ocaml/typing/ctype.ml

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(***********************************************************************)
(* *)
(* OCaml *)
(* *)
(* 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. *)
(* *)
(***********************************************************************)
(* Operations on core types *)
open Misc
open Asttypes
open Types
open Btype
(*
Type manipulation after type inference
======================================
If one wants to manipulate a type after type inference (for
instance, during code generation or in the debugger), one must
first make sure that the type levels are correct, using the
function [correct_levels]. Then, this type can be correctely
manipulated by [apply], [expand_head] and [moregeneral].
*)
(*
General notes
=============
- As much sharing as possible should be kept : it makes types
smaller and better abbreviated.
When necessary, some sharing can be lost. Types will still be
printed correctly (+++ TO DO...), and abbreviations defined by a
class do not depend on sharing thanks to constrained
abbreviations. (Of course, even if some sharing is lost, typing
will still be correct.)
- All nodes of a type have a level : that way, one know whether a
node need to be duplicated or not when instantiating a type.
- Levels of a type are decreasing (generic level being considered
as greatest).
- The level of a type constructor is superior to the binding
time of its path.
- Recursive types without limitation should be handled (even if
there is still an occur check). This avoid treating specially the
case for objects, for instance. Furthermore, the occur check
policy can then be easily changed.
*)
(*
A faire
=======
- Revoir affichage des types.
- Etendre la portee d'un alias [... as 'a] a tout le type englobant.
- #-type implementes comme de vraies abreviations.
- Niveaux plus fins pour les identificateurs :
Champ [global] renomme en [level];
Niveau -1 : global
0 : module toplevel
1 : module contenu dans module toplevel
...
En fait, incrementer le niveau a chaque fois que l'on rentre dans
un module.
3 4 6
\ / /
1 2 5
\|/
0
[Subst] doit ecreter les niveaux (pour qu'un variable non
generalisable dans un module de niveau 2 ne se retrouve pas
generalisable lorsque l'on l'utilise au niveau 0).
- Traitement de la trace de l'unification separe de la fonction
[unify].
*)
(**** Errors ****)
exception Unify of (type_expr * type_expr) list
exception Tags of label * label
exception Subtype of
(type_expr * type_expr) list * (type_expr * type_expr) list
exception Cannot_expand
exception Cannot_apply
exception Recursive_abbrev
(* GADT: recursive abbrevs can appear as a result of local constraints *)
exception Unification_recursive_abbrev of (type_expr * type_expr) list
(**** Type level management ****)
let current_level = ref 0
let nongen_level = ref 0
let global_level = ref 1
let saved_level = ref []
let get_current_level () = !current_level
let init_def level = current_level := level; nongen_level := level
let begin_def () =
saved_level := (!current_level, !nongen_level) :: !saved_level;
incr current_level; nongen_level := !current_level
let begin_class_def () =
saved_level := (!current_level, !nongen_level) :: !saved_level;
incr current_level
let raise_nongen_level () =
saved_level := (!current_level, !nongen_level) :: !saved_level;
nongen_level := !current_level
let end_def () =
let (cl, nl) = List.hd !saved_level in
saved_level := List.tl !saved_level;
current_level := cl; nongen_level := nl
let reset_global_level () =
global_level := !current_level + 1
let increase_global_level () =
let gl = !global_level in
global_level := !current_level;
gl
let restore_global_level gl =
global_level := gl
(**** Whether a path points to an object type (with hidden row variable) ****)
let is_object_type path =
let name =
match path with Path.Pident id -> Ident.name id
| Path.Pdot(_, s,_) -> s
| Path.Papply _ -> assert false
in name.[0] = '#'
(**** Abbreviations without parameters ****)
(* Shall reset after generalizing *)
let trace_gadt_instances = ref false
let check_trace_gadt_instances env =
not !trace_gadt_instances && Env.has_local_constraints env &&
(trace_gadt_instances := true; cleanup_abbrev (); true)
let simple_abbrevs = ref Mnil
let proper_abbrevs path tl abbrev =
if tl <> [] || !trace_gadt_instances || !Clflags.principal ||
is_object_type path
then abbrev
else simple_abbrevs
(**** Some type creators ****)
(* Re-export generic type creators *)
let newty2 = Btype.newty2
let newty desc = newty2 !current_level desc
let new_global_ty desc = newty2 !global_level desc
let newvar ?name () = newty2 !current_level (Tvar name)
let newvar2 ?name level = newty2 level (Tvar name)
let new_global_var ?name () = newty2 !global_level (Tvar name)
let newobj fields = newty (Tobject (fields, ref None))
let newconstr path tyl = newty (Tconstr (path, tyl, ref Mnil))
let none = newty (Ttuple []) (* Clearly ill-formed type *)
(**** Representative of a type ****)
(* Re-export repr *)
let repr = repr
(**** Type maps ****)
module TypePairs =
Hashtbl.Make (struct
type t = type_expr * type_expr
let equal (t1, t1') (t2, t2') = (t1 == t2) && (t1' == t2')
let hash (t, t') = t.id + 93 * t'.id
end)
(**** unification mode ****)
type unification_mode =
| Expression (* unification in expression *)
| Pattern (* unification in pattern which may add local constraints *)
let umode = ref Expression
let generate_equations = ref false
let set_mode mode ?(generate = (mode = Pattern)) f =
let old_unification_mode = !umode
and old_gen = !generate_equations in
try
umode := mode;
generate_equations := generate;
let ret = f () in
umode := old_unification_mode;
generate_equations := old_gen;
ret
with e ->
umode := old_unification_mode;
generate_equations := old_gen;
raise e
(*** Checks for type definitions ***)
let in_current_module = function
| Path.Pident _ -> true
| Path.Pdot _ | Path.Papply _ -> false
let in_pervasives p =
in_current_module p &&
try ignore (Env.find_type p Env.initial); true
with Not_found -> false
let is_datatype decl=
match decl.type_kind with
Type_record _ | Type_variant _ -> true
| Type_abstract -> false
(**********************************************)
(* Miscellaneous operations on object types *)
(**********************************************)
(* Note:
We need to maintain some invariants:
* cty_self must be a Tobject
* ...
*)
(**** Object field manipulation. ****)
let object_fields ty =
match (repr ty).desc with
Tobject (fields, _) -> fields
| _ -> assert false
let flatten_fields ty =
let rec flatten l ty =
let ty = repr ty in
match ty.desc with
Tfield(s, k, ty1, ty2) ->
flatten ((s, k, ty1)::l) ty2
| _ ->
(l, ty)
in
let (l, r) = flatten [] ty in
(Sort.list (fun (n, _, _) (n', _, _) -> n < n') l, r)
let build_fields level =
List.fold_right
(fun (s, k, ty1) ty2 -> newty2 level (Tfield(s, k, ty1, ty2)))
let associate_fields fields1 fields2 =
let rec associate p s s' =
function
(l, []) ->
(List.rev p, (List.rev s) @ l, List.rev s')
| ([], l') ->
(List.rev p, List.rev s, (List.rev s') @ l')
| ((n, k, t)::r, (n', k', t')::r') when n = n' ->
associate ((n, k, t, k', t')::p) s s' (r, r')
| ((n, k, t)::r, ((n', k', t')::_ as l')) when n < n' ->
associate p ((n, k, t)::s) s' (r, l')
| (((n, k, t)::r as l), (n', k', t')::r') (* when n > n' *) ->
associate p s ((n', k', t')::s') (l, r')
in
associate [] [] [] (fields1, fields2)
(**** Check whether an object is open ****)
(* +++ Il faudra penser a eventuellement expanser l'abreviation *)
let rec object_row ty =
let ty = repr ty in
match ty.desc with
Tobject (t, _) -> object_row t
| Tfield(_, _, _, t) -> object_row t
| _ -> ty
let opened_object ty =
match (object_row ty).desc with
| Tvar _ | Tunivar _ | Tconstr _ -> true
| _ -> false
let concrete_object ty =
match (object_row ty).desc with
| Tvar _ -> false
| _ -> true
(**** Close an object ****)
let close_object ty =
let rec close ty =
let ty = repr ty in
match ty.desc with
Tvar _ ->
link_type ty (newty2 ty.level Tnil)
| Tfield(_, _, _, ty') -> close ty'
| _ -> assert false
in
match (repr ty).desc with
Tobject (ty, _) -> close ty
| _ -> assert false
(**** Row variable of an object type ****)
let row_variable ty =
let rec find ty =
let ty = repr ty in
match ty.desc with
Tfield (_, _, _, ty) -> find ty
| Tvar _ -> ty
| _ -> assert false
in
match (repr ty).desc with
Tobject (fi, _) -> find fi
| _ -> assert false
(**** Object name manipulation ****)
(* +++ Bientot obsolete *)
let set_object_name id rv params ty =
match (repr ty).desc with
Tobject (fi, nm) ->
set_name nm (Some (Path.Pident id, rv::params))
| _ ->
assert false
let remove_object_name ty =
match (repr ty).desc with
Tobject (_, nm) -> set_name nm None
| Tconstr (_, _, _) -> ()
| _ -> fatal_error "Ctype.remove_object_name"
(**** Hiding of private methods ****)
let hide_private_methods ty =
match (repr ty).desc with
Tobject (fi, nm) ->
nm := None;
let (fl, _) = flatten_fields fi in
List.iter
(function (_, k, _) ->
match field_kind_repr k with
Fvar r -> set_kind r Fabsent
| _ -> ())
fl
| _ ->
assert false
(*******************************)
(* Operations on class types *)
(*******************************)
let rec signature_of_class_type =
function
Cty_constr (_, _, cty) -> signature_of_class_type cty
| Cty_signature sign -> sign
| Cty_fun (_, ty, cty) -> signature_of_class_type cty
let self_type cty =
repr (signature_of_class_type cty).cty_self
let rec class_type_arity =
function
Cty_constr (_, _, cty) -> class_type_arity cty
| Cty_signature _ -> 0
| Cty_fun (_, _, cty) -> 1 + class_type_arity cty
(*******************************************)
(* Miscellaneous operations on row types *)
(*******************************************)
let sort_row_fields = Sort.list (fun (p,_) (q,_) -> p < q)
let rec merge_rf r1 r2 pairs fi1 fi2 =
match fi1, fi2 with
(l1,f1 as p1)::fi1', (l2,f2 as p2)::fi2' ->
if l1 = l2 then merge_rf r1 r2 ((l1,f1,f2)::pairs) fi1' fi2' else
if l1 < l2 then merge_rf (p1::r1) r2 pairs fi1' fi2 else
merge_rf r1 (p2::r2) pairs fi1 fi2'
| [], _ -> (List.rev r1, List.rev_append r2 fi2, pairs)
| _, [] -> (List.rev_append r1 fi1, List.rev r2, pairs)
let merge_row_fields fi1 fi2 =
match fi1, fi2 with
[], _ | _, [] -> (fi1, fi2, [])
| [p1], _ when not (List.mem_assoc (fst p1) fi2) -> (fi1, fi2, [])
| _, [p2] when not (List.mem_assoc (fst p2) fi1) -> (fi1, fi2, [])
| _ -> merge_rf [] [] [] (sort_row_fields fi1) (sort_row_fields fi2)
let rec filter_row_fields erase = function
[] -> []
| (l,f as p)::fi ->
let fi = filter_row_fields erase fi in
match row_field_repr f with
Rabsent -> fi
| Reither(_,_,false,e) when erase -> set_row_field e Rabsent; fi
| _ -> p :: fi
(**************************************)
(* Check genericity of type schemes *)
(**************************************)
exception Non_closed
let rec closed_schema_rec ty =
let ty = repr ty in
if ty.level >= lowest_level then begin
let level = ty.level in
ty.level <- pivot_level - level;
match ty.desc with
Tvar _ when level <> generic_level ->
raise Non_closed
| Tfield(_, kind, t1, t2) ->
if field_kind_repr kind = Fpresent then
closed_schema_rec t1;
closed_schema_rec t2
| Tvariant row ->
let row = row_repr row in
iter_row closed_schema_rec row;
if not (static_row row) then closed_schema_rec row.row_more
| _ ->
iter_type_expr closed_schema_rec ty
end
(* Return whether all variables of type [ty] are generic. *)
let closed_schema ty =
try
closed_schema_rec ty;
unmark_type ty;
true
with Non_closed ->
unmark_type ty;
false
exception Non_closed of type_expr * bool
let free_variables = ref []
let really_closed = ref None
let rec free_vars_rec real ty =
let ty = repr ty in
if ty.level >= lowest_level then begin
ty.level <- pivot_level - ty.level;
begin match ty.desc, !really_closed with
Tvar _, _ ->
free_variables := (ty, real) :: !free_variables
| Tconstr (path, tl, _), Some env ->
begin try
let (_, body, _) = Env.find_type_expansion path env in
if (repr body).level <> generic_level then
free_variables := (ty, real) :: !free_variables
with Not_found -> ()
end;
List.iter (free_vars_rec true) tl
(* Do not count "virtual" free variables
| Tobject(ty, {contents = Some (_, p)}) ->
free_vars_rec false ty; List.iter (free_vars_rec true) p
*)
| Tobject (ty, _), _ ->
free_vars_rec false ty
| Tfield (_, _, ty1, ty2), _ ->
free_vars_rec true ty1; free_vars_rec false ty2
| Tvariant row, _ ->
let row = row_repr row in
iter_row (free_vars_rec true) row;
if not (static_row row) then free_vars_rec false row.row_more
| _ ->
iter_type_expr (free_vars_rec true) ty
end;
end
let free_vars ?env ty =
free_variables := [];
really_closed := env;
free_vars_rec true ty;
let res = !free_variables in
free_variables := [];
really_closed := None;
res
let free_variables ?env ty =
let tl = List.map fst (free_vars ?env ty) in
unmark_type ty;
tl
let closed_type ty =
match free_vars ty with
[] -> ()
| (v, real) :: _ -> raise (Non_closed (v, real))
let closed_parameterized_type params ty =
List.iter mark_type params;
let ok =
try closed_type ty; true with Non_closed _ -> false in
List.iter unmark_type params;
unmark_type ty;
ok
let closed_type_decl decl =
try
List.iter mark_type decl.type_params;
begin match decl.type_kind with
Type_abstract ->
()
| Type_variant v ->
List.iter
(fun (_, tyl,ret_type_opt) ->
match ret_type_opt with
| Some _ -> ()
| None ->
List.iter closed_type tyl)
v
| Type_record(r, rep) ->
List.iter (fun (_, _, ty) -> closed_type ty) r
end;
begin match decl.type_manifest with
None -> ()
| Some ty -> closed_type ty
end;
unmark_type_decl decl;
None
with Non_closed (ty, _) ->
unmark_type_decl decl;
Some ty
type closed_class_failure =
CC_Method of type_expr * bool * string * type_expr
| CC_Value of type_expr * bool * string * type_expr
exception Failure of closed_class_failure
let closed_class params sign =
let ty = object_fields (repr sign.cty_self) in
let (fields, rest) = flatten_fields ty in
List.iter mark_type params;
mark_type rest;
List.iter
(fun (lab, _, ty) -> if lab = dummy_method then mark_type ty)
fields;
try
mark_type_node (repr sign.cty_self);
List.iter
(fun (lab, kind, ty) ->
if field_kind_repr kind = Fpresent then
try closed_type ty with Non_closed (ty0, real) ->
raise (Failure (CC_Method (ty0, real, lab, ty))))
fields;
mark_type_params (repr sign.cty_self);
List.iter unmark_type params;
unmark_class_signature sign;
None
with Failure reason ->
mark_type_params (repr sign.cty_self);
List.iter unmark_type params;
unmark_class_signature sign;
Some reason
(**********************)
(* Type duplication *)
(**********************)
(* Duplicate a type, preserving only type variables *)
let duplicate_type ty =
Subst.type_expr Subst.identity ty
(* Same, for class types *)
let duplicate_class_type ty =
Subst.class_type Subst.identity ty
(*****************************)
(* Type level manipulation *)
(*****************************)
(*
It would be a bit more efficient to remove abbreviation expansions
rather than generalizing them: these expansions will usually not be
used anymore. However, this is not possible in the general case, as
[expand_abbrev] (via [subst]) requires these expansions to be
preserved. Does it worth duplicating this code ?
*)
let rec iter_generalize tyl ty =
let ty = repr ty in
if (ty.level > !current_level) && (ty.level <> generic_level) then begin
set_level ty generic_level;
begin match ty.desc with
Tconstr (_, _, abbrev) ->
iter_abbrev (iter_generalize tyl) !abbrev
| _ -> ()
end;
iter_type_expr (iter_generalize tyl) ty
end else
tyl := ty :: !tyl
let iter_generalize tyl ty =
simple_abbrevs := Mnil;
iter_generalize tyl ty
let generalize ty =
iter_generalize (ref []) ty
(* Efficient repeated generalisation of the same type *)
let iterative_generalization min_level tyl =
let tyl' = ref [] in
List.iter (iter_generalize tyl') tyl;
List.fold_right (fun ty l -> if ty.level <= min_level then l else ty::l)
!tyl' []
(* Generalize the structure and lower the variables *)
let rec generalize_structure var_level ty =
let ty = repr ty in
if ty.level <> generic_level then begin
if is_Tvar ty && ty.level > var_level then
set_level ty var_level
else if
ty.level > !current_level &&
match ty.desc with
Tconstr (p, _, abbrev) ->
not (is_object_type p) && (abbrev := Mnil; true)
| _ -> true
then begin
set_level ty generic_level;
iter_type_expr (generalize_structure var_level) ty
end
end
let generalize_structure var_level ty =
simple_abbrevs := Mnil;
generalize_structure var_level ty
(* Generalize the spine of a function, if the level >= !current_level *)
let rec generalize_spine ty =
let ty = repr ty in
if ty.level < !current_level || ty.level = generic_level then () else
match ty.desc with
Tarrow (_, ty1, ty2, _) ->
set_level ty generic_level;
generalize_spine ty1;
generalize_spine ty2;
| Tpoly (ty', _) ->
set_level ty generic_level;
generalize_spine ty'
| Ttuple tyl
| Tpackage (_, _, tyl) ->
set_level ty generic_level;
List.iter generalize_spine tyl
| Tconstr (p, tyl, memo) when not (is_object_type p) ->
set_level ty generic_level;
memo := Mnil;
List.iter generalize_spine tyl
| _ -> ()
let forward_try_expand_once = (* Forward declaration *)
ref (fun env ty -> raise Cannot_expand)
(*
Lower the levels of a type (assume [level] is not
[generic_level]).
