diff --git a/src/Pure/sign.ML b/src/Pure/sign.ML
--- a/src/Pure/sign.ML
+++ b/src/Pure/sign.ML
@@ -1,547 +1,545 @@
 (*  Title:      Pure/sign.ML
     Author:     Lawrence C Paulson and Markus Wenzel
 
 Logical signature content: naming conventions, concrete syntax, type
 signature, polymorphic constants.
 *)
 
 signature SIGN =
 sig
   val change_begin: theory -> theory
   val change_end: theory -> theory
   val change_end_local: Proof.context -> Proof.context
   val change_check: theory -> theory
   val syn_of: theory -> Syntax.syntax
   val tsig_of: theory -> Type.tsig
   val classes_of: theory -> Sorts.algebra
   val all_classes: theory -> class list
   val super_classes: theory -> class -> class list
   val minimize_sort: theory -> sort -> sort
   val complete_sort: theory -> sort -> sort
   val set_defsort: sort -> theory -> theory
   val defaultS: theory -> sort
   val subsort: theory -> sort * sort -> bool
   val of_sort: theory -> typ * sort -> bool
   val inter_sort: theory -> sort * sort -> sort
   val witness_sorts: theory -> (typ * sort) list -> sort list -> (typ * sort) list
   val logical_types: theory -> string list
   val typ_instance: theory -> typ * typ -> bool
   val typ_equiv: theory -> typ * typ -> bool
   val typ_match: theory -> typ * typ -> Type.tyenv -> Type.tyenv
   val typ_unify: theory -> typ * typ -> Type.tyenv * int -> Type.tyenv * int
   val consts_of: theory -> Consts.T
   val the_const_constraint: theory -> string -> typ
   val const_type: theory -> string -> typ option
   val the_const_type: theory -> string -> typ
   val declared_tyname: theory -> string -> bool
   val declared_const: theory -> string -> bool
   val naming_of: theory -> Name_Space.naming
   val map_naming: (Name_Space.naming -> Name_Space.naming) -> theory -> theory
   val restore_naming: theory -> theory -> theory
   val inherit_naming: theory -> Proof.context -> Context.generic
   val full_name: theory -> binding -> string
   val full_name_path: theory -> string -> binding -> string
   val full_bname: theory -> bstring -> string
   val full_bname_path: theory -> string -> bstring -> string
   val const_monomorphic: theory -> string -> bool
   val const_typargs: theory -> string * typ -> typ list
   val const_instance: theory -> string * typ list -> typ
   val mk_const: theory -> string * typ list -> term
   val class_space: theory -> Name_Space.T
   val type_space: theory -> Name_Space.T
   val const_space: theory -> Name_Space.T
   val intern_class: theory -> xstring -> string
   val intern_type: theory -> xstring -> string
   val intern_const: theory -> xstring -> string
   val type_alias: binding -> string -> theory -> theory
   val const_alias: binding -> string -> theory -> theory
   val arity_number: theory -> string -> int
   val arity_sorts: theory -> string -> sort -> sort list
   val certify_class: theory -> class -> class
   val certify_sort: theory -> sort -> sort
   val certify_typ: theory -> typ -> typ
   val certify_typ_mode: Type.mode -> theory -> typ -> typ
   val certify': bool -> Context.generic -> bool -> Consts.T -> theory -> term -> term * typ * int
   val certify_term: theory -> term -> term * typ * int
   val cert_term: theory -> term -> term
   val cert_prop: theory -> term -> term
   val no_frees: Proof.context -> term -> term
   val no_vars: Proof.context -> term -> term
   val add_type: Proof.context -> binding * int * mixfix -> theory -> theory
   val add_types_global: (binding * int * mixfix) list -> theory -> theory
   val add_nonterminals: Proof.context -> binding list -> theory -> theory
   val add_nonterminals_global: binding list -> theory -> theory
   val add_type_abbrev: Proof.context -> binding * string list * typ -> theory -> theory
   val add_syntax: Syntax.mode -> (string * typ * mixfix) list -> theory -> theory
   val add_syntax_cmd: Syntax.mode -> (string * string * mixfix) list -> theory -> theory
   val del_syntax: Syntax.mode -> (string * typ * mixfix) list -> theory -> theory
   val del_syntax_cmd: Syntax.mode -> (string * string * mixfix) list -> theory -> theory
   val type_notation: bool -> Syntax.mode -> (typ * mixfix) list -> theory -> theory
   val notation: bool -> Syntax.mode -> (term * mixfix) list -> theory -> theory
   val declare_const: Proof.context -> (binding * typ) * mixfix -> theory -> term * theory
   val declare_const_global: (binding * typ) * mixfix -> theory -> term * theory
   val add_consts: (binding * typ * mixfix) list -> theory -> theory
   val add_consts_cmd: (binding * string * mixfix) list -> theory -> theory
   val add_abbrev: string -> binding * term -> theory -> (term * term) * theory
   val revert_abbrev: string -> string -> theory -> theory
   val add_const_constraint: string * typ option -> theory -> theory
   val primitive_class: binding * class list -> theory -> theory
   val primitive_classrel: class * class -> theory -> theory
   val primitive_arity: arity -> theory -> theory
   val parse_ast_translation:
     (string * (Proof.context -> Ast.ast list -> Ast.ast)) list -> theory -> theory
   val parse_translation:
     (string * (Proof.context -> term list -> term)) list -> theory -> theory
   val print_translation:
     (string * (Proof.context -> term list -> term)) list -> theory -> theory
   val typed_print_translation:
     (string * (Proof.context -> typ -> term list -> term)) list -> theory -> theory
   val print_ast_translation:
     (string * (Proof.context -> Ast.ast list -> Ast.ast)) list -> theory -> theory
   val add_trrules: Ast.ast Syntax.trrule list -> theory -> theory
   val del_trrules: Ast.ast Syntax.trrule list -> theory -> theory
   val get_scope: theory -> Binding.scope option
   val new_scope: theory -> Binding.scope * theory
   val new_group: theory -> theory
   val reset_group: theory -> theory
   val add_path: string -> theory -> theory
   val root_path: theory -> theory
   val parent_path: theory -> theory
   val mandatory_path: string -> theory -> theory
   val qualified_path: bool -> binding -> theory -> theory
   val local_path: theory -> theory
   val init_naming: theory -> theory
   val private_scope: Binding.scope -> theory -> theory
   val private: Position.T -> theory -> theory
   val qualified_scope: Binding.scope -> theory -> theory
   val qualified: Position.T -> theory -> theory
   val concealed: theory -> theory
   val hide_class: bool -> string -> theory -> theory
   val hide_type: bool -> string -> theory -> theory
   val hide_const: bool -> string -> theory -> theory
 end
 
