           filter (free_in var #> not) (find bod)
         end
       | _ => []
   in
     find ct
   end
 
 (* find all "x=y", where x has type metric_ty *)
 fun find_eq metric_ty ct =
   let
     fun find ct =
       case Thm.term_of ct of
         Const (\<^const_name>\<open>HOL.eq\<close>, ty) $ _ $ _ =>
           if fst (dest_funT ty) = metric_ty
           then [ct]
           else app_union_ct_pair find (Thm.dest_binop ct)
       | _ $ _ => app_union_ct_pair find (Thm.dest_comb ct)
       | Abs (_, _, _) =>
         let val (var, bod) = Thm.dest_abs_global ct in
           filter (free_in var #> not) (find bod)
         end
       | _ => []
   in
     find ct
   end
 
 (* rewrite ct of the form "dist x y" using maxdist_thm *)
 fun maxdist_conv ctxt fset_ct ct =
   let
     val (xct, yct) = Thm.dest_binop ct
     val solve_prems =
       rule_by_tactic ctxt (ALLGOALS (simp_tac (put_simpset HOL_ss ctxt
         addsimps @{thms finite.emptyI finite_insert empty_iff insert_iff})))
     val image_simp =
       Simplifier.rewrite (put_simpset HOL_ss ctxt addsimps @{thms image_empty image_insert})
     val dist_refl_sym_simp =
       Simplifier.rewrite (put_simpset HOL_ss ctxt addsimps @{thms dist_commute dist_self})
     val algebra_simp =
       Simplifier.rewrite (put_simpset HOL_ss ctxt addsimps
         @{thms diff_self diff_0_right diff_0 abs_zero abs_minus_cancel abs_minus_commute})
     val insert_simp =
       Simplifier.rewrite (put_simpset HOL_ss ctxt addsimps @{thms insert_absorb2 insert_commute})
     val sup_simp =
       Simplifier.rewrite (put_simpset HOL_ss ctxt addsimps @{thms cSup_singleton Sup_insert_insert})
     val real_abs_dist_simp =
       Simplifier.rewrite (put_simpset HOL_ss ctxt addsimps @{thms real_abs_dist})
     val maxdist_thm =
       @{thm maxdist_thm} |>
       infer_instantiate' ctxt [SOME fset_ct, SOME xct, SOME yct] |>
       solve_prems
   in
     ((Conv.rewr_conv maxdist_thm) then_conv
     (* SUP to Sup *)
     image_simp then_conv
     dist_refl_sym_simp then_conv
     algebra_simp then_conv
     (* eliminate duplicate terms in set *)
     insert_simp then_conv
     (* Sup to max *)
     sup_simp then_conv
     real_abs_dist_simp) ct
   end
 
 (* rewrite ct of the form "x=y" using metric_eq_thm *)
 fun metric_eq_conv ctxt fset_ct ct =
   let
     val (xct, yct) = Thm.dest_binop ct
     val solve_prems =
       rule_by_tactic ctxt (ALLGOALS (simp_tac (put_simpset HOL_ss ctxt
         addsimps @{thms empty_iff insert_iff})))
     val ball_simp =
       Simplifier.rewrite (put_simpset HOL_ss ctxt addsimps
         @{thms Set.ball_empty ball_insert})
     val dist_refl_sym_simp =
       Simplifier.rewrite (put_simpset HOL_ss ctxt addsimps @{thms dist_commute dist_self})
     val metric_eq_thm =
       @{thm metric_eq_thm} |>
       infer_instantiate' ctxt [SOME xct, SOME fset_ct, SOME yct] |>
       solve_prems
   in
     ((Conv.rewr_conv metric_eq_thm) then_conv
     (* convert \<forall>x\<in>{x\<^sub>1,...,x\<^sub>n}. P x to P x\<^sub>1 \<and> ... \<and> P x\<^sub>n *)
     ball_simp then_conv
     dist_refl_sym_simp) ct
   end
 
 (* build list of theorems "0 \<le> dist x y" for all dist terms in ct *)
 fun augment_dist_pos ctxt metric_ty ct =
   let fun inst dist_ct =
     let val (xct, yct) = Thm.dest_binop dist_ct
     in infer_instantiate' ctxt [SOME xct, SOME yct] @{thm zero_le_dist} end
   in map inst (find_dist metric_ty ct) end
 
 (* apply maxdist_conv and metric_eq_conv to the goal, thereby embedding the goal in (\<real>\<^sup>n,dist\<^sub>\<infinity>) *)
-fun embedding_tac ctxt metric_ty i goal =
+fun embedding_tac ctxt metric_ty = CSUBGOAL (fn (goal, i) =>
   let
-    val ct = (Thm.cprem_of goal 1)
-    val points = find_points ctxt metric_ty ct
+    val points = find_points ctxt metric_ty goal
     val fset_ct = mk_ct_set ctxt metric_ty points
     (* embed all subterms of the form "dist x y" in (\<real>\<^sup>n,dist\<^sub>\<infinity>) *)
-    val eq1 = map (maxdist_conv ctxt fset_ct) (find_dist metric_ty ct)
+    val eq1 = map (maxdist_conv ctxt fset_ct) (find_dist metric_ty goal)
     (* replace point equality by equality of components in \<real>\<^sup>n *)
-    val eq2 = map (metric_eq_conv ctxt fset_ct) (find_eq metric_ty ct)
+    val eq2 = map (metric_eq_conv ctxt fset_ct) (find_eq metric_ty goal)
   in
     (K (trace_tac ctxt "Embedding into \<real>\<^sup>n") THEN'
-      CONVERSION (Conv.top_sweep_rewrs_conv (eq1 @ eq2) ctxt)) i goal
-  end
+      CONVERSION (Conv.top_sweep_rewrs_conv (eq1 @ eq2) ctxt)) i
+  end)
 
