src/Pure/Isar/locale.ML

refined activate_notes: simultaneous transformation before activation;
actually export all_registrations_of;

(*  Title:      Pure/Isar/locale.ML
    Author:     Clemens Ballarin, TU Muenchen

Locales -- managed Isar proof contexts, based on Pure predicates.

Draws basic ideas from Florian Kammueller's original version of
locales, but uses the richer infrastructure of Isar instead of the raw
meta-logic.  Furthermore, structured import of contexts (with merge
and rename operations) are provided, as well as type-inference of the
signature parts, and predicate definitions of the specification text.

Interpretation enables the reuse of theorems of locales in other
contexts, namely those defined by theories, structured proofs and
locales themselves.

See also:

[1] Clemens Ballarin. Locales and Locale Expressions in Isabelle/Isar.
    In Stefano Berardi et al., Types for Proofs and Programs: International
    Workshop, TYPES 2003, Torino, Italy, LNCS 3085, pages 34-50, 2004.
[2] Clemens Ballarin. Interpretation of Locales in Isabelle: Managing
    Dependencies between Locales. Technical Report TUM-I0607, Technische
    Universitaet Muenchen, 2006.
[3] Clemens Ballarin. Interpretation of Locales in Isabelle: Theories and
    Proof Contexts. In J.M. Borwein and W.M. Farmer, MKM 2006, LNAI 4108,
    pages 31-43, 2006.
*)

signature LOCALE =
sig
  (* Locale specification *)
  val register_locale: binding ->
    (string * sort) list * ((string * typ) * mixfix) list ->
    term option * term list ->
    thm option * thm option -> thm list ->
    declaration list ->
    (string * (Attrib.binding * (thm list * Attrib.src list) list) list) list ->
    (string * morphism) list -> theory -> theory
  val intern: theory -> xstring -> string
  val check: theory -> xstring * Position.T -> string
  val extern: theory -> string -> xstring
  val defined: theory -> string -> bool
  val params_of: theory -> string -> ((string * typ) * mixfix) list
  val intros_of: theory -> string -> thm option * thm option
  val axioms_of: theory -> string -> thm list
  val instance_of: theory -> string -> morphism -> term list
  val specification_of: theory -> string -> term option * term list

  (* Storing results *)
  val add_thmss: string -> string -> (Attrib.binding * (thm list * Attrib.src list) list) list ->
    Proof.context -> Proof.context
  val add_declaration: string -> declaration -> Proof.context -> Proof.context
  val add_syntax_declaration: string -> declaration -> Proof.context -> Proof.context

  (* Activation *)
  val activate_declarations: string * morphism -> Proof.context -> Proof.context
  val activate_facts: morphism option -> string * morphism -> Context.generic -> Context.generic
  val init: string -> theory -> Proof.context

  (* Reasoning about locales *)
  val get_witnesses: Proof.context -> thm list
  val get_intros: Proof.context -> thm list
  val get_unfolds: Proof.context -> thm list
  val witness_add: attribute
  val intro_add: attribute
  val unfold_add: attribute
  val intro_locales_tac: bool -> Proof.context -> thm list -> tactic

  (* Registrations and dependencies *)
  val add_registration: string * morphism -> (morphism * bool) option ->
    morphism -> Context.generic -> Context.generic
  val amend_registration: string * morphism -> morphism * bool ->
    morphism -> Context.generic -> Context.generic
  val registrations_of: Context.generic -> string -> (string * morphism) list
  val all_registrations_of: Context.generic -> (string * morphism) list
  val add_dependency: string -> string * morphism -> (morphism * bool) option ->
    morphism -> theory -> theory

  (* Diagnostic *)
  val all_locales: theory -> string list
  val print_locales: theory -> unit
  val print_locale: theory -> bool -> xstring -> unit
  val print_registrations: Proof.context -> string -> unit
  val print_dependencies: Proof.context -> bool -> morphism -> (string * morphism) list -> unit
  val locale_deps: theory ->
    {params: ((string * typ) * mixfix) list, axioms: term list, registrations: term list list} Graph.T
      * term list list Symtab.table Symtab.table
end;

structure Locale: LOCALE =
struct

datatype ctxt = datatype Element.ctxt;