*)
(*
The level of a type constructor must be greater than its binding
time. That way, a type constructor cannot escape the scope of its
definition, as would be the case in
let x = ref []
module M = struct type t let _ = (x : t list ref) end
(without this constraint, the type system would actually be unsound.)
*)
let get_level env p =
try
match (Env.find_type p env).type_newtype_level with
| None -> Path.binding_time p
| Some (x, _) -> x
with
| Not_found ->
(* no newtypes in predef *)
Path.binding_time p
let rec update_level env level ty =
let ty = repr ty in
if ty.level > level then begin
begin match Env.gadt_instance_level env ty with
Some lv -> if level < lv then raise (Unify [(ty, newvar2 level)])
| None -> ()
end;
match ty.desc with
Tconstr(p, tl, abbrev) when level < get_level env p ->
(* Try first to replace an abbreviation by its expansion. *)
begin try
(* if is_newtype env p then raise Cannot_expand; *)
link_type ty (!forward_try_expand_once env ty);
update_level env level ty
with Cannot_expand ->
(* +++ Levels should be restored... *)
(* Format.printf "update_level: %i < %i@." level (get_level env p); *)
if level < get_level env p then raise (Unify [(ty, newvar2 level)]);
iter_type_expr (update_level env level) ty
end
| Tpackage (p, _, _) when level < get_level env p ->
raise (Unify [(ty, newvar2 level)])
| Tobject(_, ({contents=Some(p, tl)} as nm))
when level < get_level env p ->
set_name nm None;
update_level env level ty
| Tvariant row ->
let row = row_repr row in
begin match row.row_name with
| Some (p, tl) when level < get_level env p ->
log_type ty;
ty.desc <- Tvariant {row with row_name = None}
| _ -> ()
end;
set_level ty level;
iter_type_expr (update_level env level) ty
| Tfield(lab, _, ty1, _)
when lab = dummy_method && (repr ty1).level > level->
raise (Unify [(ty, newvar2 level)])
| _ ->
set_level ty level;
(* XXX what about abbreviations in Tconstr ? *)
iter_type_expr (update_level env level) ty
end
(* Generalize and lower levels of contravariant branches simultaneously *)
let generalize_contravariant env =
if !Clflags.principal then generalize_structure else update_level env
let rec generalize_expansive env var_level ty =
let ty = repr ty in
if ty.level <> generic_level then begin
if ty.level > var_level then begin
set_level ty generic_level;
match ty.desc with
Tconstr (path, tyl, abbrev) ->
let variance =
try (Env.find_type path env).type_variance
with Not_found -> List.map (fun _ -> (true,true,true)) tyl in
abbrev := Mnil;
List.iter2
(fun (co,cn,ct) t ->
if ct then generalize_contravariant env var_level t
else generalize_expansive env var_level t)
variance tyl
| Tpackage (_, _, tyl) ->
List.iter (generalize_contravariant env var_level) tyl
| Tarrow (_, t1, t2, _) ->
generalize_contravariant env var_level t1;
generalize_expansive env var_level t2
| _ ->
iter_type_expr (generalize_expansive env var_level) ty
end
end
let generalize_expansive env ty =
simple_abbrevs := Mnil;
try
generalize_expansive env !nongen_level ty
with Unify ([_, ty'] as tr) ->
raise (Unify ((ty, ty') :: tr))
let generalize_global ty = generalize_structure !global_level ty
let generalize_structure ty = generalize_structure !current_level ty
(* Correct the levels of type [ty]. *)
let correct_levels ty =
duplicate_type ty
(* Only generalize the type ty0 in ty *)
let limited_generalize ty0 ty =
let ty0 = repr ty0 in
let graph = Hashtbl.create 17 in
let idx = ref lowest_level in
let roots = ref [] in
let rec inverse pty ty =
let ty = repr ty in
if (ty.level > !current_level) || (ty.level = generic_level) then begin
decr idx;
Hashtbl.add graph !idx (ty, ref pty);
if (ty.level = generic_level) || (ty == ty0) then
roots := ty :: !roots;
set_level ty !idx;
iter_type_expr (inverse [ty]) ty
end else if ty.level < lowest_level then begin
let (_, parents) = Hashtbl.find graph ty.level in
parents := pty @ !parents
end
and generalize_parents ty =
let idx = ty.level in
if idx <> generic_level then begin
set_level ty generic_level;
List.iter generalize_parents !(snd (Hashtbl.find graph idx));
(* Special case for rows: must generalize the row variable *)
match ty.desc with
Tvariant row ->
let more = row_more row in
let lv = more.level in
if (lv < lowest_level || lv > !current_level)
&& lv <> generic_level then set_level more generic_level
| _ -> ()
end
in
inverse [] ty;
if ty0.level < lowest_level then
iter_type_expr (inverse []) ty0;
List.iter generalize_parents !roots;
Hashtbl.iter
(fun _ (ty, _) ->
if ty.level <> generic_level then set_level ty !current_level)
graph
(* Compute statically the free univars of all nodes in a type *)
(* This avoids doing it repeatedly during instantiation *)
type inv_type_expr =
{ inv_type : type_expr;
mutable inv_parents : inv_type_expr list }
let rec inv_type hash pty ty =
let ty = repr ty in
try
let inv = TypeHash.find hash ty in
inv.inv_parents <- pty @ inv.inv_parents
with Not_found ->
let inv = { inv_type = ty; inv_parents = pty } in
TypeHash.add hash ty inv;
iter_type_expr (inv_type hash [inv]) ty
let compute_univars ty =
let inverted = TypeHash.create 17 in
inv_type inverted [] ty;
let node_univars = TypeHash.create 17 in
let rec add_univar univ inv =
match inv.inv_type.desc with
Tpoly (ty, tl) when List.memq univ (List.map repr tl) -> ()
| _ ->
try
let univs = TypeHash.find node_univars inv.inv_type in
if not (TypeSet.mem univ !univs) then begin
univs := TypeSet.add univ !univs;
List.iter (add_univar univ) inv.inv_parents
end
with Not_found ->
TypeHash.add node_univars inv.inv_type (ref(TypeSet.singleton univ));
List.iter (add_univar univ) inv.inv_parents
in
TypeHash.iter (fun ty inv -> if is_Tunivar ty then add_univar ty inv)
inverted;
fun ty ->
try !(TypeHash.find node_univars ty) with Not_found -> TypeSet.empty
(*******************)
(* Instantiation *)
(*******************)
let rec find_repr p1 =
function
Mnil ->
None
| Mcons (Public, p2, ty, _, _) when Path.same p1 p2 ->
Some ty
| Mcons (_, _, _, _, rem) ->
find_repr p1 rem
| Mlink {contents = rem} ->
find_repr p1 rem
(*
Generic nodes are duplicated, while non-generic nodes are left
as-is.
During instantiation, the description of a generic node is first
replaced by a link to a stub ([Tsubst (newvar ())]). Once the
copy is made, it replaces the stub.
After instantiation, the description of generic node, which was
stored by [save_desc], must be put back, using [cleanup_types].
*)
let abbreviations = ref (ref Mnil)
(* Abbreviation memorized. *)
(* partial: we may not wish to copy the non generic types
before we call type_pat *)
let rec copy ?env ?partial ?keep_names ty =
let copy = copy ?env ?partial ?keep_names in
let ty = repr ty in
match ty.desc with
Tsubst ty -> ty
| _ ->
if ty.level <> generic_level && partial = None then ty else
(* We only forget types that are non generic and do not contain
free univars *)
let forget =
if ty.level = generic_level then generic_level else
match partial with
None -> assert false
| Some (free_univars, keep) ->
if TypeSet.is_empty (free_univars ty) then
if keep then ty.level else !current_level
else generic_level
in
if forget <> generic_level then newty2 forget (Tvar None) else
let desc = ty.desc in
save_desc ty desc;
let t = newvar() in (* Stub *)
begin match env with
Some env when Env.has_local_constraints env ->
begin match Env.gadt_instance_level env ty with
Some lv -> Env.add_gadt_instances env lv [t]
| None -> ()
end
| _ -> ()
end;
ty.desc <- Tsubst t;
t.desc <-
begin match desc with
| Tconstr (p, tl, _) ->
let abbrevs = proper_abbrevs p tl !abbreviations in
begin match find_repr p !abbrevs with
Some ty when repr ty != t -> (* XXX Commentaire... *)
Tlink ty
| _ ->
(*
One must allocate a new reference, so that abbrevia-
tions belonging to different branches of a type are
independent.
Moreover, a reference containing a [Mcons] must be
shared, so that the memorized expansion of an abbrevi-
ation can be released by changing the content of just
one reference.
*)
Tconstr (p, List.map copy tl,
ref (match !(!abbreviations) with
Mcons _ -> Mlink !abbreviations
| abbrev -> abbrev))
end
| Tvariant row0 ->
let row = row_repr row0 in
let more = repr row.row_more in
(* We must substitute in a subtle way *)
(* Tsubst takes a tuple containing the row var and the variant *)
begin match more.desc with
Tsubst {desc = Ttuple [_;ty2]} ->
(* This variant type has been already copied *)
ty.desc <- Tsubst ty2; (* avoid Tlink in the new type *)
Tlink ty2
| _ ->
(* If the row variable is not generic, we must keep it *)
let keep = more.level <> generic_level in
let more' =
match more.desc with
Tsubst ty -> ty
| Tconstr _ | Tnil ->
if keep then save_desc more more.desc;
copy more
| Tvar _ | Tunivar _ ->
save_desc more more.desc;
if keep then more else newty more.desc
| _ -> assert false
in
(* Open row if partial for pattern and contains Reither *)
let more', row =
match partial with
Some (free_univars, false) when row.row_closed
&& not row.row_fixed && TypeSet.is_empty (free_univars ty) ->
let not_reither (_, f) =
match row_field_repr f with
Reither _ -> false
| _ -> true
in
if List.for_all not_reither row.row_fields
then (more', row) else
(newty2 (if keep then more.level else !current_level)
(Tvar None),
{row_fields = List.filter not_reither row.row_fields;
row_more = more; row_bound = ();
row_closed = false; row_fixed = false; row_name = None})
| _ -> (more', row)
in
(* Register new type first for recursion *)
more.desc <- Tsubst(newgenty(Ttuple[more';t]));
(* Return a new copy *)
Tvariant (copy_row copy true row keep more')
end
| Tfield (p, k, ty1, ty2) ->
begin match field_kind_repr k with
Fabsent -> Tlink (copy ty2)
| Fpresent -> copy_type_desc copy desc
| Fvar r ->
dup_kind r;
copy_type_desc copy desc
end
| Tobject (ty1, _) when partial <> None ->
Tobject (copy ty1, ref None)
| _ -> copy_type_desc ?keep_names copy desc
end;
t
(**** Variants of instantiations ****)
let gadt_env env =
if Env.has_local_constraints env
then Some env
else None
let instance ?partial env sch =
let env = gadt_env env in
let partial =
match partial with
None -> None
| Some keep -> Some (compute_univars sch, keep)
in
let ty = copy ?env ?partial sch in
cleanup_types ();
ty
let instance_def sch =
let ty = copy sch in
cleanup_types ();
ty
let instance_list env schl =
let env = gadt_env env in
let tyl = List.map (copy ?env) schl in
cleanup_types ();
tyl
let reified_var_counter = ref Vars.empty
(* names given to new type constructors.
Used for existential types and
local constraints *)
let get_new_abstract_name s =
let index =
try Vars.find s !reified_var_counter + 1
with Not_found -> 0 in
reified_var_counter := Vars.add s index !reified_var_counter;
Printf.sprintf "%s#%d" s index
let new_declaration newtype manifest =
{
type_params = [];
type_arity = 0;
type_kind = Type_abstract;
type_private = Public;
type_manifest = manifest;
type_variance = [];
type_newtype_level = newtype;
type_loc = Location.none;
}
let instance_constructor ?in_pattern cstr =
begin match in_pattern with
| None -> ()
| Some (env, newtype_lev) ->
let process existential =
let decl = new_declaration (Some (newtype_lev, newtype_lev)) None in
let name =
match repr existential with
{desc = Tvar (Some name)} -> name
| _ -> "ex"
in
let (id, new_env) =
Env.enter_type (get_new_abstract_name name) decl !env in
env := new_env;
let to_unify = newty (Tconstr (Path.Pident id,[],ref Mnil)) in
let tv = copy existential in
assert (is_Tvar tv);
link_type tv to_unify
in
List.iter process cstr.cstr_existentials
end;
let ty_res = copy cstr.cstr_res in
let ty_args = List.map copy cstr.cstr_args in
cleanup_types ();
(ty_args, ty_res)
let instance_parameterized_type ?keep_names sch_args sch =
let ty_args = List.map (copy ?keep_names) sch_args in
let ty = copy sch in
cleanup_types ();
(ty_args, ty)
let instance_parameterized_type_2 sch_args sch_lst sch =
let ty_args = List.map copy sch_args in
let ty_lst = List.map copy sch_lst in
let ty = copy sch in
cleanup_types ();
(ty_args, ty_lst, ty)
let instance_declaration decl =
let decl =
{decl with type_params = List.map copy decl.type_params;
type_manifest = may_map copy decl.type_manifest;
type_kind = match decl.type_kind with
| Type_abstract -> Type_abstract
| Type_variant cl ->
Type_variant (
List.map (fun (s,tl,ot) -> (s, List.map copy tl, may_map copy ot))
cl)
| Type_record (fl, rr) ->
Type_record (List.map (fun (s,m,ty) -> (s, m, copy ty)) fl, rr)}
in
cleanup_types ();
decl
let instance_class params cty =
let rec copy_class_type =
function
Cty_constr (path, tyl, cty) ->
Cty_constr (path, List.map copy tyl, copy_class_type cty)
| Cty_signature sign ->
Cty_signature
{cty_self = copy sign.cty_self;
cty_vars =
Vars.map (function (m, v, ty) -> (m, v, copy ty)) sign.cty_vars;
cty_concr = sign.cty_concr;
cty_inher =
List.map (fun (p,tl) -> (p, List.map copy tl)) sign.cty_inher}
| Cty_fun (l, ty, cty) ->
Cty_fun (l, copy ty, copy_class_type cty)
in
let params' = List.map copy params in
let cty' = copy_class_type cty in
cleanup_types ();
(params', cty')
(**** Instanciation for types with free universal variables ****)
let rec diff_list l1 l2 =
if l1 == l2 then [] else
match l1 with [] -> invalid_arg "Ctype.diff_list"
| a :: l1 -> a :: diff_list l1 l2
let conflicts free bound =
let bound = List.map repr bound in
TypeSet.exists (fun t -> List.memq (repr t) bound) free
let delayed_copy = ref []
(* copying to do later *)
(* Copy without sharing until there are no free univars left *)
(* all free univars must be included in [visited] *)
let rec copy_sep fixed free bound visited ty =
let ty = repr ty in
let univars = free ty in
if TypeSet.is_empty univars then
if ty.level <> generic_level then ty else
let t = newvar () in
delayed_copy :=
lazy (t.desc <- Tlink (copy ty))
:: !delayed_copy;
t
else try
let t, bound_t = List.assq ty visited in
let dl = if is_Tunivar ty then [] else diff_list bound bound_t in
if dl <> [] && conflicts univars dl then raise Not_found;
t
with Not_found -> begin
let t = newvar() in (* Stub *)
let visited =
match ty.desc with
Tarrow _ | Ttuple _ | Tvariant _ | Tconstr _ | Tobject _ | Tpackage _ ->
(ty,(t,bound)) :: visited
| _ -> visited in
let copy_rec = copy_sep fixed free bound visited in
t.desc <-
begin match ty.desc with
| Tvariant row0 ->
let row = row_repr row0 in
let more = repr row.row_more in
(* We shall really check the level on the row variable *)
let keep = is_Tvar more && more.level <> generic_level in
let more' = copy_rec more in
let fixed' = fixed && is_Tvar (repr more') in
let row = copy_row copy_rec fixed' row keep more' in
Tvariant row
| Tpoly (t1, tl) ->
let tl = List.map repr tl in
let tl' = List.map (fun t -> newty t.desc) tl in
let bound = tl @ bound in
let visited =
List.map2 (fun ty t -> ty,(t,bound)) tl tl' @ visited in
Tpoly (copy_sep fixed free bound visited t1, tl')
| _ -> copy_type_desc copy_rec ty.desc
end;
t
end
let instance_poly ?(keep_names=false) fixed univars sch =
let univars = List.map repr univars in
let copy_var ty =
match ty.desc with
Tunivar name -> if keep_names then newty (Tvar name) else newvar ()
| _ -> assert false
in
let vars = List.map copy_var univars in
let pairs = List.map2 (fun u v -> u, (v, [])) univars vars in
delayed_copy := [];
let ty = copy_sep fixed (compute_univars sch) [] pairs sch in
List.iter Lazy.force !delayed_copy;
delayed_copy := [];
cleanup_types ();
vars, ty
let instance_label fixed lbl =
let ty_res = copy lbl.lbl_res in
let vars, ty_arg =
match repr lbl.lbl_arg with
{desc = Tpoly (ty, tl)} ->
instance_poly fixed tl ty
| ty ->
[], copy lbl.lbl_arg
in
cleanup_types ();
(vars, ty_arg, ty_res)
(**** Instantiation with parameter substitution ****)
let unify' = (* Forward declaration *)
ref (fun env ty1 ty2 -> raise (Unify []))
let subst env level priv abbrev ty params args body =
if List.length params <> List.length args then raise (Unify []);
let old_level = !current_level in
current_level := level;
try
let body0 = newvar () in (* Stub *)
begin match ty with
None -> ()
| Some ({desc = Tconstr (path, tl, _)} as ty) ->
let abbrev = proper_abbrevs path tl abbrev in
memorize_abbrev abbrev priv path ty body0
| _ ->
assert false
end;
abbreviations := abbrev;
let (params', body') = instance_parameterized_type params body in
abbreviations := ref Mnil;
!unify' env body0 body';
List.iter2 (!unify' env) params' args;
current_level := old_level;
body'
with Unify _ as exn ->
current_level := old_level;
raise exn
(*
Only the shape of the type matters, not whether is is generic or
not. [generic_level] might be somewhat slower, but it ensures
invariants on types are enforced (decreasing levels.), and we don't
care about efficiency here.
