(**************************************************************************)
(*                                                                        *)
(*                                 OCaml                                  *)
(*                                                                        *)
     and   , 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 GNU Lesser General Public License version 2.1 , with the          
(*   special exception on linking described in the file LICENSE.          *)
(*                                                                        *)
(**************************************************************************)

(**** Typing of type definitions ****)

open Misc
open Asttypes
open Parsetree
open Primitive
open Types
open Typetexp

module String = Misc.Stdlib.String

type native_repr_kind = Unboxed | Untagged

type error =
    Repeated_parameter
  | Duplicate_constructor of string
  | Too_many_constructors
  | Duplicate_label of string
  | Recursive_abbrev of string
  | Cycle_in_def of string * type_expr
  | Definition_mismatch of type_expr * Includecore.type_mismatch option
  | Constraint_failed of type_expr * type_expr
  | Inconsistent_constraint of Env.t * Ctype.Unification_trace.t
  | Type_clash of Env.t * Ctype.Unification_trace.t
  | Parameters_differ of Path.t * type_expr * type_expr
  | Null_arity_external
  | Missing_native_external
  | Unbound_type_var of type_expr * type_declaration
  | Cannot_extend_private_type of Path.t
  | Not_extensible_type of Path.t
  | Extension_mismatch of Path.t * Includecore.type_mismatch
  | Rebind_wrong_type of Longident.t * Env.t * Ctype.Unification_trace.t
  | Rebind_mismatch of Longident.t * Path.t * Path.t
  | Rebind_private of Longident.t
  | Variance of Typedecl_variance.error
  | Unavailable_type_constructor of Path.t
  | Bad_fixed_type of string
  | Unbound_type_var_ext of type_expr * extension_constructor
  | Val_in_structure
  | Multiple_native_repr_attributes
  | Cannot_unbox_or_untag_type of native_repr_kind
  | Deep_unbox_or_untag_attribute of native_repr_kind
  | Immediacy of Typedecl_immediacy.error
  | Bad_unboxed_attribute of string
  | Wrong_unboxed_type_float
  | Boxed_and_unboxed
  | Nonrec_gadt

open Typedtree

exception Error of Location.t * error

(* Note: do not factor the branches in the following pattern-matching:
   the records must be constants for the compiler to do sharing on them.
*)
let get_unboxed_from_attributes sdecl =
  let unboxed = Builtin_attributes.has_unboxed sdecl.ptype_attributes in
  let boxed = Builtin_attributes.has_boxed sdecl.ptype_attributes in
  match boxed, unboxed, !Clflags.unboxed_types with
  | true, true, _ -> raise (Error(sdecl.ptype_loc, Boxed_and_unboxed))
  | true, false, _ -> unboxed_false_default_false
  | false, true, _ -> unboxed_true_default_false
  | false, false, false -> unboxed_false_default_true
  | false, false, true -> unboxed_true_default_true

(* Enter all declared types in the environment as abstract types *)

let add_type ~check id decl env =
  Builtin_attributes.warning_scope ~ppwarning:false decl.type_attributes
    (fun () -> Env.add_type ~check id decl env)

let enter_type rec_flag env sdecl id =
  let needed =
    match rec_flag with
    | Asttypes.Nonrecursive ->
        begin match sdecl.ptype_kind with
        | Ptype_variant scds ->
            List.iter (fun cd ->
              if cd.pcd_res <> None then raise (Error(cd.pcd_loc, Nonrec_gadt)))
              scds
        | _ -> ()
        end;
        Btype.is_row_name (Ident.name id)
    | Asttypes.Recursive -> true
  in
  if not needed then env else
  let decl =
    { type_params =
        List.map (fun _ -> Btype.newgenvar ()) sdecl.ptype_params;
      type_arity = List.length sdecl.ptype_params;
      type_kind = Type_abstract;
      type_private = sdecl.ptype_private;
      type_manifest =
        begin match sdecl.ptype_manifest with None -> None
        | Some _ -> Some(Ctype.newvar ()) end;
      type_variance = List.map (fun _ -> Variance.full) sdecl.ptype_params;
      type_is_newtype = false;
      type_expansion_scope = Btype.lowest_level;
      type_loc = sdecl.ptype_loc;
      type_attributes = sdecl.ptype_attributes;
      type_immediate = Unknown;
      type_unboxed = unboxed_false_default_false;
    }
  in
  add_type ~check:true id decl env

let update_type temp_env env id loc =
  let path = Path.Pident id in
  let decl = Env.find_type path temp_env in
  match decl.type_manifest with None -> ()
  | Some ty ->
      let params = List.map (fun _ -> Ctype.newvar ()) decl.type_params in
      try Ctype.unify env (Ctype.newconstr path params) ty
      with Ctype.Unify trace ->
        raise (Error(loc, Type_clash (env, trace)))

let get_unboxed_type_representation env ty =
  match Typedecl_unboxed.get_unboxed_type_representation env ty with
  | Typedecl_unboxed.This x -> Some x
  | _ -> None

(* Determine if a type's values are represented by floats at run-time. *)
let is_float env ty =
  match get_unboxed_type_representation env ty with
    Some {desc = Tconstr(p, _, _); _} -> Path.same p Predef.path_float
  | _ -> false

  Determine if a type definition defines a fixed type . ( PW )
let is_fixed_type sd =
  let rec has_row_var sty =
    match sty.ptyp_desc with
      Ptyp_alias (sty, _) -> has_row_var sty
    | Ptyp_class _
    | Ptyp_object (_, Open)
    | Ptyp_variant (_, Open, _)
    | Ptyp_variant (_, Closed, Some _) -> true
    | _ -> false
  in
  match sd.ptype_manifest with
    None -> false
  | Some sty ->
      sd.ptype_kind = Ptype_abstract &&
      sd.ptype_private = Private &&
      has_row_var sty

(* Set the row variable in a fixed type *)
let set_fixed_row env loc p decl =
  let tm =
    match decl.type_manifest with
      None -> assert false
    | Some t -> Ctype.expand_head env t
  in
  let rv =
    match tm.desc with
      Tvariant row ->
        let row = Btype.row_repr row in
        tm.desc <- Tvariant {row with row_fixed = Some Fixed_private};
        if Btype.static_row row then Btype.newgenty Tnil
        else row.row_more
    | Tobject (ty, _) ->
        snd (Ctype.flatten_fields ty)
    | _ ->
        raise (Error (loc, Bad_fixed_type "is not an object or variant"))
  in
  if not (Btype.is_Tvar rv) then
    raise (Error (loc, Bad_fixed_type "has no row variable"));
  rv.desc <- Tconstr (p, decl.type_params, ref Mnil)

  Translate one type declaration

let make_params env params =
  let make_param (sty, v) =
    try
      (transl_type_param env sty, v)
    with Already_bound ->
      raise(Error(sty.ptyp_loc, Repeated_parameter))
  in
    List.map make_param params

let transl_labels env closed lbls =
  assert (lbls <> []);
  let all_labels = ref String.Set.empty in
  List.iter
    (fun {pld_name = {txt=name; loc}} ->
       if String.Set.mem name !all_labels then
         raise(Error(loc, Duplicate_label name));
       all_labels := String.Set.add name !all_labels)
    lbls;
  let mk {pld_name=name;pld_mutable=mut;pld_type=arg;pld_loc=loc;
          pld_attributes=attrs} =
    Builtin_attributes.warning_scope attrs
      (fun () ->
         let arg = Ast_helper.Typ.force_poly arg in
         let cty = transl_simple_type env closed arg in
         {ld_id = Ident.create_local name.txt;
          ld_name = name; ld_mutable = mut;
          ld_type = cty; ld_loc = loc; ld_attributes = attrs}
      )
  in
  let lbls = List.map mk lbls in
  let lbls' =
    List.map
      (fun ld ->
         let ty = ld.ld_type.ctyp_type in
         let ty = match ty.desc with Tpoly(t,[]) -> t | _ -> ty in
         {Types.ld_id = ld.ld_id;
          ld_mutable = ld.ld_mutable;
          ld_type = ty;
          ld_loc = ld.ld_loc;
          ld_attributes = ld.ld_attributes
         }
      )
      lbls in
  lbls, lbls'

let transl_constructor_arguments env closed = function
  | Pcstr_tuple l ->
      let l = List.map (transl_simple_type env closed) l in
      Types.Cstr_tuple (List.map (fun t -> t.ctyp_type) l),
      Cstr_tuple l
  | Pcstr_record l ->
      let lbls, lbls' = transl_labels env closed l in
      Types.Cstr_record lbls',
      Cstr_record lbls

let make_constructor env type_path type_params sargs sret_type =
  match sret_type with
  | None ->
      let args, targs =
        transl_constructor_arguments env true sargs
      in
        targs, None, args, None, type_params
  | Some sret_type ->
  if it 's a generalized constructor we must first narrow and 
          then widen so as to not introduce any new constraints
         then widen so as to not introduce any new constraints *)
      let z = narrow () in
      reset_type_variables ();
      let args, targs =
        transl_constructor_arguments env false sargs
      in
      let tret_type = transl_simple_type env false sret_type in
      let ret_type = tret_type.ctyp_type in
      let params =
        match (Ctype.repr ret_type).desc with
        | Tconstr (p', params, _) when Path.same type_path p' ->
            params
        | _ ->
            raise (Error (sret_type.ptyp_loc, Constraint_failed
                            (ret_type, Ctype.newconstr type_path type_params)))
      in
      widen z;
      targs, Some tret_type, args, Some ret_type, params

(* Check that the variable [id] is present in the [univ] list. *)
let check_type_var loc univ id =
  let f t = (Btype.repr t).id = id in
  if not (List.exists f univ) then raise (Error (loc, Wrong_unboxed_type_float))

(* Check that all the variables found in [ty] are in [univ].
   Because [ty] is the argument to an abstract type, the representation
   of that abstract type could be any subexpression of [ty], in particular
   any type variable present in [ty].
*)
let rec check_unboxed_abstract_arg loc univ ty =
  match ty.desc with
  | Tvar _ -> check_type_var loc univ ty.id
  | Tarrow (_, t1, t2, _)
  | Tfield (_, _, t1, t2) ->
    check_unboxed_abstract_arg loc univ t1;
    check_unboxed_abstract_arg loc univ t2
  | Ttuple args
  | Tconstr (_, args, _)
  | Tpackage (_, _, args) ->
    List.iter (check_unboxed_abstract_arg loc univ) args
  | Tobject (fields, r) ->
    check_unboxed_abstract_arg loc univ fields;
    begin match !r with
    | None -> ()
    | Some (_, args) -> List.iter (check_unboxed_abstract_arg loc univ) args
    end
  | Tnil
  | Tunivar _ -> ()
  | Tlink e -> check_unboxed_abstract_arg loc univ e
  | Tsubst _ -> assert false
  | Tvariant { row_fields; row_more; row_name } ->
    List.iter (check_unboxed_abstract_row_field loc univ) row_fields;
    check_unboxed_abstract_arg loc univ row_more;
    begin match row_name with
    | None -> ()
    | Some (_, args) -> List.iter (check_unboxed_abstract_arg loc univ) args
    end
  | Tpoly (t, _) -> check_unboxed_abstract_arg loc univ t

and check_unboxed_abstract_row_field loc univ (_, field) =
  match field with
  | Rpresent (Some ty) -> check_unboxed_abstract_arg loc univ ty
  | Reither (_, args, _, r) ->
    List.iter (check_unboxed_abstract_arg loc univ) args;
    begin match !r with
    | None -> ()
    | Some f -> check_unboxed_abstract_row_field loc univ ("", f)
    end
  | Rabsent
  | Rpresent None -> ()

let make_effect_constructor env type_param sargs sret =
  let type_path = Predef.path_eff in
  let type_lid = Location.mknoloc (Longident.Lident "eff") in
  let z = narrow () in
  reset_type_variables ();
  let targs = List.map (transl_simple_type env false) sargs in
  let args = List.map (fun cty -> cty.ctyp_type) targs in
  let tret = transl_simple_type env false sret in
  Ctype.unify_var env (Ctype.instance type_param) tret.ctyp_type;
  let ret_type = Ctype.newconstr type_path [tret.ctyp_type] in
  let tret_type =
    { ctyp_desc = Ttyp_constr (type_path, type_lid, targs);
      ctyp_type = ret_type; ctyp_env = env;
      ctyp_loc = {sret.ptyp_loc with Location.loc_ghost = true};
      ctyp_attributes = [] }
  in
  widen z;
  targs, Some tret_type, args, Some ret_type

  Check that the argument to a GADT constructor is compatible with unboxing 
    the type , given the universal parameters of the type .
   the type, given the universal parameters of the type. *)
let rec check_unboxed_gadt_arg loc univ env ty =
  match get_unboxed_type_representation env ty with
  | Some {desc = Tvar _; id} -> check_type_var loc univ id
  | Some {desc = Tarrow _ | Ttuple _ | Tpackage _ | Tobject _ | Tnil
                 | Tvariant _; _} ->
    ()
    (* A comment in [Translcore.transl_exp0] claims the above cannot be
       represented by floats. *)
  | Some {desc = Tconstr (p, args, _); _} ->
    let tydecl = Env.find_type p env in
    assert (not tydecl.type_unboxed.unboxed);
    if tydecl.type_kind = Type_abstract then
      List.iter (check_unboxed_abstract_arg loc univ) args
  | Some {desc = Tfield _ | Tlink _ | Tsubst _; _} -> assert false
  | Some {desc = Tunivar _; _} -> ()
  | Some {desc = Tpoly (t2, _); _} -> check_unboxed_gadt_arg loc univ env t2
  | None -> ()
      (* This case is tricky: the argument is another (or the same) type
         in the same recursive definition. In this case we don't have to
         check because we will also check that other type for correctness. *)