(*** Locales ***)

type mixins = (((morphism * bool) * serial) list) Inttab.table;
  (* table of mixin lists, per list mixins in reverse order of declaration;
     lists indexed by registration/dependency serial,
     entries for empty lists may be omitted *)

fun lookup_mixins serial' mixins = Inttab.lookup_list mixins serial';

fun merge_mixins mixs : mixins = Inttab.merge_list (eq_snd op =) mixs;

fun insert_mixin serial' mixin = Inttab.cons_list (serial', (mixin, serial ()));

fun rename_mixin (old, new) mix =
  (case Inttab.lookup mix old of
    NONE => mix
  | SOME mxs => Inttab.delete old mix |> Inttab.update_new (new, mxs));

fun compose_mixins mixins =
  fold_rev Morphism.compose (map (fst o fst) mixins) Morphism.identity;

datatype locale = Loc of {
  (** static part **)
  parameters: (string * sort) list * ((string * typ) * mixfix) list,
    (* type and term parameters *)
  spec: term option * term list,
    (* assumptions (as a single predicate expression) and defines *)
  intros: thm option * thm option,
  axioms: thm list,
  (** dynamic part **)
  syntax_decls: (declaration * serial) list,
    (* syntax declarations *)
  notes: ((string * (Attrib.binding * (thm list * Attrib.src list) list) list) * serial) list,
    (* theorem declarations *)
  dependencies: ((string * (morphism * morphism)) * serial) list
    (* locale dependencies (sublocale relation) in reverse order *),
  mixins: mixins
    (* mixin part of dependencies *)
};

fun mk_locale ((parameters, spec, intros, axioms),
    ((syntax_decls, notes), (dependencies, mixins))) =
  Loc {parameters = parameters, intros = intros, axioms = axioms, spec = spec,
    syntax_decls = syntax_decls, notes = notes, dependencies = dependencies, mixins = mixins};

fun map_locale f (Loc {parameters, spec, intros, axioms,
    syntax_decls, notes, dependencies, mixins}) =
  mk_locale (f ((parameters, spec, intros, axioms),
    ((syntax_decls, notes), (dependencies, mixins))));

fun merge_locale
 (Loc {parameters, spec, intros, axioms, syntax_decls, notes, dependencies, mixins},
  Loc {syntax_decls = syntax_decls', notes = notes',
      dependencies = dependencies', mixins = mixins', ...}) =
    mk_locale
      ((parameters, spec, intros, axioms),
        ((merge (eq_snd op =) (syntax_decls, syntax_decls'),
          merge (eq_snd op =) (notes, notes')),
            (merge (eq_snd op =) (dependencies, dependencies'),
              (merge_mixins (mixins, mixins')))));

structure Locales = Theory_Data
(
  type T = locale Name_Space.table;
  val empty : T = Name_Space.empty_table "locale";
  val extend = I;
  val merge = Name_Space.join_tables (K merge_locale);
);

val intern = Name_Space.intern o #1 o Locales.get;
fun check thy = #1 o Name_Space.check (Proof_Context.init_global thy) (Locales.get thy);
fun extern thy = Name_Space.extern (Proof_Context.init_global thy) (#1 (Locales.get thy));

val get_locale = Symtab.lookup o #2 o Locales.get;
val defined = Symtab.defined o #2 o Locales.get;

fun the_locale thy name =
  (case get_locale thy name of
    SOME (Loc loc) => loc
  | NONE => error ("Unknown locale " ^ quote name));

fun register_locale binding parameters spec intros axioms syntax_decls notes dependencies thy =
  thy |> Locales.map (Name_Space.define (Proof_Context.init_global thy) true (Sign.naming_of thy)
    (binding,
      mk_locale ((parameters, spec, intros, axioms),
        ((map (fn decl => (decl, serial ())) syntax_decls, map (fn n => (n, serial ())) notes),
          (map (fn d => (d |> apsnd (rpair Morphism.identity), serial ())) dependencies,
            Inttab.empty)))) #> snd);
          (* FIXME Morphism.identity *)

fun change_locale name =
  Locales.map o apsnd o Symtab.map_entry name o map_locale o apsnd;


(** Primitive operations **)

fun params_of thy = snd o #parameters o the_locale thy;

fun intros_of thy = #intros o the_locale thy;

fun axioms_of thy = #axioms o the_locale thy;

fun instance_of thy name morph = params_of thy name |>
  map (Morphism.term morph o Free o #1);

fun specification_of thy = #spec o the_locale thy;

fun dependencies_of thy name = the_locale thy name |>
  #dependencies;

fun mixins_of thy name serial = the_locale thy name |>
  #mixins |> lookup_mixins serial;

(* FIXME unused *)
fun identity_on thy name morph =
  let val mk_instance = instance_of thy name
  in ListPair.all Term.aconv_untyped (mk_instance Morphism.identity, mk_instance morph) end;