 structure Sign: SIGN =
 struct
 
 (** datatype sign **)
 
 datatype sign = Sign of
  {syn: Syntax.syntax,           (*concrete syntax for terms, types, sorts*)
   tsig: Type.tsig,              (*order-sorted signature of types*)
   consts: Consts.T};            (*polymorphic constants*)
 
 fun make_sign (syn, tsig, consts) = Sign {syn = syn, tsig = tsig, consts = consts};
 
 structure Data = Theory_Data'
 (
   type T = sign;
-  fun extend (Sign {syn, tsig, consts, ...}) = make_sign (syn, tsig, consts);
-
+  val extend = I;
   val empty = make_sign (Syntax.empty_syntax, Type.empty_tsig, Consts.empty);
-
   fun merge old_thys (sign1, sign2) =
     let
       val Sign {syn = syn1, tsig = tsig1, consts = consts1} = sign1;
       val Sign {syn = syn2, tsig = tsig2, consts = consts2} = sign2;
 
       val syn = Syntax.merge_syntax (syn1, syn2);
       val tsig = Type.merge_tsig (Context.Theory (fst old_thys)) (tsig1, tsig2);
       val consts = Consts.merge (consts1, consts2);
     in make_sign (syn, tsig, consts) end;
 );
 
 fun rep_sg thy = Data.get thy |> (fn Sign args => args);
 
 fun map_sign f = Data.map (fn Sign {syn, tsig, consts} => make_sign (f (syn, tsig, consts)));
 
 fun map_syn f = map_sign (fn (syn, tsig, consts) => (f syn, tsig, consts));
 fun map_tsig f = map_sign (fn (syn, tsig, consts) => (syn, f tsig, consts));
 fun map_consts f = map_sign (fn (syn, tsig, consts) => (syn, tsig, f consts));
 
