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|
(***********************************************************************)
(* *)
(* Objective Caml *)
(* *)
(* Xavier Leroy, 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. *)
(* *)
(***********************************************************************)
(* typetexp.ml,v 1.34.4.9 2002/01/07 08:39:16 garrigue Exp *)
(* Typechecking of type expressions for the core language *)
open Misc
open Parsetree
open Types
open Ctype
exception Already_bound
type error =
Unbound_type_variable of string
| Unbound_type_constructor of Longident.t
| Unbound_type_constructor_2 of Path.t
| Type_arity_mismatch of Longident.t * int * int
| Bound_type_variable of string
| Recursive_type
| Unbound_class of Longident.t
| Unbound_row_variable of Longident.t
| Type_mismatch of (type_expr * type_expr) list
| Alias_type_mismatch of (type_expr * type_expr) list
| Present_has_conjunction of string
| Present_has_no_type of string
| Constructor_mismatch of type_expr * type_expr
| Not_a_variant of type_expr
| Variant_tags of string * string
| No_row_variable of string
| Bad_alias of string
exception Error of Location.t * error
type variable_context = int * (string, type_expr) Tbl.t
(* Translation of type expressions *)
let type_variables = ref (Tbl.empty : (string, type_expr) Tbl.t)
let univars = ref ([] : (string * (type_expr * type_expr ref)) list)
let pre_univars = ref ([] : type_expr list)
let used_variables = ref (Tbl.empty : (string, type_expr) Tbl.t)
let bindings = ref ([] : (Location.t * type_expr * type_expr) list)
(* These two variables are used for the "delayed" policy. *)
let reset_type_variables () =
reset_global_level ();
type_variables := Tbl.empty
let narrow () =
(increase_global_level (), !type_variables)
let widen (gl, tv) =
restore_global_level gl;
type_variables := tv
let enter_type_variable strict name =
try
let v = Tbl.find name !type_variables in
if strict then raise Already_bound;
v
with Not_found ->
let v = new_global_var() in
type_variables := Tbl.add name v !type_variables;
v
let type_variable loc name =
try
Tbl.find name !type_variables
with Not_found ->
raise(Error(loc, Unbound_type_variable ("'" ^ name)))
let wrap_method ty =
match (Ctype.repr ty).desc with
Tpoly _ -> ty
| _ -> Ctype.newty (Tpoly (ty, []))
let new_pre_univar () =
let v = newvar () in pre_univars := v :: !pre_univars; v
let rec swap_list = function
x :: y :: l -> y :: x :: swap_list l
| l -> l
type policy = Fixed | Extensible | Delayed | Univars
let rec transl_type env policy rowvar styp =
if rowvar <> None then begin
match styp.ptyp_desc with
Ptyp_variant _ | Ptyp_object _ | Ptyp_class _ -> ()
| _ -> raise(Error(styp.ptyp_loc, No_row_variable ""))
end;
match styp.ptyp_desc with
Ptyp_any ->
if policy = Univars then new_pre_univar () else newvar ()
| Ptyp_var name ->
begin try
instance (fst (List.assoc name !univars))
with Not_found ->
match policy with
Fixed ->
begin try
instance (Tbl.find name !type_variables)
with Not_found ->
raise(Error(styp.ptyp_loc, Unbound_type_variable ("'" ^ name)))
end
| Extensible ->
begin try
instance (Tbl.find name !type_variables)