*)
let apply env params body args =
try
subst env generic_level Public (ref Mnil) None params args body
with
Unify _ -> raise Cannot_apply
(****************************)
(* Abbreviation expansion *)
(****************************)
(*
If the environnement has changed, memorized expansions might not
be correct anymore, and so we flush the cache. This is safe but
quite pessimistic: it would be enough to flush the cache when a
type or module definition is overridden in the environnement.
*)
let previous_env = ref Env.empty
let string_of_kind = function Public -> "public" | Private -> "private"
let check_abbrev_env env =
if env != !previous_env then begin
(* prerr_endline "cleanup expansion cache"; *)
cleanup_abbrev ();
previous_env := env
end
(* Expand an abbreviation. The expansion is memorized. *)
(*
Assume the level is greater than the path binding time of the
expanded abbreviation.
*)
(*
An abbreviation expansion will fail in either of these cases:
1. The type constructor does not correspond to a manifest type.
2. The type constructor is defined in an external file, and this
file is not in the path (missing -I options).
3. The type constructor is not in the "local" environment. This can
happens when a non-generic type variable has been instantiated
afterwards to the not yet defined type constructor. (Actually,
this cannot happen at the moment due to the strong constraints
between type levels and constructor binding time.)
4. The expansion requires the expansion of another abbreviation,
and this other expansion fails.
*)
let expand_abbrev_gen kind find_type_expansion env ty =
check_abbrev_env env;
match ty with
{desc = Tconstr (path, args, abbrev); level = level} ->
let lookup_abbrev = proper_abbrevs path args abbrev in
begin match find_expans kind path !lookup_abbrev with
Some ty ->
(* prerr_endline
("found a "^string_of_kind kind^" expansion for "^Path.name path);*)
if level <> generic_level then
begin try
update_level env level ty
with Unify _ ->
(* XXX This should not happen.
However, levels are not correctly restored after a
typing error *)
()
end;
ty
| None ->
let (params, body, lv) =
try find_type_expansion level path env with Not_found ->
raise Cannot_expand
in
(* prerr_endline
("add a "^string_of_kind kind^" expansion for "^Path.name path);*)
let ty' = subst env level kind abbrev (Some ty) params args body in
(* Hack to name the variant type *)
begin match repr ty' with
{desc=Tvariant row} as ty when static_row row ->
ty.desc <- Tvariant { row with row_name = Some (path, args) }
| _ -> ()
end;
(* For gadts, remember type as non exportable *)
(* The ambiguous level registered for ty' should be the highest *)
if !trace_gadt_instances then begin
match max lv (Env.gadt_instance_level env ty) with
None -> ()
| Some lv ->
if level < lv then raise (Unify [(ty, newvar2 level)]);
Env.add_gadt_instances env lv [ty; ty']
end;
ty'
end
| _ ->
assert false
(* inside objects and variants we do not want to
use local constraints *)
let expand_abbrev ty =
expand_abbrev_gen Public (fun level -> Env.find_type_expansion ~level) ty
(* Expand once the head of a type *)
let expand_head_once env ty =
try expand_abbrev env (repr ty) with Cannot_expand -> assert false
(* Check whether a type can be expanded *)
let safe_abbrev env ty =
let snap = Btype.snapshot () in
try ignore (expand_abbrev env ty); true
with Cannot_expand | Unify _ ->
Btype.backtrack snap;
false
(* Expand the head of a type once.
Raise Cannot_expand if the type cannot be expanded.
May raise Unify, if a recursion was hidden in the type. *)
let try_expand_once env ty =
let ty = repr ty in
match ty.desc with
Tconstr (p, _, _) -> repr (expand_abbrev env ty)
| _ -> raise Cannot_expand
(* This one only raises Cannot_expand *)
let try_expand_safe env ty =
let snap = Btype.snapshot () in
try try_expand_once env ty
with Unify _ ->
Btype.backtrack snap; raise Cannot_expand
(* Fully expand the head of a type. *)
let rec try_expand_head try_once env ty =
let ty' = try_once env ty in
try try_expand_head try_once env ty'
with Cannot_expand -> ty'
let try_expand_head try_once env ty =
let ty' = try_expand_head try_once env ty in
begin match Env.gadt_instance_level env ty' with
None -> ()
| Some lv -> Env.add_gadt_instance_chain env lv ty
end;
ty'
(* Unsafe full expansion, may raise Unify. *)
let expand_head_unif env ty =
try try_expand_head try_expand_once env ty with Cannot_expand -> repr ty
(* Safe version of expand_head, never fails *)
let expand_head env ty =
try try_expand_head try_expand_safe env ty with Cannot_expand -> repr ty
let _ = forward_try_expand_once := try_expand_safe
(* Expand until we find a non-abstract type declaration *)
let rec extract_concrete_typedecl env ty =
let ty = repr ty in
match ty.desc with
Tconstr (p, _, _) ->
let decl = Env.find_type p env in
if decl.type_kind <> Type_abstract then (p, p, decl) else
let ty =
try try_expand_once env ty with Cannot_expand -> raise Not_found
in
let (_, p', decl) = extract_concrete_typedecl env ty in
(p, p', decl)
| _ -> raise Not_found
(* Implementing function [expand_head_opt], the compiler's own version of
[expand_head] used for type-based optimisations.
[expand_head_opt] uses [Env.find_type_expansion_opt] to access the
manifest type information of private abstract data types which is
normally hidden to the type-checker out of the implementation module of
the private abbreviation. *)
let expand_abbrev_opt =
expand_abbrev_gen Private (fun level -> Env.find_type_expansion_opt)
let try_expand_once_opt env ty =
let ty = repr ty in
match ty.desc with
Tconstr _ -> repr (expand_abbrev_opt env ty)
| _ -> raise Cannot_expand
let rec try_expand_head_opt env ty =
let ty' = try_expand_once_opt env ty in
begin try
try_expand_head_opt env ty'
with Cannot_expand ->
ty'
end
let expand_head_opt env ty =
let snap = Btype.snapshot () in
try try_expand_head_opt env ty
with Cannot_expand | Unify _ -> (* expand_head shall never fail *)
Btype.backtrack snap;
repr ty
(* Make sure that the type parameters of the type constructor [ty]
respect the type constraints *)
let enforce_constraints env ty =
match ty with
{desc = Tconstr (path, args, abbrev); level = level} ->
begin try
let decl = Env.find_type path env in
ignore
(subst env level Public (ref Mnil) None decl.type_params args
(newvar2 level))
with Not_found -> ()
end
| _ ->
assert false
(* Recursively expand the head of a type.
Also expand #-types. *)
let full_expand env ty =
let ty = repr (expand_head env ty) in
match ty.desc with
Tobject (fi, {contents = Some (_, v::_)}) when is_Tvar (repr v) ->
newty2 ty.level (Tobject (fi, ref None))
| _ ->
ty
(*
Check whether the abbreviation expands to a well-defined type.
During the typing of a class, abbreviations for correspondings
types expand to non-generic types.
*)
let generic_abbrev env path =
try
let (_, body, _) = Env.find_type_expansion path env in
(repr body).level = generic_level
with
Not_found ->
false
(*****************)
(* Occur check *)
(*****************)
exception Occur
(* The marks are already used by [expand_abbrev]... *)
let visited = ref []
let rec non_recursive_abbrev env ty0 ty =
let ty = repr ty in
if ty == repr ty0 then raise Recursive_abbrev;
if not (List.memq ty !visited) then begin
visited := ty :: !visited;
match ty.desc with
Tconstr(p, args, abbrev) ->
begin try
non_recursive_abbrev env ty0 (try_expand_once_opt env ty)
with Cannot_expand ->
if !Clflags.recursive_types &&
(in_pervasives p ||
try is_datatype (Env.find_type p env) with Not_found -> false)
then ()
else iter_type_expr (non_recursive_abbrev env ty0) ty
end
| Tobject _ | Tvariant _ ->
()
| _ ->
if !Clflags.recursive_types then () else
iter_type_expr (non_recursive_abbrev env ty0) ty
end
let correct_abbrev env path params ty =
check_abbrev_env env;
let ty0 = newgenvar () in
visited := [];
let abbrev = Mcons (Public, path, ty0, ty0, Mnil) in
simple_abbrevs := abbrev;
try
non_recursive_abbrev env ty0
(subst env generic_level Public (ref abbrev) None [] [] ty);
simple_abbrevs := Mnil;
visited := []
with exn ->
simple_abbrevs := Mnil;
visited := [];
raise exn
let rec occur_rec env visited ty0 ty =
if ty == ty0 then raise Occur;
match ty.desc with
Tconstr(p, tl, abbrev) ->
begin try
if List.memq ty visited || !Clflags.recursive_types then raise Occur;
iter_type_expr (occur_rec env (ty::visited) ty0) ty
with Occur -> try
let ty' = try_expand_head try_expand_once env ty in
(* Maybe we could simply make a recursive call here,
but it seems it could make the occur check loop
(see change in rev. 1.58) *)
if ty' == ty0 || List.memq ty' visited then raise Occur;
match ty'.desc with
Tobject _ | Tvariant _ -> ()
| _ ->
if not !Clflags.recursive_types then
iter_type_expr (occur_rec env (ty'::visited) ty0) ty'
with Cannot_expand ->
if not !Clflags.recursive_types then raise Occur
end
| Tobject _ | Tvariant _ ->
()
| _ ->
if not !Clflags.recursive_types then
iter_type_expr (occur_rec env visited ty0) ty
let type_changed = ref false (* trace possible changes to the studied type *)
let merge r b = if b then r := true
let occur env ty0 ty =
let old = !type_changed in
try
while type_changed := false; occur_rec env [] ty0 ty; !type_changed
do () (* prerr_endline "changed" *) done;
merge type_changed old
with exn ->
merge type_changed old;
raise (match exn with Occur -> Unify [] | _ -> exn)
let occur_in env ty0 t =
try occur env ty0 t; false with Unify _ -> true
(* checks that a local constraint is non recursive *)
let rec local_non_recursive_abbrev visited env p ty =
let ty = repr ty in
if not (List.memq ty !visited) then begin
visited := ty :: !visited;
match ty.desc with
Tconstr(p', args, abbrev) ->
if Path.same p p' then raise Recursive_abbrev;
begin try
local_non_recursive_abbrev visited env p (try_expand_once_opt env ty)
with Cannot_expand ->
if !Clflags.recursive_types then () else
iter_type_expr (local_non_recursive_abbrev visited env p) ty
end
| Tobject _ | Tvariant _ ->
()
| _ ->
if !Clflags.recursive_types then () else
iter_type_expr (local_non_recursive_abbrev visited env p) ty
end
let local_non_recursive_abbrev = local_non_recursive_abbrev (ref [])
(*****************************)
(* Polymorphic Unification *)
(*****************************)
(* Since we cannot duplicate universal variables, unification must
be done at meta-level, using bindings in univar_pairs *)
let rec unify_univar t1 t2 = function
(cl1, cl2) :: rem ->
let find_univ t cl =
try
let (_, r) = List.find (fun (t',_) -> t == repr t') cl in
Some r
with Not_found -> None
in
begin match find_univ t1 cl1, find_univ t2 cl2 with
Some {contents=Some t'2}, Some _ when t2 == repr t'2 ->
()
| Some({contents=None} as r1), Some({contents=None} as r2) ->
set_univar r1 t2; set_univar r2 t1
| None, None ->
unify_univar t1 t2 rem
| _ ->
raise (Unify [])
end
| [] -> raise (Unify [])
(* Test the occurence of free univars in a type *)
(* that's way too expansive. Must do some kind of cacheing *)
let occur_univar env ty =
let visited = ref TypeMap.empty in
let rec occur_rec bound ty =
let ty = repr ty in
if ty.level >= lowest_level &&
if TypeSet.is_empty bound then
(ty.level <- pivot_level - ty.level; true)
else try
let bound' = TypeMap.find ty !visited in
if TypeSet.exists (fun x -> not (TypeSet.mem x bound)) bound' then
(visited := TypeMap.add ty (TypeSet.inter bound bound') !visited;
true)
else false
with Not_found ->
visited := TypeMap.add ty bound !visited;
true
then
match ty.desc with
Tunivar _ ->
if not (TypeSet.mem ty bound) then raise (Unify [ty, newgenvar ()])
| Tpoly (ty, tyl) ->
let bound = List.fold_right TypeSet.add (List.map repr tyl) bound in
occur_rec bound ty
| Tconstr (_, [], _) -> ()
| Tconstr (p, tl, _) ->
begin try
let td = Env.find_type p env in
List.iter2
(fun t (pos,neg,_) -> if pos || neg then occur_rec bound t)
tl td.type_variance
with Not_found ->
List.iter (occur_rec bound) tl
end
| _ -> iter_type_expr (occur_rec bound) ty
in
try
occur_rec TypeSet.empty ty; unmark_type ty
with exn ->
unmark_type ty; raise exn
(* Grouping univars by families according to their binders *)
let add_univars =
List.fold_left (fun s (t,_) -> TypeSet.add (repr t) s)
let get_univar_family univar_pairs univars =
if univars = [] then TypeSet.empty else
let insert s = function
cl1, (_::_ as cl2) ->
if List.exists (fun (t1,_) -> TypeSet.mem (repr t1) s) cl1 then
add_univars s cl2
else s
| _ -> s
in
let s = List.fold_right TypeSet.add univars TypeSet.empty in
List.fold_left insert s univar_pairs
(* Whether a family of univars escapes from a type *)
let univars_escape env univar_pairs vl ty =
let family = get_univar_family univar_pairs vl in
let visited = ref TypeSet.empty in
let rec occur t =
let t = repr t in
if TypeSet.mem t !visited then () else begin
visited := TypeSet.add t !visited;
match t.desc with
Tpoly (t, tl) ->
if List.exists (fun t -> TypeSet.mem (repr t) family) tl then ()
else occur t
| Tunivar _ ->
if TypeSet.mem t family then raise Occur
| Tconstr (_, [], _) -> ()
| Tconstr (p, tl, _) ->
begin try
let td = Env.find_type p env in
List.iter2 (fun t (pos,neg,_) -> if pos || neg then occur t)
tl td.type_variance
with Not_found ->
List.iter occur tl
end
| _ ->
iter_type_expr occur t
end
in
try occur ty; false with Occur -> true
(* Wrapper checking that no variable escapes and updating univar_pairs *)
let enter_poly env univar_pairs t1 tl1 t2 tl2 f =
let old_univars = !univar_pairs in
let known_univars =
List.fold_left (fun s (cl,_) -> add_univars s cl)
TypeSet.empty old_univars
in
let tl1 = List.map repr tl1 and tl2 = List.map repr tl2 in
if List.exists (fun t -> TypeSet.mem t known_univars) tl1 &&
univars_escape env old_univars tl1 (newty(Tpoly(t2,tl2)))
|| List.exists (fun t -> TypeSet.mem t known_univars) tl2 &&
univars_escape env old_univars tl2 (newty(Tpoly(t1,tl1)))
then raise (Unify []);
let cl1 = List.map (fun t -> t, ref None) tl1
and cl2 = List.map (fun t -> t, ref None) tl2 in
univar_pairs := (cl1,cl2) :: (cl2,cl1) :: old_univars;
try let res = f t1 t2 in univar_pairs := old_univars; res
with exn -> univar_pairs := old_univars; raise exn
let univar_pairs = ref []
(*****************)
(* Unification *)
(*****************)
let rec has_cached_expansion p abbrev =
match abbrev with
Mnil -> false
| Mcons(_, p', _, _, rem) -> Path.same p p' || has_cached_expansion p rem
| Mlink rem -> has_cached_expansion p !rem
(**** Transform error trace ****)
(* +++ Move it to some other place ? *)
let expand_trace env trace =
List.fold_right
(fun (t1, t2) rem ->
(repr t1, full_expand env t1)::(repr t2, full_expand env t2)::rem)
trace []
(* build a dummy variant type *)
let mkvariant fields closed =
newgenty
(Tvariant
{row_fields = fields; row_closed = closed; row_more = newvar();
row_bound = (); row_fixed = false; row_name = None })
(* force unification in Reither when one side has as non-conjunctive type *)
let rigid_variants = ref false
(**** Unification ****)
(* Return whether [t0] occurs in [ty]. Objects are also traversed. *)
let deep_occur t0 ty =
let rec occur_rec ty =
let ty = repr ty in
if ty.level >= lowest_level then begin
if ty == t0 then raise Occur;
ty.level <- pivot_level - ty.level;
iter_type_expr occur_rec ty
end
in
try
occur_rec ty; unmark_type ty; false
with Occur ->
unmark_type ty; true
(*
1. When unifying two non-abbreviated types, one type is made a link
to the other. When unifying an abbreviated type with a
non-abbreviated type, the non-abbreviated type is made a link to
the other one. When unifying to abbreviated types, these two
types are kept distincts, but they are made to (temporally)
expand to the same type.