 
 (* linear change discipline *)
 
 fun change_base begin = map_sign (fn (syn, tsig, consts) =>
   (syn, Type.change_base begin tsig, Consts.change_base begin consts));
 
 val change_begin = change_base true;
 val change_end = change_base false;
 
 fun change_end_local ctxt =
   Context.raw_transfer (change_end (Proof_Context.theory_of ctxt)) ctxt;
 
 fun change_check thy =
   if can change_end thy
   then raise Fail "Unfinished linear change of theory content" else thy;
 
 
 (* syntax *)
 
 val syn_of = #syn o rep_sg;
 
 
 (* type signature *)
 
 val tsig_of = #tsig o rep_sg;
 
 val classes_of = #2 o #classes o Type.rep_tsig o tsig_of;
 val all_classes = Sorts.all_classes o classes_of;
 val super_classes = Sorts.super_classes o classes_of;
 val minimize_sort = Sorts.minimize_sort o classes_of;
 val complete_sort = Sorts.complete_sort o classes_of;
 
 val set_defsort = map_tsig o Type.set_defsort;
 val defaultS = Type.defaultS o tsig_of;
 val subsort = Type.subsort o tsig_of;
 val of_sort = Type.of_sort o tsig_of;
 val inter_sort = Type.inter_sort o tsig_of;
 val witness_sorts = Type.witness_sorts o tsig_of;
 val logical_types = Type.logical_types o tsig_of;
 
 val typ_instance = Type.typ_instance o tsig_of;
 fun typ_equiv thy (T, U) = typ_instance thy (T, U) andalso typ_instance thy (U, T);
 val typ_match = Type.typ_match o tsig_of;
 val typ_unify = Type.unify o tsig_of;
 
 
 (* polymorphic constants *)
 
 val consts_of = #consts o rep_sg;
 val the_const_constraint = Consts.the_constraint o consts_of;
 val the_const_type = #2 oo (Consts.the_const o consts_of);
 val const_type = try o the_const_type;
 val const_monomorphic = Consts.is_monomorphic o consts_of;
 val const_typargs = Consts.typargs o consts_of;
 val const_instance = Consts.instance o consts_of;
 
 fun mk_const thy (c, Ts) = Const (c, const_instance thy (c, Ts));
 
 fun declared_tyname ctxt c = can (Type.the_decl (tsig_of ctxt)) (c, Position.none);
 val declared_const = can o the_const_constraint;
 
 
 (* naming *)
 
 val naming_of = Name_Space.naming_of o Context.Theory;
 val map_naming = Context.theory_map o Name_Space.map_naming;
 val restore_naming = map_naming o K o naming_of;
 fun inherit_naming thy = Name_Space.map_naming (K (naming_of thy)) o Context.Proof;
 
 val full_name = Name_Space.full_name o naming_of;
 fun full_name_path thy path = Name_Space.full_name (Name_Space.add_path path (naming_of thy));
 
 fun full_bname thy = Name_Space.full_name (naming_of thy) o Binding.name;
 fun full_bname_path thy path = full_name_path thy path o Binding.name;
 
 
 
 (** name spaces **)
 
 val class_space = Type.class_space o tsig_of;
 val type_space = Type.type_space o tsig_of;
 val const_space = Consts.space_of o consts_of;
 
 val intern_class = Name_Space.intern o class_space;
 val intern_type = Name_Space.intern o type_space;
 val intern_const = Name_Space.intern o const_space;
 
 fun type_alias b c thy = map_tsig (Type.type_alias (naming_of thy) b c) thy;
 fun const_alias b c thy = map_consts (Consts.alias (naming_of thy) b c) thy;
 
 
 
 (** certify entities **)    (*exception TYPE*)
 