with Not_found ->
let v = new_global_var () in
type_variables := Tbl.add name v !type_variables;
v
end
| Univars ->
begin try
instance (Tbl.find name !type_variables)
with Not_found ->
let v = new_pre_univar () in
type_variables := Tbl.add name v !type_variables;
v
end
| Delayed ->
begin try
instance (Tbl.find name !used_variables)
with Not_found -> try
let v1 = instance (Tbl.find name !type_variables) in
let v2 = new_global_var () in
used_variables := Tbl.add name v2 !used_variables;
bindings := (styp.ptyp_loc, v1, v2)::!bindings;
v2
with Not_found ->
let v = new_global_var () in
type_variables := Tbl.add name v !type_variables;
used_variables := Tbl.add name v !used_variables;
v
end
end
| Ptyp_arrow(l, st1, st2) ->
let ty1 = transl_type env policy None st1 in
let ty2 = transl_type env policy None st2 in
newty (Tarrow(l, ty1, ty2, Cok))
| Ptyp_tuple stl ->
newty (Ttuple(List.map (transl_type env policy None) stl))
| Ptyp_constr(lid, stl) ->
let (path, decl) =
try
Env.lookup_type lid env
with Not_found ->
raise(Error(styp.ptyp_loc, Unbound_type_constructor lid)) in
if List.length stl <> decl.type_arity then
raise(Error(styp.ptyp_loc, Type_arity_mismatch(lid, decl.type_arity,
List.length stl)));
let args = List.map (transl_type env policy None) stl in
let params = List.map (fun _ -> Ctype.newvar ()) args in
let cstr = newty (Tconstr(path, params, ref Mnil)) in
begin try
Ctype.enforce_constraints env cstr
with Unify trace ->
raise (Error(styp.ptyp_loc, Type_mismatch trace))
end;
List.iter2
(fun (sty, ty) ty' ->
try unify_var env ty' ty with Unify trace ->
raise (Error(sty.ptyp_loc, Type_mismatch (swap_list trace))))
(List.combine stl args) params;
cstr
| Ptyp_object fields ->
begin try
newobj (transl_fields env policy rowvar fields)
with Error (loc, No_row_variable _) when loc = Location.none ->
raise (Error(styp.ptyp_loc, No_row_variable "object "))
end
| Ptyp_class(lid, stl, present) ->
if policy = Fixed & rowvar = None then
raise(Error(styp.ptyp_loc, Unbound_row_variable lid));
let (path, decl, is_variant) =
try
let (path, decl) = Env.lookup_type lid env in
let rec check decl =
match decl.type_manifest with
None -> raise Not_found
| Some ty ->
match (repr ty).desc with
Tvariant row when Btype.static_row row -> ()
| Tconstr (path, _, _) ->
check (Env.find_type path env)
| _ -> raise Not_found
in check decl;
Location.prerr_warning styp.ptyp_loc Warnings.Deprecated;
(path, decl,true)
with Not_found -> try
if present <> [] then raise Not_found;
let lid2 =
match lid with
Longident.Lident s -> Longident.Lident ("#" ^ s)
| Longident.Ldot(r, s) -> Longident.Ldot (r, "#" ^ s)
| Longident.Lapply(_, _) -> fatal_error "Typetexp.transl_type"
in
let (path, decl) = Env.lookup_type lid2 env in
(path, decl, false)
with Not_found ->
raise(Error(styp.ptyp_loc, Unbound_class lid))
in
if List.length stl <> decl.type_arity then
raise(Error(styp.ptyp_loc, Type_arity_mismatch(lid, decl.type_arity,
List.length stl)));
let args = List.map (transl_type env policy None) stl in
let cstr = newty (Tconstr(path, args, ref Mnil)) in
let ty =
try Ctype.expand_head env cstr