let transl_declaration env sdecl id =
  (* Bind type parameters *)
  reset_type_variables();
  Ctype.begin_def ();
  let tparams = make_params env sdecl.ptype_params in
  let params = List.map (fun (cty, _) -> cty.ctyp_type) tparams in
  let cstrs = List.map
    (fun (sty, sty', loc) ->
      transl_simple_type env false sty,
      transl_simple_type env false sty', loc)
    sdecl.ptype_cstrs
  in
  let raw_status = get_unboxed_from_attributes sdecl in
  if raw_status.unboxed && not raw_status.default then begin
    match sdecl.ptype_kind with
    | Ptype_abstract ->
        raise(Error(sdecl.ptype_loc, Bad_unboxed_attribute
                      "it is abstract"))
    | Ptype_variant [{pcd_args = Pcstr_tuple []; _}] ->
      raise(Error(sdecl.ptype_loc, Bad_unboxed_attribute
                    "its constructor has no argument"))
    | Ptype_variant [{pcd_args = Pcstr_tuple [_]; _}] -> ()
    | Ptype_variant [{pcd_args = Pcstr_tuple _; _}] ->
      raise(Error(sdecl.ptype_loc, Bad_unboxed_attribute
                    "its constructor has more than one argument"))
    | Ptype_variant [{pcd_args = Pcstr_record
                        [{pld_mutable=Immutable; _}]; _}] -> ()
    | Ptype_variant [{pcd_args = Pcstr_record [{pld_mutable=Mutable; _}]; _}] ->
      raise(Error(sdecl.ptype_loc, Bad_unboxed_attribute "it is mutable"))
    | Ptype_variant [{pcd_args = Pcstr_record _; _}] ->
      raise(Error(sdecl.ptype_loc, Bad_unboxed_attribute
                    "its constructor has more than one argument"))
    | Ptype_variant _ ->
      raise(Error(sdecl.ptype_loc, Bad_unboxed_attribute
                    "it has more than one constructor"))
    | Ptype_record [{pld_mutable=Immutable; _}] -> ()
    | Ptype_record [{pld_mutable=Mutable; _}] ->
      raise(Error(sdecl.ptype_loc, Bad_unboxed_attribute
                    "it is mutable"))
    | Ptype_record _ ->
      raise(Error(sdecl.ptype_loc, Bad_unboxed_attribute
                    "it has more than one field"))
    | Ptype_open ->
      raise(Error(sdecl.ptype_loc, Bad_unboxed_attribute
                    "extensible variant types cannot be unboxed"))
  end;
  let unboxed_status =
    match sdecl.ptype_kind with
    | Ptype_variant [{pcd_args = Pcstr_tuple [_]; _}]
      | Ptype_variant [{pcd_args = Pcstr_record
                          [{pld_mutable = Immutable; _}]; _}]
      | Ptype_record [{pld_mutable = Immutable; _}] ->
    raw_status
    | _ -> (* The type is not unboxable, mark it as boxed *)
      unboxed_false_default_false
  in
  let unbox = unboxed_status.unboxed in
  let (tkind, kind) =
    match sdecl.ptype_kind with
      | Ptype_abstract -> Ttype_abstract, Type_abstract
      | Ptype_variant scstrs ->
        if List.exists (fun cstr -> cstr.pcd_res <> None) scstrs then begin
          match cstrs with
            [] -> ()
          | (_,_,loc)::_ ->
              Location.prerr_warning loc Warnings.Constraint_on_gadt
        end;
        let all_constrs = ref String.Set.empty in
        List.iter
          (fun {pcd_name = {txt = name}} ->
            if String.Set.mem name !all_constrs then
              raise(Error(sdecl.ptype_loc, Duplicate_constructor name));
            all_constrs := String.Set.add name !all_constrs)
          scstrs;
        if List.length
            (List.filter (fun cd -> cd.pcd_args <> Pcstr_tuple []) scstrs)
           > (Config.max_tag + 1) then
          raise(Error(sdecl.ptype_loc, Too_many_constructors));
        let make_cstr scstr =
          let name = Ident.create_local scstr.pcd_name.txt in
          let targs, tret_type, args, ret_type, cstr_params =
            make_constructor env (Path.Pident id) params
                             scstr.pcd_args scstr.pcd_res
          in
          if Config.flat_float_array && unbox then begin
  Can not unbox a type when the argument can be both float and 
                non - float because it interferes with the dynamic float array 
                optimization . This can only happen when the type is a GADT 
                and the argument is an existential type variable or an 
                unboxed ( or abstract ) type constructor applied to some 
                existential type variable . Of course we also have to rule 
                out any abstract type constructor applied to anything that 
                might be an existential type variable . 
                There is a difficulty with existential variables created 
                out of thin air ( rather than bound by the declaration ) . 
                See PR#7511 and GPR#1133 for details .
               non-float because it interferes with the dynamic float array
               optimization. This can only happen when the type is a GADT
               and the argument is an existential type variable or an
               unboxed (or abstract) type constructor applied to some
               existential type variable. Of course we also have to rule
               out any abstract type constructor applied to anything that
               might be an existential type variable.
               There is a difficulty with existential variables created
               out of thin air (rather than bound by the declaration).
               See PR#7511 and GPR#1133 for details. *)
            match Datarepr.constructor_existentials args ret_type with
            | _, [] -> ()
            | [argty], _ex ->
                check_unboxed_gadt_arg sdecl.ptype_loc cstr_params env argty
            | _ -> assert false
          end;
          let tcstr =
            { cd_id = name;
              cd_name = scstr.pcd_name;
              cd_args = targs;
              cd_res = tret_type;
              cd_loc = scstr.pcd_loc;
              cd_attributes = scstr.pcd_attributes }
          in
          let cstr =
            { Types.cd_id = name;
              cd_args = args;
              cd_res = ret_type;
              cd_loc = scstr.pcd_loc;
              cd_attributes = scstr.pcd_attributes }
          in
            tcstr, cstr
        in
        let make_cstr scstr =
          Builtin_attributes.warning_scope scstr.pcd_attributes
            (fun () -> make_cstr scstr)
        in
        let tcstrs, cstrs = List.split (List.map make_cstr scstrs) in
          Ttype_variant tcstrs, Type_variant cstrs
      | Ptype_record lbls ->
          let lbls, lbls' = transl_labels env true lbls in
          let rep =
            if unbox then Record_unboxed false
            else if List.for_all (fun l -> is_float env l.Types.ld_type) lbls'
            then Record_float
            else Record_regular
          in
          Ttype_record lbls, Type_record(lbls', rep)
      | Ptype_open -> Ttype_open, Type_open
      in
    let (tman, man) = match sdecl.ptype_manifest with
        None -> None, None
      | Some sty ->
        let no_row = not (is_fixed_type sdecl) in
        let cty = transl_simple_type env no_row sty in
        Some cty, Some cty.ctyp_type
    in
    let decl =
      { type_params = params;
        type_arity = List.length params;
        type_kind = kind;
        type_private = sdecl.ptype_private;
        type_manifest = man;
        type_variance = List.map (fun _ -> Variance.full) params;
        type_is_newtype = false;
        type_expansion_scope = Btype.lowest_level;
        type_loc = sdecl.ptype_loc;
        type_attributes = sdecl.ptype_attributes;
        type_immediate = Unknown;
        type_unboxed = unboxed_status;
      } in

  (* Check constraints *)
    List.iter
      (fun (cty, cty', loc) ->
        let ty = cty.ctyp_type in
        let ty' = cty'.ctyp_type in
        try Ctype.unify env ty ty' with Ctype.Unify tr ->
          raise(Error(loc, Inconsistent_constraint (env, tr))))
      cstrs;
    Ctype.end_def ();
  (* Add abstract row *)
    if is_fixed_type sdecl then begin
      let p, _ =
        try Env.find_type_by_name
              (Longident.Lident(Ident.name id ^ "#row")) env
        with Not_found -> assert false
      in
      set_fixed_row env sdecl.ptype_loc p decl
    end;
  (* Check for cyclic abbreviations *)
    begin match decl.type_manifest with None -> ()
      | Some ty ->
        if Ctype.cyclic_abbrev env id ty then
          raise(Error(sdecl.ptype_loc, Recursive_abbrev sdecl.ptype_name.txt));
    end;
    {
      typ_id = id;
      typ_name = sdecl.ptype_name;
      typ_params = tparams;
      typ_type = decl;
      typ_cstrs = cstrs;
      typ_loc = sdecl.ptype_loc;
      typ_manifest = tman;
      typ_kind = tkind;
      typ_private = sdecl.ptype_private;
      typ_attributes = sdecl.ptype_attributes;
    }

   a type declaration

let generalize_decl decl =
  List.iter Ctype.generalize decl.type_params;
  Btype.iter_type_expr_kind Ctype.generalize decl.type_kind;
  begin match decl.type_manifest with
  | None    -> ()
  | Some ty -> Ctype.generalize ty
  end

(* Check that all constraints are enforced *)

module TypeSet = Btype.TypeSet
module TypeMap = Btype.TypeMap

let rec check_constraints_rec env loc visited ty =
  let ty = Ctype.repr ty in
  if TypeSet.mem ty !visited then () else begin
  visited := TypeSet.add ty !visited;
  match ty.desc with
  | Tconstr (path, args, _) ->
      let args' = List.map (fun _ -> Ctype.newvar ()) args in
      let ty' = Ctype.newconstr path args' in
      begin try Ctype.enforce_constraints env ty'
      with Ctype.Unify _ -> assert false
      | Not_found -> raise (Error(loc, Unavailable_type_constructor path))
      end;
      if not (Ctype.matches env ty ty') then
        raise (Error(loc, Constraint_failed (ty, ty')));
      List.iter (check_constraints_rec env loc visited) args
  | Tpoly (ty, tl) ->
      let _, ty = Ctype.instance_poly false tl ty in
      check_constraints_rec env loc visited ty
  | _ ->
      Btype.iter_type_expr (check_constraints_rec env loc visited) ty
  end

let check_constraints_labels env visited l pl =
  let rec get_loc name = function
      [] -> assert false
    | pld :: tl ->
        if name = pld.pld_name.txt then pld.pld_type.ptyp_loc
        else get_loc name tl
  in
  List.iter
    (fun {Types.ld_id=name; ld_type=ty} ->
       check_constraints_rec env (get_loc (Ident.name name) pl) visited ty)
    l

let check_constraints env sdecl (_, decl) =
  let visited = ref TypeSet.empty in
  begin match decl.type_kind with
  | Type_abstract -> ()
  | Type_variant l ->
      let find_pl = function
          Ptype_variant pl -> pl
        | Ptype_record _ | Ptype_abstract | Ptype_open -> assert false
      in
      let pl = find_pl sdecl.ptype_kind in
      let pl_index =
        let foldf acc x =
          String.Map.add x.pcd_name.txt x acc
        in
        List.fold_left foldf String.Map.empty pl
      in
      List.iter
        (fun {Types.cd_id=name; cd_args; cd_res} ->
          let {pcd_args; pcd_res; _} =
            try String.Map.find (Ident.name name) pl_index
            with Not_found -> assert false in
          begin match cd_args, pcd_args with
          | Cstr_tuple tyl, Pcstr_tuple styl ->
              List.iter2
                (fun sty ty ->
                   check_constraints_rec env sty.ptyp_loc visited ty)
                styl tyl
          | Cstr_record tyl, Pcstr_record styl ->
              check_constraints_labels env visited tyl styl
          | _ -> assert false
          end;
          match pcd_res, cd_res with
          | Some sr, Some r ->
              check_constraints_rec env sr.ptyp_loc visited r
          | _ ->
              () )
        l
  | Type_record (l, _) ->
      let find_pl = function
          Ptype_record pl -> pl
        | Ptype_variant _ | Ptype_abstract | Ptype_open -> assert false
      in
      let pl = find_pl sdecl.ptype_kind in
      check_constraints_labels env visited l pl
  | Type_open -> ()
  end;
  begin match decl.type_manifest with
  | None -> ()
  | Some ty ->
      let sty =
        match sdecl.ptype_manifest with Some sty -> sty | _ -> assert false
      in
      check_constraints_rec env sty.ptyp_loc visited ty
  end

(*
   If both a variant/record definition and a type equation are given,
   need to check that the equation refers to a type of the same kind
   with the same constructors and labels.
*)
let check_coherence env loc dpath decl =
  match decl with
    { type_kind = (Type_variant _ | Type_record _| Type_open);
      type_manifest = Some ty } ->
      begin match (Ctype.repr ty).desc with
        Tconstr(path, args, _) ->
          begin try
            let decl' = Env.find_type path env in
            let err =
              if List.length args <> List.length decl.type_params
              then Some Includecore.Arity
              else if not (Ctype.equal env false args decl.type_params)
              then Some Includecore.Constraint
              else
                Includecore.type_declarations ~loc ~equality:true env
                  ~mark:true
                  (Path.last path)
                  decl'
                  dpath
                  (Subst.type_declaration
                     (Subst.add_type_path dpath path Subst.identity) decl)
            in
            if err <> None then
              raise(Error(loc, Definition_mismatch (ty, err)))
          with Not_found ->
            raise(Error(loc, Unavailable_type_constructor path))
          end
      | _ -> raise(Error(loc, Definition_mismatch (ty, None)))
      end
  | _ -> ()

let check_abbrev env sdecl (id, decl) =
  check_coherence env sdecl.ptype_loc (Path.Pident id) decl

(* Check that recursion is well-founded *)

let check_well_founded env loc path to_check ty =
  let visited = ref TypeMap.empty in
  let rec check ty0 parents ty =
    let ty = Btype.repr ty in
    if TypeSet.mem ty parents then begin
      (*Format.eprintf "@[%a@]@." Printtyp.raw_type_expr ty;*)
      if match ty0.desc with
      | Tconstr (p, _, _) -> Path.same p path
      | _ -> false
      then raise (Error (loc, Recursive_abbrev (Path.name path)))
      else raise (Error (loc, Cycle_in_def (Path.name path, ty0)))
    end;
    let (fini, parents) =
      try
        let prev = TypeMap.find ty !visited in
        if TypeSet.subset parents prev then (true, parents) else
        (false, TypeSet.union parents prev)
      with Not_found ->
        (false, parents)
    in
    if fini then () else
    let rec_ok =
      match ty.desc with
        Tconstr(p,_,_) ->
          !Clflags.recursive_types && Ctype.is_contractive env p
      | Tobject _ | Tvariant _ -> true
      | _ -> !Clflags.recursive_types
    in
    let visited' = TypeMap.add ty parents !visited in
    let arg_exn =
      try
        visited := visited';
        let parents =
          if rec_ok then TypeSet.empty else TypeSet.add ty parents in
        Btype.iter_type_expr (check ty0 parents) ty;
        None
      with e ->
        visited := visited'; Some e
    in
    match ty.desc with
    | Tconstr(p, _, _) when arg_exn <> None || to_check p ->
        if to_check p then Option.iter raise arg_exn
        else Btype.iter_type_expr (check ty0 TypeSet.empty) ty;
        begin try
          let ty' = Ctype.try_expand_once_opt env ty in
          let ty0 = if TypeSet.is_empty parents then ty else ty0 in
          check ty0 (TypeSet.add ty parents) ty'
        with
          Ctype.Cannot_expand -> Option.iter raise arg_exn
        end
    | _ -> Option.iter raise arg_exn
  in
  let snap = Btype.snapshot () in
  try Ctype.wrap_trace_gadt_instances env (check ty TypeSet.empty) ty
  with Ctype.Unify _ ->
    (* Will be detected by check_recursion *)
    Btype.backtrack snap

let check_well_founded_manifest env loc path decl =
  if decl.type_manifest = None then () else
  let args = List.map (fun _ -> Ctype.newvar()) decl.type_params in
  check_well_founded env loc path (Path.same path) (Ctype.newconstr path args)

let check_well_founded_decl env loc path decl to_check =
  let open Btype in
  let it =
    {type_iterators with
     it_type_expr = (fun _ -> check_well_founded env loc path to_check)} in
  it.it_type_declaration it (Ctype.generic_instance_declaration decl)

