557 lines
20 KiB
OCaml
557 lines
20 KiB
OCaml
(***********************************************************************)
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(* *)
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(* Objective Caml *)
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(* *)
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(* Xavier Leroy, projet Cristal, INRIA Rocquencourt *)
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(* *)
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(* Copyright 1996 Institut National de Recherche en Informatique et *)
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(* en Automatique. All rights reserved. This file is distributed *)
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(* under the terms of the Q Public License version 1.0. *)
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(* *)
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(***********************************************************************)
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(* typetexp.ml,v 1.34.4.9 2002/01/07 08:39:16 garrigue Exp *)
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(* Typechecking of type expressions for the core language *)
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open Misc
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open Parsetree
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open Types
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open Ctype
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exception Already_bound
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type error =
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Unbound_type_variable of string
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| Unbound_type_constructor of Longident.t
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| Unbound_type_constructor_2 of Path.t
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| Type_arity_mismatch of Longident.t * int * int
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| Bound_type_variable of string
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| Recursive_type
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| Unbound_class of Longident.t
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| Unbound_row_variable of Longident.t
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| Type_mismatch of (type_expr * type_expr) list
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| Alias_type_mismatch of (type_expr * type_expr) list
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| Present_has_conjunction of string
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| Present_has_no_type of string
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| Constructor_mismatch of type_expr * type_expr
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| Not_a_variant of type_expr
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| Variant_tags of string * string
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| Invalid_variable_name of string
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| Cannot_quantify of string * type_expr
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exception Error of Location.t * error
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type variable_context = int * (string, type_expr) Tbl.t
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(* Translation of type expressions *)
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let type_variables = ref (Tbl.empty : (string, type_expr) Tbl.t)
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let univars = ref ([] : (string * type_expr) list)
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let pre_univars = ref ([] : type_expr list)
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let used_variables = ref (Tbl.empty : (string, type_expr * Location.t) Tbl.t)
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let reset_type_variables () =
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reset_global_level ();
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type_variables := Tbl.empty
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let narrow () =
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(increase_global_level (), !type_variables)
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let widen (gl, tv) =
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restore_global_level gl;
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type_variables := tv
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let enter_type_variable strict loc name =
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try
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if name <> "" && name.[0] = '_' then
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raise (Error (loc, Invalid_variable_name ("'" ^ name)));
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let v = Tbl.find name !type_variables in
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if strict then raise Already_bound;
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v
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with Not_found ->
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let v = new_global_var() in
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type_variables := Tbl.add name v !type_variables;
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v
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let type_variable loc name =
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try
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Tbl.find name !type_variables
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with Not_found ->
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raise(Error(loc, Unbound_type_variable ("'" ^ name)))
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let wrap_method ty =
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match (Ctype.repr ty).desc with
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Tpoly _ -> ty
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| _ -> Ctype.newty (Tpoly (ty, []))
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let new_pre_univar () =
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let v = newvar () in pre_univars := v :: !pre_univars; v
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let rec swap_list = function
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x :: y :: l -> y :: x :: swap_list l
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| l -> l
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type policy = Fixed | Extensible | Univars
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let rec transl_type env policy styp =
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match styp.ptyp_desc with
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Ptyp_any ->
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if policy = Univars then new_pre_univar () else
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if policy = Fixed then
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raise (Error (styp.ptyp_loc, Unbound_type_variable "_"))
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else newvar ()
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| Ptyp_var name ->
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if name <> "" && name.[0] = '_' then
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raise (Error (styp.ptyp_loc, Invalid_variable_name ("'" ^ name)));
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begin try
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instance (List.assoc name !univars)
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with Not_found -> try
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instance (fst(Tbl.find name !used_variables))
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with Not_found ->
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let v =
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if policy = Univars then new_pre_univar () else newvar () in
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used_variables := Tbl.add name (v, styp.ptyp_loc) !used_variables;
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v
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end
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| Ptyp_arrow(l, st1, st2) ->