2. Abbreviations with at least one parameter are systematically
expanded. The overhead does not seem to high, and that way
abbreviations where some parameters does not appear in the
expansion, such as ['a t = int], are correctly handled. In
particular, for this example, unifying ['a t] with ['b t] keeps
['a] and ['b] distincts. (Is it really important ?)
3. Unifying an abbreviation ['a t = 'a] with ['a] should not yield
['a t as 'a]. Indeed, the type variable would otherwise be lost.
This problem occurs for abbreviations expanding to a type
variable, but also to many other constrained abbreviations (for
instance, [(< x : 'a > -> unit) t = <x : 'a>]). The solution is
that, if an abbreviation is unified with some subpart of its
parameters, then the parameter actually does not get
abbreviated. It would be possible to check whether some
information is indeed lost, but it probably does not worth it.
*)
let newtype_level = ref None
let get_newtype_level () =
match !newtype_level with
| None -> assert false
| Some x -> x
(* a local constraint can be added only if the rhs
of the constraint does not contain any Tvars.
They need to be removed using this function *)
let reify env t =
let newtype_level = get_newtype_level () in
let create_fresh_constr lev name =
let decl = new_declaration (Some (newtype_level, newtype_level)) None in
let name = get_new_abstract_name name in
let (id, new_env) = Env.enter_type name decl !env in
let t = newty2 lev (Tconstr (Path.Pident id,[],ref Mnil)) in
env := new_env;
t
in
let visited = ref TypeSet.empty in
let rec iterator ty =
let ty = repr ty in
if TypeSet.mem ty !visited then () else begin
visited := TypeSet.add ty !visited;
match ty.desc with
Tvar o ->
let name = match o with Some s -> s | _ -> "ex" in
let t = create_fresh_constr ty.level name in
link_type ty t
| Tvariant r ->
if not (static_row r) then iterator (row_more r);
iter_row iterator r
| Tconstr (p, _, _) when is_object_type p ->
iter_type_expr iterator (full_expand !env ty)
| _ ->
iter_type_expr iterator ty
end
in
iterator t
let is_abstract_newtype env p =
try
let decl = Env.find_type p env in
not (decl.type_newtype_level = None) &&
decl.type_manifest = None &&
decl.type_kind = Type_abstract
with Not_found -> false
let non_aliasable p decl =
(* in_pervasives p || (subsumed by in_current_module) *)
in_current_module p && decl.type_newtype_level = None
(* mcomp type_pairs subst env t1 t2 does not raise an
exception if it is possible that t1 and t2 are actually
equal, assuming the types in type_pairs are equal and
that the mapping subst holds.
Assumes that both t1 and t2 do not contain any tvars
and that both their objects and variants are closed
*)
let rec mcomp type_pairs subst env t1 t2 =
if t1 == t2 then () else
let t1 = repr t1 in
let t2 = repr t2 in
if t1 == t2 then () else
match (t1.desc, t2.desc) with
| (Tvar _, _)
| (_, Tvar _) ->
fatal_error "types should not include variables"
| (Tconstr (p1, [], _), Tconstr (p2, [], _)) when Path.same p1 p2 ->
()
| _ ->
let t1' = expand_head_opt env t1 in
let t2' = expand_head_opt env t2 in
(* Expansion may have changed the representative of the types... *)
let t1' = repr t1' and t2' = repr t2' in
if t1' == t2' then () else
begin try TypePairs.find type_pairs (t1', t2')
with Not_found ->
TypePairs.add type_pairs (t1', t2') ();
match (t1'.desc, t2'.desc) with
(Tvar _, Tvar _) -> assert false
| (Tarrow (l1, t1, u1, _), Tarrow (l2, t2, u2, _))
when l1 = l2 || not (is_optional l1 || is_optional l2) ->
mcomp type_pairs subst env t1 t2;
mcomp type_pairs subst env u1 u2;
| (Ttuple tl1, Ttuple tl2) ->
mcomp_list type_pairs subst env tl1 tl2
| (Tconstr (p1, tl1, _), Tconstr (p2, tl2, _)) ->
mcomp_type_decl type_pairs subst env p1 p2 tl1 tl2
| (Tconstr (p, _, _), _) | (_, Tconstr (p, _, _)) ->
let decl = Env.find_type p env in
if non_aliasable p decl then raise (Unify [])
| (Tpackage (p1, n1, tl1), Tpackage (p2, n2, tl2))
when Path.same p1 p2 && n1 = n2 ->
mcomp_list type_pairs subst env tl1 tl2
| (Tvariant row1, Tvariant row2) ->
mcomp_row type_pairs subst env row1 row2
| (Tobject (fi1, _), Tobject (fi2, _)) ->
mcomp_fields type_pairs subst env fi1 fi2
| (Tfield _, Tfield _) -> (* Actually unused *)
mcomp_fields type_pairs subst env t1' t2'
| (Tnil, Tnil) ->
()
| (Tpoly (t1, []), Tpoly (t2, [])) ->
mcomp type_pairs subst env t1 t2
| (Tpoly (t1, tl1), Tpoly (t2, tl2)) ->
enter_poly env univar_pairs t1 tl1 t2 tl2
(mcomp type_pairs subst env)
| (Tunivar _, Tunivar _) ->
unify_univar t1' t2' !univar_pairs
| (_, _) ->
raise (Unify [])
end
and mcomp_list type_pairs subst env tl1 tl2 =
if List.length tl1 <> List.length tl2 then
raise (Unify []);
List.iter2 (mcomp type_pairs subst env) tl1 tl2
and mcomp_fields type_pairs subst env ty1 ty2 =
if not (concrete_object ty1 && concrete_object ty2) then assert false;
let (fields2, rest2) = flatten_fields ty2 in
let (fields1, rest1) = flatten_fields ty1 in
let (pairs, miss1, miss2) = associate_fields fields1 fields2 in
mcomp type_pairs subst env rest1 rest2;
if miss1 <> [] && (object_row ty1).desc = Tnil
|| miss2 <> [] && (object_row ty2).desc = Tnil then raise (Unify []);
List.iter
(function (n, k1, t1, k2, t2) ->
mcomp_kind k1 k2;
mcomp type_pairs subst env t1 t2)
pairs
and mcomp_kind k1 k2 =
let k1 = field_kind_repr k1 in
let k2 = field_kind_repr k2 in
match k1, k2 with
(Fvar _, Fvar _)
| (Fpresent, Fpresent) -> ()
| _ -> raise (Unify [])
and mcomp_row type_pairs subst env row1 row2 =
let row1 = row_repr row1 and row2 = row_repr row2 in
let r1, r2, pairs = merge_row_fields row1.row_fields row2.row_fields in
let cannot_erase (_,f) =
match row_field_repr f with
Rpresent _ -> true
| Rabsent | Reither _ -> false
in
if row1.row_closed && List.exists cannot_erase r2
|| row2.row_closed && List.exists cannot_erase r1 then raise (Unify []);
List.iter
(fun (_,f1,f2) ->
match row_field_repr f1, row_field_repr f2 with
| Rpresent None, (Rpresent (Some _) | Reither (_, _::_, _, _) | Rabsent)
| Rpresent (Some _), (Rpresent None | Reither (true, _, _, _) | Rabsent)
| (Reither (_, _::_, _, _) | Rabsent), Rpresent None
| (Reither (true, _, _, _) | Rabsent), Rpresent (Some _) ->
raise (Unify [])
| Rpresent(Some t1), Rpresent(Some t2) ->
mcomp type_pairs subst env t1 t2
| Rpresent(Some t1), Reither(false, tl2, _, _) ->
List.iter (mcomp type_pairs subst env t1) tl2
| Reither(false, tl1, _, _), Rpresent(Some t2) ->
List.iter (mcomp type_pairs subst env t2) tl1
| _ -> ())
pairs
and mcomp_type_decl type_pairs subst env p1 p2 tl1 tl2 =
try
let decl = Env.find_type p1 env in
let decl' = Env.find_type p2 env in
if Path.same p1 p2 then
(if non_aliasable p1 decl then mcomp_list type_pairs subst env tl1 tl2)
else match decl.type_kind, decl'.type_kind with
| Type_record (lst,r), Type_record (lst',r') when r = r' ->
mcomp_list type_pairs subst env tl1 tl2;
mcomp_record_description type_pairs subst env lst lst'
| Type_variant v1, Type_variant v2 ->
mcomp_list type_pairs subst env tl1 tl2;
mcomp_variant_description type_pairs subst env v1 v2
| Type_variant _, Type_record _
| Type_record _, Type_variant _ -> raise (Unify [])
| _ ->
if non_aliasable p1 decl && (non_aliasable p2 decl'||is_datatype decl')
|| is_datatype decl && non_aliasable p2 decl' then raise (Unify [])
with Not_found -> ()
and mcomp_type_option type_pairs subst env t t' =
match t, t' with
None, None -> ()
| Some t, Some t' -> mcomp type_pairs subst env t t'
| _ -> raise (Unify [])
and mcomp_variant_description type_pairs subst env =
let rec iter = fun x y ->
match x, y with
(name,mflag,t) :: xs, (name', mflag', t') :: ys ->
mcomp_type_option type_pairs subst env t t';
if name = name' && mflag = mflag'
then iter xs ys
else raise (Unify [])
| [],[] -> ()
| _ -> raise (Unify [])
in
iter
and mcomp_record_description type_pairs subst env =
let rec iter = fun x y ->
match x, y with
(name, mutable_flag, t) :: xs, (name', mutable_flag', t') :: ys ->
mcomp type_pairs subst env t t';
if name = name' && mutable_flag = mutable_flag'
then iter xs ys
else raise (Unify [])
| [], [] -> ()
| _ -> raise (Unify [])
in
iter
let mcomp env t1 t2 =
mcomp (TypePairs.create 4) () env t1 t2
(* Real unification *)
let find_lowest_level ty =
let lowest = ref generic_level in
let rec find ty =
let ty = repr ty in
if ty.level >= lowest_level then begin
if ty.level < !lowest then lowest := ty.level;
ty.level <- pivot_level - ty.level;
iter_type_expr find ty
end
in find ty; unmark_type ty; !lowest
let find_newtype_level env path =
try match (Env.find_type path env).type_newtype_level with
Some x -> x
| None -> assert false
with Not_found -> assert false
let add_gadt_equation env source destination =
let destination = duplicate_type destination in
let source_lev = find_newtype_level !env (Path.Pident source) in
let decl = new_declaration (Some source_lev) (Some destination) in
let newtype_level = get_newtype_level () in
env := Env.add_local_constraint source decl newtype_level !env;
cleanup_abbrev ()
let unify_eq_set = TypePairs.create 11
let order_type_pair t1 t2 =
if t1.id <= t2.id then (t1, t2) else (t2, t1)
let add_type_equality t1 t2 =
TypePairs.add unify_eq_set (order_type_pair t1 t2) ()
let unify_eq env t1 t2 =
t1 == t2 ||
match !umode with
| Expression -> false
| Pattern ->
try TypePairs.find unify_eq_set (order_type_pair t1 t2); true
with Not_found -> false
let rec unify (env:Env.t ref) t1 t2 =
(* First step: special cases (optimizations) *)
if t1 == t2 then () else
let t1 = repr t1 in
let t2 = repr t2 in
if unify_eq !env t1 t2 then () else
let reset_tracing = check_trace_gadt_instances !env in
try
type_changed := true;
begin match (t1.desc, t2.desc) with
(Tvar _, Tconstr _) when deep_occur t1 t2 ->
unify2 env t1 t2
| (Tconstr _, Tvar _) when deep_occur t2 t1 ->
unify2 env t1 t2
| (Tvar _, _) ->
occur !env t1 t2;
occur_univar !env t2;
link_type t1 t2;
update_level !env t1.level t2
| (_, Tvar _) ->
occur !env t2 t1;
occur_univar !env t1;
link_type t2 t1;
update_level !env t2.level t1
| (Tunivar _, Tunivar _) ->
unify_univar t1 t2 !univar_pairs;
update_level !env t1.level t2;
link_type t1 t2
| (Tconstr (p1, [], a1), Tconstr (p2, [], a2))
when Path.same p1 p2 (* && actual_mode !env = Old *)
(* This optimization assumes that t1 does not expand to t2
(and conversely), so we fall back to the general case
when any of the types has a cached expansion. *)
&& not (has_cached_expansion p1 !a1
|| has_cached_expansion p2 !a2) ->
update_level !env t1.level t2;
link_type t1 t2
| _ ->
unify2 env t1 t2
end;
if reset_tracing then trace_gadt_instances := false;
with Unify trace ->
if reset_tracing then trace_gadt_instances := false;
raise (Unify ((t1, t2)::trace))
and unify2 env t1 t2 =
(* Second step: expansion of abbreviations *)
let rec expand_both t1'' t2'' =
let t1' = expand_head_unif !env t1 in
let t2' = expand_head_unif !env t2 in
(* Expansion may have changed the representative of the types... *)
if unify_eq !env t1' t1'' && unify_eq !env t2' t2'' then (t1',t2') else
expand_both t1' t2'
in
let t1', t2' = expand_both t1 t2 in
let lv = min t1'.level t2'.level in
update_level !env lv t2;
update_level !env lv t1;
if unify_eq !env t1' t2' then () else
let t1 = repr t1 and t2 = repr t2 in
if !trace_gadt_instances then begin
(* All types in chains already have the same ambiguity levels *)
let ilevel t =
match Env.gadt_instance_level !env t with None -> 0 | Some lv -> lv in
let lv1 = ilevel t1 and lv2 = ilevel t2 in
if lv1 > lv2 then Env.add_gadt_instance_chain !env lv1 t2 else
if lv2 > lv1 then Env.add_gadt_instance_chain !env lv2 t1
end;
let t1, t2 =
if !Clflags.principal
&& (find_lowest_level t1' < lv || find_lowest_level t2' < lv) then
(* Expand abbreviations hiding a lower level *)
(* Should also do it for parameterized types, after unification... *)
(match t1.desc with Tconstr (_, [], _) -> t1' | _ -> t1),
(match t2.desc with Tconstr (_, [], _) -> t2' | _ -> t2)
else (t1, t2)
in
if unify_eq !env t1 t1' || not (unify_eq !env t2 t2') then
unify3 env t1 t1' t2 t2'
else
try unify3 env t2 t2' t1 t1' with Unify trace ->
raise (Unify (List.map (fun (x, y) -> (y, x)) trace))
and unify3 env t1 t1' t2 t2' =
(* Third step: truly unification *)
(* Assumes either [t1 == t1'] or [t2 != t2'] *)
let d1 = t1'.desc and d2 = t2'.desc in
let create_recursion = (t2 != t2') && (deep_occur t1' t2) in
begin match (d1, d2) with (* handle vars and univars specially *)
(Tunivar _, Tunivar _) ->
unify_univar t1' t2' !univar_pairs;
link_type t1' t2'
| (Tvar _, _) ->
occur !env t1' t2;
occur_univar !env t2;
link_type t1' t2;
| (_, Tvar _) ->
occur !env t2' t1;
occur_univar !env t1;
link_type t2' t1;
| (Tfield _, Tfield _) -> (* special case for GADTs *)
unify_fields env t1' t2'
| _ ->
begin match !umode with
| Expression ->
occur !env t1' t2';
link_type t1' t2
| Pattern ->
add_type_equality t1' t2'
end;
try
begin match (d1, d2) with
(Tarrow (l1, t1, u1, c1), Tarrow (l2, t2, u2, c2)) when l1 = l2 ||