with Unify trace ->
raise (Error(styp.ptyp_loc, Type_mismatch trace))
in
let params = Ctype.instance_list decl.type_params in
List.iter2
(fun (sty, ty') ty ->
try unify_var env ty ty' with Unify trace ->
raise (Error(sty.ptyp_loc, Type_mismatch (swap_list trace))))
(List.combine stl args) params;
begin match ty.desc with
Tvariant row ->
let row = Btype.row_repr row in
List.iter
(fun l -> if not (List.mem_assoc l row.row_fields) then
raise(Error(styp.ptyp_loc, Present_has_no_type l)))
present;
let bound = ref row.row_bound in
let fixed = rowvar <> None || policy = Univars in
let single = List.length row.row_fields = 1 in
let fields =
if single then row.row_fields else
List.map
(fun (l,f) -> l,
if List.mem l present then f else
match Btype.row_field_repr f with
| Rpresent (Some ty) ->
bound := ty :: !bound;
Reither(false, [ty], fixed, [], ref None)
| Rpresent None ->
Reither (true, [], fixed, [], ref None)
| _ -> f)
row.row_fields
in
let row = { row_closed = true; row_fields = fields;
row_bound = !bound; row_name = Some (path, args);
row_fixed = fixed; row_more = newvar () } in
let static = Btype.static_row row in
let row =
if static then row else
{ row with row_more = match rowvar with Some v -> v
| None ->
if policy = Univars then new_pre_univar ()
else newvar () } in
newty (Tvariant row)
| Tobject (fi, _) ->
let _, tv = flatten_fields fi in
if policy = Univars then pre_univars := tv :: !pre_univars;
begin match rowvar with None -> ()
| Some rv ->
let _, tv = flatten_fields fi in
try unify_var env tv rv with Unify trace ->
raise(Error(styp.ptyp_loc, Alias_type_mismatch trace))
end;
ty
| _ ->
assert false
end
| Ptyp_alias(st, alias) ->
if List.mem_assoc alias !univars then
match List.assoc alias !univars with
({desc=Tunivar} as tc), tr when tc == !tr ->
tr := Btype.newty2 tc.level Tunivar;
tc.desc <- Tvar;
let ty = transl_type env policy (Some !tr) st in
begin try unify_var env tc ty with Unify trace ->
let trace = swap_list trace in
raise(Error(styp.ptyp_loc, Alias_type_mismatch trace))
end;
ty
| _ ->
raise(Error(styp.ptyp_loc, Bound_type_variable alias))
else begin
try
let v1 = instance (Tbl.find alias !type_variables) in
let t =
(* Special case if using indirect variable bindings *)
if policy = Delayed then
try instance (Tbl.find alias !used_variables)
with Not_found ->
let v2 = new_global_var () in
used_variables := Tbl.add alias v2 !used_variables;
bindings := (styp.ptyp_loc, v1, v2)::!bindings;
v2
else v1
in
let ty = transl_type env policy None st in
begin try unify_var env t ty with Unify trace ->
let trace = swap_list trace in
raise(Error(styp.ptyp_loc, Alias_type_mismatch trace))
end;
ty
with Not_found ->
begin_def ();
let t = newvar () in
type_variables := Tbl.add alias t !type_variables;
if policy = Delayed then
used_variables := Tbl.add alias t !used_variables;
let ty = transl_type env policy None st in
begin try unify_var env t ty with Unify trace ->
let trace = swap_list trace in
raise(Error(styp.ptyp_loc, Alias_type_mismatch trace))
end;
end_def ();
generalize_global t;
instance t
end
| Ptyp_variant(fields, closed, present) ->
if rowvar <> None && present = None && closed then