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let ty1 = transl_type env policy st1 in
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let ty2 = transl_type env policy st2 in
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newty (Tarrow(l, ty1, ty2, Cok))
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| Ptyp_tuple stl ->
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newty (Ttuple(List.map (transl_type env policy) stl))
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| Ptyp_constr(lid, stl) ->
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let (path, decl) =
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try
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Env.lookup_type lid env
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with Not_found ->
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raise(Error(styp.ptyp_loc, Unbound_type_constructor lid)) in
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if List.length stl <> decl.type_arity then
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raise(Error(styp.ptyp_loc, Type_arity_mismatch(lid, decl.type_arity,
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List.length stl)));
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let args = List.map (transl_type env policy) stl in
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let params = Ctype.instance_list decl.type_params in
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let unify_param =
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match decl.type_manifest with
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None -> unify_var
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| Some ty ->
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if (repr ty).level = Btype.generic_level then unify_var else unify
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in
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List.iter2
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(fun (sty, ty) ty' ->
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try unify_param env ty' ty with Unify trace ->
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raise (Error(sty.ptyp_loc, Type_mismatch (swap_list trace))))
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(List.combine stl args) params;
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let constr = newconstr path args in
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begin try
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Ctype.enforce_constraints env constr
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with Unify trace ->
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raise (Error(styp.ptyp_loc, Type_mismatch trace))
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end;
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constr
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| Ptyp_object fields ->
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newobj (transl_fields env policy fields)
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| Ptyp_class(lid, stl, present) ->
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let (path, decl, is_variant) =
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try
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let (path, decl) = Env.lookup_type lid env in
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let rec check decl =
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match decl.type_manifest with
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None -> raise Not_found
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| Some ty ->
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match (repr ty).desc with
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Tvariant row when Btype.static_row row -> ()
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| Tconstr (path, _, _) ->
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check (Env.find_type path env)
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| _ -> raise Not_found
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in check decl;
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Location.prerr_warning styp.ptyp_loc Warnings.Deprecated;
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(path, decl,true)
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with Not_found -> try
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if present <> [] then raise Not_found;
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let lid2 =
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match lid with
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Longident.Lident s -> Longident.Lident ("#" ^ s)
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| Longident.Ldot(r, s) -> Longident.Ldot (r, "#" ^ s)
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| Longident.Lapply(_, _) -> fatal_error "Typetexp.transl_type"
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in
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let (path, decl) = Env.lookup_type lid2 env in
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(path, decl, false)
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with Not_found ->
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raise(Error(styp.ptyp_loc, Unbound_class lid))
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in
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if List.length stl <> decl.type_arity then
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raise(Error(styp.ptyp_loc, Type_arity_mismatch(lid, decl.type_arity,
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List.length stl)));
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let args = List.map (transl_type env policy) stl in
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let params = Ctype.instance_list decl.type_params in
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List.iter2
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(fun (sty, ty) ty' ->
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try unify_var env ty' ty with Unify trace ->
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raise (Error(sty.ptyp_loc, Type_mismatch (swap_list trace))))
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(List.combine stl args) params;
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let ty =
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try Ctype.expand_head env (newconstr path args)
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with Unify trace ->
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raise (Error(styp.ptyp_loc, Type_mismatch trace))
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in
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begin match ty.desc with
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Tvariant row ->
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let row = Btype.row_repr row in
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List.iter
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(fun l -> if not (List.mem_assoc l row.row_fields) then
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raise(Error(styp.ptyp_loc, Present_has_no_type l)))
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present;
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let bound = ref row.row_bound in
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let fields =
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List.map
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(fun (l,f) -> l,
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if List.mem l present then f else
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match Btype.row_field_repr f with
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| Rpresent (Some ty) ->
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bound := ty :: !bound;
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Reither(false, [ty], false, ref None)
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| Rpresent None ->
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Reither (true, [], false, ref None)
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| _ -> f)
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row.row_fields
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in
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let row = { row_closed = true; row_fields = fields;
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row_bound = !bound; row_name = Some (path, args);
