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(* *)
(* Objective Caml *)
(* *)
(* Xavier Leroy and Jerome Vouillon, projet Cristal, INRIA Rocquencourt*)
(* *)
(* Copyright 1996 Institut National de Recherche en Informatique et *)
(* en Automatique. All rights reserved. This file is distributed *)
(* under the terms of the Q Public License version 1.0. *)
(* *)
(***********************************************************************)
(* $Id: btype.ml 9547 2010-01-22 12:48:24Z doligez $ *)
(* Basic operations on core types *)
open Types
(**** Type level management ****)
let generic_level = 100000000
(* Used to mark a type during a traversal. *)
let lowest_level = 0
let pivot_level = 2 * lowest_level - 1
(* pivot_level - lowest_level < lowest_level *)
(**** Some type creators ****)
let new_id = ref (-1)
let newty2 level desc =
incr new_id; { desc = desc; level = level; id = !new_id }
let newgenty desc = newty2 generic_level desc
let newgenvar () = newgenty Tvar
(*
let newmarkedvar level =
incr new_id; { desc = Tvar; level = pivot_level - level; id = !new_id }
let newmarkedgenvar () =
incr new_id;
{ desc = Tvar; level = pivot_level - generic_level; id = !new_id }
*)
(**** Representative of a type ****)
let rec field_kind_repr =
function
Fvar {contents = Some kind} -> field_kind_repr kind
| kind -> kind
let rec repr =
function
{desc = Tlink t'} ->
(*
We do no path compression. Path compression does not seem to
improve notably efficiency, and it prevents from changing a
[Tlink] into another type (for instance, for undoing a
unification).
*)
repr t'
| {desc = Tfield (_, k, _, t')} when field_kind_repr k = Fabsent ->
repr t'
| t -> t
let rec commu_repr = function
Clink r when !r <> Cunknown -> commu_repr !r
| c -> c
let rec row_field_repr_aux tl = function
Reither(_, tl', _, {contents = Some fi}) ->
row_field_repr_aux (tl@tl') fi
| Reither(c, tl', m, r) ->
Reither(c, tl@tl', m, r)
| Rpresent (Some _) when tl <> [] ->
Rpresent (Some (List.hd tl))
| fi -> fi
let row_field_repr fi = row_field_repr_aux [] fi
let rec rev_concat l ll =
match ll with
[] -> l
| l'::ll -> rev_concat (l'@l) ll
let rec row_repr_aux ll row =
match (repr row.row_more).desc with
| Tvariant row' ->
let f = row.row_fields in
row_repr_aux (if f = [] then ll else f::ll) row'
| _ ->
if ll = [] then row else
{row with row_fields = rev_concat row.row_fields ll}
let row_repr row = row_repr_aux [] row
let rec row_field tag row =
let rec find = function
| (tag',f) :: fields ->
if tag = tag' then row_field_repr f else find fields
| [] ->
match repr row.row_more with
| {desc=Tvariant row'} -> row_field tag row'
| _ -> Rabsent
in find row.row_fields
let rec row_more row =
match repr row.row_more with
| {desc=Tvariant row'} -> row_more row'
| ty -> ty
let static_row row =
let row = row_repr row in
row.row_closed &&
List.for_all
(fun (_,f) -> match row_field_repr f with Reither _ -> false | _ -> true)
row.row_fields
let hash_variant s =
let accu = ref 0 in
for i = 0 to String.length s - 1 do
accu := 223 * !accu + Char.code s.[i]
done;
(* reduce to 31 bits *)
accu := !accu land (1 lsl 31 - 1);
(* make it signed for 64 bits architectures *)
if !accu > 0x3FFFFFFF then !accu - (1 lsl 31) else !accu
let proxy ty =
let ty0 = repr ty in
match ty0.desc with
| Tvariant row when not (static_row row) ->
row_more row
| Tobject (ty, _) ->
let rec proxy_obj ty =
match ty.desc with
Tfield (_, _, _, ty) | Tlink ty -> proxy_obj ty
| Tvar | Tunivar | Tconstr _ -> ty
| Tnil -> ty0
| _ -> assert false
in proxy_obj ty
| _ -> ty0
(**** Utilities for fixed row private types ****)
let has_constr_row t =