  Check for ill - defined 

let check_recursion env loc path decl to_check =
  to_check is true for potentially mutually recursive paths . 
      ( path ,  ) is the type declaration to be checked .
     (path, decl) is the type declaration to be checked. *)

  if decl.type_params = [] then () else

  let visited = ref [] in

  let rec check_regular cpath args prev_exp ty =
    let ty = Ctype.repr ty in
    if not (List.memq ty !visited) then begin
      visited := ty :: !visited;
      match ty.desc with
      | Tconstr(path', args', _) ->
          if Path.same path path' then begin
            if not (Ctype.equal env false args args') then
              raise (Error(loc,
                     Parameters_differ(cpath, ty, Ctype.newconstr path args)))
          end
          (* Attempt to expand a type abbreviation if:
              1- [to_check path'] holds
                 (otherwise the expansion cannot involve [path]);
              2- we haven't expanded this type constructor before
                 (otherwise we could loop if [path'] is itself
                 a non-regular abbreviation). *)
          else if to_check path' && not (List.mem path' prev_exp) then begin
            try
              (* Attempt expansion *)
              let (params0, body0, _) = Env.find_type_expansion path' env in
              let (params, body) =
                Ctype.instance_parameterized_type params0 body0 in
              begin
                try List.iter2 (Ctype.unify env) params args'
                with Ctype.Unify _ ->
                  raise (Error(loc, Constraint_failed
                                 (ty, Ctype.newconstr path' params0)));
              end;
              check_regular path' args (path' :: prev_exp) body
            with Not_found -> ()
          end;
          List.iter (check_regular cpath args prev_exp) args'
      | Tpoly (ty, tl) ->
          let (_, ty) = Ctype.instance_poly ~keep_names:true false tl ty in
          check_regular cpath args prev_exp ty
      | _ ->
          Btype.iter_type_expr (check_regular cpath args prev_exp) ty
    end in

  Option.iter
    (fun body ->
      let (args, body) =
        Ctype.instance_parameterized_type
          ~keep_names:true decl.type_params body in
      check_regular path args [] body)
    decl.type_manifest

let check_abbrev_recursion env id_loc_list to_check tdecl =
  let decl = tdecl.typ_type in
  let id = tdecl.typ_id in
  check_recursion env (List.assoc id id_loc_list) (Path.Pident id) decl to_check

(* Check multiple declarations of labels/constructors *)

let check_duplicates sdecl_list =
  let labels = Hashtbl.create 7 and constrs = Hashtbl.create 7 in
  List.iter
    (fun sdecl -> match sdecl.ptype_kind with
      Ptype_variant cl ->
        List.iter
          (fun pcd ->
            try
              let name' = Hashtbl.find constrs pcd.pcd_name.txt in
              Location.prerr_warning pcd.pcd_loc
                (Warnings.Duplicate_definitions
                   ("constructor", pcd.pcd_name.txt, name',
                    sdecl.ptype_name.txt))
            with Not_found ->
              Hashtbl.add constrs pcd.pcd_name.txt sdecl.ptype_name.txt)
          cl
    | Ptype_record fl ->
        List.iter
          (fun {pld_name=cname;pld_loc=loc} ->
            try
              let name' = Hashtbl.find labels cname.txt in
              Location.prerr_warning loc
                (Warnings.Duplicate_definitions
                   ("label", cname.txt, name', sdecl.ptype_name.txt))
            with Not_found -> Hashtbl.add labels cname.txt sdecl.ptype_name.txt)
          fl
    | Ptype_abstract -> ()
    | Ptype_open -> ())
    sdecl_list

  Force recursion to go through i d for private types
let name_recursion sdecl id decl =
  match decl with
  | { type_kind = Type_abstract;
      type_manifest = Some ty;
      type_private = Private; } when is_fixed_type sdecl ->
    let ty = Ctype.repr ty in
    let ty' = Btype.newty2 ty.level ty.desc in
    if Ctype.deep_occur ty ty' then
      let td = Tconstr(Path.Pident id, decl.type_params, ref Mnil) in
      Btype.link_type ty (Btype.newty2 ty.level td);
      {decl with type_manifest = Some ty'}
    else decl
  | _ -> decl

let name_recursion_decls sdecls decls =
  List.map2 (fun sdecl (id, decl) -> (id, name_recursion sdecl id decl))
    sdecls decls

(* Warn on definitions of type "type foo = ()" which redefine a different unit
   type and are likely a mistake. *)
let check_redefined_unit (td: Parsetree.type_declaration) =
  let open Parsetree in
  let is_unit_constructor cd = cd.pcd_name.txt = "()" in
  match td with
  | { ptype_name = { txt = name };
      ptype_manifest = None;
      ptype_kind = Ptype_variant [ cd ] }
    when is_unit_constructor cd ->
      Location.prerr_warning td.ptype_loc (Warnings.Redefining_unit name)
  | _ ->
      ()

let add_types_to_env decls env =
  List.fold_right
    (fun (id, decl) env -> add_type ~check:true id decl env)
    decls env

(* Translate a set of type declarations, mutually recursive or not *)
let transl_type_decl env rec_flag sdecl_list =
  List.iter check_redefined_unit sdecl_list;
  (* Add dummy types for fixed rows *)
  let fixed_types = List.filter is_fixed_type sdecl_list in
  let sdecl_list =
    List.map
      (fun sdecl ->
         let ptype_name =
           let loc = { sdecl.ptype_name.loc with Location.loc_ghost = true } in
           mkloc (sdecl.ptype_name.txt ^"#row") loc
         in
         let ptype_kind = Ptype_abstract in
         let ptype_manifest = None in
         let ptype_loc = { sdecl.ptype_loc with Location.loc_ghost = true } in
        {sdecl with
           ptype_name; ptype_kind; ptype_manifest; ptype_loc })
      fixed_types
    @ sdecl_list
  in

  (* Create identifiers. *)
  let scope = Ctype.create_scope () in
  let id_list =
    List.map (fun sdecl -> Ident.create_scoped ~scope sdecl.ptype_name.txt)
      sdecl_list
  in
  Ctype.begin_def();
  (* Enter types. *)
  let temp_env =
    List.fold_left2 (enter_type rec_flag) env sdecl_list id_list in
  (* Translate each declaration. *)
  let current_slot = ref None in
  let warn_unused = Warnings.is_active (Warnings.Unused_type_declaration "") in
  let id_slots id =
    match rec_flag with
    | Asttypes.Recursive when warn_unused ->
        (* See typecore.ml for a description of the algorithm used
             to detect unused declarations in a set of recursive definitions. *)
        let slot = ref [] in
        let td = Env.find_type (Path.Pident id) temp_env in
        let name = Ident.name id in
        Env.set_type_used_callback
          name td
          (fun old_callback ->
             match !current_slot with
             | Some slot -> slot := (name, td) :: !slot
             | None ->
                 List.iter (fun (name, d) -> Env.mark_type_used name d)
                   (get_ref slot);
                 old_callback ()
          );
        id, Some slot
    | Asttypes.Recursive | Asttypes.Nonrecursive ->
        id, None
  in
  let transl_declaration name_sdecl (id, slot) =
    current_slot := slot;
    Builtin_attributes.warning_scope
      name_sdecl.ptype_attributes
      (fun () -> transl_declaration temp_env name_sdecl id)
  in
  let tdecls =
    List.map2 transl_declaration sdecl_list (List.map id_slots id_list) in
  let decls =
    List.map (fun tdecl -> (tdecl.typ_id, tdecl.typ_type)) tdecls in
  current_slot := None;
  (* Check for duplicates *)
  check_duplicates sdecl_list;
  (* Build the final env. *)
  let new_env = add_types_to_env decls env in
  (* Update stubs *)
  begin match rec_flag with
    | Asttypes.Nonrecursive -> ()
    | Asttypes.Recursive ->
      List.iter2
        (fun id sdecl -> update_type temp_env new_env id sdecl.ptype_loc)
        id_list sdecl_list
  end;
  Generalize type declarations .
  Ctype.end_def();
  List.iter (fun (_, decl) -> generalize_decl decl) decls;
  Check for ill - formed 
  let id_loc_list =
    List.map2 (fun id sdecl -> (id, sdecl.ptype_loc))
      id_list sdecl_list
  in
  List.iter (fun (id, decl) ->
    check_well_founded_manifest new_env (List.assoc id id_loc_list)
      (Path.Pident id) decl)
    decls;
  let to_check =
    function Path.Pident id -> List.mem_assoc id id_loc_list | _ -> false in
  List.iter (fun (id, decl) ->
    check_well_founded_decl new_env (List.assoc id id_loc_list) (Path.Pident id)
      decl to_check)
    decls;
  List.iter (check_abbrev_recursion new_env id_loc_list to_check) tdecls;
  (* Check that all type variables are closed *)
  List.iter2
    (fun sdecl tdecl ->
      let decl = tdecl.typ_type in
       match Ctype.closed_type_decl decl with
         Some ty -> raise(Error(sdecl.ptype_loc, Unbound_type_var(ty,decl)))
       | None   -> ())
    sdecl_list tdecls;
  (* Check that constraints are enforced *)
  List.iter2 (check_constraints new_env) sdecl_list decls;
  (* Add type properties to declarations *)
  let decls =
    try
      decls
      |> name_recursion_decls sdecl_list
      |> Typedecl_variance.update_decls env sdecl_list
      |> Typedecl_immediacy.update_decls env
    with
    | Typedecl_variance.Error (loc, err) -> raise (Error (loc, Variance err))
    | Typedecl_immediacy.Error (loc, err) -> raise (Error (loc, Immediacy err))
  in
  (* Compute the final environment with variance and immediacy *)
  let final_env = add_types_to_env decls env in
  (* Check re-exportation *)
  List.iter2 (check_abbrev final_env) sdecl_list decls;
  (* Keep original declaration *)
  let final_decls =
    List.map2
      (fun tdecl (_id2, decl) ->
        { tdecl with typ_type = decl }
      ) tdecls decls
  in
  (* Done *)
  (final_decls, final_env)

(* Translating type extensions *)
let transl_extension_rebind env type_path type_params typext_params priv lid =
  let usage = if priv = Public then Env.Positive else Env.Privatize in
  let cdescr = Env.lookup_constructor ~loc:lid.loc usage lid.txt env in
  let (args, cstr_res) = Ctype.instance_constructor cdescr in
  let res, ret_type =
    if cdescr.cstr_generalized then
      let params = Ctype.instance_list type_params in
      let res = Ctype.newconstr type_path params in
      let ret_type = Some (Ctype.newconstr type_path params) in
        res, ret_type
    else (Ctype.newconstr type_path typext_params), None
  in
  begin
    try
      Ctype.unify env cstr_res res
    with Ctype.Unify trace ->
      raise (Error(lid.loc,
               Rebind_wrong_type(lid.txt, env, trace)))
  end;
  (* Remove "_" names from parameters used in the constructor *)
  if not cdescr.cstr_generalized then begin
    let vars =
      Ctype.free_variables (Btype.newgenty (Ttuple args))
    in
      List.iter
        (function {desc = Tvar (Some "_")} as ty ->
                    if List.memq ty vars then ty.desc <- Tvar None
                  | _ -> ())
        typext_params
  end;
  (* Ensure that constructor's type matches the type being extended *)
  let cstr_type_path, cstr_type_params =
    match cdescr.cstr_res.desc with
      Tconstr (p, _, _) ->
        let decl = Env.find_type p env in
          p, decl.type_params
    | _ -> assert false
  in
  let cstr_types =
    (Btype.newgenty
       (Tconstr(cstr_type_path, cstr_type_params, ref Mnil)))
    :: cstr_type_params
  in
  let ext_types =
    (Btype.newgenty
       (Tconstr(type_path, type_params, ref Mnil)))
    :: type_params
  in
  if not (Ctype.equal env true cstr_types ext_types) then
    raise (Error(lid.loc,
                 Rebind_mismatch(lid.txt, cstr_type_path, type_path)));
  (* Disallow rebinding private constructors to non-private *)
  begin
    match cdescr.cstr_private, priv with
      Private, Public ->
        raise (Error(lid.loc, Rebind_private lid.txt))
    | _ -> ()
  end;
  let path =
    match cdescr.cstr_tag with
      Cstr_extension(path, _) -> path
    | _ -> assert false
  in
    args, ret_type, Text_rebind(path, lid)

let transl_extension_constructor env type_path type_params
                                 typext_params priv sext =
  let scope = Ctype.create_scope () in
  let id = Ident.create_scoped ~scope sext.pext_name.txt in
  let args, ret_type, kind =
    match sext.pext_kind with
      Pext_decl(sargs, sret_type) ->
        let targs, tret_type, args, ret_type, _ =
          make_constructor env type_path typext_params
            sargs sret_type
        in
          args, ret_type, Text_decl(targs, tret_type)
    | Pext_rebind lid ->
        let usage = if priv = Public then Env.Positive else Env.Privatize in
        let cdescr = Env.lookup_constructor ~loc:lid.loc usage lid.txt env in
        let (args, cstr_res) = Ctype.instance_constructor cdescr in
        let res, ret_type =
          if cdescr.cstr_generalized then
            let params = Ctype.instance_list type_params in
            let res = Ctype.newconstr type_path params in
            let ret_type = Some (Ctype.newconstr type_path params) in
              res, ret_type
          else (Ctype.newconstr type_path typext_params), None
        in
        begin
          try
            Ctype.unify env cstr_res res
          with Ctype.Unify trace ->
            raise (Error(lid.loc,
                     Rebind_wrong_type(lid.txt, env, trace)))
        end;
        (* Remove "_" names from parameters used in the constructor *)
        if not cdescr.cstr_generalized then begin
          let vars =
            Ctype.free_variables (Btype.newgenty (Ttuple args))
          in
            List.iter
              (function {desc = Tvar (Some "_")} as ty ->
                          if List.memq ty vars then ty.desc <- Tvar None
                        | _ -> ())
              typext_params
        end;
        (* Ensure that constructor's type matches the type being extended *)
        let cstr_type_path, cstr_type_params =
          match cdescr.cstr_res.desc with
            Tconstr (p, _, _) ->
              let decl = Env.find_type p env in
                p, decl.type_params
          | _ -> assert false
        in
        let cstr_types =
          (Btype.newgenty
             (Tconstr(cstr_type_path, cstr_type_params, ref Mnil)))
          :: cstr_type_params
        in
        let ext_types =
          (Btype.newgenty
             (Tconstr(type_path, type_params, ref Mnil)))
          :: type_params
        in
        if not (Ctype.equal env true cstr_types ext_types) then
          raise (Error(lid.loc,
                       Rebind_mismatch(lid.txt, cstr_type_path, type_path)));
        (* Disallow rebinding private constructors to non-private *)
        begin
          match cdescr.cstr_private, priv with
            Private, Public ->
              raise (Error(lid.loc, Rebind_private lid.txt))
          | _ -> ()
        end;
        let path =
          match cdescr.cstr_tag with
            Cstr_extension(path, _) -> path
          | _ -> assert false
        in
        let args =
          match cdescr.cstr_inlined with
          | None ->
              Types.Cstr_tuple args
          | Some decl ->
              let tl =
                match args with
                | [ {desc=Tconstr(_, tl, _)} ] -> tl
                | _ -> assert false
              in
              let decl = Ctype.instance_declaration decl in
              assert (List.length decl.type_params = List.length tl);
              List.iter2 (Ctype.unify env) decl.type_params tl;
              let lbls =
                match decl.type_kind with
                | Type_record (lbls, Record_extension _) -> lbls
                | _ -> assert false
              in
              Types.Cstr_record lbls
        in
        args, ret_type, Text_rebind(path, lid)
  in
  let ext =
    { ext_type_path = type_path;
      ext_type_params = typext_params;
      ext_args = args;
      ext_ret_type = ret_type;
      ext_private = priv;
      Types.ext_loc = sext.pext_loc;
      Types.ext_attributes = sext.pext_attributes; }
  in
    { ext_id = id;
      ext_name = sext.pext_name;
      ext_type = ext;
      ext_kind = kind;
      Typedtree.ext_loc = sext.pext_loc;
      Typedtree.ext_attributes = sext.pext_attributes; }