 (* decision procedure for linear real arithmetic *)
 fun lin_real_arith_tac ctxt metric_ty i goal =
   let
     val dist_thms = augment_dist_pos ctxt metric_ty (Thm.cprem_of goal 1)
     val ctxt' = argo_trace_ctxt ctxt
   in (Argo_Tactic.argo_tac ctxt' dist_thms) i goal end
 
 fun basic_metric_arith_tac ctxt metric_ty =
   HEADGOAL (dist_refl_sym_tac ctxt THEN'
   IF_UNSOLVED' (embedding_tac ctxt metric_ty) THEN'
   IF_UNSOLVED' (pre_arith_tac ctxt) THEN'
   IF_UNSOLVED' (lin_real_arith_tac ctxt metric_ty))
 
 (* tries to infer the metric space from ct from dist terms,
    if no dist terms are present, equality terms will be used *)
 fun guess_metric ctxt ct =
 let
   fun find_dist ct =
     case Thm.term_of ct of
       Const (\<^const_name>\<open>dist\<close>, ty) $ _ $ _  => SOME (fst (dest_funT ty))
     | _ $ _ =>
       let val (s, t) = Thm.dest_comb ct in
         default (find_dist t) (find_dist s)
       end
     | Abs (_, _, _) => find_dist (snd (Thm.dest_abs_global ct))
     | _ => NONE
   fun find_eq ct =
     case Thm.term_of ct of
       Const (\<^const_name>\<open>HOL.eq\<close>, ty) $ x $ _ =>
       let val (l, r) = Thm.dest_binop ct in
         if Sign.of_sort (Proof_Context.theory_of ctxt) (type_of x, \<^sort>\<open>metric_space\<close>)
         then SOME (fst (dest_funT ty))
         else default (find_dist r) (find_eq l)
       end
     | _ $ _ =>
       let val (s, t) = Thm.dest_comb ct in
         default (find_eq t) (find_eq s)
       end
     | Abs (_, _, _) => find_eq (snd (Thm.dest_abs_global ct))
     | _ => NONE
   in
     case default (find_eq ct) (find_dist ct) of
       SOME ty => ty
     | NONE => error "No Metric Space was found"
   end
 
 (* eliminate \<exists> by proving the goal for a single witness from the metric space *)
 fun elim_exists ctxt goal =
   let
     val ct = Thm.cprem_of goal 1
     val metric_ty = guess_metric ctxt ct
     val points = find_points ctxt metric_ty ct
 
     fun try_point ctxt pt =
       let val ex_rule = infer_instantiate' ctxt [NONE, SOME pt] @{thm exI}
       in
         HEADGOAL (resolve_tac ctxt [ex_rule] ORELSE'
         (* variable doesn't occur in body *)
         resolve_tac ctxt @{thms exI}) THEN
         trace_tac ctxt ("Removed existential quantifier, try " ^ @{make_string} pt) THEN
         try_points ctxt
       end
     and try_points ctxt goal = (
       if is_exists (Thm.cprem_of goal 1) then
         FIRST (map (try_point ctxt) points)
       else if is_forall (Thm.cprem_of goal 1) then
         HEADGOAL (resolve_tac ctxt @{thms HOL.allI} THEN'
         Subgoal.FOCUS (fn {context = ctxt', ...} =>
           trace_tac ctxt "Removed universal quantifier" THEN
           try_points ctxt') ctxt)
       else basic_metric_arith_tac ctxt metric_ty) goal
   in
     try_points ctxt goal
   end
 
 fun metric_arith_tac ctxt =
   (* unfold common definitions to get rid of sets *)
   unfold_tac ctxt THEN'
   (* remove all meta-level connectives *)
   IF_UNSOLVED' (Object_Logic.full_atomize_tac ctxt) THEN'
   (* convert goal to prenex form *)
   IF_UNSOLVED' (prenex_tac ctxt) THEN'
   (* and NNF to ? *)
   IF_UNSOLVED' (nnf_tac ctxt) THEN'
   (* turn all universally quantified variables into free variables, by focusing the subgoal *)
   REPEAT' (resolve_tac ctxt @{thms HOL.allI}) THEN'
   IF_UNSOLVED' (SUBPROOF (fn {context=ctxt', ...} =>
     trace_tac ctxt' "Focused on subgoal" THEN
     elim_exists ctxt') ctxt)
 
 end