 (* certify wrt. type signature *)
 
 val arity_number = Type.arity_number o tsig_of;
 fun arity_sorts thy = Type.arity_sorts (Context.Theory thy) (tsig_of thy);
 
 val certify_class = Type.cert_class o tsig_of;
 val certify_sort = Type.cert_sort o tsig_of;
 val certify_typ = Type.cert_typ o tsig_of;
 fun certify_typ_mode mode = Type.cert_typ_mode mode o tsig_of;
 
 
 (* certify term/prop *)
 
 local
 
 fun type_check context tm =
   let
     fun err_appl bs t T u U =
       let
         val xs = map Free bs;           (*we do not rename here*)
         val t' = subst_bounds (xs, t);
         val u' = subst_bounds (xs, u);
         val msg = Type.appl_error (Syntax.init_pretty context) t' T u' U;
       in raise TYPE (msg, [T, U], [t', u']) end;
 
     fun typ_of (_, Const (_, T)) = T
       | typ_of (_, Free  (_, T)) = T
       | typ_of (_, Var (_, T)) = T
       | typ_of (bs, Bound i) = snd (nth bs i handle General.Subscript =>
           raise TYPE ("Loose bound variable: B." ^ string_of_int i, [], [Bound i]))
       | typ_of (bs, Abs (x, T, body)) = T --> typ_of ((x, T) :: bs, body)
       | typ_of (bs, t $ u) =
           let val T = typ_of (bs, t) and U = typ_of (bs, u) in
             (case T of
               Type ("fun", [T1, T2]) =>
                 if T1 = U then T2 else err_appl bs t T u U
             | _ => err_appl bs t T u U)
           end;
   in typ_of ([], tm) end;
 
 fun err msg = raise TYPE (msg, [], []);
 
 fun check_vars (t $ u) = (check_vars t; check_vars u)
   | check_vars (Abs (_, _, t)) = check_vars t
   | check_vars (Free (x, _)) =
       if Long_Name.is_qualified x then err ("Malformed variable: " ^ quote x) else ()
   | check_vars (Var (xi as (_, i), _)) =
       if i < 0 then err ("Malformed variable: " ^ quote (Term.string_of_vname xi)) else ()
   | check_vars _ = ();
 
 in
 
 fun certify' prop context do_expand consts thy tm =
   let
     val _ = check_vars tm;
     val tm' = Term.map_types (certify_typ thy) tm;
     val T = type_check context tm';
     val _ = if prop andalso T <> propT then err "Term not of type prop" else ();
     val tm'' = tm'
       |> Consts.certify context (tsig_of thy) do_expand consts
       |> Soft_Type_System.global_purge thy;
   in (if tm = tm'' then tm else tm'', T, Term.maxidx_of_term tm'') end;
 
 fun certify_term thy = certify' false (Context.Theory thy) true (consts_of thy) thy;
 fun cert_term_abbrev thy = #1 o certify' false (Context.Theory thy) false (consts_of thy) thy;
 val cert_term = #1 oo certify_term;
 fun cert_prop thy = #1 o certify' true (Context.Theory thy) true (consts_of thy) thy;
 
 end;
 
 
 (* specifications *)
 
 fun no_variables kind add addT mk mkT ctxt tm =
   (case (add tm [], addT tm []) of
     ([], []) => tm
   | (frees, tfrees) => error (Pretty.string_of (Pretty.block
       (Pretty.str ("Illegal " ^ kind ^ " variable(s) in term:") :: Pretty.brk 1 ::
        Pretty.commas
         (map (Syntax.pretty_term ctxt o mk) frees @ map (Syntax.pretty_typ ctxt o mkT) tfrees)))));
 
 val no_frees = no_variables "free" Term.add_frees Term.add_tfrees Free TFree;
 val no_vars = no_variables "schematic" Term.add_vars Term.add_tvars Var TVar;
 
 
 
 (** signature extension functions **)  (*exception ERROR/TYPE*)
 
 (* add type constructors *)
 
 fun add_type ctxt (b, n, mx) thy = thy |> map_sign (fn (syn, tsig, consts) =>
   let
     val type_syntax = (Lexicon.mark_type (full_name thy b), Mixfix.make_type n, mx);
     val syn' = Syntax.update_type_gram true Syntax.mode_default [type_syntax] syn;
     val tsig' = Type.add_type (inherit_naming thy ctxt) (b, n) tsig;
   in (syn', tsig', consts) end);
 
 fun add_types_global types thy =
   fold (add_type (Syntax.init_pretty_global thy)) types thy;
 