let transl_extension_constructor env type_path type_params
    typext_params priv sext =
  Builtin_attributes.warning_scope sext.pext_attributes
    (fun () -> transl_extension_constructor env type_path type_params
        typext_params priv sext)

let transl_type_extension extend env loc styext =
  reset_type_variables();
  Ctype.begin_def();
  let type_path, type_decl =
    let lid = styext.ptyext_path in
    Env.lookup_type ~loc:lid.loc lid.txt env
  in
  begin
    match type_decl.type_kind with
    | Type_open -> begin
        match type_decl.type_private with
        | Private when extend -> begin
            match
              List.find
                (function {pext_kind = Pext_decl _} -> true
                        | {pext_kind = Pext_rebind _} -> false)
                styext.ptyext_constructors
            with
            | {pext_loc} ->
                raise (Error(pext_loc, Cannot_extend_private_type type_path))
            | exception Not_found -> ()
          end
        | _ -> ()
      end
    | _ ->
        raise (Error(loc, Not_extensible_type type_path))
  end;
  let type_variance =
    List.map (fun v ->
                let (co, cn) = Variance.get_upper v in
                  (not cn, not co, false))
             type_decl.type_variance
  in
  let err =
    if type_decl.type_arity <> List.length styext.ptyext_params then
      Some Includecore.Arity
    else
      if List.for_all2
           (fun (c1, n1, _) (c2, n2, _) -> (not c2 || c1) && (not n2 || n1))
           type_variance
           (Typedecl_variance.variance_of_params styext.ptyext_params)
      then None else Some Includecore.Variance
  in
  begin match err with
  | None -> ()
  | Some err -> raise (Error(loc, Extension_mismatch (type_path, err)))
  end;
  let ttype_params = make_params env styext.ptyext_params in
  let type_params = List.map (fun (cty, _) -> cty.ctyp_type) ttype_params in
  List.iter2 (Ctype.unify_var env)
    (Ctype.instance_list type_decl.type_params)
    type_params;
  let constructors =
    List.map (transl_extension_constructor env type_path
               type_decl.type_params type_params styext.ptyext_private)
      styext.ptyext_constructors
  in
  Ctype.end_def();
   types
  List.iter Ctype.generalize type_params;
  List.iter
    (fun ext ->
       Btype.iter_type_expr_cstr_args Ctype.generalize ext.ext_type.ext_args;
       Option.iter Ctype.generalize ext.ext_type.ext_ret_type)
    constructors;
  (* Check that all type variables are closed *)
  List.iter
    (fun ext ->
       match Ctype.closed_extension_constructor ext.ext_type with
         Some ty ->
           raise(Error(ext.ext_loc, Unbound_type_var_ext(ty, ext.ext_type)))
       | None -> ())
    constructors;
  (* Check variances are correct *)
  List.iter
    (fun ext->
       (* Note that [loc] here is distinct from [type_decl.type_loc], which
          makes the [loc] parameter to this function useful. [loc] is the
          location of the extension, while [type_decl] points to the original
          type declaration being extended. *)
       try Typedecl_variance.check_variance_extension
             env type_decl ext (type_variance, loc)
       with Typedecl_variance.Error (loc, err) ->
         raise (Error (loc, Variance err)))
    constructors;
  (* Add extension constructors to the environment *)
  let newenv =
    List.fold_left
      (fun env ext ->
         Env.add_extension ~check:true ext.ext_id ext.ext_type env)
      env constructors
  in
  let tyext =
    { tyext_path = type_path;
      tyext_txt = styext.ptyext_path;
      tyext_params = ttype_params;
      tyext_constructors = constructors;
      tyext_private = styext.ptyext_private;
      tyext_loc = styext.ptyext_loc;
      tyext_attributes = styext.ptyext_attributes; }
  in
    (tyext, newenv)

let transl_type_extension extend env loc styext =
  Builtin_attributes.warning_scope styext.ptyext_attributes
    (fun () -> transl_type_extension extend env loc styext)

(* Translate an exception declaration *)
let transl_exception env sext =
  reset_type_variables();
  Ctype.begin_def();
  let ext =
    transl_extension_constructor env
      Predef.path_exn [] [] Asttypes.Public sext
  in
  Ctype.end_def();
   types
  Btype.iter_type_expr_cstr_args Ctype.generalize ext.ext_type.ext_args;
  Option.iter Ctype.generalize ext.ext_type.ext_ret_type;
  (* Check that all type variables are closed *)
  begin match Ctype.closed_extension_constructor ext.ext_type with
    Some ty ->
      raise (Error(ext.ext_loc, Unbound_type_var_ext(ty, ext.ext_type)))
  | None -> ()
  end;
  let newenv = Env.add_extension ~check:true ext.ext_id ext.ext_type env in
  ext, newenv

let transl_type_exception env t =
  Builtin_attributes.check_no_alert t.ptyexn_attributes;
  let contructor, newenv =
    Builtin_attributes.warning_scope t.ptyexn_attributes
      (fun () ->
         transl_exception env t.ptyexn_constructor
      )
  in
  {tyexn_constructor = contructor;
   tyexn_loc = t.ptyexn_loc;
   tyexn_attributes = t.ptyexn_attributes}, newenv


(* Translate an effect declaration *)
let transl_effect env seff =
  reset_type_variables();
  Ctype.begin_def();
  let type_decl = Env.find_type Predef.path_eff env in
  let type_param =
    match type_decl.type_params with
    | [type_param] -> type_param
    | _ -> assert false
  in
  let typext_param = Ctype.new_global_var () in
  let id = Ident.create_local seff.peff_name.txt in
  let args, ret_type, kind =
    match seff.peff_kind with
    | Peff_decl(sargs, sret) ->
        let targs, tret_type, args, ret_type =
          make_effect_constructor env type_param sargs sret
        in
          args, ret_type, Text_decl(Cstr_tuple targs, tret_type)
    | Peff_rebind lid ->
        transl_extension_rebind env Predef.path_eff
          type_decl.type_params [typext_param] Asttypes.Public lid
  in
  let ext =
    { ext_type_path = Predef.path_eff;
      ext_type_params = [typext_param];
      ext_args = Cstr_tuple args;
      ext_ret_type = ret_type;
      ext_private = Asttypes.Public;
      Types.ext_loc = seff.peff_loc;
      Types.ext_attributes = seff.peff_attributes; }
  in
  let text =
    { ext_id = id;
      ext_name = seff.peff_name;
      ext_type = ext;
      ext_kind = kind;
      Typedtree.ext_loc = seff.peff_loc;
      Typedtree.ext_attributes = seff.peff_attributes; }
  in
  Ctype.end_def();
   types
  Btype.iter_type_expr_cstr_args Ctype.generalize ext.ext_args;
  Option.iter Ctype.generalize ext.ext_ret_type;
  (* Check that all type variable are closed *)
  begin match Ctype.closed_extension_constructor ext with
    Some ty ->
      raise (Error(ext.ext_loc, Unbound_type_var_ext(ty, ext)))
  | None -> ()
  end;
  let newenv = Env.add_extension ~check:true text.ext_id ext env in
    text, newenv

type native_repr_attribute =
  | Native_repr_attr_absent
  | Native_repr_attr_present of native_repr_kind

let get_native_repr_attribute attrs ~global_repr =
  match
    Attr_helper.get_no_payload_attribute ["unboxed"; "ocaml.unboxed"]  attrs,
    Attr_helper.get_no_payload_attribute ["untagged"; "ocaml.untagged"] attrs,
    global_repr
  with
  | None, None, None -> Native_repr_attr_absent
  | None, None, Some repr -> Native_repr_attr_present repr
  | Some _, None, None -> Native_repr_attr_present Unboxed
  | None, Some _, None -> Native_repr_attr_present Untagged
  | Some { Location.loc }, _, _
  | _, Some { Location.loc }, _ ->
    raise (Error (loc, Multiple_native_repr_attributes))

let native_repr_of_type env kind ty =
  match kind, (Ctype.expand_head_opt env ty).desc with
  | Untagged, Tconstr (path, _, _) when Path.same path Predef.path_int ->
    Some Untagged_int
  | Unboxed, Tconstr (path, _, _) when Path.same path Predef.path_float ->
    Some Unboxed_float
  | Unboxed, Tconstr (path, _, _) when Path.same path Predef.path_int32 ->
    Some (Unboxed_integer Pint32)
  | Unboxed, Tconstr (path, _, _) when Path.same path Predef.path_int64 ->
    Some (Unboxed_integer Pint64)
  | Unboxed, Tconstr (path, _, _) when Path.same path Predef.path_nativeint ->
    Some (Unboxed_integer Pnativeint)
  | _ ->
    None

  Raises an error when [ core_type ] contains an [ @unboxed ] or [ @untagged ] 
    attribute in a strict sub - term .
   attribute in a strict sub-term. *)
let error_if_has_deep_native_repr_attributes core_type =
  let open Ast_iterator in
  let this_iterator =
    { default_iterator with typ = fun iterator core_type ->
      begin
        match
          get_native_repr_attribute core_type.ptyp_attributes ~global_repr:None
        with
        | Native_repr_attr_present kind ->
           raise (Error (core_type.ptyp_loc,
                         Deep_unbox_or_untag_attribute kind))
        | Native_repr_attr_absent -> ()
      end;
      default_iterator.typ iterator core_type }
  in
  default_iterator.typ this_iterator core_type

let make_native_repr env core_type ty ~global_repr =
  error_if_has_deep_native_repr_attributes core_type;
  match get_native_repr_attribute core_type.ptyp_attributes ~global_repr with
  | Native_repr_attr_absent ->
    Same_as_ocaml_repr
  | Native_repr_attr_present kind ->
    begin match native_repr_of_type env kind ty with
    | None ->
      raise (Error (core_type.ptyp_loc, Cannot_unbox_or_untag_type kind))
    | Some repr -> repr
    end

let rec parse_native_repr_attributes env core_type ty ~global_repr =
  match core_type.ptyp_desc, (Ctype.repr ty).desc,
    get_native_repr_attribute core_type.ptyp_attributes ~global_repr:None
  with
  | Ptyp_arrow _, Tarrow _, Native_repr_attr_present kind  ->
    raise (Error (core_type.ptyp_loc, Cannot_unbox_or_untag_type kind))
  | Ptyp_arrow (_, ct1, ct2), Tarrow (_, t1, t2, _), _ ->
    let repr_arg = make_native_repr env ct1 t1 ~global_repr in
    let repr_args, repr_res =
      parse_native_repr_attributes env ct2 t2 ~global_repr
    in
    (repr_arg :: repr_args, repr_res)
  | Ptyp_arrow _, _, _ | _, Tarrow _, _ -> assert false
  | _ -> ([], make_native_repr env core_type ty ~global_repr)


let check_unboxable env loc ty =
  let check_type acc ty : Path.Set.t =
    let ty = Ctype.repr (Ctype.expand_head_opt env ty) in
    try match ty.desc with
      | Tconstr (p, _, _) ->
        let tydecl = Env.find_type p env in
        if tydecl.type_unboxed.default then
          Path.Set.add p acc
        else acc
      | _ -> acc
    with Not_found -> acc
  in
  let all_unboxable_types = Btype.fold_type_expr check_type Path.Set.empty ty in
  Path.Set.fold
    (fun p () ->
       Location.prerr_warning loc
         (Warnings.Unboxable_type_in_prim_decl (Path.name p))
    )
    all_unboxable_types
    ()

(* Translate a value declaration *)
let transl_value_decl env loc valdecl =
  let cty = Typetexp.transl_type_scheme env valdecl.pval_type in
  let ty = cty.ctyp_type in
  let v =
  match valdecl.pval_prim with
    [] when Env.is_in_signature env ->
      { val_type = ty; val_kind = Val_reg; Types.val_loc = loc;
        val_attributes = valdecl.pval_attributes }
  | [] ->
      raise (Error(valdecl.pval_loc, Val_in_structure))
  | _ ->
      let global_repr =
        match
          get_native_repr_attribute valdecl.pval_attributes ~global_repr:None
        with
        | Native_repr_attr_present repr -> Some repr
        | Native_repr_attr_absent -> None
      in
      let native_repr_args, native_repr_res =
        parse_native_repr_attributes env valdecl.pval_type ty ~global_repr
      in
      let prim =
        Primitive.parse_declaration valdecl
          ~native_repr_args
          ~native_repr_res
      in
      if prim.prim_arity = 0 &&
         (prim.prim_name = "" || prim.prim_name.[0] <> '%') then
        raise(Error(valdecl.pval_type.ptyp_loc, Null_arity_external));
      if !Clflags.native_code
      && prim.prim_arity > 5
      && prim.prim_native_name = ""
      then raise(Error(valdecl.pval_type.ptyp_loc, Missing_native_external));
      check_unboxable env loc ty;
      { val_type = ty; val_kind = Val_prim prim; Types.val_loc = loc;
        val_attributes = valdecl.pval_attributes }
  in
  let (id, newenv) =
    Env.enter_value valdecl.pval_name.txt v env
      ~check:(fun s -> Warnings.Unused_value_declaration s)
  in
  let desc =
    {
     val_id = id;
     val_name = valdecl.pval_name;
     val_desc = cty; val_val = v;
     val_prim = valdecl.pval_prim;
     val_loc = valdecl.pval_loc;
     val_attributes = valdecl.pval_attributes;
    }
  in
  desc, newenv

let transl_value_decl env loc valdecl =
  Builtin_attributes.warning_scope valdecl.pval_attributes
    (fun () -> transl_value_decl env loc valdecl)