(* Print instance and qualifiers *)

fun pretty_reg ctxt (name, morph) =
  let
    val thy = Proof_Context.theory_of ctxt;
    val name' = extern thy name;
    fun prt_qual (qual, mand) = Pretty.str (qual ^ (if mand then "!" else "?"));
    fun prt_quals qs = Pretty.separate "." (map prt_qual qs) |> Pretty.block;
    val prt_term = Pretty.quote o Syntax.pretty_term ctxt;
    fun prt_term' t =
      if Config.get ctxt show_types
      then Pretty.block [prt_term t, Pretty.brk 1, Pretty.str "::",
        Pretty.brk 1, (Pretty.quote o Syntax.pretty_typ ctxt) (type_of t)]
      else prt_term t;
    fun prt_inst ts =
      Pretty.block (Pretty.breaks (Pretty.str name' :: map prt_term' ts));

    val qs = Binding.name "x" |> Morphism.binding morph |> Binding.prefix_of;
    val ts = instance_of thy name morph;
  in
    (case qs of
      [] => prt_inst ts
    | qs => Pretty.block [prt_quals qs, Pretty.brk 1, Pretty.str ":", Pretty.brk 1, prt_inst ts])
  end;


(*** Identifiers: activated locales in theory or proof context ***)

type idents = term list list Symtab.table;  (* name ~> instance (grouped by name) *)

val empty_idents : idents = Symtab.empty;
val insert_idents = Symtab.insert_list (eq_list (op aconv));
val merge_idents = Symtab.merge_list (eq_list (op aconv));

fun redundant_ident thy idents (name, instance) =
  exists (fn pat => Pattern.matchess thy (pat, instance)) (Symtab.lookup_list idents name);

structure Idents = Generic_Data
(
  type T = idents;
  val empty = empty_idents;
  val extend = I;
  val merge = merge_idents;
);


(** Resolve locale dependencies in a depth-first fashion **)

local

val roundup_bound = 120;

fun add thy depth stem export (name, morph, mixins) (deps, marked) =
  if depth > roundup_bound
  then error "Roundup bound exceeded (sublocale relation probably not terminating)."
  else
    let
      val instance = instance_of thy name (morph $> stem $> export);
    in
      if redundant_ident thy marked (name, instance) then (deps, marked)
      else
        let
          val full_morph = morph $> compose_mixins mixins $> stem;
          (* no inheritance of mixins, regardless of requests by clients *)
          val dependencies = dependencies_of thy name |>
            map (fn ((name', (morph', export')), serial') =>
              (name', morph' $> export', mixins_of thy name serial'));
          val marked' = insert_idents (name, instance) marked;
          val (deps', marked'') =
            fold_rev (add thy (depth + 1) full_morph export) dependencies
              ([], marked');
        in
          ((name, full_morph) :: deps' @ deps, marked'')
        end
    end;

in

(* Note that while identifiers always have the external (exported) view, activate_dep
   is presented with the internal view. *)

fun roundup thy activate_dep export (name, morph) (marked, input) =
  let
    (* Find all dependencies including new ones (which are dependencies enriching
      existing registrations). *)
    val (dependencies, marked') =
      add thy 0 Morphism.identity export (name, morph, []) ([], empty_idents);
    (* Filter out fragments from marked; these won't be activated. *)
    val dependencies' = filter_out (fn (name, morph) =>
      redundant_ident thy marked (name, instance_of thy name (morph $> export))) dependencies;
  in
    (merge_idents (marked, marked'), input |> fold_rev activate_dep dependencies')
  end;

end;


(*** Registrations: interpretations in theories or proof contexts ***)

val total_ident_ord = prod_ord fast_string_ord (list_ord Term_Ord.fast_term_ord);

structure Idtab = Table(type key = string * term list val ord = total_ident_ord);

structure Registrations = Generic_Data
(
  type T = ((morphism * morphism) * serial) Idtab.table * mixins;
    (* registrations, indexed by locale name and instance;
       unique registration serial points to mixin list *)
  val empty = (Idtab.empty, Inttab.empty);
  val extend = I;
  fun merge ((reg1, mix1), (reg2, mix2)) : T =
    (Idtab.join (fn id => fn ((_, s1), (_, s2)) =>
        if s1 = s2 then raise Idtab.SAME else raise Idtab.DUP id) (reg1, reg2),
      merge_mixins (mix1, mix2))
    handle Idtab.DUP id =>
      (* distinct interpretations with same base: merge their mixins *)
      let
        val (_, s1) = Idtab.lookup reg1 id |> the;
        val (morph2, s2) = Idtab.lookup reg2 id |> the;
        val reg2' = Idtab.update (id, (morph2, s1)) reg2;
        val _ = warning "Removed duplicate interpretation after retrieving its mixins.";
        (* FIXME print interpretations,
           which is not straightforward without theory context *)
      in merge ((reg1, mix1), (reg2', rename_mixin (s2, s1) mix2)) end;
    (* FIXME consolidate with dependencies, consider one data slot only *)
);