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row_fixed = false; row_more = newvar () } in
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let static = Btype.static_row row in
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let row =
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if static || policy <> Univars then row
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else { row with row_more = new_pre_univar () }
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in
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newty (Tvariant row)
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| Tobject (fi, _) ->
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let _, tv = flatten_fields fi in
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if policy = Univars then pre_univars := tv :: !pre_univars;
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ty
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| _ ->
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assert false
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end
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| Ptyp_alias(st, alias) ->
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begin
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try
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let t =
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try List.assoc alias !univars
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with Not_found ->
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instance (fst(Tbl.find alias !used_variables))
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in
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let ty = transl_type env policy st in
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begin try unify_var env t ty with Unify trace ->
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let trace = swap_list trace in
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raise(Error(styp.ptyp_loc, Alias_type_mismatch trace))
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end;
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ty
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with Not_found ->
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if !Clflags.principal then begin_def ();
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let t = newvar () in
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used_variables := Tbl.add alias (t, styp.ptyp_loc) !used_variables;
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let ty = transl_type env policy st in
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begin try unify_var env t ty with Unify trace ->
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let trace = swap_list trace in
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raise(Error(styp.ptyp_loc, Alias_type_mismatch trace))
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end;
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if !Clflags.principal then begin
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end_def ();
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generalize_structure t;
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end;
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instance t
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end
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| Ptyp_variant(fields, closed, present) ->
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let bound = ref [] and name = ref None in
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let mkfield l f =
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newty (Tvariant {row_fields=[l,f]; row_more=newvar();
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row_bound=[]; row_closed=true;
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row_fixed=false; row_name=None}) in
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let add_typed_field loc l f fields =
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try
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let f' = List.assoc l fields in
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let ty = mkfield l f and ty' = mkfield l f' in
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if equal env false [ty] [ty'] then fields else
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try unify env ty ty'; fields
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with Unify trace -> raise(Error(loc, Constructor_mismatch (ty,ty')))
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with Not_found ->
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(l, f) :: fields
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in
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let rec add_field fields = function
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Rtag (l, c, stl) ->
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name := None;
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let f = match present with
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Some present when not (List.mem l present) ->
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let tl = List.map (transl_type env policy) stl in
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bound := tl @ !bound;
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Reither(c, tl, false, ref None)
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| _ ->
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if List.length stl > 1 || c && stl <> [] then
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raise(Error(styp.ptyp_loc, Present_has_conjunction l));
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match stl with [] -> Rpresent None
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| st :: _ -> Rpresent (Some(transl_type env policy st))
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in
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add_typed_field styp.ptyp_loc l f fields
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| Rinherit sty ->
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let ty = transl_type env policy sty in
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let nm =
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match repr ty with
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{desc=Tconstr(p, tl, _)} -> Some(p, tl)
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| _ -> None
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in
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name := if fields = [] then nm else None;
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let fl = match expand_head env ty, nm with
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{desc=Tvariant row}, _ when Btype.static_row row ->
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let row = Btype.row_repr row in
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row.row_fields
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| {desc=Tvar}, Some(p, _) ->
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raise(Error(sty.ptyp_loc, Unbound_type_constructor_2 p))
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| _ ->
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raise(Error(sty.ptyp_loc, Not_a_variant ty))
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in
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List.fold_left
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(fun fields (l, f) ->
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let f = match present with
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Some present when not (List.mem l present) ->
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begin match f with
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Rpresent(Some ty) ->
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bound := ty :: !bound;
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Reither(false, [ty], false, ref None)
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| Rpresent None ->
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Reither(true, [], false, ref None)
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| _ ->
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assert false
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end
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| _ -> f
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in