  Translate a " with " constraint -- much simplified version of 
     transl_type_decl .
    transl_type_decl. *)
let transl_with_constraint env id row_path orig_decl sdecl =
  Env.mark_type_used (Ident.name id) orig_decl;
  reset_type_variables();
  Ctype.begin_def();
  let tparams = make_params env sdecl.ptype_params in
  let params = List.map (fun (cty, _) -> cty.ctyp_type) tparams in
  let orig_decl = Ctype.instance_declaration orig_decl in
  let arity_ok = List.length params = orig_decl.type_arity in
  if arity_ok then
    List.iter2 (Ctype.unify_var env) params orig_decl.type_params;
  let constraints = List.map
    (function (ty, ty', loc) ->
       try
         let cty = transl_simple_type env false ty in
         let cty' = transl_simple_type env false ty' in
         let ty = cty.ctyp_type in
         let ty' = cty'.ctyp_type in
         Ctype.unify env ty ty';
         (cty, cty', loc)
       with Ctype.Unify tr ->
         raise(Error(loc, Inconsistent_constraint (env, tr))))
    sdecl.ptype_cstrs
  in
  let no_row = not (is_fixed_type sdecl) in
  let (tman, man) =  match sdecl.ptype_manifest with
      None -> None, None
    | Some sty ->
        let cty = transl_simple_type env no_row sty in
        Some cty, Some cty.ctyp_type
  in
  let priv =
    if sdecl.ptype_private = Private then Private else
    if arity_ok && orig_decl.type_kind <> Type_abstract
    then orig_decl.type_private else sdecl.ptype_private
  in
  if arity_ok && orig_decl.type_kind <> Type_abstract
  && sdecl.ptype_private = Private then
    Location.deprecated sdecl.ptype_loc "spurious use of private";
  let type_kind, type_unboxed =
    if arity_ok && man <> None then
      orig_decl.type_kind, orig_decl.type_unboxed
    else
      Type_abstract, unboxed_false_default_false
  in
  let decl =
    { type_params = params;
      type_arity = List.length params;
      type_kind;
      type_private = priv;
      type_manifest = man;
      type_variance = [];
      type_is_newtype = false;
      type_expansion_scope = Btype.lowest_level;
      type_loc = sdecl.ptype_loc;
      type_attributes = sdecl.ptype_attributes;
      type_immediate = Unknown;
      type_unboxed;
    }
  in
  begin match row_path with None -> ()
  | Some p -> set_fixed_row env sdecl.ptype_loc p decl
  end;
  begin match Ctype.closed_type_decl decl with None -> ()
  | Some ty -> raise(Error(sdecl.ptype_loc, Unbound_type_var(ty,decl)))
  end;
  let decl = name_recursion sdecl id decl in
  let type_variance =
    try Typedecl_variance.compute_decl
          env ~check:true decl (Typedecl_variance.variance_of_sdecl sdecl)
    with Typedecl_variance.Error (loc, err) ->
      raise (Error (loc, Variance err)) in
  let type_immediate =
    (* Typedecl_immediacy.compute_decl never raises *)
    Typedecl_immediacy.compute_decl env decl in
  let decl = {decl with type_variance; type_immediate} in
  Ctype.end_def();
  generalize_decl decl;
  {
    typ_id = id;
    typ_name = sdecl.ptype_name;
    typ_params = tparams;
    typ_type = decl;
    typ_cstrs = constraints;
    typ_loc = sdecl.ptype_loc;
    typ_manifest = tman;
    typ_kind = Ttype_abstract;
    typ_private = sdecl.ptype_private;
    typ_attributes = sdecl.ptype_attributes;
  }

(* Approximate a type declaration: just make all types abstract *)

let abstract_type_decl arity =
  let rec make_params n =
    if n <= 0 then [] else Ctype.newvar() :: make_params (n-1) in
  Ctype.begin_def();
  let decl =
    { type_params = make_params arity;
      type_arity = arity;
      type_kind = Type_abstract;
      type_private = Public;
      type_manifest = None;
      type_variance = replicate_list Variance.full arity;
      type_is_newtype = false;
      type_expansion_scope = Btype.lowest_level;
      type_loc = Location.none;
      type_attributes = [];
      type_immediate = Unknown;
      type_unboxed = unboxed_false_default_false;
     } in
  Ctype.end_def();
  generalize_decl decl;
  decl

let approx_type_decl sdecl_list =
  let scope = Ctype.create_scope () in
  List.map
    (fun sdecl ->
      (Ident.create_scoped ~scope sdecl.ptype_name.txt,
       abstract_type_decl (List.length sdecl.ptype_params)))
    sdecl_list

(* Variant of check_abbrev_recursion to check the well-formedness
   conditions on type abbreviations defined within recursive modules. *)

let check_recmod_typedecl env loc recmod_ids path decl =
  recmod_ids is the list of recursively - defined module idents . 
      ( path ,  ) is the type declaration to be checked .
     (path, decl) is the type declaration to be checked. *)
  let to_check path = Path.exists_free recmod_ids path in
  check_well_founded_decl env loc path decl to_check;
  check_recursion env loc path decl to_check;
  (* additionally check coherece, as one might build an incoherent signature,
     and use it to build an incoherent module, cf. #7851 *)
  check_coherence env loc path decl


(**** Error report ****)

open Format

let explain_unbound_gen ppf tv tl typ kwd pr =
  try
    let ti = List.find (fun ti -> Ctype.deep_occur tv (typ ti)) tl in
    let ty0 = (* Hack to force aliasing when needed *)
      Btype.newgenty (Tobject(tv, ref None)) in
    Printtyp.reset_and_mark_loops_list [typ ti; ty0];
    fprintf ppf
      ".@.@[<hov2>In %s@ %a@;<1 -2>the variable %a is unbound@]"
      kwd pr ti Printtyp.marked_type_expr tv
  with Not_found -> ()

let explain_unbound ppf tv tl typ kwd lab =
  explain_unbound_gen ppf tv tl typ kwd
    (fun ppf ti ->
       fprintf ppf "%s%a" (lab ti) Printtyp.marked_type_expr (typ ti)
    )

let explain_unbound_single ppf tv ty =
  let trivial ty =
    explain_unbound ppf tv [ty] (fun t -> t) "type" (fun _ -> "") in
  match (Ctype.repr ty).desc with
    Tobject(fi,_) ->
      let (tl, rv) = Ctype.flatten_fields fi in
      if rv == tv then trivial ty else
      explain_unbound ppf tv tl (fun (_,_,t) -> t)
        "method" (fun (lab,_,_) -> lab ^ ": ")
  | Tvariant row ->
      let row = Btype.row_repr row in
      if row.row_more == tv then trivial ty else
      explain_unbound ppf tv row.row_fields
        (fun (_l,f) -> match Btype.row_field_repr f with
          Rpresent (Some t) -> t
        | Reither (_,[t],_,_) -> t
        | Reither (_,tl,_,_) -> Btype.newgenty (Ttuple tl)
        | _ -> Btype.newgenty (Ttuple[]))
        "case" (fun (lab,_) -> "`" ^ lab ^ " of ")
  | _ -> trivial ty


let tys_of_constr_args = function
  | Types.Cstr_tuple tl -> tl
  | Types.Cstr_record lbls -> List.map (fun l -> l.Types.ld_type) lbls

let report_error ppf = function
  | Repeated_parameter ->
      fprintf ppf "A type parameter occurs several times"
  | Duplicate_constructor s ->
      fprintf ppf "Two constructors are named %s" s
  | Too_many_constructors ->
      fprintf ppf
        "@[Too many non-constant constructors@ -- maximum is %i %s@]"
        (Config.max_tag + 1) "non-constant constructors"
  | Duplicate_label s ->
      fprintf ppf "Two labels are named %s" s
  | Recursive_abbrev s ->
      fprintf ppf "The type abbreviation %s is cyclic" s
  | Cycle_in_def (s, ty) ->
      fprintf ppf "@[<v>The definition of %s contains a cycle:@ %a@]"
        s Printtyp.type_expr ty
  | Definition_mismatch (ty, None) ->
      fprintf ppf "@[<v>@[<hov>%s@ %s@;<1 2>%a@]@]"
        "This variant or record definition" "does not match that of type"
        Printtyp.type_expr ty
  | Definition_mismatch (ty, Some err) ->
      fprintf ppf "@[<v>@[<hov>%s@ %s@;<1 2>%a@]%a@]"
        "This variant or record definition" "does not match that of type"
        Printtyp.type_expr ty
        (Includecore.report_type_mismatch "the original" "this" "definition")
        err
  | Constraint_failed (ty, ty') ->
      Printtyp.reset_and_mark_loops ty;
      Printtyp.mark_loops ty';
      Printtyp.Naming_context.reset ();
      fprintf ppf "@[%s@ @[<hv>Type@ %a@ should be an instance of@ %a@]@]"
        "Constraints are not satisfied in this type."
        !Oprint.out_type (Printtyp.tree_of_typexp false ty)
        !Oprint.out_type (Printtyp.tree_of_typexp false ty')
  | Parameters_differ (path, ty, ty') ->
      Printtyp.reset_and_mark_loops ty;
      Printtyp.mark_loops ty';
      Printtyp.Naming_context.reset ();
      fprintf ppf
        "@[<hv>In the definition of %s, type@ %a@ should be@ %a@]"
        (Path.name path)
        !Oprint.out_type (Printtyp.tree_of_typexp false ty)
        !Oprint.out_type (Printtyp.tree_of_typexp false ty')
  | Inconsistent_constraint (env, trace) ->
      fprintf ppf "The type constraints are not consistent.@.";
      Printtyp.report_unification_error ppf env trace
        (fun ppf -> fprintf ppf "Type")
        (fun ppf -> fprintf ppf "is not compatible with type")
  | Type_clash (env, trace) ->
      Printtyp.report_unification_error ppf env trace
        (function ppf ->
           fprintf ppf "This type constructor expands to type")
        (function ppf ->
           fprintf ppf "but is used here with type")
  | Null_arity_external ->
      fprintf ppf "External identifiers must be functions"
  | Missing_native_external ->
      fprintf ppf "@[<hv>An external function with more than 5 arguments \
                   requires a second stub function@ \
                   for native-code compilation@]"
  | Unbound_type_var (ty, decl) ->
      fprintf ppf "A type variable is unbound in this type declaration";
      let ty = Ctype.repr ty in
      begin match decl.type_kind, decl.type_manifest with
      | Type_variant tl, _ ->
          explain_unbound_gen ppf ty tl (fun c ->
              let tl = tys_of_constr_args c.Types.cd_args in
              Btype.newgenty (Ttuple tl)
            )
            "case" (fun ppf c ->
                fprintf ppf
                  "%a of %a" Printtyp.ident c.Types.cd_id
                  Printtyp.constructor_arguments c.Types.cd_args)
      | Type_record (tl, _), _ ->
          explain_unbound ppf ty tl (fun l -> l.Types.ld_type)
            "field" (fun l -> Ident.name l.Types.ld_id ^ ": ")
      | Type_abstract, Some ty' ->
          explain_unbound_single ppf ty ty'
      | _ -> ()
      end
  | Unbound_type_var_ext (ty, ext) ->
      fprintf ppf "A type variable is unbound in this extension constructor";
      let args = tys_of_constr_args ext.ext_args in
      explain_unbound ppf ty args (fun c -> c) "type" (fun _ -> "")
  | Cannot_extend_private_type path ->
      fprintf ppf "@[%s@ %a@]"
        "Cannot extend private type definition"
        Printtyp.path path
  | Not_extensible_type path ->
      fprintf ppf "@[%s@ %a@ %s@]"
        "Type definition"
        Printtyp.path path
        "is not extensible"
  | Extension_mismatch (path, err) ->
      fprintf ppf "@[<v>@[<hov>%s@ %s@;<1 2>%s@]%a@]"
        "This extension" "does not match the definition of type"
        (Path.name path)
        (Includecore.report_type_mismatch
           "the type" "this extension" "definition")
        err
  | Rebind_wrong_type (lid, env, trace) ->
      Printtyp.report_unification_error ppf env trace
        (function ppf ->
           fprintf ppf "The constructor %a@ has type"
             Printtyp.longident lid)
        (function ppf ->
           fprintf ppf "but was expected to be of type")
  | Rebind_mismatch (lid, p, p') ->
      fprintf ppf
        "@[%s@ %a@ %s@ %s@ %s@ %s@ %s@]"
        "The constructor" Printtyp.longident lid
        "extends type" (Path.name p)
        "whose declaration does not match"
        "the declaration of type" (Path.name p')
  | Rebind_private lid ->
      fprintf ppf "@[%s@ %a@ %s@]"
        "The constructor"
        Printtyp.longident lid
        "is private"
  | Variance (Typedecl_variance.Bad_variance (n, v1, v2)) ->
      let variance (p,n,i) =
        let inj = if i then "injective " else "" in
        match p, n with
          true,  true  -> inj ^ "invariant"
        | true,  false -> inj ^ "covariant"
        | false, true  -> inj ^ "contravariant"
        | false, false -> if inj = "" then "unrestricted" else inj
      in
      let suffix n =
        let teen = (n mod 100)/10 = 1 in
        match n mod 10 with
        | 1 when not teen -> "st"
        | 2 when not teen -> "nd"
        | 3 when not teen -> "rd"
        | _ -> "th"
      in
      (match n with
       | Variance_not_reflected ->
           fprintf ppf "@[%s@ %s@ It"
             "In this definition, a type variable has a variance that"
             "is not reflected by its occurrence in type parameters."
       | No_variable ->
           fprintf ppf "@[%s@ %s@]"
             "In this definition, a type variable cannot be deduced"
             "from the type parameters."
       | Variance_not_deducible ->
           fprintf ppf "@[%s@ %s@ It"
             "In this definition, a type variable has a variance that"
             "cannot be deduced from the type parameters."
       | Variance_not_satisfied n ->
           fprintf ppf "@[%s@ %s@ The %d%s type parameter"
             "In this definition, expected parameter"
             "variances are not satisfied."
             n (suffix n));
      (match n with
       | No_variable -> ()
       | _ ->
           fprintf ppf " was expected to be %s,@ but it is %s.@]"
             (variance v2) (variance v1))
  | Unavailable_type_constructor p ->
      fprintf ppf "The definition of type %a@ is unavailable" Printtyp.path p
  | Bad_fixed_type r ->
      fprintf ppf "This fixed type %s" r
  | Variance Typedecl_variance.Varying_anonymous ->
      fprintf ppf "@[%s@ %s@ %s@]"
        "In this GADT definition," "the variance of some parameter"
        "cannot be checked"
  | Val_in_structure ->
      fprintf ppf "Value declarations are only allowed in signatures"
  | Multiple_native_repr_attributes ->
      fprintf ppf "Too many [@@unboxed]/[@@untagged] attributes"
  | Cannot_unbox_or_untag_type Unboxed ->
      fprintf ppf "@[Don't know how to unbox this type.@ \
                   Only float, int32, int64 and nativeint can be unboxed.@]"
  | Cannot_unbox_or_untag_type Untagged ->
      fprintf ppf "@[Don't know how to untag this type.@ \
                   Only int can be untagged.@]"
  | Deep_unbox_or_untag_attribute kind ->
      fprintf ppf
        "@[The attribute '%s' should be attached to@ \
         a direct argument or result of the primitive,@ \
         it should not occur deeply into its type.@]"
        (match kind with Unboxed -> "@unboxed" | Untagged -> "@untagged")
  | Immediacy (Typedecl_immediacy.Bad_immediacy_attribute violation) ->
      fprintf ppf "@[%a@]" Format.pp_print_text
        (match violation with
         | Type_immediacy.Violation.Not_always_immediate ->
             "Types marked with the immediate attribute must be \
              non-pointer types like int or bool."
         | Type_immediacy.Violation.Not_always_immediate_on_64bits ->
             "Types marked with the immediate64 attribute must be \
              produced using the Stdlib.Sys.Immediate64.Make functor.")
  | Bad_unboxed_attribute msg ->
      fprintf ppf "@[This type cannot be unboxed because@ %s.@]" msg
  | Wrong_unboxed_type_float ->
      fprintf ppf "@[This type cannot be unboxed because@ \
                   it might contain both float and non-float values.@ \
                   You should annotate it with [%@%@ocaml.boxed].@]"
  | Boxed_and_unboxed ->
      fprintf ppf "@[A type cannot be boxed and unboxed at the same time.@]"
  | Nonrec_gadt ->
      fprintf ppf
        "@[GADT case syntax cannot be used in a 'nonrec' block.@]"

let () =
  Location.register_error_of_exn
    (function
      | Error (loc, err) ->
        Some (Location.error_of_printer ~loc report_error err)
      | _ ->
        None
    )

************************************************************************
                                                                        
                                 OCaml                                  
                                                                        
                                                                        
     en Automatique.                                                    
                                                                        
   All rights reserved.  This file is distributed under the terms of    
   special exception on linking described in the file LICENSE.          
                                                                        
************************************************************************
*** Typing of type definitions ***
 Note: do not factor the branches in the following pattern-matching:
   the records must be constants for the compiler to do sharing on them.