(* Primitive operations *)

fun add_reg thy export (name, morph) =
  Registrations.map (apfst (Idtab.insert (K false)
    ((name, instance_of thy name (morph $> export)), ((morph, export), serial ()))));

fun add_mixin serial' mixin =
  (* registration to be amended identified by its serial id *)
  Registrations.map (apsnd (insert_mixin serial' mixin));

fun get_mixins context (name, morph) =
  let
    val thy = Context.theory_of context;
    val (regs, mixins) = Registrations.get context;
  in
    (case Idtab.lookup regs (name, instance_of thy name morph) of
      NONE => []
    | SOME (_, serial) => lookup_mixins serial mixins)
  end;

fun collect_mixins context (name, morph) =
  let
    val thy = Context.theory_of context;
  in
    roundup thy (fn dep => fn mixins => merge (eq_snd op =) (mixins, get_mixins context dep))
      Morphism.identity (name, morph)
      (insert_idents (name, instance_of thy name morph) empty_idents, [])
    |> snd |> filter (snd o fst)  (* only inheritable mixins *)
    |> (fn x => merge (eq_snd op =) (x, get_mixins context (name, morph)))
    |> compose_mixins
  end;

fun get_registrations context select =
  Registrations.get context
  |>> Idtab.dest |>> select
  (* with inherited mixins *)
  |-> (fn regs => fn _ => map (fn ((name, _), ((base, export) ,_)) =>
    (name, base $> (collect_mixins context (name, base $> export)) $> export)) regs);

fun registrations_of context name =
  get_registrations context (filter (curry (op =) name o fst o fst));

fun all_registrations_of context = get_registrations context I;


(*** Activate context elements of locale ***)

(* Declarations, facts and entire locale content *)

fun activate_syntax_decls (name, morph) context =
  let
    val thy = Context.theory_of context;
    val {syntax_decls, ...} = the_locale thy name;
  in
    context
    |> fold_rev (fn (decl, _) => decl morph) syntax_decls
  end;

fun activate_notes activ_elem transfer context export' (name, morph) input =
  let
    val thy = Context.theory_of context;
    val mixin =
      (case export' of
        NONE => Morphism.identity
      | SOME export => collect_mixins context (name, morph $> export) $> export);
    val morph' = transfer input $> morph $> mixin;
    val notes' = map (Element.transform_ctxt morph' o Notes o #1) (#notes (the_locale thy name));
  in
    fold_rev (fn elem => fn res => activ_elem (Element.transform_ctxt (transfer res) elem) res)
      notes' input
  end;

fun activate_all name thy activ_elem transfer (marked, input) =
  let
    val {parameters = (_, params), spec = (asm, defs), ...} = the_locale thy name;
    val input' = input |>
      (not (null params) ?
        activ_elem (Fixes (map (fn ((x, T), mx) => (Binding.name x, SOME T, mx)) params))) |>
      (* FIXME type parameters *)
      (case asm of SOME A => activ_elem (Assumes [(Attrib.empty_binding, [(A, [])])]) | _ => I) |>
      (not (null defs) ?
        activ_elem (Defines (map (fn def => (Attrib.empty_binding, (def, []))) defs)));
    val activate = activate_notes activ_elem transfer (Context.Theory thy) NONE;
  in
    roundup thy activate Morphism.identity (name, Morphism.identity) (marked, input')
  end;


(** Public activation functions **)

fun activate_declarations dep = Context.proof_map (fn context =>
  let
    val thy = Context.theory_of context;
  in
    roundup thy activate_syntax_decls Morphism.identity dep (Idents.get context, context)
    |-> Idents.put
  end);

fun activate_facts export dep context =
  let
    val thy = Context.theory_of context;
    val activate =
      activate_notes Element.init (Element.transfer_morphism o Context.theory_of) context export;
  in
    roundup thy activate (the_default Morphism.identity export) dep (Idents.get context, context)
    |-> Idents.put
  end;

fun init name thy =
  activate_all name thy Element.init (Element.transfer_morphism o Context.theory_of)
    (empty_idents, Context.Proof (Proof_Context.init_global thy))
  |-> Idents.put |> Context.proof_of;