raise (Error(styp.ptyp_loc, No_row_variable "variant "));
let bound = ref [] and name = ref None in
let fixed = rowvar <> None || policy = Univars in
let mkfield l f =
newty (Tvariant {row_fields=[l,f]; row_more=newvar();
row_bound=[]; row_closed=true;
row_fixed=fixed; row_name=None}) in
let add_typed_field loc l f fields =
try
let f' = List.assoc l fields in
let ty = mkfield l f and ty' = mkfield l f' in
if equal env false [ty] [ty'] then fields
else raise(Error(loc, Constructor_mismatch (ty,ty')))
with Not_found ->
(l, f) :: fields
in
(* closed and only one field: make it present anyway *)
let single = closed && List.length fields = 1 in
let rec add_field fields = function
Rtag (l, c, stl, stpl) ->
name := None;
let f = match present with
Some present when not (single || List.mem l present) ->
let transl_list = List.map (transl_type env policy None) in
let tl = transl_list stl in
let stpl1, stpl2 = List.split stpl in
let tpl1 = transl_list stpl1 and tpl2 = transl_list stpl2 in
bound := tl @ tpl1 @ tpl2 @ !bound;
Reither(c, tl, fixed, List.combine tpl1 tpl2, ref None)
| _ ->
if List.length stl > 1 || c && stl <> [] then
raise(Error(styp.ptyp_loc, Present_has_conjunction l));
match stl with [] -> Rpresent None
| st :: _ -> Rpresent (Some(transl_type env policy None st))
in
add_typed_field styp.ptyp_loc l f fields
| Rinherit sty ->
let ty = transl_type env policy None sty in
let nm =
match repr ty with
{desc=Tconstr(p, tl, _)} -> Some(p, tl)
| _ -> None
in
name := if fields = [] then nm else None;
let fl = match expand_head env ty, nm with
{desc=Tvariant row}, _ when Btype.static_row row ->
let row = Btype.row_repr row in
row.row_fields
| {desc=Tvar}, Some(p, _) ->
raise(Error(sty.ptyp_loc, Unbound_type_constructor_2 p))
| _ ->
raise(Error(sty.ptyp_loc, Not_a_variant ty))
in
let single = single && List.length fl = 1 in
List.fold_left
(fun fields (l, f) ->
let f = match present with
Some present when not (single || List.mem l present) ->
begin match f with
Rpresent(Some ty) ->
bound := ty :: !bound;
Reither(false, [ty], fixed, [], ref None)
| Rpresent None ->
Reither(true, [], fixed, [], ref None)
| _ ->
assert false
end
| _ -> f
in
add_typed_field sty.ptyp_loc l f fields)
fields fl
in
let fields = List.fold_left add_field [] fields in
begin match present with None -> ()
| Some present ->
List.iter
(fun l -> if not (List.mem_assoc l fields) then
raise(Error(styp.ptyp_loc, Present_has_no_type l)))
present
end;
ignore begin
List.fold_left
(fun hl (l,_) ->
let h = Btype.hash_variant l in
try
let l' = List.assoc h hl in
if l <> l' then raise(Error(styp.ptyp_loc, Variant_tags(l, l')));
hl
with Not_found -> (h,l) :: hl)
[]
fields
end;
let row =
{ row_fields = List.rev fields; row_more = newvar ();
row_bound = !bound; row_closed = closed;
row_fixed = fixed; row_name = !name } in
let static = Btype.static_row row in
let row =
if static then row else
{ row with row_more = match rowvar with Some v -> v
| None ->
if policy = Univars then new_pre_univar () else
if policy = Fixed && not static then
raise(Error(styp.ptyp_loc, Unbound_type_variable "[..]"))