 Enter all declared types in the environment as abstract types 
 Determine if a type's values are represented by floats at run-time. 
 Set the row variable in a fixed type 
 Check that the variable [id] is present in the [univ] list. 
 Check that all the variables found in [ty] are in [univ].
   Because [ty] is the argument to an abstract type, the representation
   of that abstract type could be any subexpression of [ty], in particular
   any type variable present in [ty].

 A comment in [Translcore.transl_exp0] claims the above cannot be
       represented by floats. 
 This case is tricky: the argument is another (or the same) type
         in the same recursive definition. In this case we don't have to
         check because we will also check that other type for correctness. 
 Bind type parameters 
 The type is not unboxable, mark it as boxed 
 Check constraints 
 Add abstract row 
 Check for cyclic abbreviations 
 Check that all constraints are enforced 

   If both a variant/record definition and a type equation are given,
   need to check that the equation refers to a type of the same kind
   with the same constructors and labels.

 Check that recursion is well-founded 
Format.eprintf "@[%a@]@." Printtyp.raw_type_expr ty;
 Will be detected by check_recursion 
 Attempt to expand a type abbreviation if:
              1- [to_check path'] holds
                 (otherwise the expansion cannot involve [path]);
              2- we haven't expanded this type constructor before
                 (otherwise we could loop if [path'] is itself
                 a non-regular abbreviation). 
 Attempt expansion 
 Check multiple declarations of labels/constructors 
 Warn on definitions of type "type foo = ()" which redefine a different unit
   type and are likely a mistake. 
 Translate a set of type declarations, mutually recursive or not 
 Add dummy types for fixed rows 
 Create identifiers. 
 Enter types. 
 Translate each declaration. 
 See typecore.ml for a description of the algorithm used
             to detect unused declarations in a set of recursive definitions. 
 Check for duplicates 
 Build the final env. 
 Update stubs 
 Check that all type variables are closed 
 Check that constraints are enforced 
 Add type properties to declarations 
 Compute the final environment with variance and immediacy 
 Check re-exportation 
 Keep original declaration 
 Done 
 Translating type extensions 
 Remove "_" names from parameters used in the constructor 
 Ensure that constructor's type matches the type being extended 
 Disallow rebinding private constructors to non-private 
 Remove "_" names from parameters used in the constructor 
 Ensure that constructor's type matches the type being extended 
 Disallow rebinding private constructors to non-private 
 Check that all type variables are closed 
 Check variances are correct 
 Note that [loc] here is distinct from [type_decl.type_loc], which
          makes the [loc] parameter to this function useful. [loc] is the
          location of the extension, while [type_decl] points to the original
          type declaration being extended. 
 Add extension constructors to the environment 
 Translate an exception declaration 
 Check that all type variables are closed 
 Translate an effect declaration 
 Check that all type variable are closed 
 Translate a value declaration 
 Typedecl_immediacy.compute_decl never raises 
 Approximate a type declaration: just make all types abstract 
 Variant of check_abbrev_recursion to check the well-formedness
   conditions on type abbreviations defined within recursive modules. 
 additionally check coherece, as one might build an incoherent signature,
     and use it to build an incoherent module, cf. #7851 
*** Error report ***
 Hack to force aliasing when needed 
     and   , projet Cristal , INRIA Rocquencourt  
    Copyright 1996 Institut National de Recherche en Informatique et     
    the GNU Lesser General Public License version 2.1 , with the          


open Misc
open Asttypes
open Parsetree
open Primitive
open Types
open Typetexp

module String = Misc.Stdlib.String

type native_repr_kind = Unboxed | Untagged

type error =
    Repeated_parameter
  | Duplicate_constructor of string
  | Too_many_constructors
  | Duplicate_label of string
  | Recursive_abbrev of string
  | Cycle_in_def of string * type_expr
  | Definition_mismatch of type_expr * Includecore.type_mismatch option
  | Constraint_failed of type_expr * type_expr
  | Inconsistent_constraint of Env.t * Ctype.Unification_trace.t
  | Type_clash of Env.t * Ctype.Unification_trace.t
  | Parameters_differ of Path.t * type_expr * type_expr
  | Null_arity_external
  | Missing_native_external
  | Unbound_type_var of type_expr * type_declaration
  | Cannot_extend_private_type of Path.t
  | Not_extensible_type of Path.t
  | Extension_mismatch of Path.t * Includecore.type_mismatch
  | Rebind_wrong_type of Longident.t * Env.t * Ctype.Unification_trace.t
  | Rebind_mismatch of Longident.t * Path.t * Path.t
  | Rebind_private of Longident.t
  | Variance of Typedecl_variance.error
  | Unavailable_type_constructor of Path.t
  | Bad_fixed_type of string
  | Unbound_type_var_ext of type_expr * extension_constructor
  | Val_in_structure
  | Multiple_native_repr_attributes
  | Cannot_unbox_or_untag_type of native_repr_kind
  | Deep_unbox_or_untag_attribute of native_repr_kind
  | Immediacy of Typedecl_immediacy.error
  | Bad_unboxed_attribute of string
  | Wrong_unboxed_type_float
  | Boxed_and_unboxed
  | Nonrec_gadt

open Typedtree

exception Error of Location.t * error

let get_unboxed_from_attributes sdecl =
  let unboxed = Builtin_attributes.has_unboxed sdecl.ptype_attributes in
  let boxed = Builtin_attributes.has_boxed sdecl.ptype_attributes in
  match boxed, unboxed, !Clflags.unboxed_types with
  | true, true, _ -> raise (Error(sdecl.ptype_loc, Boxed_and_unboxed))
  | true, false, _ -> unboxed_false_default_false
  | false, true, _ -> unboxed_true_default_false
  | false, false, false -> unboxed_false_default_true
  | false, false, true -> unboxed_true_default_true


let add_type ~check id decl env =
  Builtin_attributes.warning_scope ~ppwarning:false decl.type_attributes
    (fun () -> Env.add_type ~check id decl env)

let enter_type rec_flag env sdecl id =
  let needed =
    match rec_flag with
    | Asttypes.Nonrecursive ->
        begin match sdecl.ptype_kind with
        | Ptype_variant scds ->
            List.iter (fun cd ->
              if cd.pcd_res <> None then raise (Error(cd.pcd_loc, Nonrec_gadt)))
              scds
        | _ -> ()
        end;
        Btype.is_row_name (Ident.name id)
    | Asttypes.Recursive -> true
  in
  if not needed then env else
  let decl =
    { type_params =
        List.map (fun _ -> Btype.newgenvar ()) sdecl.ptype_params;
      type_arity = List.length sdecl.ptype_params;
      type_kind = Type_abstract;
      type_private = sdecl.ptype_private;
      type_manifest =
        begin match sdecl.ptype_manifest with None -> None
        | Some _ -> Some(Ctype.newvar ()) end;
      type_variance = List.map (fun _ -> Variance.full) sdecl.ptype_params;
      type_is_newtype = false;
      type_expansion_scope = Btype.lowest_level;
      type_loc = sdecl.ptype_loc;
      type_attributes = sdecl.ptype_attributes;
      type_immediate = Unknown;
      type_unboxed = unboxed_false_default_false;
    }
  in
  add_type ~check:true id decl env

let update_type temp_env env id loc =
  let path = Path.Pident id in
  let decl = Env.find_type path temp_env in
  match decl.type_manifest with None -> ()
  | Some ty ->
      let params = List.map (fun _ -> Ctype.newvar ()) decl.type_params in
      try Ctype.unify env (Ctype.newconstr path params) ty
      with Ctype.Unify trace ->
        raise (Error(loc, Type_clash (env, trace)))

let get_unboxed_type_representation env ty =
  match Typedecl_unboxed.get_unboxed_type_representation env ty with
  | Typedecl_unboxed.This x -> Some x
  | _ -> None

let is_float env ty =
  match get_unboxed_type_representation env ty with
    Some {desc = Tconstr(p, _, _); _} -> Path.same p Predef.path_float
  | _ -> false

  Determine if a type definition defines a fixed type . ( PW )
let is_fixed_type sd =
  let rec has_row_var sty =
    match sty.ptyp_desc with
      Ptyp_alias (sty, _) -> has_row_var sty
    | Ptyp_class _
    | Ptyp_object (_, Open)
    | Ptyp_variant (_, Open, _)
    | Ptyp_variant (_, Closed, Some _) -> true
    | _ -> false
  in
  match sd.ptype_manifest with
    None -> false
  | Some sty ->
      sd.ptype_kind = Ptype_abstract &&
      sd.ptype_private = Private &&
      has_row_var sty

let set_fixed_row env loc p decl =
  let tm =
    match decl.type_manifest with
      None -> assert false
    | Some t -> Ctype.expand_head env t
  in
  let rv =
    match tm.desc with
      Tvariant row ->
        let row = Btype.row_repr row in
        tm.desc <- Tvariant {row with row_fixed = Some Fixed_private};
        if Btype.static_row row then Btype.newgenty Tnil
        else row.row_more
    | Tobject (ty, _) ->
        snd (Ctype.flatten_fields ty)
    | _ ->
        raise (Error (loc, Bad_fixed_type "is not an object or variant"))
  in
  if not (Btype.is_Tvar rv) then
    raise (Error (loc, Bad_fixed_type "has no row variable"));
  rv.desc <- Tconstr (p, decl.type_params, ref Mnil)

  Translate one type declaration

let make_params env params =
  let make_param (sty, v) =
    try
      (transl_type_param env sty, v)
    with Already_bound ->
      raise(Error(sty.ptyp_loc, Repeated_parameter))
  in
    List.map make_param params

let transl_labels env closed lbls =
  assert (lbls <> []);
  let all_labels = ref String.Set.empty in
  List.iter
    (fun {pld_name = {txt=name; loc}} ->
       if String.Set.mem name !all_labels then
         raise(Error(loc, Duplicate_label name));
       all_labels := String.Set.add name !all_labels)
    lbls;
  let mk {pld_name=name;pld_mutable=mut;pld_type=arg;pld_loc=loc;
          pld_attributes=attrs} =
    Builtin_attributes.warning_scope attrs
      (fun () ->
         let arg = Ast_helper.Typ.force_poly arg in
         let cty = transl_simple_type env closed arg in
         {ld_id = Ident.create_local name.txt;
          ld_name = name; ld_mutable = mut;
          ld_type = cty; ld_loc = loc; ld_attributes = attrs}
      )
  in
  let lbls = List.map mk lbls in
  let lbls' =
    List.map
      (fun ld ->
         let ty = ld.ld_type.ctyp_type in
         let ty = match ty.desc with Tpoly(t,[]) -> t | _ -> ty in
         {Types.ld_id = ld.ld_id;
          ld_mutable = ld.ld_mutable;
          ld_type = ty;
          ld_loc = ld.ld_loc;
          ld_attributes = ld.ld_attributes
         }
      )
      lbls in
  lbls, lbls'

let transl_constructor_arguments env closed = function
  | Pcstr_tuple l ->
      let l = List.map (transl_simple_type env closed) l in
      Types.Cstr_tuple (List.map (fun t -> t.ctyp_type) l),
      Cstr_tuple l
  | Pcstr_record l ->
      let lbls, lbls' = transl_labels env closed l in
      Types.Cstr_record lbls',
      Cstr_record lbls

let make_constructor env type_path type_params sargs sret_type =
  match sret_type with
  | None ->
      let args, targs =
        transl_constructor_arguments env true sargs
      in
        targs, None, args, None, type_params
  | Some sret_type ->
  if it 's a generalized constructor we must first narrow and 
          then widen so as to not introduce any new constraints
         then widen so as to not introduce any new constraints *)
      let z = narrow () in
      reset_type_variables ();
      let args, targs =
        transl_constructor_arguments env false sargs
      in
      let tret_type = transl_simple_type env false sret_type in
      let ret_type = tret_type.ctyp_type in
      let params =
        match (Ctype.repr ret_type).desc with
        | Tconstr (p', params, _) when Path.same type_path p' ->
            params
        | _ ->
            raise (Error (sret_type.ptyp_loc, Constraint_failed
                            (ret_type, Ctype.newconstr type_path type_params)))
      in
      widen z;
      targs, Some tret_type, args, Some ret_type, params

let check_type_var loc univ id =
  let f t = (Btype.repr t).id = id in
  if not (List.exists f univ) then raise (Error (loc, Wrong_unboxed_type_float))

let rec check_unboxed_abstract_arg loc univ ty =
  match ty.desc with
  | Tvar _ -> check_type_var loc univ ty.id
  | Tarrow (_, t1, t2, _)
  | Tfield (_, _, t1, t2) ->
    check_unboxed_abstract_arg loc univ t1;
    check_unboxed_abstract_arg loc univ t2
  | Ttuple args
  | Tconstr (_, args, _)
  | Tpackage (_, _, args) ->
    List.iter (check_unboxed_abstract_arg loc univ) args
  | Tobject (fields, r) ->
    check_unboxed_abstract_arg loc univ fields;
    begin match !r with
    | None -> ()
    | Some (_, args) -> List.iter (check_unboxed_abstract_arg loc univ) args
    end
  | Tnil
  | Tunivar _ -> ()
  | Tlink e -> check_unboxed_abstract_arg loc univ e
  | Tsubst _ -> assert false
  | Tvariant { row_fields; row_more; row_name } ->
    List.iter (check_unboxed_abstract_row_field loc univ) row_fields;
    check_unboxed_abstract_arg loc univ row_more;
    begin match row_name with
    | None -> ()
    | Some (_, args) -> List.iter (check_unboxed_abstract_arg loc univ) args
    end
  | Tpoly (t, _) -> check_unboxed_abstract_arg loc univ t

and check_unboxed_abstract_row_field loc univ (_, field) =
  match field with
  | Rpresent (Some ty) -> check_unboxed_abstract_arg loc univ ty
  | Reither (_, args, _, r) ->
    List.iter (check_unboxed_abstract_arg loc univ) args;
    begin match !r with
    | None -> ()
    | Some f -> check_unboxed_abstract_row_field loc univ ("", f)
    end
  | Rabsent
  | Rpresent None -> ()

let make_effect_constructor env type_param sargs sret =
  let type_path = Predef.path_eff in
  let type_lid = Location.mknoloc (Longident.Lident "eff") in
  let z = narrow () in
  reset_type_variables ();
  let targs = List.map (transl_simple_type env false) sargs in
  let args = List.map (fun cty -> cty.ctyp_type) targs in
  let tret = transl_simple_type env false sret in
  Ctype.unify_var env (Ctype.instance type_param) tret.ctyp_type;
  let ret_type = Ctype.newconstr type_path [tret.ctyp_type] in
  let tret_type =
    { ctyp_desc = Ttyp_constr (type_path, type_lid, targs);
      ctyp_type = ret_type; ctyp_env = env;
      ctyp_loc = {sret.ptyp_loc with Location.loc_ghost = true};
      ctyp_attributes = [] }
  in
  widen z;
  targs, Some tret_type, args, Some ret_type