!Clflags.classic && not (is_optional l1 || is_optional l2) ->
unify env t1 t2; unify env u1 u2;
begin match commu_repr c1, commu_repr c2 with
Clink r, c2 -> set_commu r c2
| c1, Clink r -> set_commu r c1
| _ -> ()
end
| (Ttuple tl1, Ttuple tl2) ->
unify_list env tl1 tl2
| (Tconstr (p1, tl1, _), Tconstr (p2, tl2, _)) when Path.same p1 p2 ->
if !umode = Expression || not !generate_equations
|| in_current_module p1 (* || in_pervasives p1 *)
|| try is_datatype (Env.find_type p1 !env) with Not_found -> false
then
unify_list env tl1 tl2
else
set_mode Pattern ~generate:false (fun () -> unify_list env tl1 tl2)
| (Tconstr ((Path.Pident p) as path,[],_),
Tconstr ((Path.Pident p') as path',[],_))
when is_abstract_newtype !env path && is_abstract_newtype !env path'
&& !generate_equations ->
let source,destination =
if find_newtype_level !env path > find_newtype_level !env path'
then p,t2'
else p',t1'
in add_gadt_equation env source destination
| (Tconstr ((Path.Pident p) as path,[],_), _)
when is_abstract_newtype !env path && !generate_equations ->
reify env t2';
local_non_recursive_abbrev !env (Path.Pident p) t2';
add_gadt_equation env p t2'
| (_, Tconstr ((Path.Pident p) as path,[],_))
when is_abstract_newtype !env path && !generate_equations ->
reify env t1' ;
local_non_recursive_abbrev !env (Path.Pident p) t1';
add_gadt_equation env p t1'
| (Tconstr (_,[],_), _) | (_, Tconstr (_,[],_)) when !umode = Pattern ->
reify env t1';
reify env t2';
mcomp !env t1' t2'
| (Tobject (fi1, nm1), Tobject (fi2, _)) ->
unify_fields env fi1 fi2;
(* Type [t2'] may have been instantiated by [unify_fields] *)
(* XXX One should do some kind of unification... *)
begin match (repr t2').desc with
Tobject (_, {contents = Some (_, va::_)}) when
(match (repr va).desc with
Tvar _|Tunivar _|Tnil -> true | _ -> false) -> ()
| Tobject (_, nm2) -> set_name nm2 !nm1
| _ -> ()
end
| (Tvariant row1, Tvariant row2) ->
unify_row env row1 row2
| (Tfield(f,kind,_,rem), Tnil) | (Tnil, Tfield(f,kind,_,rem)) ->
begin match field_kind_repr kind with
Fvar r when f <> dummy_method ->
set_kind r Fabsent;
if d2 = Tnil then unify env rem t2'
else unify env (newty2 rem.level Tnil) rem
| _ -> raise (Unify [])
end
| (Tnil, Tnil) ->
()
| (Tpoly (t1, []), Tpoly (t2, [])) ->
unify env t1 t2
| (Tpoly (t1, tl1), Tpoly (t2, tl2)) ->
enter_poly !env univar_pairs t1 tl1 t2 tl2 (unify env)
| (Tpackage (p1, n1, tl1), Tpackage (p2, n2, tl2))
when Path.same p1 p2 && n1 = n2 ->
unify_list env tl1 tl2
| (_, _) ->
raise (Unify [])
end;
(* XXX Commentaires + changer "create_recursion" *)
if create_recursion then
match t2.desc with
Tconstr (p, tl, abbrev) ->
forget_abbrev abbrev p;
let t2'' = expand_head_unif !env t2 in
if not (closed_parameterized_type tl t2'') then
link_type (repr t2) (repr t2')
| _ ->
() (* t2 has already been expanded by update_level *)
with Unify trace ->
t1'.desc <- d1;
raise (Unify trace)
end
and unify_list env tl1 tl2 =
if List.length tl1 <> List.length tl2 then
raise (Unify []);
List.iter2 (unify env) tl1 tl2
(* Build a fresh row variable for unification *)
and make_rowvar level use1 rest1 use2 rest2 =
let set_name ty name =
match ty.desc with
Tvar None -> log_type ty; ty.desc <- Tvar name
| _ -> ()
in
let name =
match rest1.desc, rest2.desc with
Tvar (Some _ as name1), Tvar (Some _ as name2) ->
if rest1.level <= rest2.level then name1 else name2
| Tvar (Some _ as name), _ ->
if use2 then set_name rest2 name; name
| _, Tvar (Some _ as name) ->
if use1 then set_name rest2 name; name
| _ -> None
in
if use1 then rest1 else
if use2 then rest2 else newvar2 ?name level
and unify_fields env ty1 ty2 = (* Optimization *)
let (fields1, rest1) = flatten_fields ty1
and (fields2, rest2) = flatten_fields ty2 in
let (pairs, miss1, miss2) = associate_fields fields1 fields2 in
let l1 = (repr ty1).level and l2 = (repr ty2).level in
let va = make_rowvar (min l1 l2) (miss2=[]) rest1 (miss1=[]) rest2 in
let d1 = rest1.desc and d2 = rest2.desc in
try
unify env (build_fields l1 miss1 va) rest2;
unify env rest1 (build_fields l2 miss2 va);
List.iter
(fun (n, k1, t1, k2, t2) ->
unify_kind k1 k2;
try
if !trace_gadt_instances then update_level !env va.level t1;
unify env t1 t2
with Unify trace ->
raise (Unify ((newty (Tfield(n, k1, t1, newty Tnil)),
newty (Tfield(n, k2, t2, newty Tnil)))::trace)))
pairs
with exn ->
log_type rest1; rest1.desc <- d1;
log_type rest2; rest2.desc <- d2;
raise exn
and unify_kind k1 k2 =
let k1 = field_kind_repr k1 in
let k2 = field_kind_repr k2 in
if k1 == k2 then () else
match k1, k2 with
(Fvar r, (Fvar _ | Fpresent)) -> set_kind r k2
| (Fpresent, Fvar r) -> set_kind r k1
| (Fpresent, Fpresent) -> ()
| _ -> assert false
and unify_pairs mode env tpl =
List.iter (fun (t1, t2) -> unify env t1 t2) tpl
and unify_row env row1 row2 =
let row1 = row_repr row1 and row2 = row_repr row2 in
let rm1 = row_more row1 and rm2 = row_more row2 in
if unify_eq !env rm1 rm2 then () else
let r1, r2, pairs = merge_row_fields row1.row_fields row2.row_fields in
if r1 <> [] && r2 <> [] then begin
let ht = Hashtbl.create (List.length r1) in
List.iter (fun (l,_) -> Hashtbl.add ht (hash_variant l) l) r1;
List.iter
(fun (l,_) ->
try raise (Tags(l, Hashtbl.find ht (hash_variant l)))
with Not_found -> ())
r2
end;
let fixed1 = row_fixed row1 and fixed2 = row_fixed row2 in
let more =
if fixed1 then rm1 else
if fixed2 then rm2 else
newty2 (min rm1.level rm2.level) (Tvar None) in
let fixed = fixed1 || fixed2
and closed = row1.row_closed || row2.row_closed in
let keep switch =
List.for_all
(fun (_,f1,f2) ->
let f1, f2 = switch f1 f2 in
row_field_repr f1 = Rabsent || row_field_repr f2 <> Rabsent)
pairs
in
let empty fields =
List.for_all (fun (_,f) -> row_field_repr f = Rabsent) fields in
(* Check whether we are going to build an empty type *)
if closed && (empty r1 || row2.row_closed) && (empty r2 || row1.row_closed)
&& List.for_all
(fun (_,f1,f2) ->
row_field_repr f1 = Rabsent || row_field_repr f2 = Rabsent)
pairs
then raise (Unify [mkvariant [] true, mkvariant [] true]);
let name =
if row1.row_name <> None && (row1.row_closed || empty r2) &&
(not row2.row_closed || keep (fun f1 f2 -> f1, f2) && empty r1)
then row1.row_name
else if row2.row_name <> None && (row2.row_closed || empty r1) &&
(not row1.row_closed || keep (fun f1 f2 -> f2, f1) && empty r2)
then row2.row_name
else None
in
let row0 = {row_fields = []; row_more = more; row_bound = ();
row_closed = closed; row_fixed = fixed; row_name = name} in
let set_more row rest =
let rest =
if closed then
filter_row_fields row.row_closed rest
else rest in
if rest <> [] && (row.row_closed || row_fixed row)
|| closed && row_fixed row && not row.row_closed then begin
let t1 = mkvariant [] true and t2 = mkvariant rest false in
raise (Unify [if row == row1 then (t1,t2) else (t2,t1)])
end;
(* The following test is not principal... should rather use Tnil *)
let rm = row_more row in
if !trace_gadt_instances && rm.desc = Tnil then () else
if !trace_gadt_instances then
update_level !env rm.level (newgenty (Tvariant row));
if row_fixed row then
if more == rm then () else
if is_Tvar rm then link_type rm more else unify env rm more
else
let ty = newgenty (Tvariant {row0 with row_fields = rest}) in
update_level !env rm.level ty;
link_type rm ty
in
let md1 = rm1.desc and md2 = rm2.desc in
begin try
set_more row2 r1;
set_more row1 r2;
List.iter
(fun (l,f1,f2) ->
try unify_row_field env fixed1 fixed2 more l f1 f2
with Unify trace ->
raise (Unify ((mkvariant [l,f1] true,
mkvariant [l,f2] true) :: trace)))
pairs;
with exn ->
log_type rm1; rm1.desc <- md1; log_type rm2; rm2.desc <- md2; raise exn
end
and unify_row_field env fixed1 fixed2 more l f1 f2 =
let f1 = row_field_repr f1 and f2 = row_field_repr f2 in
if f1 == f2 then () else
match f1, f2 with
Rpresent(Some t1), Rpresent(Some t2) -> unify env t1 t2
| Rpresent None, Rpresent None -> ()
| Reither(c1, tl1, m1, e1), Reither(c2, tl2, m2, e2) ->
if e1 == e2 then () else
let redo =
(m1 || m2 || fixed1 || fixed2 ||
!rigid_variants && (List.length tl1 = 1 || List.length tl2 = 1)) &&
begin match tl1 @ tl2 with [] -> false
| t1 :: tl ->
if c1 || c2 then raise (Unify []);
List.iter (unify env t1) tl;
!e1 <> None || !e2 <> None
end in
if redo then unify_row_field env fixed1 fixed2 more l f1 f2 else
let tl1 = List.map repr tl1 and tl2 = List.map repr tl2 in
let rec remq tl = function [] -> []
| ty :: tl' ->
if List.memq ty tl then remq tl tl' else ty :: remq tl tl'
in
let tl2' = remq tl2 tl1 and tl1' = remq tl1 tl2 in
(* Is this handling of levels really principal? *)
List.iter (update_level !env (repr more).level) (tl1' @ tl2');
let e = ref None in
let f1' = Reither(c1 || c2, tl1', m1 || m2, e)
and f2' = Reither(c1 || c2, tl2', m1 || m2, e) in
set_row_field e1 f1'; set_row_field e2 f2';
| Reither(_, _, false, e1), Rabsent when not fixed1 -> set_row_field e1 f2
| Rabsent, Reither(_, _, false, e2) when not fixed2 -> set_row_field e2 f1
| Rabsent, Rabsent -> ()
| Reither(false, tl, _, e1), Rpresent(Some t2) when not fixed1 ->
set_row_field e1 f2;
update_level !env (repr more).level t2;
(try List.iter (fun t1 -> unify env t1 t2) tl
with exn -> e1 := None; raise exn)
| Rpresent(Some t1), Reither(false, tl, _, e2) when not fixed2 ->
set_row_field e2 f1;
update_level !env (repr more).level t1;
(try List.iter (unify env t1) tl
with exn -> e2 := None; raise exn)
| Reither(true, [], _, e1), Rpresent None when not fixed1 ->
set_row_field e1 f2
| Rpresent None, Reither(true, [], _, e2) when not fixed2 ->
set_row_field e2 f1
| _ -> raise (Unify [])
let unify env ty1 ty2 =
try
unify env ty1 ty2
with
Unify trace ->
raise (Unify (expand_trace !env trace))
| Recursive_abbrev ->
raise (Unification_recursive_abbrev (expand_trace !env [(ty1,ty2)]))
let unify_gadt ~newtype_level:lev (env:Env.t ref) ty1 ty2 =
try
univar_pairs := [];
newtype_level := Some lev;
set_mode Pattern (fun () -> unify env ty1 ty2);
newtype_level := None;
TypePairs.clear unify_eq_set;
with e ->
TypePairs.clear unify_eq_set;
match e with
Unify e -> raise (Unify e)
| e -> newtype_level := None; raise e
let unify_var env t1 t2 =
let t1 = repr t1 and t2 = repr t2 in
if t1 == t2 then () else
match t1.desc with
Tvar _ ->
let reset_tracing = check_trace_gadt_instances env in
begin try
occur env t1 t2;
update_level env t1.level t2;
link_type t1 t2;
if reset_tracing then trace_gadt_instances := false;
with Unify trace ->
if reset_tracing then trace_gadt_instances := false;
let expanded_trace = expand_trace env ((t1,t2)::trace) in
raise (Unify expanded_trace)
end
| _ ->
unify (ref env) t1 t2
let _ = unify' := unify_var
let unify_pairs env ty1 ty2 pairs =
univar_pairs := pairs;
unify env ty1 ty2
let unify env ty1 ty2 =
unify_pairs (ref env) ty1 ty2 []
(**** Special cases of unification ****)
let expand_head_trace env t =
let reset_tracing = check_trace_gadt_instances env in
let t = expand_head_unif env t in
if reset_tracing then trace_gadt_instances := false;
t
(*
Unify [t] and [l:'a -> 'b]. Return ['a] and ['b].
In label mode, label mismatch is accepted when
(1) the requested label is ""
(2) the original label is not optional
*)
let filter_arrow env t l =
let t = expand_head_trace env t in
match t.desc with
Tvar _ ->
let lv = t.level in
let t1 = newvar2 lv and t2 = newvar2 lv in
let t' = newty2 lv (Tarrow (l, t1, t2, Cok)) in
link_type t t';
(t1, t2)
| Tarrow(l', t1, t2, _)
when l = l' || !Clflags.classic && l = "" && not (is_optional l') ->
(t1, t2)
| _ ->
raise (Unify [])
(* Used by [filter_method]. *)
let rec filter_method_field env name priv ty =
let ty = expand_head_trace env ty in
match ty.desc with
Tvar _ ->
let level = ty.level in
let ty1 = newvar2 level and ty2 = newvar2 level in
let ty' = newty2 level (Tfield (name,
begin match priv with
Private -> Fvar (ref None)
| Public -> Fpresent
end,
ty1, ty2))
in
link_type ty ty';
ty1
| Tfield(n, kind, ty1, ty2) ->
let kind = field_kind_repr kind in
if (n = name) && (kind <> Fabsent) then begin
if priv = Public then
unify_kind kind Fpresent;
ty1
end else
filter_method_field env name priv ty2
| _ ->
raise (Unify [])
(* Unify [ty] and [< name : 'a; .. >]. Return ['a]. *)
let filter_method env name priv ty =
let ty = expand_head_trace env ty in
match ty.desc with
Tvar _ ->
let ty1 = newvar () in
let ty' = newobj ty1 in
update_level env ty.level ty';
link_type ty ty';
filter_method_field env name priv ty1
| Tobject(f, _) ->
filter_method_field env name priv f
| _ ->
raise (Unify [])
let check_filter_method env name priv ty =
ignore(filter_method env name priv ty)
let filter_self_method env lab priv meths ty =
let ty' = filter_method env lab priv ty in
try
Meths.find lab !meths
with Not_found ->
let pair = (Ident.create lab, ty') in
meths := Meths.add lab pair !meths;
pair
(***********************************)
(* Matching between type schemes *)
(***********************************)
(*
Update the level of [ty]. First check that the levels of generic
variables from the subject are not lowered.