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add_typed_field sty.ptyp_loc l f fields)
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fields fl
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in
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let fields = List.fold_left add_field [] fields in
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begin match present with None -> ()
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| Some present ->
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List.iter
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(fun l -> if not (List.mem_assoc l fields) then
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raise(Error(styp.ptyp_loc, Present_has_no_type l)))
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present
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end;
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(* Check for tag conflicts *)
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let ht = Hashtbl.create (List.length fields + 1) in
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List.iter
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(fun (l,_) ->
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let h = Btype.hash_variant l in
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try
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let l' = Hashtbl.find ht h in
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if l <> l' then raise(Error(styp.ptyp_loc, Variant_tags(l, l')))
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with Not_found ->
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Hashtbl.add ht h l)
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fields;
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let row =
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{ row_fields = List.rev fields; row_more = newvar ();
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row_bound = !bound; row_closed = closed;
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row_fixed = false; row_name = !name } in
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let static = Btype.static_row row in
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let row =
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if static || policy <> Univars then row
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else { row with row_more = new_pre_univar () }
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in
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newty (Tvariant row)
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| Ptyp_poly(vars, st) ->
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begin_def();
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let new_univars = List.map (fun name -> name, newvar()) vars in
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let old_univars = !univars in
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univars := new_univars @ !univars;
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let ty = transl_type env policy st in
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univars := old_univars;
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end_def();
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generalize ty;
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let ty_list =
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List.fold_left
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(fun tyl (name, ty1) ->
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let v = Btype.proxy ty1 in
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if deep_occur v ty then begin
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if v.level <> Btype.generic_level || v.desc <> Tvar then
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raise (Error (styp.ptyp_loc, Cannot_quantify (name, v)));
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v.desc <- Tunivar;
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v :: tyl
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end else tyl)
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[] new_univars
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in
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let ty' = Btype.newgenty (Tpoly(ty, List.rev ty_list)) in
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unify_var env (newvar()) ty';
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ty'
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and transl_fields env policy =
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function
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[] ->
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newty Tnil
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| {pfield_desc = Pfield_var}::_ ->
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if policy = Univars then new_pre_univar () else newvar ()
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| {pfield_desc = Pfield(s, e)}::l ->
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let ty1 = transl_type env policy e in
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let ty2 = transl_fields env policy l in
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newty (Tfield (s, Fpresent, ty1, ty2))
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(* Make the rows "fixed" in this type, to make universal check easier *)
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let rec make_fixed_univars ty =
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let ty = repr ty in
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if ty.level >= Btype.lowest_level then begin
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Btype.mark_type_node ty;
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match ty.desc with
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| Tvariant row ->
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let row = Btype.row_repr row in
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if (Btype.row_more row).desc = Tunivar then
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ty.desc <- Tvariant
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{row with row_fixed=true;
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row_fields = List.map
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(fun (s,f as p) -> match Btype.row_field_repr f with
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Reither (c, tl, m, r) -> s, Reither (c, tl, true, r)
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| _ -> p)
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row.row_fields};
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Btype.iter_row make_fixed_univars row
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| _ ->
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Btype.iter_type_expr make_fixed_univars ty
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end
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let make_fixed_univars ty =
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make_fixed_univars ty;
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Btype.unmark_type ty
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let globalize_used_variables env fixed =
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let r = ref [] in
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Tbl.iter
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(fun name (ty, loc) ->
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let v = new_global_var () in
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let snap = Btype.snapshot () in
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if try unify env v ty; true with _ -> Btype.backtrack snap; false
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then try
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r := (loc, v, Tbl.find name !type_variables) :: !r
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with Not_found ->
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if fixed && (repr ty).desc = Tvar then
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raise(Error(loc, Unbound_type_variable ("'"^name)));
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let v2 = new_global_var () in
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r := (loc, v, v2) :: !r;
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type_variables := Tbl.add name v2 !type_variables)