  Check that the argument to a GADT constructor is compatible with unboxing 
    the type , given the universal parameters of the type .
   the type, given the universal parameters of the type. *)
let rec check_unboxed_gadt_arg loc univ env ty =
  match get_unboxed_type_representation env ty with
  | Some {desc = Tvar _; id} -> check_type_var loc univ id
  | Some {desc = Tarrow _ | Ttuple _ | Tpackage _ | Tobject _ | Tnil
                 | Tvariant _; _} ->
    ()
  | Some {desc = Tconstr (p, args, _); _} ->
    let tydecl = Env.find_type p env in
    assert (not tydecl.type_unboxed.unboxed);
    if tydecl.type_kind = Type_abstract then
      List.iter (check_unboxed_abstract_arg loc univ) args
  | Some {desc = Tfield _ | Tlink _ | Tsubst _; _} -> assert false
  | Some {desc = Tunivar _; _} -> ()
  | Some {desc = Tpoly (t2, _); _} -> check_unboxed_gadt_arg loc univ env t2
  | None -> ()

let transl_declaration env sdecl id =
  reset_type_variables();
  Ctype.begin_def ();
  let tparams = make_params env sdecl.ptype_params in
  let params = List.map (fun (cty, _) -> cty.ctyp_type) tparams in
  let cstrs = List.map
    (fun (sty, sty', loc) ->
      transl_simple_type env false sty,
      transl_simple_type env false sty', loc)
    sdecl.ptype_cstrs
  in
  let raw_status = get_unboxed_from_attributes sdecl in
  if raw_status.unboxed && not raw_status.default then begin
    match sdecl.ptype_kind with
    | Ptype_abstract ->
        raise(Error(sdecl.ptype_loc, Bad_unboxed_attribute
                      "it is abstract"))
    | Ptype_variant [{pcd_args = Pcstr_tuple []; _}] ->
      raise(Error(sdecl.ptype_loc, Bad_unboxed_attribute
                    "its constructor has no argument"))
    | Ptype_variant [{pcd_args = Pcstr_tuple [_]; _}] -> ()
    | Ptype_variant [{pcd_args = Pcstr_tuple _; _}] ->
      raise(Error(sdecl.ptype_loc, Bad_unboxed_attribute
                    "its constructor has more than one argument"))
    | Ptype_variant [{pcd_args = Pcstr_record
                        [{pld_mutable=Immutable; _}]; _}] -> ()
    | Ptype_variant [{pcd_args = Pcstr_record [{pld_mutable=Mutable; _}]; _}] ->
      raise(Error(sdecl.ptype_loc, Bad_unboxed_attribute "it is mutable"))
    | Ptype_variant [{pcd_args = Pcstr_record _; _}] ->
      raise(Error(sdecl.ptype_loc, Bad_unboxed_attribute
                    "its constructor has more than one argument"))
    | Ptype_variant _ ->
      raise(Error(sdecl.ptype_loc, Bad_unboxed_attribute
                    "it has more than one constructor"))
    | Ptype_record [{pld_mutable=Immutable; _}] -> ()
    | Ptype_record [{pld_mutable=Mutable; _}] ->
      raise(Error(sdecl.ptype_loc, Bad_unboxed_attribute
                    "it is mutable"))
    | Ptype_record _ ->
      raise(Error(sdecl.ptype_loc, Bad_unboxed_attribute
                    "it has more than one field"))
    | Ptype_open ->
      raise(Error(sdecl.ptype_loc, Bad_unboxed_attribute
                    "extensible variant types cannot be unboxed"))
  end;
  let unboxed_status =
    match sdecl.ptype_kind with
    | Ptype_variant [{pcd_args = Pcstr_tuple [_]; _}]
      | Ptype_variant [{pcd_args = Pcstr_record
                          [{pld_mutable = Immutable; _}]; _}]
      | Ptype_record [{pld_mutable = Immutable; _}] ->
    raw_status
      unboxed_false_default_false
  in
  let unbox = unboxed_status.unboxed in
  let (tkind, kind) =
    match sdecl.ptype_kind with
      | Ptype_abstract -> Ttype_abstract, Type_abstract
      | Ptype_variant scstrs ->
        if List.exists (fun cstr -> cstr.pcd_res <> None) scstrs then begin
          match cstrs with
            [] -> ()
          | (_,_,loc)::_ ->
              Location.prerr_warning loc Warnings.Constraint_on_gadt
        end;
        let all_constrs = ref String.Set.empty in
        List.iter
          (fun {pcd_name = {txt = name}} ->
            if String.Set.mem name !all_constrs then
              raise(Error(sdecl.ptype_loc, Duplicate_constructor name));
            all_constrs := String.Set.add name !all_constrs)
          scstrs;
        if List.length
            (List.filter (fun cd -> cd.pcd_args <> Pcstr_tuple []) scstrs)
           > (Config.max_tag + 1) then
          raise(Error(sdecl.ptype_loc, Too_many_constructors));
        let make_cstr scstr =
          let name = Ident.create_local scstr.pcd_name.txt in
          let targs, tret_type, args, ret_type, cstr_params =
            make_constructor env (Path.Pident id) params
                             scstr.pcd_args scstr.pcd_res
          in
          if Config.flat_float_array && unbox then begin
  Can not unbox a type when the argument can be both float and 
                non - float because it interferes with the dynamic float array 
                optimization . This can only happen when the type is a GADT 
                and the argument is an existential type variable or an 
                unboxed ( or abstract ) type constructor applied to some 
                existential type variable . Of course we also have to rule 
                out any abstract type constructor applied to anything that 
                might be an existential type variable . 
                There is a difficulty with existential variables created 
                out of thin air ( rather than bound by the declaration ) . 
                See PR#7511 and GPR#1133 for details .
               non-float because it interferes with the dynamic float array
               optimization. This can only happen when the type is a GADT
               and the argument is an existential type variable or an
               unboxed (or abstract) type constructor applied to some
               existential type variable. Of course we also have to rule
               out any abstract type constructor applied to anything that
               might be an existential type variable.
               There is a difficulty with existential variables created
               out of thin air (rather than bound by the declaration).
               See PR#7511 and GPR#1133 for details. *)
            match Datarepr.constructor_existentials args ret_type with
            | _, [] -> ()
            | [argty], _ex ->
                check_unboxed_gadt_arg sdecl.ptype_loc cstr_params env argty
            | _ -> assert false
          end;
          let tcstr =
            { cd_id = name;
              cd_name = scstr.pcd_name;
              cd_args = targs;
              cd_res = tret_type;
              cd_loc = scstr.pcd_loc;
              cd_attributes = scstr.pcd_attributes }
          in
          let cstr =
            { Types.cd_id = name;
              cd_args = args;
              cd_res = ret_type;
              cd_loc = scstr.pcd_loc;
              cd_attributes = scstr.pcd_attributes }
          in
            tcstr, cstr
        in
        let make_cstr scstr =
          Builtin_attributes.warning_scope scstr.pcd_attributes
            (fun () -> make_cstr scstr)
        in
        let tcstrs, cstrs = List.split (List.map make_cstr scstrs) in
          Ttype_variant tcstrs, Type_variant cstrs
      | Ptype_record lbls ->
          let lbls, lbls' = transl_labels env true lbls in
          let rep =
            if unbox then Record_unboxed false
            else if List.for_all (fun l -> is_float env l.Types.ld_type) lbls'
            then Record_float
            else Record_regular
          in
          Ttype_record lbls, Type_record(lbls', rep)
      | Ptype_open -> Ttype_open, Type_open
      in
    let (tman, man) = match sdecl.ptype_manifest with
        None -> None, None
      | Some sty ->
        let no_row = not (is_fixed_type sdecl) in
        let cty = transl_simple_type env no_row sty in
        Some cty, Some cty.ctyp_type
    in
    let decl =
      { type_params = params;
        type_arity = List.length params;
        type_kind = kind;
        type_private = sdecl.ptype_private;
        type_manifest = man;
        type_variance = List.map (fun _ -> Variance.full) params;
        type_is_newtype = false;
        type_expansion_scope = Btype.lowest_level;
        type_loc = sdecl.ptype_loc;
        type_attributes = sdecl.ptype_attributes;
        type_immediate = Unknown;
        type_unboxed = unboxed_status;
      } in

    List.iter
      (fun (cty, cty', loc) ->
        let ty = cty.ctyp_type in
        let ty' = cty'.ctyp_type in
        try Ctype.unify env ty ty' with Ctype.Unify tr ->
          raise(Error(loc, Inconsistent_constraint (env, tr))))
      cstrs;
    Ctype.end_def ();
    if is_fixed_type sdecl then begin
      let p, _ =
        try Env.find_type_by_name
              (Longident.Lident(Ident.name id ^ "#row")) env
        with Not_found -> assert false
      in
      set_fixed_row env sdecl.ptype_loc p decl
    end;
    begin match decl.type_manifest with None -> ()
      | Some ty ->
        if Ctype.cyclic_abbrev env id ty then
          raise(Error(sdecl.ptype_loc, Recursive_abbrev sdecl.ptype_name.txt));
    end;
    {
      typ_id = id;
      typ_name = sdecl.ptype_name;
      typ_params = tparams;
      typ_type = decl;
      typ_cstrs = cstrs;
      typ_loc = sdecl.ptype_loc;
      typ_manifest = tman;
      typ_kind = tkind;
      typ_private = sdecl.ptype_private;
      typ_attributes = sdecl.ptype_attributes;
    }

   a type declaration

let generalize_decl decl =
  List.iter Ctype.generalize decl.type_params;
  Btype.iter_type_expr_kind Ctype.generalize decl.type_kind;
  begin match decl.type_manifest with
  | None    -> ()
  | Some ty -> Ctype.generalize ty
  end


module TypeSet = Btype.TypeSet
module TypeMap = Btype.TypeMap

let rec check_constraints_rec env loc visited ty =
  let ty = Ctype.repr ty in
  if TypeSet.mem ty !visited then () else begin
  visited := TypeSet.add ty !visited;
  match ty.desc with
  | Tconstr (path, args, _) ->
      let args' = List.map (fun _ -> Ctype.newvar ()) args in
      let ty' = Ctype.newconstr path args' in
      begin try Ctype.enforce_constraints env ty'
      with Ctype.Unify _ -> assert false
      | Not_found -> raise (Error(loc, Unavailable_type_constructor path))
      end;
      if not (Ctype.matches env ty ty') then
        raise (Error(loc, Constraint_failed (ty, ty')));
      List.iter (check_constraints_rec env loc visited) args
  | Tpoly (ty, tl) ->
      let _, ty = Ctype.instance_poly false tl ty in
      check_constraints_rec env loc visited ty
  | _ ->
      Btype.iter_type_expr (check_constraints_rec env loc visited) ty
  end

let check_constraints_labels env visited l pl =
  let rec get_loc name = function
      [] -> assert false
    | pld :: tl ->
        if name = pld.pld_name.txt then pld.pld_type.ptyp_loc
        else get_loc name tl
  in
  List.iter
    (fun {Types.ld_id=name; ld_type=ty} ->
       check_constraints_rec env (get_loc (Ident.name name) pl) visited ty)
    l

let check_constraints env sdecl (_, decl) =
  let visited = ref TypeSet.empty in
  begin match decl.type_kind with
  | Type_abstract -> ()
  | Type_variant l ->
      let find_pl = function
          Ptype_variant pl -> pl
        | Ptype_record _ | Ptype_abstract | Ptype_open -> assert false
      in
      let pl = find_pl sdecl.ptype_kind in
      let pl_index =
        let foldf acc x =
          String.Map.add x.pcd_name.txt x acc
        in
        List.fold_left foldf String.Map.empty pl
      in
      List.iter
        (fun {Types.cd_id=name; cd_args; cd_res} ->
          let {pcd_args; pcd_res; _} =
            try String.Map.find (Ident.name name) pl_index
            with Not_found -> assert false in
          begin match cd_args, pcd_args with
          | Cstr_tuple tyl, Pcstr_tuple styl ->
              List.iter2
                (fun sty ty ->
                   check_constraints_rec env sty.ptyp_loc visited ty)
                styl tyl
          | Cstr_record tyl, Pcstr_record styl ->
              check_constraints_labels env visited tyl styl
          | _ -> assert false
          end;
          match pcd_res, cd_res with
          | Some sr, Some r ->
              check_constraints_rec env sr.ptyp_loc visited r
          | _ ->
              () )
        l
  | Type_record (l, _) ->
      let find_pl = function
          Ptype_record pl -> pl
        | Ptype_variant _ | Ptype_abstract | Ptype_open -> assert false
      in
      let pl = find_pl sdecl.ptype_kind in
      check_constraints_labels env visited l pl
  | Type_open -> ()
  end;
  begin match decl.type_manifest with
  | None -> ()
  | Some ty ->
      let sty =
        match sdecl.ptype_manifest with Some sty -> sty | _ -> assert false
      in
      check_constraints_rec env sty.ptyp_loc visited ty
  end

let check_coherence env loc dpath decl =
  match decl with
    { type_kind = (Type_variant _ | Type_record _| Type_open);
      type_manifest = Some ty } ->
      begin match (Ctype.repr ty).desc with
        Tconstr(path, args, _) ->
          begin try
            let decl' = Env.find_type path env in
            let err =
              if List.length args <> List.length decl.type_params
              then Some Includecore.Arity
              else if not (Ctype.equal env false args decl.type_params)
              then Some Includecore.Constraint
              else
                Includecore.type_declarations ~loc ~equality:true env
                  ~mark:true
                  (Path.last path)
                  decl'
                  dpath
                  (Subst.type_declaration
                     (Subst.add_type_path dpath path Subst.identity) decl)
            in
            if err <> None then
              raise(Error(loc, Definition_mismatch (ty, err)))
          with Not_found ->
            raise(Error(loc, Unavailable_type_constructor path))
          end
      | _ -> raise(Error(loc, Definition_mismatch (ty, None)))
      end
  | _ -> ()

let check_abbrev env sdecl (id, decl) =
  check_coherence env sdecl.ptype_loc (Path.Pident id) decl


let check_well_founded env loc path to_check ty =
  let visited = ref TypeMap.empty in
  let rec check ty0 parents ty =
    let ty = Btype.repr ty in
    if TypeSet.mem ty parents then begin
      if match ty0.desc with
      | Tconstr (p, _, _) -> Path.same p path
      | _ -> false
      then raise (Error (loc, Recursive_abbrev (Path.name path)))
      else raise (Error (loc, Cycle_in_def (Path.name path, ty0)))
    end;
    let (fini, parents) =
      try
        let prev = TypeMap.find ty !visited in
        if TypeSet.subset parents prev then (true, parents) else
        (false, TypeSet.union parents prev)
      with Not_found ->
        (false, parents)
    in
    if fini then () else
    let rec_ok =
      match ty.desc with
        Tconstr(p,_,_) ->
          !Clflags.recursive_types && Ctype.is_contractive env p
      | Tobject _ | Tvariant _ -> true
      | _ -> !Clflags.recursive_types
    in
    let visited' = TypeMap.add ty parents !visited in
    let arg_exn =
      try
        visited := visited';
        let parents =
          if rec_ok then TypeSet.empty else TypeSet.add ty parents in
        Btype.iter_type_expr (check ty0 parents) ty;
        None
      with e ->
        visited := visited'; Some e
    in
    match ty.desc with
    | Tconstr(p, _, _) when arg_exn <> None || to_check p ->
        if to_check p then Option.iter raise arg_exn
        else Btype.iter_type_expr (check ty0 TypeSet.empty) ty;
        begin try
          let ty' = Ctype.try_expand_once_opt env ty in
          let ty0 = if TypeSet.is_empty parents then ty else ty0 in
          check ty0 (TypeSet.add ty parents) ty'
        with
          Ctype.Cannot_expand -> Option.iter raise arg_exn
        end
    | _ -> Option.iter raise arg_exn
  in
  let snap = Btype.snapshot () in
  try Ctype.wrap_trace_gadt_instances env (check ty TypeSet.empty) ty
  with Ctype.Unify _ ->
    Btype.backtrack snap

let check_well_founded_manifest env loc path decl =
  if decl.type_manifest = None then () else
  let args = List.map (fun _ -> Ctype.newvar()) decl.type_params in
  check_well_founded env loc path (Path.same path) (Ctype.newconstr path args)

let check_well_founded_decl env loc path decl to_check =
  let open Btype in
  let it =
    {type_iterators with
     it_type_expr = (fun _ -> check_well_founded env loc path to_check)} in
  it.it_type_declaration it (Ctype.generic_instance_declaration decl)