match (repr t).desc with
Tobject(t,_) ->
let rec check_row t =
match (repr t).desc with
Tfield(_,_,_,t) -> check_row t
| Tconstr _ -> true
| _ -> false
in check_row t
| Tvariant row ->
(match row_more row with {desc=Tconstr _} -> true | _ -> false)
| _ ->
false
let is_row_name s =
let l = String.length s in
if l < 4 then false else String.sub s (l-4) 4 = "#row"
(**********************************)
(* Utilities for type traversal *)
(**********************************)
let rec iter_row f row =
List.iter
(fun (_, fi) ->
match row_field_repr fi with
| Rpresent(Some ty) -> f ty
| Reither(_, tl, _, _) -> List.iter f tl
| _ -> ())
row.row_fields;
match (repr row.row_more).desc with
Tvariant row -> iter_row f row
| Tvar | Tunivar | Tsubst _ | Tconstr _ ->
Misc.may (fun (_,l) -> List.iter f l) row.row_name
| _ -> assert false
let iter_type_expr f ty =
match ty.desc with
Tvar -> ()
| Tarrow (_, ty1, ty2, _) -> f ty1; f ty2
| Ttuple l -> List.iter f l
| Tconstr (_, l, _) -> List.iter f l
| Tobject(ty, {contents = Some (_, p)})
-> f ty; List.iter f p
| Tobject (ty, _) -> f ty
| Tvariant row -> iter_row f row; f (row_more row)
| Tfield (_, _, ty1, ty2) -> f ty1; f ty2
| Tnil -> ()
| Tlink ty -> f ty
| Tsubst ty -> f ty
| Tunivar -> ()
| Tpoly (ty, tyl) -> f ty; List.iter f tyl
| Tpackage (_, _, l) -> List.iter f l
let rec iter_abbrev f = function
Mnil -> ()
| Mcons(_, _, ty, ty', rem) -> f ty; f ty'; iter_abbrev f rem
| Mlink rem -> iter_abbrev f !rem
let copy_row f fixed row keep more =
let fields = List.map
(fun (l, fi) -> l,
match row_field_repr fi with
| Rpresent(Some ty) -> Rpresent(Some(f ty))
| Reither(c, tl, m, e) ->
let e = if keep then e else ref None in
let m = if row.row_fixed then fixed else m in
let tl = List.map f tl in
Reither(c, tl, m, e)
| _ -> fi)
row.row_fields in
let name =
match row.row_name with None -> None
| Some (path, tl) -> Some (path, List.map f tl) in
{ row_fields = fields; row_more = more;
row_bound = (); row_fixed = row.row_fixed && fixed;
row_closed = row.row_closed; row_name = name; }
let rec copy_kind = function
Fvar{contents = Some k} -> copy_kind k
| Fvar _ -> Fvar (ref None)
| Fpresent -> Fpresent
| Fabsent -> assert false
let copy_commu c =
if commu_repr c = Cok then Cok else Clink (ref Cunknown)
(* Since univars may be used as row variables, we need to do some
encoding during substitution *)
let rec norm_univar ty =
match ty.desc with
Tunivar | Tsubst _ -> ty
| Tlink ty -> norm_univar ty
| Ttuple (ty :: _) -> norm_univar ty
| _ -> assert false
let rec copy_type_desc f = function
Tvar -> Tvar
| Tarrow (p, ty1, ty2, c)-> Tarrow (p, f ty1, f ty2, copy_commu c)
| Ttuple l -> Ttuple (List.map f l)
| Tconstr (p, l, _) -> Tconstr (p, List.map f l, ref Mnil)
| Tobject(ty, {contents = Some (p, tl)})
-> Tobject (f ty, ref (Some(p, List.map f tl)))
| Tobject (ty, _) -> Tobject (f ty, ref None)
| Tvariant row -> assert false (* too ambiguous *)
| Tfield (p, k, ty1, ty2) -> (* the kind is kept shared *)
Tfield (p, field_kind_repr k, f ty1, f ty2)
| Tnil -> Tnil
| Tlink ty -> copy_type_desc f ty.desc
| Tsubst ty -> assert false
| Tunivar -> Tunivar
| Tpoly (ty, tyl) ->
let tyl = List.map (fun x -> norm_univar (f x)) tyl in
Tpoly (f ty, tyl)
| Tpackage (p, n, l) -> Tpackage (p, n, List.map f l)
(* Utilities for copying *)
let saved_desc = ref []
(* Saved association of generic nodes with their description. *)
let save_desc ty desc =
saved_desc := (ty, desc)::!saved_desc
let saved_kinds = ref [] (* duplicated kind variables *)
let new_kinds = ref [] (* new kind variables *)
let dup_kind r =