 
 (* add nonterminals *)
 
 fun add_nonterminals ctxt ns thy = thy |> map_sign (fn (syn, tsig, consts) =>
   (syn, fold (Type.add_nonterminal (inherit_naming thy ctxt)) ns tsig, consts));
 
 fun add_nonterminals_global ns thy =
   add_nonterminals (Syntax.init_pretty_global thy) ns thy;
 
 
 (* add type abbreviations *)
 
 fun add_type_abbrev ctxt abbr thy = thy |> map_sign (fn (syn, tsig, consts) =>
   (syn, Type.add_abbrev (inherit_naming thy ctxt) abbr tsig, consts));
 
 
 (* modify syntax *)
 
 fun gen_syntax change_gram parse_typ mode args thy =
   let
     val ctxt = Type.set_mode Type.mode_syntax (Proof_Context.init_global thy);
     fun prep (c, T, mx) = (c, certify_typ_mode Type.mode_syntax thy (parse_typ ctxt T), mx)
       handle ERROR msg => cat_error msg ("in syntax declaration " ^ quote c);
   in thy |> map_syn (change_gram (logical_types thy) mode (map prep args)) end;
 
 fun gen_add_syntax x = gen_syntax (Syntax.update_const_gram true) x;
 
 val add_syntax = gen_add_syntax (K I);
 val add_syntax_cmd = gen_add_syntax Syntax.read_typ;
 val del_syntax = gen_syntax (Syntax.update_const_gram false) (K I);
 val del_syntax_cmd = gen_syntax (Syntax.update_const_gram false) Syntax.read_typ;
 
 fun type_notation add mode args =
   let
     fun type_syntax (Type (c, args), mx) =
           SOME (Lexicon.mark_type c, Mixfix.make_type (length args), mx)
       | type_syntax _ = NONE;
   in map_syn (Syntax.update_type_gram add mode (map_filter type_syntax args)) end;
 
 fun notation add mode args thy =
   let
     fun const_syntax (Const (c, _), mx) =
           (case try (Consts.type_scheme (consts_of thy)) c of
             SOME T => SOME (Lexicon.mark_const c, T, mx)
           | NONE => NONE)
       | const_syntax _ = NONE;
   in gen_syntax (Syntax.update_const_gram add) (K I) mode (map_filter const_syntax args) thy end;
 
 
 (* add constants *)
 
 local
 
 fun gen_add_consts prep_typ ctxt raw_args thy =
   let
     val prepT = Type.no_tvars o Term.no_dummyT o certify_typ thy o prep_typ ctxt;
     fun prep (b, raw_T, mx) =
       let
         val c = full_name thy b;
         val T = (prepT raw_T handle TYPE (msg, _, _) => error msg) handle ERROR msg =>
           cat_error msg ("in declaration of constant " ^ Binding.print b);
         val T' = Logic.varifyT_global T;
       in ((b, T'), (Lexicon.mark_const c, T', mx), Const (c, T)) end;
     val args = map prep raw_args;
   in
     thy
     |> map_consts (fold (Consts.declare (inherit_naming thy ctxt) o #1) args)
     |> add_syntax Syntax.mode_default (map #2 args)
     |> pair (map #3 args)
   end;
 
 in
 
 fun add_consts args thy =
   #2 (gen_add_consts (K I) (Proof_Context.init_global thy) args thy);
 
 fun add_consts_cmd args thy =
   #2 (gen_add_consts Syntax.read_typ (Proof_Context.init_global thy) args thy);
 
 fun declare_const ctxt ((b, T), mx) = yield_singleton (gen_add_consts (K I) ctxt) (b, T, mx);
 fun declare_const_global arg thy = declare_const (Proof_Context.init_global thy) arg thy;
 
 end;
 