(*** Add and extend registrations ***)

fun amend_registration (name, morph) mixin export context =
  let
    val thy = Context.theory_of context;
    val regs = Registrations.get context |> fst;
    val base = instance_of thy name (morph $> export);
  in
    (case Idtab.lookup regs (name, base) of
      NONE =>
        error ("No interpretation of locale " ^
          quote (extern thy name) ^ " with\nparameter instantiation " ^
          space_implode " " (map (quote o Syntax.string_of_term_global thy) base) ^
          " available")
    | SOME (_, serial') => add_mixin serial' mixin context)
  end;

(* Note that a registration that would be subsumed by an existing one will not be
   generated, and it will not be possible to amend it. *)

fun add_registration (name, base_morph) mixin export context =
  let
    val thy = Context.theory_of context;
    val mix = (case mixin of NONE => Morphism.identity | SOME (mix, _) => mix);
    val morph = base_morph $> mix;
    val inst = instance_of thy name morph;
  in
    if redundant_ident thy (Idents.get context) (name, inst)
    then context  (* FIXME amend mixins? *)
    else
      (Idents.get context, context)
      (* add new registrations with inherited mixins *)
      |> (snd o roundup thy (add_reg thy export) export (name, morph))
      (* add mixin *)
      |> (case mixin of NONE => I | SOME mixin => amend_registration (name, morph) mixin export)
      (* activate import hierarchy as far as not already active *)
      |> activate_facts (SOME export) (name, morph)
  end;


(*** Dependencies ***)

(*
fun amend_dependency loc (name, morph) mixin export thy =
  let
    val deps = dependencies_of thy loc;
  in
    case AList.lookup (fn ((name, morph), ((name', (morph', _)), _)) =>
      total_ident_ord ((name, instance_of thy name morph), (name', instance_of thy name' morph')) = EQUAL) deps (name, morph) of
        NONE => error ("Locale " ^
          quote (extern thy name) ^ " with\parameter instantiation " ^
          space_implode " " (map (quote o Syntax.string_of_term_global thy) morph) ^
          " not a sublocale of " ^ quote (extern thy loc))
      | SOME (_, serial') => change_locale ...
  end;
*)

fun add_dependency loc (name, morph) mixin export thy =
  let
    val serial' = serial ();
    val thy' = thy |>
      (change_locale loc o apsnd)
        (apfst (cons ((name, (morph, export)), serial')) #>
          apsnd (case mixin of NONE => I | SOME mixin => insert_mixin serial' mixin));
    val context' = Context.Theory thy';
    val (_, regs) =
      fold_rev (roundup thy' cons export)
        (registrations_of context' loc) (Idents.get context', []);
  in
    thy'
    |> fold_rev (fn dep => Context.theory_map (add_registration dep NONE export)) regs
  end;


(*** Storing results ***)

(* Theorems *)

fun add_thmss loc kind facts ctxt =
  ctxt
  |> Proof_Context.note_thmss kind
    (Attrib.map_facts (map (Attrib.attribute_i (Proof_Context.theory_of ctxt))) facts)
  |> snd
  |> Proof_Context.background_theory
    ((change_locale loc o apfst o apsnd) (cons ((kind, facts), serial ())) #>
      (* Registrations *)
      (fn thy => fold_rev (fn (_, morph) =>
            let
              val facts' = facts
                |> Element.transform_facts morph
                |> Attrib.map_facts (map (Attrib.attribute_i thy));
            in snd o Global_Theory.note_thmss kind facts' end)
        (registrations_of (Context.Theory thy) loc) thy));


(* Declarations *)

fun add_declaration loc decl =
  add_thmss loc ""
    [((Binding.conceal Binding.empty,
        [Attrib.internal (fn phi => Thm.declaration_attribute (K (decl phi)))]),
      [([Drule.dummy_thm], [])])];

fun add_syntax_declaration loc decl =
  Proof_Context.background_theory ((change_locale loc o apfst o apfst) (cons (decl, serial ())))
  #> add_declaration loc decl;


(*** Reasoning about locales ***)