(match !r with None -> () | Some _ -> assert false);
if not (List.memq r !new_kinds) then begin
saved_kinds := r :: !saved_kinds;
let r' = ref None in
new_kinds := r' :: !new_kinds;
r := Some (Fvar r')
end
(* Restored type descriptions. *)
let cleanup_types () =
List.iter (fun (ty, desc) -> ty.desc <- desc) !saved_desc;
List.iter (fun r -> r := None) !saved_kinds;
saved_desc := []; saved_kinds := []; new_kinds := []
(* Mark a type. *)
let rec mark_type ty =
let ty = repr ty in
if ty.level >= lowest_level then begin
ty.level <- pivot_level - ty.level;
iter_type_expr mark_type ty
end
let mark_type_node ty =
let ty = repr ty in
if ty.level >= lowest_level then begin
ty.level <- pivot_level - ty.level;
end
let mark_type_params ty =
iter_type_expr mark_type ty
(* Remove marks from a type. *)
let rec unmark_type ty =
let ty = repr ty in
if ty.level < lowest_level then begin
ty.level <- pivot_level - ty.level;
iter_type_expr unmark_type ty
end
let unmark_type_decl decl =
List.iter unmark_type decl.type_params;
begin match decl.type_kind with
Type_abstract -> ()
| Type_variant cstrs ->
List.iter (fun (c, tl) -> List.iter unmark_type tl) cstrs
| Type_record(lbls, rep) ->
List.iter (fun (c, mut, t) -> unmark_type t) lbls
end;
begin match decl.type_manifest with
None -> ()
| Some ty -> unmark_type ty
end
let unmark_class_signature sign =
unmark_type sign.cty_self;
Vars.iter (fun l (m, v, t) -> unmark_type t) sign.cty_vars
let rec unmark_class_type =
function
Tcty_constr (p, tyl, cty) ->
List.iter unmark_type tyl; unmark_class_type cty
| Tcty_signature sign ->
unmark_class_signature sign
| Tcty_fun (_, ty, cty) ->
unmark_type ty; unmark_class_type cty
(*******************************************)
(* Memorization of abbreviation expansion *)
(*******************************************)
(* Search whether the expansion has been memorized. *)
let rec find_expans priv p1 = function
Mnil -> None
| Mcons (priv', p2, ty0, ty, _)
when priv' >= priv && Path.same p1 p2 -> Some ty
| Mcons (_, _, _, _, rem) -> find_expans priv p1 rem
| Mlink {contents = rem} -> find_expans priv p1 rem
(* debug: check for cycles in abbreviation. only works with -principal
let rec check_expans visited ty =
let ty = repr ty in
assert (not (List.memq ty visited));
match ty.desc with
Tconstr (path, args, abbrev) ->
begin match find_expans path !abbrev with
Some ty' -> check_expans (ty :: visited) ty'
| None -> ()
end
| _ -> ()
*)
let memo = ref []
(* Contains the list of saved abbreviation expansions. *)
let cleanup_abbrev () =
(* Remove all memorized abbreviation expansions. *)
List.iter (fun abbr -> abbr := Mnil) !memo;
memo := []
let memorize_abbrev mem priv path v v' =
(* Memorize the expansion of an abbreviation. *)
mem := Mcons (priv, path, v, v', !mem);
(* check_expans [] v; *)
memo := mem :: !memo
let rec forget_abbrev_rec mem path =
match mem with
Mnil ->
assert false
| Mcons (_, path', _, _, rem) when Path.same path path' ->
rem
| Mcons (priv, path', v, v', rem) ->
Mcons (priv, path', v, v', forget_abbrev_rec rem path)
| Mlink mem' ->
mem' := forget_abbrev_rec !mem' path;
raise Exit
let forget_abbrev mem path =
try mem := forget_abbrev_rec !mem path with Exit -> ()
(* debug: check for invalid abbreviations
let rec check_abbrev_rec = function
Mnil -> true
| Mcons (_, ty1, ty2, rem) ->
repr ty1 != repr ty2
| Mlink mem' ->
check_abbrev_rec !mem'
let check_memorized_abbrevs () =
List.for_all (fun mem -> check_abbrev_rec !mem) !memo
*)
(**********************************)
(* Utilities for labels *)
(**********************************)
let is_optional l =
String.length l > 0 && l.[0] = '?'