 
 (* abbreviations *)
 
 fun add_abbrev mode (b, raw_t) thy =  (* FIXME proper ctxt (?) *)
   let
     val ctxt = Syntax.init_pretty_global thy;
     val prep_tm = no_frees ctxt o Term.no_dummy_patterns o cert_term_abbrev thy;
     val t = (prep_tm raw_t handle TYPE (msg, _, _) => error msg | TERM (msg, _) => error msg)
       handle ERROR msg => cat_error msg ("in constant abbreviation " ^ Binding.print b);
     val (res, consts') = consts_of thy
       |> Consts.abbreviate (inherit_naming thy ctxt) (tsig_of thy) mode (b, t);
   in (res, thy |> map_consts (K consts')) end;
 
 fun revert_abbrev mode c = map_consts (Consts.revert_abbrev mode c);
 
 
 (* add constraints *)
 
 fun add_const_constraint (c, opt_T) thy =
   let
     fun prepT raw_T =
       let val T = Logic.varifyT_global (Type.no_tvars (Term.no_dummyT (certify_typ thy raw_T)))
       in cert_term thy (Const (c, T)); T end
       handle TYPE (msg, _, _) => error msg;
   in thy |> map_consts (Consts.constrain (c, Option.map prepT opt_T)) end;
 
 
 (* primitive classes and arities *)
 
 fun primitive_class (bclass, classes) thy =
   thy
   |> map_sign (fn (syn, tsig, consts) =>
       let val tsig' = Type.add_class (Context.Theory thy) (bclass, classes) tsig;
       in (syn, tsig', consts) end)
   |> add_consts [(Binding.map_name Logic.const_of_class bclass, Term.a_itselfT --> propT, NoSyn)];
 
 fun primitive_classrel arg thy =
   thy |> map_tsig (Type.add_classrel (Context.Theory thy) arg);
 
 fun primitive_arity arg thy =
   thy |> map_tsig (Type.add_arity (Context.Theory thy) arg);
 
 
 (* add translation functions *)
 
 local
 
 fun mk trs = map Syntax_Ext.mk_trfun trs;
 
 in
 
 fun parse_ast_translation atrs = map_syn (Syntax.update_trfuns (mk atrs, [], [], []));
 fun parse_translation trs = map_syn (Syntax.update_trfuns ([], mk trs, [], []));
 fun print_translation tr's =
   map_syn (Syntax.update_trfuns ([], [], mk (map (apsnd Syntax_Trans.non_typed_tr') tr's), []));
 fun typed_print_translation tr's = map_syn (Syntax.update_trfuns ([], [], mk tr's, []));
 fun print_ast_translation atr's = map_syn (Syntax.update_trfuns ([], [], [], mk atr's));
 
 end;
 
 
 (* translation rules *)
 
 val add_trrules = map_syn o Syntax.update_trrules;
 val del_trrules = map_syn o Syntax.remove_trrules;
 
 
 (* naming *)
 
 val get_scope = Name_Space.get_scope o naming_of;
 
 fun new_scope thy =
   let
     val (scope, naming') = Name_Space.new_scope (naming_of thy);
     val thy' = map_naming (K naming') thy;
   in (scope, thy') end;
 
 val new_group = map_naming Name_Space.new_group;
 val reset_group = map_naming Name_Space.reset_group;
 
 val add_path = map_naming o Name_Space.add_path;
 val root_path = map_naming Name_Space.root_path;
 val parent_path = map_naming Name_Space.parent_path;
 val mandatory_path = map_naming o Name_Space.mandatory_path;
 val qualified_path = map_naming oo Name_Space.qualified_path;
 
 fun local_path thy = thy |> root_path |> add_path (Context.theory_name thy);
 
 fun init_naming thy =
   let
     val theory_naming = Name_Space.global_naming
       |> Name_Space.set_theory_long_name (Context.theory_long_name thy);
   in map_naming (K theory_naming) thy end;
 
 val private_scope = map_naming o Name_Space.private_scope;
 val private = map_naming o Name_Space.private;
 val qualified_scope = map_naming o Name_Space.qualified_scope;
 val qualified = map_naming o Name_Space.qualified;
 val concealed = map_naming Name_Space.concealed;
 
 
 (* hide names *)
 
 val hide_class = map_tsig oo Type.hide_class;
 val hide_type = map_tsig oo Type.hide_type;
 val hide_const = map_consts oo Consts.hide;
 
 end;