*)
let moregen_occur env level ty =
let rec occur ty =
let ty = repr ty in
if ty.level > level then begin
if is_Tvar ty && ty.level >= generic_level - 1 then raise Occur;
ty.level <- pivot_level - ty.level;
match ty.desc with
Tvariant row when static_row row ->
iter_row occur row
| _ ->
iter_type_expr occur ty
end
in
begin try
occur ty; unmark_type ty
with Occur ->
unmark_type ty; raise (Unify [])
end;
(* also check for free univars *)
occur_univar env ty;
update_level env level ty
let may_instantiate inst_nongen t1 =
if inst_nongen then t1.level <> generic_level - 1
else t1.level = generic_level
let rec moregen inst_nongen type_pairs env t1 t2 =
if t1 == t2 then () else
let t1 = repr t1 in
let t2 = repr t2 in
if t1 == t2 then () else
try
match (t1.desc, t2.desc) with
(Tvar _, _) when may_instantiate inst_nongen t1 ->
moregen_occur env t1.level t2;
occur env t1 t2;
link_type t1 t2
| (Tconstr (p1, [], _), Tconstr (p2, [], _)) when Path.same p1 p2 ->
()
| _ ->
let t1' = expand_head env t1 in
let t2' = expand_head env t2 in
(* Expansion may have changed the representative of the types... *)
let t1' = repr t1' and t2' = repr t2' in
if t1' == t2' then () else
begin try
TypePairs.find type_pairs (t1', t2')
with Not_found ->
TypePairs.add type_pairs (t1', t2') ();
match (t1'.desc, t2'.desc) with
(Tvar _, _) when may_instantiate inst_nongen t1' ->
moregen_occur env t1'.level t2;
link_type t1' t2
| (Tarrow (l1, t1, u1, _), Tarrow (l2, t2, u2, _)) when l1 = l2
|| !Clflags.classic && not (is_optional l1 || is_optional l2) ->
moregen inst_nongen type_pairs env t1 t2;
moregen inst_nongen type_pairs env u1 u2
| (Ttuple tl1, Ttuple tl2) ->
moregen_list inst_nongen type_pairs env tl1 tl2
| (Tconstr (p1, tl1, _), Tconstr (p2, tl2, _))
when Path.same p1 p2 ->
moregen_list inst_nongen type_pairs env tl1 tl2
| (Tpackage (p1, n1, tl1), Tpackage (p2, n2, tl2))
when Path.same p1 p2 && n1 = n2 ->
moregen_list inst_nongen type_pairs env tl1 tl2
| (Tvariant row1, Tvariant row2) ->
moregen_row inst_nongen type_pairs env row1 row2
| (Tobject (fi1, nm1), Tobject (fi2, nm2)) ->
moregen_fields inst_nongen type_pairs env fi1 fi2
| (Tfield _, Tfield _) -> (* Actually unused *)
moregen_fields inst_nongen type_pairs env t1' t2'
| (Tnil, Tnil) ->
()
| (Tpoly (t1, []), Tpoly (t2, [])) ->
moregen inst_nongen type_pairs env t1 t2
| (Tpoly (t1, tl1), Tpoly (t2, tl2)) ->
enter_poly env univar_pairs t1 tl1 t2 tl2
(moregen inst_nongen type_pairs env)
| (Tunivar _, Tunivar _) ->
unify_univar t1' t2' !univar_pairs
| (_, _) ->
raise (Unify [])
end
with Unify trace ->
raise (Unify ((t1, t2)::trace))
and moregen_list inst_nongen type_pairs env tl1 tl2 =
if List.length tl1 <> List.length tl2 then
raise (Unify []);
List.iter2 (moregen inst_nongen type_pairs env) tl1 tl2
and moregen_fields inst_nongen type_pairs env ty1 ty2 =
let (fields1, rest1) = flatten_fields ty1
and (fields2, rest2) = flatten_fields ty2 in
let (pairs, miss1, miss2) = associate_fields fields1 fields2 in
if miss1 <> [] then raise (Unify []);
moregen inst_nongen type_pairs env rest1
(build_fields (repr ty2).level miss2 rest2);
List.iter
(fun (n, k1, t1, k2, t2) ->
moregen_kind k1 k2;
try moregen inst_nongen type_pairs env t1 t2 with Unify trace ->
raise (Unify ((newty (Tfield(n, k1, t1, rest2)),
newty (Tfield(n, k2, t2, rest2)))::trace)))
pairs
and moregen_kind k1 k2 =
let k1 = field_kind_repr k1 in
let k2 = field_kind_repr k2 in
if k1 == k2 then () else
match k1, k2 with
(Fvar r, (Fvar _ | Fpresent)) -> set_kind r k2
| (Fpresent, Fpresent) -> ()
| _ -> raise (Unify [])
and moregen_row inst_nongen type_pairs env row1 row2 =
let row1 = row_repr row1 and row2 = row_repr row2 in
let rm1 = repr row1.row_more and rm2 = repr row2.row_more in
if rm1 == rm2 then () else
let may_inst =
is_Tvar rm1 && may_instantiate inst_nongen rm1 || rm1.desc = Tnil in
let r1, r2, pairs = merge_row_fields row1.row_fields row2.row_fields in
let r1, r2 =
if row2.row_closed then
filter_row_fields may_inst r1, filter_row_fields false r2
else r1, r2
in
if r1 <> [] || row1.row_closed && (not row2.row_closed || r2 <> [])
then raise (Unify []);
begin match rm1.desc, rm2.desc with
Tunivar _, Tunivar _ ->
unify_univar rm1 rm2 !univar_pairs
| Tunivar _, _ | _, Tunivar _ ->
raise (Unify [])
| _ when static_row row1 -> ()
| _ when may_inst ->
if not (static_row row2) then moregen_occur env rm1.level rm2;
let ext =
if r2 = [] then rm2 else
let row_ext = {row2 with row_fields = r2} in
iter_row (moregen_occur env rm1.level) row_ext;
newty2 rm1.level (Tvariant row_ext)
in
link_type rm1 ext
| Tconstr _, Tconstr _ ->
moregen inst_nongen type_pairs env rm1 rm2
| _ -> raise (Unify [])
end;
List.iter
(fun (l,f1,f2) ->
let f1 = row_field_repr f1 and f2 = row_field_repr f2 in
if f1 == f2 then () else
match f1, f2 with
Rpresent(Some t1), Rpresent(Some t2) ->
moregen inst_nongen type_pairs env t1 t2
| Rpresent None, Rpresent None -> ()
| Reither(false, tl1, _, e1), Rpresent(Some t2) when may_inst ->
set_row_field e1 f2;
List.iter (fun t1 -> moregen inst_nongen type_pairs env t1 t2) tl1
| Reither(c1, tl1, _, e1), Reither(c2, tl2, m2, e2) ->
if e1 != e2 then begin
if c1 && not c2 then raise(Unify []);
set_row_field e1 (Reither (c2, [], m2, e2));
if List.length tl1 = List.length tl2 then
List.iter2 (moregen inst_nongen type_pairs env) tl1 tl2
else match tl2 with
t2 :: _ ->
List.iter (fun t1 -> moregen inst_nongen type_pairs env t1 t2)
tl1
| [] ->
if tl1 <> [] then raise (Unify [])
end
| Reither(true, [], _, e1), Rpresent None when may_inst ->
set_row_field e1 f2
| Reither(_, _, _, e1), Rabsent when may_inst ->
set_row_field e1 f2
| Rabsent, Rabsent -> ()
| _ -> raise (Unify []))
pairs
(* Must empty univar_pairs first *)
let moregen inst_nongen type_pairs env patt subj =
univar_pairs := [];
moregen inst_nongen type_pairs env patt subj
(*
Non-generic variable can be instanciated only if [inst_nongen] is
true. So, [inst_nongen] should be set to false if the subject might
contain non-generic variables (and we do not want them to be
instanciated).
Usually, the subject is given by the user, and the pattern
is unimportant. So, no need to propagate abbreviations.
*)
let moregeneral env inst_nongen pat_sch subj_sch =
let old_level = !current_level in
current_level := generic_level - 1;
(*
Generic variables are first duplicated with [instance]. So,
their levels are lowered to [generic_level - 1]. The subject is
then copied with [duplicate_type]. That way, its levels won't be
changed.
*)
let subj = duplicate_type (instance env subj_sch) in
current_level := generic_level;
(* Duplicate generic variables *)
let patt = instance env pat_sch in
let res =
try moregen inst_nongen (TypePairs.create 13) env patt subj; true with
Unify _ -> false
in
current_level := old_level;
res
(* Alternative approach: "rigidify" a type scheme,
and check validity after unification *)
(* Simpler, no? *)
let rec rigidify_rec vars ty =
let ty = repr ty in
if ty.level >= lowest_level then begin
ty.level <- pivot_level - ty.level;
match ty.desc with
| Tvar _ ->
if not (List.memq ty !vars) then vars := ty :: !vars
| Tvariant row ->
let row = row_repr row in
let more = repr row.row_more in
if is_Tvar more && not (row_fixed row) then begin
let more' = newty2 more.level more.desc in
let row' = {row with row_fixed=true; row_fields=[]; row_more=more'}
in link_type more (newty2 ty.level (Tvariant row'))
end;
iter_row (rigidify_rec vars) row;
(* only consider the row variable if the variant is not static *)
if not (static_row row) then rigidify_rec vars (row_more row)
| _ ->
iter_type_expr (rigidify_rec vars) ty
end
let rigidify ty =
let vars = ref [] in
rigidify_rec vars ty;
unmark_type ty;
!vars
let all_distinct_vars env vars =
let tyl = ref [] in
List.for_all
(fun ty ->
let ty = expand_head env ty in
if List.memq ty !tyl then false else
(tyl := ty :: !tyl; is_Tvar ty))
vars
let matches env ty ty' =
let snap = snapshot () in
let vars = rigidify ty in
cleanup_abbrev ();
let ok =
try unify env ty ty'; all_distinct_vars env vars
with Unify _ -> false
in
backtrack snap;
ok
(*********************************************)
(* Equivalence between parameterized types *)
(*********************************************)
let rec get_object_row ty =
match repr ty with
| {desc=Tfield (_, _, _, tl)} -> get_object_row tl
| ty -> ty
let expand_head_rigid env ty =
let old = !rigid_variants in
rigid_variants := true;
let ty' = expand_head env ty in
rigid_variants := old; ty'
let normalize_subst subst =
if List.exists
(function {desc=Tlink _}, _ | _, {desc=Tlink _} -> true | _ -> false)
!subst
then subst := List.map (fun (t1,t2) -> repr t1, repr t2) !subst
let rec eqtype rename type_pairs subst env t1 t2 =
if t1 == t2 then () else
let t1 = repr t1 in
let t2 = repr t2 in
if t1 == t2 then () else
try
match (t1.desc, t2.desc) with
(Tvar _, Tvar _) when rename ->
begin try
normalize_subst subst;
if List.assq t1 !subst != t2 then raise (Unify [])
with Not_found ->
if List.exists (fun (_, t) -> t == t2) !subst then raise (Unify []);
subst := (t1, t2) :: !subst
end
| (Tconstr (p1, [], _), Tconstr (p2, [], _)) when Path.same p1 p2 ->
()
| _ ->
let t1' = expand_head_rigid env t1 in
let t2' = expand_head_rigid env t2 in
(* Expansion may have changed the representative of the types... *)
let t1' = repr t1' and t2' = repr t2' in
if t1' == t2' then () else
begin try
TypePairs.find type_pairs (t1', t2')
with Not_found ->
TypePairs.add type_pairs (t1', t2') ();
match (t1'.desc, t2'.desc) with
(Tvar _, Tvar _) when rename ->
begin try
normalize_subst subst;
if List.assq t1' !subst != t2' then raise (Unify [])
with Not_found ->
if List.exists (fun (_, t) -> t == t2') !subst
then raise (Unify []);
subst := (t1', t2') :: !subst
end
| (Tarrow (l1, t1, u1, _), Tarrow (l2, t2, u2, _)) when l1 = l2
|| !Clflags.classic && not (is_optional l1 || is_optional l2) ->
eqtype rename type_pairs subst env t1 t2;
eqtype rename type_pairs subst env u1 u2;
| (Ttuple tl1, Ttuple tl2) ->
eqtype_list rename type_pairs subst env tl1 tl2
| (Tconstr (p1, tl1, _), Tconstr (p2, tl2, _))
when Path.same p1 p2 ->
eqtype_list rename type_pairs subst env tl1 tl2
| (Tpackage (p1, n1, tl1), Tpackage (p2, n2, tl2))
when Path.same p1 p2 && n1 = n2 ->
eqtype_list rename type_pairs subst env tl1 tl2
| (Tvariant row1, Tvariant row2) ->
eqtype_row rename type_pairs subst env row1 row2
| (Tobject (fi1, nm1), Tobject (fi2, nm2)) ->
eqtype_fields rename type_pairs subst env fi1 fi2
| (Tfield _, Tfield _) -> (* Actually unused *)
eqtype_fields rename type_pairs subst env t1' t2'
| (Tnil, Tnil) ->
()
| (Tpoly (t1, []), Tpoly (t2, [])) ->
eqtype rename type_pairs subst env t1 t2
| (Tpoly (t1, tl1), Tpoly (t2, tl2)) ->
enter_poly env univar_pairs t1 tl1 t2 tl2
(eqtype rename type_pairs subst env)
| (Tunivar _, Tunivar _) ->
unify_univar t1' t2' !univar_pairs
| (_, _) ->
raise (Unify [])
end
with Unify trace ->
raise (Unify ((t1, t2)::trace))
and eqtype_list rename type_pairs subst env tl1 tl2 =
if List.length tl1 <> List.length tl2 then
raise (Unify []);
List.iter2 (eqtype rename type_pairs subst env) tl1 tl2
and eqtype_fields rename type_pairs subst env ty1 ty2 =
let (fields1, rest1) = flatten_fields ty1 in
let (fields2, rest2) = flatten_fields ty2 in
(* First check if same row => already equal *)
let same_row =
rest1 == rest2 || TypePairs.mem type_pairs (rest1,rest2) ||
(rename && List.mem (rest1, rest2) !subst)
in
if same_row then () else
(* Try expansion, needed when called from Includecore.type_manifest *)
match expand_head_rigid env rest2 with
{desc=Tobject(ty2,_)} -> eqtype_fields rename type_pairs subst env ty1 ty2
| _ ->
let (pairs, miss1, miss2) = associate_fields fields1 fields2 in
eqtype rename type_pairs subst env rest1 rest2;
if (miss1 <> []) || (miss2 <> []) then raise (Unify []);
List.iter
(function (n, k1, t1, k2, t2) ->
eqtype_kind k1 k2;
try eqtype rename type_pairs subst env t1 t2 with Unify trace ->
raise (Unify ((newty (Tfield(n, k1, t1, rest2)),
newty (Tfield(n, k2, t2, rest2)))::trace)))
pairs
and eqtype_kind k1 k2 =
let k1 = field_kind_repr k1 in
let k2 = field_kind_repr k2 in
match k1, k2 with
(Fvar _, Fvar _)
| (Fpresent, Fpresent) -> ()
| _ -> raise (Unify [])
and eqtype_row rename type_pairs subst env row1 row2 =
(* Try expansion, needed when called from Includecore.type_manifest *)
match expand_head_rigid env (row_more row2) with
{desc=Tvariant row2} -> eqtype_row rename type_pairs subst env row1 row2
| _ ->
let row1 = row_repr row1 and row2 = row_repr row2 in
let r1, r2, pairs = merge_row_fields row1.row_fields row2.row_fields in
if row1.row_closed <> row2.row_closed
|| not row1.row_closed && (r1 <> [] || r2 <> [])
|| filter_row_fields false (r1 @ r2) <> []
then raise (Unify []);
if not (static_row row1) then
eqtype rename type_pairs subst env row1.row_more row2.row_more;
List.iter
(fun (_,f1,f2) ->
match row_field_repr f1, row_field_repr f2 with
Rpresent(Some t1), Rpresent(Some t2) ->
eqtype rename type_pairs subst env t1 t2
| Reither(true, [], _, _), Reither(true, [], _, _) ->
()
| Reither(false, t1::tl1, _, _), Reither(false, t2::tl2, _, _) ->
eqtype rename type_pairs subst env t1 t2;
if List.length tl1 = List.length tl2 then
(* if same length allow different types (meaning?) *)
List.iter2 (eqtype rename type_pairs subst env) tl1 tl2
else begin
(* otherwise everything must be equal *)
List.iter (eqtype rename type_pairs subst env t1) tl2;
List.iter (fun t1 -> eqtype rename type_pairs subst env t1 t2) tl1
end
| Rpresent None, Rpresent None -> ()
| Rabsent, Rabsent -> ()
| _ -> raise (Unify []))
pairs
(* Two modes: with or without renaming of variables *)
let equal env rename tyl1 tyl2 =
try
univar_pairs := [];
eqtype_list rename (TypePairs.create 11) (ref []) env tyl1 tyl2; true
with
Unify _ -> false
(* Must empty univar_pairs first *)
let eqtype rename type_pairs subst env t1 t2 =
univar_pairs := [];
eqtype rename type_pairs subst env t1 t2
(*************************)
(* Class type matching *)
(*************************)
type class_match_failure =
CM_Virtual_class
| CM_Parameter_arity_mismatch of int * int
| CM_Type_parameter_mismatch of Env.t * (type_expr * type_expr) list
| CM_Class_type_mismatch of Env.t * class_type * class_type
| CM_Parameter_mismatch of Env.t * (type_expr * type_expr) list
| CM_Val_type_mismatch of string * Env.t * (type_expr * type_expr) list
| CM_Meth_type_mismatch of string * Env.t * (type_expr * type_expr) list
| CM_Non_mutable_value of string
| CM_Non_concrete_value of string
| CM_Missing_value of string
| CM_Missing_method of string
| CM_Hide_public of string
| CM_Hide_virtual of string * string
| CM_Public_method of string
| CM_Private_method of string
| CM_Virtual_method of string
exception Failure of class_match_failure list
let rec moregen_clty trace type_pairs env cty1 cty2 =
try
match cty1, cty2 with
Cty_constr (_, _, cty1), _ ->
moregen_clty true type_pairs env cty1 cty2
| _, Cty_constr (_, _, cty2) ->
moregen_clty true type_pairs env cty1 cty2
| Cty_fun (l1, ty1, cty1'), Cty_fun (l2, ty2, cty2') when l1 = l2 ->
begin try moregen true type_pairs env ty1 ty2 with Unify trace ->
raise (Failure [CM_Parameter_mismatch (env, expand_trace env trace)])
end;
moregen_clty false type_pairs env cty1' cty2'
| Cty_signature sign1, Cty_signature sign2 ->
let ty1 = object_fields (repr sign1.cty_self) in
let ty2 = object_fields (repr sign2.cty_self) in
let (fields1, rest1) = flatten_fields ty1
and (fields2, rest2) = flatten_fields ty2 in
let (pairs, miss1, miss2) = associate_fields fields1 fields2 in
List.iter
(fun (lab, k1, t1, k2, t2) ->
begin try moregen true type_pairs env t1 t2 with Unify trace ->
raise (Failure [CM_Meth_type_mismatch
(lab, env, expand_trace env trace)])
end)
pairs;
Vars.iter
(fun lab (mut, v, ty) ->
let (mut', v', ty') = Vars.find lab sign1.cty_vars in
try moregen true type_pairs env ty' ty with Unify trace ->
raise (Failure [CM_Val_type_mismatch
(lab, env, expand_trace env trace)]))
sign2.cty_vars
| _ ->
raise (Failure [])
with
Failure error when trace || error = [] ->
raise (Failure (CM_Class_type_mismatch (env, cty1, cty2)::error))
let match_class_types ?(trace=true) env pat_sch subj_sch =
let type_pairs = TypePairs.create 53 in
let old_level = !current_level in
current_level := generic_level - 1;
(*
Generic variables are first duplicated with [instance]. So,
their levels are lowered to [generic_level - 1]. The subject is
then copied with [duplicate_type]. That way, its levels won't be
changed.