(* Storage for witnesses, intro and unfold rules *)

structure Thms = Generic_Data
(
  type T = thm list * thm list * thm list;
  val empty = ([], [], []);
  val extend = I;
  fun merge ((witnesses1, intros1, unfolds1), (witnesses2, intros2, unfolds2)) =
   (Thm.merge_thms (witnesses1, witnesses2),
    Thm.merge_thms (intros1, intros2),
    Thm.merge_thms (unfolds1, unfolds2));
);

val get_witnesses = #1 o Thms.get o Context.Proof;
val get_intros = #2 o Thms.get o Context.Proof;
val get_unfolds = #3 o Thms.get o Context.Proof;

val witness_add =
  Thm.declaration_attribute (fn th => Thms.map (fn (x, y, z) => (Thm.add_thm th x, y, z)));
val intro_add =
  Thm.declaration_attribute (fn th => Thms.map (fn (x, y, z) => (x, Thm.add_thm th y, z)));
val unfold_add =
  Thm.declaration_attribute (fn th => Thms.map (fn (x, y, z) => (x, y, Thm.add_thm th z)));


(* Tactics *)

fun gen_intro_locales_tac intros_tac eager ctxt =
  intros_tac
    (get_witnesses ctxt @ get_intros ctxt @ (if eager then get_unfolds ctxt else []));

val intro_locales_tac = gen_intro_locales_tac Method.intros_tac;
val try_intro_locales_tac= gen_intro_locales_tac Method.try_intros_tac;

val _ = Context.>> (Context.map_theory
 (Method.setup (Binding.name "intro_locales") (Scan.succeed (METHOD o try_intro_locales_tac false))
    "back-chain introduction rules of locales without unfolding predicates" #>
  Method.setup (Binding.name "unfold_locales") (Scan.succeed (METHOD o try_intro_locales_tac true))
    "back-chain all introduction rules of locales"));


(*** diagnostic commands and interfaces ***)

val all_locales = Symtab.keys o snd o Locales.get;

fun print_locales thy =
  Pretty.strs ("locales:" ::
    map #1 (Name_Space.extern_table (Proof_Context.init_global thy) (Locales.get thy)))
  |> Pretty.writeln;

fun print_locale thy show_facts raw_name =
  let
    val name = intern thy raw_name;
    val ctxt = init name thy;
    fun cons_elem (elem as Notes _) = show_facts ? cons elem
      | cons_elem elem = cons elem;
    val elems =
      activate_all name thy cons_elem (K (Element.transfer_morphism thy)) (empty_idents, [])
      |> snd |> rev;
  in
    Pretty.big_list "locale elements:" (map (Pretty.chunks o Element.pretty_ctxt ctxt) elems)
    |> Pretty.writeln
  end;

fun print_registrations ctxt raw_name =
  let
    val thy = Proof_Context.theory_of ctxt;
    val name = intern thy raw_name;
    val _ = the_locale thy name;  (* error if locale unknown *)
  in
    (case registrations_of (Context.Proof ctxt) (* FIXME *) name of
      [] => Pretty.str "no interpretations"
    | regs => Pretty.big_list "interpretations:" (map (pretty_reg ctxt) (rev regs)))
  end |> Pretty.writeln;

fun print_dependencies ctxt clean export insts =
  let
    val thy = Proof_Context.theory_of ctxt;
    val idents = if clean then empty_idents else Idents.get (Context.Proof ctxt);
  in
    (case fold (roundup thy cons export) insts (idents, []) |> snd of
      [] => Pretty.str "no dependencies"
    | deps => Pretty.big_list "dependencies:" (map (pretty_reg ctxt) (rev deps)))
  end |> Pretty.writeln;

fun locale_deps thy =
  let
    val names = all_locales thy;
    fun add_locale_node name =
      let
        val params = params_of thy name;
        val axioms =
          these (Option.map (Logic.strip_imp_prems o Thm.prop_of) (fst (intros_of thy name)));
        val registrations =
          map (instance_of thy name o snd) (registrations_of (Context.Theory thy) name);
      in
        Graph.new_node (name, {params = params, axioms = axioms, registrations = registrations})
      end;
    fun add_locale_deps name =
      let
        val dependencies =
          map (apsnd (instance_of thy name o op $>) o fst) (dependencies_of thy name);
      in
        fold (fn (super, ts) => fn (gr, deps) =>
         (gr |> Graph.add_edge (super, name),
          deps |> Symtab.map_default (super, Symtab.empty) (Symtab.cons_list (name, ts))))
            dependencies
      end;
  in
    Graph.empty
    |> fold add_locale_node names
    |> rpair Symtab.empty
    |> fold add_locale_deps names
  end;

end;