let label_name l =
if is_optional l then String.sub l 1 (String.length l - 1)
else l
let rec extract_label_aux hd l = function
[] -> raise Not_found
| (l',t as p) :: ls ->
if label_name l' = l then (l', t, List.rev hd, ls)
else extract_label_aux (p::hd) l ls
let extract_label l ls = extract_label_aux [] l ls
(**********************************)
(* Utilities for backtracking *)
(**********************************)
type change =
Ctype of type_expr * type_desc
| Clevel of type_expr * int
| Cname of
(Path.t * type_expr list) option ref * (Path.t * type_expr list) option
| Crow of row_field option ref * row_field option
| Ckind of field_kind option ref * field_kind option
| Ccommu of commutable ref * commutable
| Cuniv of type_expr option ref * type_expr option
let undo_change = function
Ctype (ty, desc) -> ty.desc <- desc
| Clevel (ty, level) -> ty.level <- level
| Cname (r, v) -> r := v
| Crow (r, v) -> r := v
| Ckind (r, v) -> r := v
| Ccommu (r, v) -> r := v
| Cuniv (r, v) -> r := v
type changes =
Change of change * changes ref
| Unchanged
| Invalid
type snapshot = changes ref * int
let trail = Weak.create 1
let last_snapshot = ref 0
let log_change ch =
match Weak.get trail 0 with None -> ()
| Some r ->
let r' = ref Unchanged in
r := Change (ch, r');
Weak.set trail 0 (Some r')
let log_type ty =
if ty.id <= !last_snapshot then log_change (Ctype (ty, ty.desc))
let link_type ty ty' = log_type ty; ty.desc <- Tlink ty'
(* ; assert (check_memorized_abbrevs ()) *)
(* ; check_expans [] ty' *)
let set_level ty level =
if ty.id <= !last_snapshot then log_change (Clevel (ty, ty.level));
ty.level <- level
let set_univar rty ty =
log_change (Cuniv (rty, !rty)); rty := Some ty
let set_name nm v =
log_change (Cname (nm, !nm)); nm := v
let set_row_field e v =
log_change (Crow (e, !e)); e := Some v
let set_kind rk k =
log_change (Ckind (rk, !rk)); rk := Some k
let set_commu rc c =
log_change (Ccommu (rc, !rc)); rc := c
let snapshot () =
let old = !last_snapshot in
last_snapshot := !new_id;
match Weak.get trail 0 with Some r -> (r, old)
| None ->
let r = ref Unchanged in
Weak.set trail 0 (Some r);
(r, old)
let rec rev_log accu = function
Unchanged -> accu
| Invalid -> assert false
| Change (ch, next) ->
let d = !next in
next := Invalid;
rev_log (ch::accu) d
let backtrack (changes, old) =
match !changes with
Unchanged -> last_snapshot := old
| Invalid -> failwith "Btype.backtrack"
| Change _ as change ->
cleanup_abbrev ();
let backlog = rev_log [] change in
List.iter undo_change backlog;
changes := Unchanged;
last_snapshot := old;
Weak.set trail 0 (Some changes)
|