*)
let (_, subj_inst) = instance_class [] subj_sch in
let subj = duplicate_class_type subj_inst in
current_level := generic_level;
(* Duplicate generic variables *)
let (_, patt) = instance_class [] pat_sch in
let res =
let sign1 = signature_of_class_type patt in
let sign2 = signature_of_class_type subj in
let t1 = repr sign1.cty_self in
let t2 = repr sign2.cty_self in
TypePairs.add type_pairs (t1, t2) ();
let (fields1, rest1) = flatten_fields (object_fields t1)
and (fields2, rest2) = flatten_fields (object_fields t2) in
let (pairs, miss1, miss2) = associate_fields fields1 fields2 in
let error =
List.fold_right
(fun (lab, k, _) err ->
let err =
let k = field_kind_repr k in
begin match k with
Fvar r -> set_kind r Fabsent; err
| _ -> CM_Hide_public lab::err
end
in
if Concr.mem lab sign1.cty_concr then err
else CM_Hide_virtual ("method", lab) :: err)
miss1 []
in
let missing_method = List.map (fun (m, _, _) -> m) miss2 in
let error =
(List.map (fun m -> CM_Missing_method m) missing_method) @ error
in
(* Always succeeds *)
moregen true type_pairs env rest1 rest2;
let error =
List.fold_right
(fun (lab, k1, t1, k2, t2) err ->
try moregen_kind k1 k2; err with
Unify _ -> CM_Public_method lab::err)
pairs error
in
let error =
Vars.fold
(fun lab (mut, vr, ty) err ->
try
let (mut', vr', ty') = Vars.find lab sign1.cty_vars in
if mut = Mutable && mut' <> Mutable then
CM_Non_mutable_value lab::err
else if vr = Concrete && vr' <> Concrete then
CM_Non_concrete_value lab::err
else
err
with Not_found ->
CM_Missing_value lab::err)
sign2.cty_vars error
in
let error =
Vars.fold
(fun lab (_,vr,_) err ->
if vr = Virtual && not (Vars.mem lab sign2.cty_vars) then
CM_Hide_virtual ("instance variable", lab) :: err
else err)
sign1.cty_vars error
in
let error =
List.fold_right
(fun e l ->
if List.mem e missing_method then l else CM_Virtual_method e::l)
(Concr.elements (Concr.diff sign2.cty_concr sign1.cty_concr))
error
in
match error with
[] ->
begin try
moregen_clty trace type_pairs env patt subj;
[]
with
Failure r -> r
end
| error ->
CM_Class_type_mismatch (env, patt, subj)::error
in
current_level := old_level;
res
let rec equal_clty trace type_pairs subst env cty1 cty2 =
try
match cty1, cty2 with
Cty_constr (_, _, cty1), Cty_constr (_, _, cty2) ->
equal_clty true type_pairs subst env cty1 cty2
| Cty_constr (_, _, cty1), _ ->
equal_clty true type_pairs subst env cty1 cty2
| _, Cty_constr (_, _, cty2) ->
equal_clty true type_pairs subst env cty1 cty2
| Cty_fun (l1, ty1, cty1'), Cty_fun (l2, ty2, cty2') when l1 = l2 ->
begin try eqtype true type_pairs subst env ty1 ty2 with Unify trace ->
raise (Failure [CM_Parameter_mismatch (env, expand_trace env trace)])
end;
equal_clty false type_pairs subst env cty1' cty2'
| Cty_signature sign1, Cty_signature sign2 ->
let ty1 = object_fields (repr sign1.cty_self) in
let ty2 = object_fields (repr sign2.cty_self) in
let (fields1, rest1) = flatten_fields ty1
and (fields2, rest2) = flatten_fields ty2 in
let (pairs, miss1, miss2) = associate_fields fields1 fields2 in
List.iter
(fun (lab, k1, t1, k2, t2) ->
begin try eqtype true type_pairs subst env t1 t2 with
Unify trace ->
raise (Failure [CM_Meth_type_mismatch
(lab, env, expand_trace env trace)])
end)
pairs;
Vars.iter
(fun lab (_, _, ty) ->
let (_, _, ty') = Vars.find lab sign1.cty_vars in
try eqtype true type_pairs subst env ty' ty with Unify trace ->
raise (Failure [CM_Val_type_mismatch
(lab, env, expand_trace env trace)]))
sign2.cty_vars
| _ ->
raise
(Failure (if trace then []
else [CM_Class_type_mismatch (env, cty1, cty2)]))
with
Failure error when trace ->
raise (Failure (CM_Class_type_mismatch (env, cty1, cty2)::error))
let match_class_declarations env patt_params patt_type subj_params subj_type =
let type_pairs = TypePairs.create 53 in
let subst = ref [] in
let sign1 = signature_of_class_type patt_type in
let sign2 = signature_of_class_type subj_type in
let t1 = repr sign1.cty_self in
let t2 = repr sign2.cty_self in
TypePairs.add type_pairs (t1, t2) ();
let (fields1, rest1) = flatten_fields (object_fields t1)
and (fields2, rest2) = flatten_fields (object_fields t2) in
let (pairs, miss1, miss2) = associate_fields fields1 fields2 in
let error =
List.fold_right
(fun (lab, k, _) err ->
let err =
let k = field_kind_repr k in
begin match k with
Fvar r -> err
| _ -> CM_Hide_public lab::err
end
in
if Concr.mem lab sign1.cty_concr then err
else CM_Hide_virtual ("method", lab) :: err)
miss1 []
in
let missing_method = List.map (fun (m, _, _) -> m) miss2 in
let error =
(List.map (fun m -> CM_Missing_method m) missing_method) @ error
in
(* Always succeeds *)
eqtype true type_pairs subst env rest1 rest2;
let error =
List.fold_right
(fun (lab, k1, t1, k2, t2) err ->
let k1 = field_kind_repr k1 in
let k2 = field_kind_repr k2 in
match k1, k2 with
(Fvar _, Fvar _)
| (Fpresent, Fpresent) -> err
| (Fvar _, Fpresent) -> CM_Private_method lab::err
| (Fpresent, Fvar _) -> CM_Public_method lab::err
| _ -> assert false)
pairs error
in
let error =
Vars.fold
(fun lab (mut, vr, ty) err ->
try
let (mut', vr', ty') = Vars.find lab sign1.cty_vars in
if mut = Mutable && mut' <> Mutable then
CM_Non_mutable_value lab::err
else if vr = Concrete && vr' <> Concrete then
CM_Non_concrete_value lab::err
else
err
with Not_found ->
CM_Missing_value lab::err)
sign2.cty_vars error
in
let error =
Vars.fold
(fun lab (_,vr,_) err ->
if vr = Virtual && not (Vars.mem lab sign2.cty_vars) then
CM_Hide_virtual ("instance variable", lab) :: err
else err)
sign1.cty_vars error
in
let error =
List.fold_right
(fun e l ->
if List.mem e missing_method then l else CM_Virtual_method e::l)
(Concr.elements (Concr.diff sign2.cty_concr sign1.cty_concr))
error
in
match error with
[] ->
begin try
let lp = List.length patt_params in
let ls = List.length subj_params in
if lp <> ls then
raise (Failure [CM_Parameter_arity_mismatch (lp, ls)]);
List.iter2 (fun p s ->
try eqtype true type_pairs subst env p s with Unify trace ->
raise (Failure [CM_Type_parameter_mismatch
(env, expand_trace env trace)]))
patt_params subj_params;
(* old code: equal_clty false type_pairs subst env patt_type subj_type; *)
equal_clty false type_pairs subst env
(Cty_signature sign1) (Cty_signature sign2);
(* Use moregeneral for class parameters, need to recheck everything to
keeps relationships (PR#4824) *)
let clty_params =
List.fold_right (fun ty cty -> Cty_fun ("*",ty,cty)) in
match_class_types ~trace:false env
(clty_params patt_params patt_type)
(clty_params subj_params subj_type)
with
Failure r -> r
end
| error ->
error
(***************)
(* Subtyping *)
(***************)
(**** Build a subtype of a given type. ****)
(* build_subtype:
[visited] traces traversed object and variant types
[loops] is a mapping from variables to variables, to reproduce
positive loops in a class type
[posi] true if the current variance is positive
[level] number of expansions/enlargement allowed on this branch *)
let warn = ref false (* whether double coercion might do better *)
let pred_expand n = if n mod 2 = 0 && n > 0 then pred n else n
let pred_enlarge n = if n mod 2 = 1 then pred n else n
type change = Unchanged | Equiv | Changed
let collect l = List.fold_left (fun c1 (_, c2) -> max c1 c2) Unchanged l
let rec filter_visited = function
[] -> []
| {desc=Tobject _|Tvariant _} :: _ as l -> l
| _ :: l -> filter_visited l
let memq_warn t visited =
if List.memq t visited then (warn := true; true) else false
let rec lid_of_path ?(sharp="") = function
Path.Pident id ->
Longident.Lident (sharp ^ Ident.name id)
| Path.Pdot (p1, s, _) ->
Longident.Ldot (lid_of_path p1, sharp ^ s)
| Path.Papply (p1, p2) ->
Longident.Lapply (lid_of_path ~sharp p1, lid_of_path p2)
let find_cltype_for_path env p =
let path, cl_abbr = Env.lookup_type (lid_of_path ~sharp:"#" p) env in
match cl_abbr.type_manifest with
Some ty ->
begin match (repr ty).desc with
Tobject(_,{contents=Some(p',_)}) when Path.same p p' -> cl_abbr, ty
| _ -> raise Not_found
end
| None -> assert false
let has_constr_row' env t =
has_constr_row (expand_abbrev env t)
let rec build_subtype env visited loops posi level t =
let t = repr t in
match t.desc with
Tvar _ ->
if posi then
try
let t' = List.assq t loops in
warn := true;
(t', Equiv)
with Not_found ->
(t, Unchanged)
else
(t, Unchanged)
| Tarrow(l, t1, t2, _) ->
if memq_warn t visited then (t, Unchanged) else
let visited = t :: visited in
let (t1', c1) = build_subtype env visited loops (not posi) level t1 in
let (t2', c2) = build_subtype env visited loops posi level t2 in
let c = max c1 c2 in
if c > Unchanged then (newty (Tarrow(l, t1', t2', Cok)), c)
else (t, Unchanged)
| Ttuple tlist ->
if memq_warn t visited then (t, Unchanged) else
let visited = t :: visited in
let tlist' =
List.map (build_subtype env visited loops posi level) tlist
in
let c = collect tlist' in
if c > Unchanged then (newty (Ttuple (List.map fst tlist')), c)
else (t, Unchanged)
| Tconstr(p, tl, abbrev)
when level > 0 && generic_abbrev env p && safe_abbrev env t
&& not (has_constr_row' env t) ->
let t' = repr (expand_abbrev env t) in
let level' = pred_expand level in
begin try match t'.desc with
Tobject _ when posi && not (opened_object t') ->
let cl_abbr, body = find_cltype_for_path env p in
let ty =
subst env !current_level Public abbrev None
cl_abbr.type_params tl body in
let ty = repr ty in
let ty1, tl1 =
match ty.desc with
Tobject(ty1,{contents=Some(p',tl1)}) when Path.same p p' ->
ty1, tl1
| _ -> raise Not_found
in
(* Fix PR4505: do not set ty to Tvar when it appears in tl1,
as this occurence might break the occur check.
XXX not clear whether this correct anyway... *)
if List.exists (deep_occur ty) tl1 then raise Not_found;
ty.desc <- Tvar None;
let t'' = newvar () in
let loops = (ty, t'') :: loops in
(* May discard [visited] as level is going down *)
let (ty1', c) =
build_subtype env [t'] loops posi (pred_enlarge level') ty1 in
assert (is_Tvar t'');
let nm =
if c > Equiv || deep_occur ty ty1' then None else Some(p,tl1) in
t''.desc <- Tobject (ty1', ref nm);
(try unify_var env ty t with Unify _ -> assert false);
(t'', Changed)
| _ -> raise Not_found
with Not_found ->
let (t'',c) = build_subtype env visited loops posi level' t' in
if c > Unchanged then (t'',c)
else (t, Unchanged)
end
| Tconstr(p, tl, abbrev) ->
(* Must check recursion on constructors, since we do not always
expand them *)
if memq_warn t visited then (t, Unchanged) else
let visited = t :: visited in
begin try
let decl = Env.find_type p env in
if level = 0 && generic_abbrev env p && safe_abbrev env t
&& not (has_constr_row' env t)
then warn := true;
let tl' =
List.map2
(fun (co,cn,_) t ->
if cn then
if co then (t, Unchanged)
else build_subtype env visited loops (not posi) level t
else
if co then build_subtype env visited loops posi level t
else (newvar(), Changed))
decl.type_variance tl
in
let c = collect tl' in
if c > Unchanged then (newconstr p (List.map fst tl'), c)
else (t, Unchanged)
with Not_found ->
(t, Unchanged)
end
| Tvariant row ->
let row = row_repr row in
if memq_warn t visited || not (static_row row) then (t, Unchanged) else
let level' = pred_enlarge level in
let visited =
t :: if level' < level then [] else filter_visited visited in
let fields = filter_row_fields false row.row_fields in
let fields =
List.map
(fun (l,f as orig) -> match row_field_repr f with
Rpresent None ->
if posi then
(l, Reither(true, [], false, ref None)), Unchanged
else
orig, Unchanged
| Rpresent(Some t) ->
let (t', c) = build_subtype env visited loops posi level' t in
let f =
if posi && level > 0
then Reither(false, [t'], false, ref None)
else Rpresent(Some t')
in (l, f), c
| _ -> assert false)
fields
in
let c = collect fields in
let row =
{ row_fields = List.map fst fields; row_more = newvar();
row_bound = (); row_closed = posi; row_fixed = false;
row_name = if c > Unchanged then None else row.row_name }
in
(newty (Tvariant row), Changed)
| Tobject (t1, _) ->
if memq_warn t visited || opened_object t1 then (t, Unchanged) else
let level' = pred_enlarge level in
let visited =
t :: if level' < level then [] else filter_visited visited in
let (t1', c) = build_subtype env visited loops posi level' t1 in
if c > Unchanged then (newty (Tobject (t1', ref None)), c)
else (t, Unchanged)
| Tfield(s, _, t1, t2) (* Always present *) ->
let (t1', c1) = build_subtype env visited loops posi level t1 in
let (t2', c2) = build_subtype env visited loops posi level t2 in
let c = max c1 c2 in
if c > Unchanged then (newty (Tfield(s, Fpresent, t1', t2')), c)
else (t, Unchanged)
| Tnil ->
if posi then
let v = newvar () in
(v, Changed)
else begin
warn := true;
(t, Unchanged)
end
| Tsubst _ | Tlink _ ->
assert false
| Tpoly(t1, tl) ->
let (t1', c) = build_subtype env visited loops posi level t1 in
if c > Unchanged then (newty (Tpoly(t1', tl)), c)
else (t, Unchanged)
| Tunivar _ | Tpackage _ ->
(t, Unchanged)
let enlarge_type env ty =
warn := false;
(* [level = 4] allows 2 expansions involving objects/variants *)
let (ty', _) = build_subtype env [] [] true 4 ty in
(ty', !warn)
(**** Check whether a type is a subtype of another type. ****)
(*
During the traversal, a trace of visited types is maintained. It
is printed in case of error.
Constraints (pairs of types that must be equals) are accumulated
rather than being enforced straight. Indeed, the result would
otherwise depend on the order in which these constraints are
enforced.
A function enforcing these constraints is returned. That way, type
variables can be bound to their actual values before this function
is called (see Typecore).
Only well-defined abbreviations are expanded (hence the tests
[generic_abbrev ...]).