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!used_variables;
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used_variables := Tbl.empty;
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fun () ->
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List.iter
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(function (loc, t1, t2) ->
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try unify env t1 t2 with Unify trace ->
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raise (Error(loc, Type_mismatch trace)))
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!r
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let transl_simple_type env fixed styp =
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univars := []; used_variables := Tbl.empty;
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let typ = transl_type env (if fixed then Fixed else Extensible) styp in
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globalize_used_variables env fixed ();
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make_fixed_univars typ;
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typ
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let transl_simple_type_univars env styp =
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univars := []; used_variables := Tbl.empty; pre_univars := [];
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begin_def ();
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let typ = transl_type env Univars styp in
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(* Only keep already global variables in used_variables *)
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let new_variables = !used_variables in
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used_variables := Tbl.empty;
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Tbl.iter
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(fun name p ->
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if Tbl.mem name !type_variables then
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used_variables := Tbl.add name p !used_variables)
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new_variables;
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globalize_used_variables env false ();
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end_def ();
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generalize typ;
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let univs =
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List.fold_left
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(fun acc v ->
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let v = repr v in
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if v.level <> Btype.generic_level || v.desc <> Tvar then acc
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else (v.desc <- Tunivar ; v :: acc))
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[] !pre_univars
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in
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make_fixed_univars typ;
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instance (Btype.newgenty (Tpoly (typ, univs)))
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let transl_simple_type_delayed env styp =
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univars := []; used_variables := Tbl.empty;
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let typ = transl_type env Extensible styp in
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(typ, globalize_used_variables env false)
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let transl_type_scheme env styp =
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reset_type_variables();
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begin_def();
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let typ = transl_simple_type env false styp in
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end_def();
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generalize typ;
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typ
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(* Error report *)
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open Format
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open Printtyp
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let report_error ppf = function
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| Unbound_type_variable name ->
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fprintf ppf "Unbound type parameter %s" name
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| Unbound_type_constructor lid ->
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fprintf ppf "Unbound type constructor %a" longident lid
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| Unbound_type_constructor_2 p ->
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fprintf ppf "The type constructor@ %a@ is not yet completely defined"
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path p
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| Type_arity_mismatch(lid, expected, provided) ->
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fprintf ppf
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"@[The type constructor %a@ expects %i argument(s),@ \
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but is here applied to %i argument(s)@]"
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longident lid expected provided
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| Bound_type_variable name ->
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fprintf ppf "Already bound type parameter '%s" name
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| Recursive_type ->
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fprintf ppf "This type is recursive"
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| Unbound_class lid ->
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fprintf ppf "Unbound class %a" longident lid
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| Unbound_row_variable lid ->
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fprintf ppf "Unbound row variable in #%a" longident lid
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| Type_mismatch trace ->
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Printtyp.unification_error true trace
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|
(function ppf ->
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fprintf ppf "This type")
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|
ppf
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|
(function ppf ->
|
|
fprintf ppf "should be an instance of type")
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| Alias_type_mismatch trace ->
|
|
Printtyp.unification_error true trace
|
|
(function ppf ->
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|
fprintf ppf "This alias is bound to type")
|
|
ppf
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|
(function ppf ->
|
|
fprintf ppf "but is used as an instance of type")
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| Present_has_conjunction l ->
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|
fprintf ppf "The present constructor %s has a conjunctive type" l
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|
| Present_has_no_type l ->
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|
fprintf ppf "The present constructor %s has no type" l
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| Constructor_mismatch (ty, ty') ->
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|
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
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| Variant_tags (lab1, lab2) ->
|
|
fprintf ppf
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|
"Variant tags `%s@ and `%s have same hash value.@ Change one of them."
|
|
lab1 lab2
|
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| Invalid_variable_name name ->
|
|
fprintf ppf "The type variable name %s is not allowed in programs" name
|
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| Cannot_quantify (name, v) ->
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|
fprintf ppf "This type scheme cannot quantify '%s :@ %s." name
|
|
(if v.desc = Tvar then "it escapes this scope" else
|
|
if v.desc = Tunivar then "it is aliased to another variable"
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|
else "it is not a variable")
|