else row.row_more
} in
newty (Tvariant row)
| Ptyp_poly(vars, st) ->
(* aliases are stubs, in case one wants to redefine them *)
let tr_list = List.map (fun _ -> ref (newty Tunivar)) vars in
let new_univars =
List.map2 (fun name tr -> name, (!tr, tr)) vars tr_list in
let old_univars = !univars in
univars := new_univars @ !univars;
let ty = transl_type env policy None st in
univars := old_univars;
let ty_list = List.map (!) tr_list in
let ty_list = List.filter (fun tu -> deep_occur (repr tu) ty) ty_list in
newty (Tpoly(ty, ty_list))
and transl_fields env policy rowvar =
function
[] ->
newty Tnil
| {pfield_desc = Pfield_var} as field::_ ->
begin match rowvar with
None ->
if policy = Fixed then
raise(Error(field.pfield_loc, Unbound_type_variable ".."));
if policy = Univars then new_pre_univar () else newvar ()
| Some v -> v
end
| {pfield_desc = Pfield(s, e)}::l ->
let ty1 = transl_type env policy None e in
let ty2 = transl_fields env policy rowvar l in
newty (Tfield (s, Fpresent, ty1, ty2))
let transl_simple_type env fixed styp =
univars := [];
let typ = transl_type env (if fixed then Fixed else Extensible) None styp in
typ
let transl_simple_type_univars env styp =
univars := [];
pre_univars := [];
begin_def ();
let typ = transl_type env Univars None styp in
end_def ();
generalize typ;
let univs =
List.fold_left
(fun acc v ->
let v = repr v in
if v.desc <> Tvar || v.level <> Btype.generic_level || List.memq v acc
then acc
else (v.desc <- Tunivar ; v :: acc))
[] !pre_univars
in
pre_univars := [];
Tbl.iter
(fun name ty ->
if List.exists (fun tu -> repr ty == repr tu) univs
then type_variables := Tbl.remove name !type_variables)
!type_variables;
instance (Btype.newgenty (Tpoly (typ, univs)))
let transl_simple_type_delayed env styp =
univars := [];
used_variables := Tbl.empty;
bindings := [];
let typ = transl_type env Delayed None styp in
let b = !bindings in
used_variables := Tbl.empty;
bindings := [];
(typ,
function () ->
List.iter
(function (loc, t1, t2) ->
try unify env t1 t2 with Unify trace ->
raise (Error(loc, Type_mismatch trace)))
b)
let transl_type_scheme env styp =
reset_type_variables();
begin_def();
let typ = transl_simple_type env false styp in
end_def();
generalize typ;
typ
(* Error report *)
open Format
open Printtyp
let report_error ppf = function
| Unbound_type_variable name ->
fprintf ppf "Unbound type parameter %s" name
| Unbound_type_constructor lid ->
fprintf ppf "Unbound type constructor %a" longident lid
| Unbound_type_constructor_2 p ->
fprintf ppf "The type constructor@ %a@ is not yet completely defined"
path p
| Type_arity_mismatch(lid, expected, provided) ->
fprintf ppf
"@[The type constructor %a@ expects %i argument(s),@ \
but is here applied to %i argument(s)@]"
longident lid expected provided
| Bound_type_variable name ->
fprintf ppf "Already bound type parameter '%s" name
| Recursive_type ->
fprintf ppf "This type is recursive"
| Unbound_class lid ->
fprintf ppf "Unbound class %a" longident lid
| Unbound_row_variable lid ->
fprintf ppf "Unbound row variable in #%a" longident lid
| Type_mismatch trace ->
Printtyp.unification_error true trace
(function ppf ->
fprintf ppf "This type")
ppf
(function ppf ->
fprintf ppf "should be an instance of type")
| Alias_type_mismatch trace ->
Printtyp.unification_error true trace
(function ppf ->
fprintf ppf "This alias is bound to type")
ppf
(function ppf ->
fprintf ppf "but is used as an instance of type")
| Present_has_conjunction l ->
fprintf ppf "The present constructor %s has a conjunctive type" l
| Present_has_no_type l ->
fprintf ppf "The present constructor %s has no type" l
| Constructor_mismatch (ty, ty') ->
Printtyp.reset_and_mark_loops_list [ty; ty'];
fprintf ppf "@[<hov>%s %a@ %s@ %a@]"
"This variant type contains a constructor"
Printtyp.type_expr ty
"which should be"
Printtyp.type_expr ty'
| Not_a_variant ty ->
Printtyp.reset_and_mark_loops ty;
fprintf ppf "@[The type %a@ is not a polymorphic variant type@]"
Printtyp.type_expr ty
| Variant_tags (lab1, lab2) ->
fprintf ppf
"Variant tags `%s@ and `%s have same hash value.@ Change one of them."
lab1 lab2
| No_row_variable s ->
fprintf ppf "This %stype has no row variable" s
| Bad_alias name ->
fprintf ppf
"The alias %s cannot be used here. It captures universal variables."
name
|