*)
let subtypes = TypePairs.create 17
let subtype_error env trace =
raise (Subtype (expand_trace env (List.rev trace), []))
let private_abbrev env path =
try
let decl = Env.find_type path env in
decl.type_private = Private && decl.type_manifest <> None
with Not_found -> false
(* check list inclusion, assuming lists are ordered *)
let rec included nl1 nl2 =
match nl1, nl2 with
(a::nl1', b::nl2') ->
if a = b then included nl1' nl2' else
a > b && included nl1 nl2'
| ([], _) -> true
| (_, []) -> false
let rec extract_assoc nl1 nl2 tl2 =
match (nl1, nl2, tl2) with
(a::nl1', b::nl2, t::tl2) ->
if a = b then t :: extract_assoc nl1' nl2 tl2
else extract_assoc nl1 nl2 tl2
| ([], _, _) -> []
| _ -> assert false
let rec subtype_rec env trace t1 t2 cstrs =
let t1 = repr t1 in
let t2 = repr t2 in
if t1 == t2 then cstrs else
begin try
TypePairs.find subtypes (t1, t2);
cstrs
with Not_found ->
TypePairs.add subtypes (t1, t2) ();
match (t1.desc, t2.desc) with
(Tvar _, _) | (_, Tvar _) ->
(trace, t1, t2, !univar_pairs)::cstrs
| (Tarrow(l1, t1, u1, _), Tarrow(l2, t2, u2, _)) when l1 = l2
|| !Clflags.classic && not (is_optional l1 || is_optional l2) ->
let cstrs = subtype_rec env ((t2, t1)::trace) t2 t1 cstrs in
subtype_rec env ((u1, u2)::trace) u1 u2 cstrs
| (Ttuple tl1, Ttuple tl2) ->
subtype_list env trace tl1 tl2 cstrs
| (Tconstr(p1, [], _), Tconstr(p2, [], _)) when Path.same p1 p2 ->
cstrs
| (Tconstr(p1, tl1, abbrev1), _)
when generic_abbrev env p1 && safe_abbrev env t1 ->
subtype_rec env trace (expand_abbrev env t1) t2 cstrs
| (_, Tconstr(p2, tl2, abbrev2))
when generic_abbrev env p2 && safe_abbrev env t2 ->
subtype_rec env trace t1 (expand_abbrev env t2) cstrs
| (Tconstr(p1, tl1, _), Tconstr(p2, tl2, _)) when Path.same p1 p2 ->
begin try
let decl = Env.find_type p1 env in
List.fold_left2
(fun cstrs (co, cn, _) (t1, t2) ->
if co then
if cn then
(trace, newty2 t1.level (Ttuple[t1]),
newty2 t2.level (Ttuple[t2]), !univar_pairs) :: cstrs
else subtype_rec env ((t1, t2)::trace) t1 t2 cstrs
else
if cn then subtype_rec env ((t2, t1)::trace) t2 t1 cstrs
else cstrs)
cstrs decl.type_variance (List.combine tl1 tl2)
with Not_found ->
(trace, t1, t2, !univar_pairs)::cstrs
end
| (Tconstr(p1, tl1, _), _) when private_abbrev env p1 ->
subtype_rec env trace (expand_abbrev_opt env t1) t2 cstrs
| (Tobject (f1, _), Tobject (f2, _))
when is_Tvar (object_row f1) && is_Tvar (object_row f2) ->
(* Same row variable implies same object. *)
(trace, t1, t2, !univar_pairs)::cstrs
| (Tobject (f1, _), Tobject (f2, _)) ->
subtype_fields env trace f1 f2 cstrs
| (Tvariant row1, Tvariant row2) ->
begin try
subtype_row env trace row1 row2 cstrs
with Exit ->
(trace, t1, t2, !univar_pairs)::cstrs
end
| (Tpoly (u1, []), Tpoly (u2, [])) ->
subtype_rec env trace u1 u2 cstrs
| (Tpoly (u1, tl1), Tpoly (u2, [])) ->
let _, u1' = instance_poly false tl1 u1 in
subtype_rec env trace u1' u2 cstrs
| (Tpoly (u1, tl1), Tpoly (u2,tl2)) ->
begin try
enter_poly env univar_pairs u1 tl1 u2 tl2
(fun t1 t2 -> subtype_rec env trace t1 t2 cstrs)
with Unify _ ->
(trace, t1, t2, !univar_pairs)::cstrs
end
| (Tpackage (p1, nl1, tl1), Tpackage (p2, nl2, tl2))
when Path.same p1 p2 && included nl2 nl1 ->
List.map2 (fun t1 t2 -> (trace, t1, t2, !univar_pairs))
(extract_assoc nl2 nl1 tl1) tl2
@ cstrs
| (_, _) ->
(trace, t1, t2, !univar_pairs)::cstrs
end
and subtype_list env trace tl1 tl2 cstrs =
if List.length tl1 <> List.length tl2 then
subtype_error env trace;
List.fold_left2
(fun cstrs t1 t2 -> subtype_rec env ((t1, t2)::trace) t1 t2 cstrs)
cstrs tl1 tl2
and subtype_fields env trace ty1 ty2 cstrs =
(* Assume that either rest1 or rest2 is not Tvar *)
let (fields1, rest1) = flatten_fields ty1 in
let (fields2, rest2) = flatten_fields ty2 in
let (pairs, miss1, miss2) = associate_fields fields1 fields2 in
let cstrs =
if rest2.desc = Tnil then cstrs else
if miss1 = [] then
subtype_rec env ((rest1, rest2)::trace) rest1 rest2 cstrs
else
(trace, build_fields (repr ty1).level miss1 rest1, rest2,
!univar_pairs) :: cstrs
in
let cstrs =
if miss2 = [] then cstrs else
(trace, rest1, build_fields (repr ty2).level miss2 (newvar ()),
!univar_pairs) :: cstrs
in
List.fold_left
(fun cstrs (_, k1, t1, k2, t2) ->
(* Theses fields are always present *)
subtype_rec env ((t1, t2)::trace) t1 t2 cstrs)
cstrs pairs
and subtype_row env trace row1 row2 cstrs =
let row1 = row_repr row1 and row2 = row_repr row2 in
let r1, r2, pairs =
merge_row_fields row1.row_fields row2.row_fields in
let more1 = repr row1.row_more
and more2 = repr row2.row_more in
match more1.desc, more2.desc with
Tconstr(p1,_,_), Tconstr(p2,_,_) when Path.same p1 p2 ->
subtype_rec env ((more1,more2)::trace) more1 more2 cstrs
| (Tvar _|Tconstr _|Tnil), (Tvar _|Tconstr _|Tnil)
when row1.row_closed && r1 = [] ->
List.fold_left
(fun cstrs (_,f1,f2) ->
match row_field_repr f1, row_field_repr f2 with
(Rpresent None|Reither(true,_,_,_)), Rpresent None ->
cstrs
| Rpresent(Some t1), Rpresent(Some t2) ->
subtype_rec env ((t1, t2)::trace) t1 t2 cstrs
| Reither(false, t1::_, _, _), Rpresent(Some t2) ->
subtype_rec env ((t1, t2)::trace) t1 t2 cstrs
| Rabsent, _ -> cstrs
| _ -> raise Exit)
cstrs pairs
| Tunivar _, Tunivar _
when row1.row_closed = row2.row_closed && r1 = [] && r2 = [] ->
let cstrs =
subtype_rec env ((more1,more2)::trace) more1 more2 cstrs in
List.fold_left
(fun cstrs (_,f1,f2) ->
match row_field_repr f1, row_field_repr f2 with
Rpresent None, Rpresent None
| Reither(true,[],_,_), Reither(true,[],_,_)
| Rabsent, Rabsent ->
cstrs
| Rpresent(Some t1), Rpresent(Some t2)
| Reither(false,[t1],_,_), Reither(false,[t2],_,_) ->
subtype_rec env ((t1, t2)::trace) t1 t2 cstrs
| _ -> raise Exit)
cstrs pairs
| _ ->
raise Exit
let subtype env ty1 ty2 =
TypePairs.clear subtypes;
univar_pairs := [];
(* Build constraint set. *)
let cstrs = subtype_rec env [(ty1, ty2)] ty1 ty2 [] in
TypePairs.clear subtypes;
(* Enforce constraints. *)
function () ->
List.iter
(function (trace0, t1, t2, pairs) ->
try unify_pairs (ref env) t1 t2 pairs with Unify trace ->
raise (Subtype (expand_trace env (List.rev trace0),
List.tl (List.tl trace))))
(List.rev cstrs)
(*******************)
(* Miscellaneous *)
(*******************)
(* Utility for printing. The resulting type is not used in computation. *)
let rec unalias_object ty =
let ty = repr ty in
match ty.desc with
Tfield (s, k, t1, t2) ->
newty2 ty.level (Tfield (s, k, t1, unalias_object t2))
| Tvar _ | Tnil ->
newty2 ty.level ty.desc
| Tunivar _ ->
ty
| Tconstr _ ->
newvar2 ty.level
| _ ->
assert false
let unalias ty =
let ty = repr ty in
match ty.desc with
Tvar _ | Tunivar _ ->
ty
| Tvariant row ->
let row = row_repr row in
let more = row.row_more in
newty2 ty.level
(Tvariant {row with row_more = newty2 more.level more.desc})
| Tobject (ty, nm) ->
newty2 ty.level (Tobject (unalias_object ty, nm))
| _ ->
newty2 ty.level ty.desc
(* Return the arity (as for curried functions) of the given type. *)
let rec arity ty =
match (repr ty).desc with
Tarrow(_, t1, t2, _) -> 1 + arity t2
| _ -> 0
(* Check whether an abbreviation expands to itself. *)
let cyclic_abbrev env id ty =
let rec check_cycle seen ty =
let ty = repr ty in
match ty.desc with
Tconstr (p, tl, abbrev) ->
p = Path.Pident id || List.memq ty seen ||
begin try
check_cycle (ty :: seen) (expand_abbrev_opt env ty)
with
Cannot_expand -> false
| Unify _ -> true
end
| _ ->
false
in check_cycle [] ty
(* Normalize a type before printing, saving... *)
(* Cannot use mark_type because deep_occur uses it too *)
let rec normalize_type_rec env visited ty =
let ty = repr ty in
if not (TypeSet.mem ty !visited) then begin
visited := TypeSet.add ty !visited;
begin match ty.desc with
| Tvariant row ->
let row = row_repr row in
let fields = List.map
(fun (l,f0) ->
let f = row_field_repr f0 in l,
match f with Reither(b, ty::(_::_ as tyl), m, e) ->
let tyl' =
List.fold_left
(fun tyl ty ->
if List.exists (fun ty' -> equal env false [ty] [ty']) tyl
then tyl else ty::tyl)
[ty] tyl
in
if f != f0 || List.length tyl' < List.length tyl then
Reither(b, List.rev tyl', m, e)
else f
| _ -> f)
row.row_fields in
let fields =
List.sort (fun (p,_) (q,_) -> compare p q)
(List.filter (fun (_,fi) -> fi <> Rabsent) fields) in
log_type ty;
ty.desc <- Tvariant {row with row_fields = fields}
| Tobject (fi, nm) ->
begin match !nm with
| None -> ()
| Some (n, v :: l) ->
if deep_occur ty (newgenty (Ttuple l)) then
(* The abbreviation may be hiding something, so remove it *)
set_name nm None
else let v' = repr v in
begin match v'.desc with
| Tvar _ | Tunivar _ ->
if v' != v then set_name nm (Some (n, v' :: l))
| Tnil ->
log_type ty; ty.desc <- Tconstr (n, l, ref Mnil)
| _ -> set_name nm None
end
| _ ->
fatal_error "Ctype.normalize_type_rec"
end;
let fi = repr fi in
if fi.level < lowest_level then () else
let fields, row = flatten_fields fi in
let fi' = build_fields fi.level fields row in
log_type ty; fi.desc <- fi'.desc
| _ -> ()
end;
iter_type_expr (normalize_type_rec env visited) ty
end
let normalize_type env ty =
normalize_type_rec env (ref TypeSet.empty) ty
(*************************)
(* Remove dependencies *)
(*************************)
(*
Variables are left unchanged. Other type nodes are duplicated, with
levels set to generic level.
We cannot use Tsubst here, because unification may be called by
expand_abbrev.
*)
let nondep_hash = TypeHash.create 47
let nondep_variants = TypeHash.create 17
let clear_hash () =
TypeHash.clear nondep_hash; TypeHash.clear nondep_variants
let rec nondep_type_rec env id ty =
match ty.desc with
Tvar _ | Tunivar _ -> ty
| Tlink ty -> nondep_type_rec env id ty
| _ -> try TypeHash.find nondep_hash ty
with Not_found ->
let ty' = newgenvar () in (* Stub *)
TypeHash.add nondep_hash ty ty';
ty'.desc <-
begin match ty.desc with
| Tconstr(p, tl, abbrev) ->
if Path.isfree id p then
begin try
Tlink (nondep_type_rec env id
(expand_abbrev env (newty2 ty.level ty.desc)))
(*
The [Tlink] is important. The expanded type may be a
variable, or may not be completely copied yet
(recursive type), so one cannot just take its
description.
*)
with Cannot_expand | Unify _ ->
raise Not_found
end
else
Tconstr(p, List.map (nondep_type_rec env id) tl, ref Mnil)
| Tpackage(p, _, _) when Path.isfree id p ->
raise Not_found
| Tobject (t1, name) ->
Tobject (nondep_type_rec env id t1,
ref (match !name with
None -> None
| Some (p, tl) ->
if Path.isfree id p then None
else Some (p, List.map (nondep_type_rec env id) tl)))
| Tvariant row ->
let row = row_repr row in
let more = repr row.row_more in
(* We must keep sharing according to the row variable *)
begin try
let ty2 = TypeHash.find nondep_variants more in
(* This variant type has been already copied *)
TypeHash.add nondep_hash ty ty2;
Tlink ty2
with Not_found ->
(* Register new type first for recursion *)
TypeHash.add nondep_variants more ty';
let static = static_row row in
let more' = if static then newgenty Tnil else more in
(* Return a new copy *)
let row =
copy_row (nondep_type_rec env id) true row true more' in
match row.row_name with
Some (p, tl) when Path.isfree id p ->
Tvariant {row with row_name = None}
| _ -> Tvariant row
end
| _ -> copy_type_desc (nondep_type_rec env id) ty.desc
end;
ty'
let nondep_type env id ty =
try
let ty' = nondep_type_rec env id ty in
clear_hash ();
ty'
with Not_found ->
clear_hash ();
raise Not_found
let unroll_abbrev id tl ty =
let ty = repr ty and path = Path.Pident id in
if is_Tvar ty || (List.exists (deep_occur ty) tl)
|| is_object_type path then
ty
else
let ty' = newty2 ty.level ty.desc in
link_type ty (newty2 ty.level (Tconstr (path, tl, ref Mnil)));
ty'
(* Preserve sharing inside type declarations. *)
let nondep_type_decl env mid id is_covariant decl =
try
let params = List.map (nondep_type_rec env mid) decl.type_params in
let tk =
try match decl.type_kind with
Type_abstract ->
Type_abstract
| Type_variant cstrs ->
Type_variant
(List.map
(fun (c, tl,ret_type_opt) ->
let ret_type_opt =
may_map (nondep_type_rec env mid) ret_type_opt
in
(c, List.map (nondep_type_rec env mid) tl,ret_type_opt))
cstrs)
| Type_record(lbls, rep) ->
Type_record
(List.map
(fun (c, mut, t) -> (c, mut, nondep_type_rec env mid t))
lbls,
rep)
with Not_found when is_covariant -> Type_abstract
and tm =
try match decl.type_manifest with
None -> None
| Some ty ->
Some (unroll_abbrev id params (nondep_type_rec env mid ty))
with Not_found when is_covariant ->
None
in
clear_hash ();
let priv =
match tm with
| Some ty when Btype.has_constr_row ty -> Private
| _ -> decl.type_private
in
{ type_params = params;
type_arity = decl.type_arity;
type_kind = tk;
type_manifest = tm;
type_private = priv;
type_variance = decl.type_variance;
type_newtype_level = None;
type_loc = decl.type_loc;
}
with Not_found ->
clear_hash ();
raise Not_found
(* Preserve sharing inside class types. *)
let nondep_class_signature env id sign =
{ cty_self = nondep_type_rec env id sign.cty_self;
cty_vars =
Vars.map (function (m, v, t) -> (m, v, nondep_type_rec env id t))
sign.cty_vars;
cty_concr = sign.cty_concr;
cty_inher =
List.map (fun (p,tl) -> (p, List.map (nondep_type_rec env id) tl))
sign.cty_inher }
let rec nondep_class_type env id =
function
Cty_constr (p, _, cty) when Path.isfree id p ->
nondep_class_type env id cty
| Cty_constr (p, tyl, cty) ->
Cty_constr (p, List.map (nondep_type_rec env id) tyl,
nondep_class_type env id cty)
| Cty_signature sign ->
Cty_signature (nondep_class_signature env id sign)
| Cty_fun (l, ty, cty) ->
Cty_fun (l, nondep_type_rec env id ty, nondep_class_type env id cty)
let nondep_class_declaration env id decl =
assert (not (Path.isfree id decl.cty_path));
let decl =
{ cty_params = List.map (nondep_type_rec env id) decl.cty_params;
cty_variance = decl.cty_variance;
cty_type = nondep_class_type env id decl.cty_type;
cty_path = decl.cty_path;
cty_new =
begin match decl.cty_new with
None -> None
| Some ty -> Some (nondep_type_rec env id ty)
end }
in
clear_hash ();
decl
let nondep_cltype_declaration env id decl =
assert (not (Path.isfree id decl.clty_path));
let decl =
{ clty_params = List.map (nondep_type_rec env id) decl.clty_params;
clty_variance = decl.clty_variance;
clty_type = nondep_class_type env id decl.clty_type;
clty_path = decl.clty_path }
in
clear_hash ();
decl
(* collapse conjonctive types in class parameters *)
let rec collapse_conj env visited ty =
let ty = repr ty in
if List.memq ty visited then () else
let visited = ty :: visited in
match ty.desc with
Tvariant row ->
let row = row_repr row in
List.iter
(fun (l,fi) ->
match row_field_repr fi with
Reither (c, t1::(_::_ as tl), m, e) ->
List.iter (unify env t1) tl;
set_row_field e (Reither (c, [t1], m, ref None))
| _ ->
())
row.row_fields;
iter_row (collapse_conj env visited) row
| _ ->
iter_type_expr (collapse_conj env visited) ty
let collapse_conj_params env params =
List.iter (collapse_conj env []) params