  Check for ill - defined 

let check_recursion env loc path decl to_check =
  to_check is true for potentially mutually recursive paths . 
      ( path ,  ) is the type declaration to be checked .
     (path, decl) is the type declaration to be checked. *)

  if decl.type_params = [] then () else

  let visited = ref [] in

  let rec check_regular cpath args prev_exp ty =
    let ty = Ctype.repr ty in
    if not (List.memq ty !visited) then begin
      visited := ty :: !visited;
      match ty.desc with
      | Tconstr(path', args', _) ->
          if Path.same path path' then begin
            if not (Ctype.equal env false args args') then
              raise (Error(loc,
                     Parameters_differ(cpath, ty, Ctype.newconstr path args)))
          end
          else if to_check path' && not (List.mem path' prev_exp) then begin
            try
              let (params0, body0, _) = Env.find_type_expansion path' env in
              let (params, body) =
                Ctype.instance_parameterized_type params0 body0 in
              begin
                try List.iter2 (Ctype.unify env) params args'
                with Ctype.Unify _ ->
                  raise (Error(loc, Constraint_failed
                                 (ty, Ctype.newconstr path' params0)));
              end;
              check_regular path' args (path' :: prev_exp) body
            with Not_found -> ()
          end;
          List.iter (check_regular cpath args prev_exp) args'
      | Tpoly (ty, tl) ->
          let (_, ty) = Ctype.instance_poly ~keep_names:true false tl ty in
          check_regular cpath args prev_exp ty
      | _ ->
          Btype.iter_type_expr (check_regular cpath args prev_exp) ty
    end in

  Option.iter
    (fun body ->
      let (args, body) =
        Ctype.instance_parameterized_type
          ~keep_names:true decl.type_params body in
      check_regular path args [] body)
    decl.type_manifest

let check_abbrev_recursion env id_loc_list to_check tdecl =
  let decl = tdecl.typ_type in
  let id = tdecl.typ_id in
  check_recursion env (List.assoc id id_loc_list) (Path.Pident id) decl to_check


let check_duplicates sdecl_list =
  let labels = Hashtbl.create 7 and constrs = Hashtbl.create 7 in
  List.iter
    (fun sdecl -> match sdecl.ptype_kind with
      Ptype_variant cl ->
        List.iter
          (fun pcd ->
            try
              let name' = Hashtbl.find constrs pcd.pcd_name.txt in
              Location.prerr_warning pcd.pcd_loc
                (Warnings.Duplicate_definitions
                   ("constructor", pcd.pcd_name.txt, name',
                    sdecl.ptype_name.txt))
            with Not_found ->
              Hashtbl.add constrs pcd.pcd_name.txt sdecl.ptype_name.txt)
          cl
    | Ptype_record fl ->
        List.iter
          (fun {pld_name=cname;pld_loc=loc} ->
            try
              let name' = Hashtbl.find labels cname.txt in
              Location.prerr_warning loc
                (Warnings.Duplicate_definitions
                   ("label", cname.txt, name', sdecl.ptype_name.txt))
            with Not_found -> Hashtbl.add labels cname.txt sdecl.ptype_name.txt)
          fl
    | Ptype_abstract -> ()
    | Ptype_open -> ())
    sdecl_list

  Force recursion to go through i d for private types
let name_recursion sdecl id decl =
  match decl with
  | { type_kind = Type_abstract;
      type_manifest = Some ty;
      type_private = Private; } when is_fixed_type sdecl ->
    let ty = Ctype.repr ty in
    let ty' = Btype.newty2 ty.level ty.desc in
    if Ctype.deep_occur ty ty' then
      let td = Tconstr(Path.Pident id, decl.type_params, ref Mnil) in
      Btype.link_type ty (Btype.newty2 ty.level td);
      {decl with type_manifest = Some ty'}
    else decl
  | _ -> decl

let name_recursion_decls sdecls decls =
  List.map2 (fun sdecl (id, decl) -> (id, name_recursion sdecl id decl))
    sdecls decls

let check_redefined_unit (td: Parsetree.type_declaration) =
  let open Parsetree in
  let is_unit_constructor cd = cd.pcd_name.txt = "()" in
  match td with
  | { ptype_name = { txt = name };
      ptype_manifest = None;
      ptype_kind = Ptype_variant [ cd ] }
    when is_unit_constructor cd ->
      Location.prerr_warning td.ptype_loc (Warnings.Redefining_unit name)
  | _ ->
      ()

let add_types_to_env decls env =
  List.fold_right
    (fun (id, decl) env -> add_type ~check:true id decl env)
    decls env

let transl_type_decl env rec_flag sdecl_list =
  List.iter check_redefined_unit sdecl_list;
  let fixed_types = List.filter is_fixed_type sdecl_list in
  let sdecl_list =
    List.map
      (fun sdecl ->
         let ptype_name =
           let loc = { sdecl.ptype_name.loc with Location.loc_ghost = true } in
           mkloc (sdecl.ptype_name.txt ^"#row") loc
         in
         let ptype_kind = Ptype_abstract in
         let ptype_manifest = None in
         let ptype_loc = { sdecl.ptype_loc with Location.loc_ghost = true } in
        {sdecl with
           ptype_name; ptype_kind; ptype_manifest; ptype_loc })
      fixed_types
    @ sdecl_list
  in

  let scope = Ctype.create_scope () in
  let id_list =
    List.map (fun sdecl -> Ident.create_scoped ~scope sdecl.ptype_name.txt)
      sdecl_list
  in
  Ctype.begin_def();
  let temp_env =
    List.fold_left2 (enter_type rec_flag) env sdecl_list id_list in
  let current_slot = ref None in
  let warn_unused = Warnings.is_active (Warnings.Unused_type_declaration "") in
  let id_slots id =
    match rec_flag with
    | Asttypes.Recursive when warn_unused ->
        let slot = ref [] in
        let td = Env.find_type (Path.Pident id) temp_env in
        let name = Ident.name id in
        Env.set_type_used_callback
          name td
          (fun old_callback ->
             match !current_slot with
             | Some slot -> slot := (name, td) :: !slot
             | None ->
                 List.iter (fun (name, d) -> Env.mark_type_used name d)
                   (get_ref slot);
                 old_callback ()
          );
        id, Some slot
    | Asttypes.Recursive | Asttypes.Nonrecursive ->
        id, None
  in
  let transl_declaration name_sdecl (id, slot) =
    current_slot := slot;
    Builtin_attributes.warning_scope
      name_sdecl.ptype_attributes
      (fun () -> transl_declaration temp_env name_sdecl id)
  in
  let tdecls =
    List.map2 transl_declaration sdecl_list (List.map id_slots id_list) in
  let decls =
    List.map (fun tdecl -> (tdecl.typ_id, tdecl.typ_type)) tdecls in
  current_slot := None;
  check_duplicates sdecl_list;
  let new_env = add_types_to_env decls env in
  begin match rec_flag with
    | Asttypes.Nonrecursive -> ()
    | Asttypes.Recursive ->
      List.iter2
        (fun id sdecl -> update_type temp_env new_env id sdecl.ptype_loc)
        id_list sdecl_list
  end;
  Generalize type declarations .
  Ctype.end_def();
  List.iter (fun (_, decl) -> generalize_decl decl) decls;
  Check for ill - formed 
  let id_loc_list =
    List.map2 (fun id sdecl -> (id, sdecl.ptype_loc))
      id_list sdecl_list
  in
  List.iter (fun (id, decl) ->
    check_well_founded_manifest new_env (List.assoc id id_loc_list)
      (Path.Pident id) decl)
    decls;
  let to_check =
    function Path.Pident id -> List.mem_assoc id id_loc_list | _ -> false in
  List.iter (fun (id, decl) ->
    check_well_founded_decl new_env (List.assoc id id_loc_list) (Path.Pident id)
      decl to_check)
    decls;
  List.iter (check_abbrev_recursion new_env id_loc_list to_check) tdecls;
  List.iter2
    (fun sdecl tdecl ->
      let decl = tdecl.typ_type in
       match Ctype.closed_type_decl decl with
         Some ty -> raise(Error(sdecl.ptype_loc, Unbound_type_var(ty,decl)))
       | None   -> ())
    sdecl_list tdecls;
  List.iter2 (check_constraints new_env) sdecl_list decls;
  let decls =
    try
      decls
      |> name_recursion_decls sdecl_list
      |> Typedecl_variance.update_decls env sdecl_list
      |> Typedecl_immediacy.update_decls env
    with
    | Typedecl_variance.Error (loc, err) -> raise (Error (loc, Variance err))
    | Typedecl_immediacy.Error (loc, err) -> raise (Error (loc, Immediacy err))
  in
  let final_env = add_types_to_env decls env in
  List.iter2 (check_abbrev final_env) sdecl_list decls;
  let final_decls =
    List.map2
      (fun tdecl (_id2, decl) ->
        { tdecl with typ_type = decl }
      ) tdecls decls
  in
  (final_decls, final_env)

let transl_extension_rebind env type_path type_params typext_params priv lid =
  let usage = if priv = Public then Env.Positive else Env.Privatize in
  let cdescr = Env.lookup_constructor ~loc:lid.loc usage lid.txt env in
  let (args, cstr_res) = Ctype.instance_constructor cdescr in
  let res, ret_type =
    if cdescr.cstr_generalized then
      let params = Ctype.instance_list type_params in
      let res = Ctype.newconstr type_path params in
      let ret_type = Some (Ctype.newconstr type_path params) in
        res, ret_type
    else (Ctype.newconstr type_path typext_params), None
  in
  begin
    try
      Ctype.unify env cstr_res res
    with Ctype.Unify trace ->
      raise (Error(lid.loc,
               Rebind_wrong_type(lid.txt, env, trace)))
  end;
  if not cdescr.cstr_generalized then begin
    let vars =
      Ctype.free_variables (Btype.newgenty (Ttuple args))
    in
      List.iter
        (function {desc = Tvar (Some "_")} as ty ->
                    if List.memq ty vars then ty.desc <- Tvar None
                  | _ -> ())
        typext_params
  end;
  let cstr_type_path, cstr_type_params =
    match cdescr.cstr_res.desc with
      Tconstr (p, _, _) ->
        let decl = Env.find_type p env in
          p, decl.type_params
    | _ -> assert false
  in
  let cstr_types =
    (Btype.newgenty
       (Tconstr(cstr_type_path, cstr_type_params, ref Mnil)))
    :: cstr_type_params
  in
  let ext_types =
    (Btype.newgenty
       (Tconstr(type_path, type_params, ref Mnil)))
    :: type_params
  in
  if not (Ctype.equal env true cstr_types ext_types) then
    raise (Error(lid.loc,
                 Rebind_mismatch(lid.txt, cstr_type_path, type_path)));
  begin
    match cdescr.cstr_private, priv with
      Private, Public ->
        raise (Error(lid.loc, Rebind_private lid.txt))
    | _ -> ()
  end;
  let path =
    match cdescr.cstr_tag with
      Cstr_extension(path, _) -> path
    | _ -> assert false
  in
    args, ret_type, Text_rebind(path, lid)

let transl_extension_constructor env type_path type_params
                                 typext_params priv sext =
  let scope = Ctype.create_scope () in
  let id = Ident.create_scoped ~scope sext.pext_name.txt in
  let args, ret_type, kind =
    match sext.pext_kind with
      Pext_decl(sargs, sret_type) ->
        let targs, tret_type, args, ret_type, _ =
          make_constructor env type_path typext_params
            sargs sret_type
        in
          args, ret_type, Text_decl(targs, tret_type)
    | Pext_rebind lid ->
        let usage = if priv = Public then Env.Positive else Env.Privatize in
        let cdescr = Env.lookup_constructor ~loc:lid.loc usage lid.txt env in
        let (args, cstr_res) = Ctype.instance_constructor cdescr in
        let res, ret_type =
          if cdescr.cstr_generalized then
            let params = Ctype.instance_list type_params in
            let res = Ctype.newconstr type_path params in
            let ret_type = Some (Ctype.newconstr type_path params) in
              res, ret_type
          else (Ctype.newconstr type_path typext_params), None
        in
        begin
          try
            Ctype.unify env cstr_res res
          with Ctype.Unify trace ->
            raise (Error(lid.loc,
                     Rebind_wrong_type(lid.txt, env, trace)))
        end;
        if not cdescr.cstr_generalized then begin
          let vars =
            Ctype.free_variables (Btype.newgenty (Ttuple args))
          in
            List.iter
              (function {desc = Tvar (Some "_")} as ty ->
                          if List.memq ty vars then ty.desc <- Tvar None
                        | _ -> ())
              typext_params
        end;
        let cstr_type_path, cstr_type_params =
          match cdescr.cstr_res.desc with
            Tconstr (p, _, _) ->
              let decl = Env.find_type p env in
                p, decl.type_params
          | _ -> assert false
        in
        let cstr_types =
          (Btype.newgenty
             (Tconstr(cstr_type_path, cstr_type_params, ref Mnil)))
          :: cstr_type_params
        in
        let ext_types =
          (Btype.newgenty
             (Tconstr(type_path, type_params, ref Mnil)))
          :: type_params
        in
        if not (Ctype.equal env true cstr_types ext_types) then
          raise (Error(lid.loc,
                       Rebind_mismatch(lid.txt, cstr_type_path, type_path)));
        begin
          match cdescr.cstr_private, priv with
            Private, Public ->
              raise (Error(lid.loc, Rebind_private lid.txt))
          | _ -> ()
        end;
        let path =
          match cdescr.cstr_tag with
            Cstr_extension(path, _) -> path
          | _ -> assert false
        in
        let args =
          match cdescr.cstr_inlined with
          | None ->
              Types.Cstr_tuple args
          | Some decl ->
              let tl =
                match args with
                | [ {desc=Tconstr(_, tl, _)} ] -> tl
                | _ -> assert false
              in
              let decl = Ctype.instance_declaration decl in
              assert (List.length decl.type_params = List.length tl);
              List.iter2 (Ctype.unify env) decl.type_params tl;
              let lbls =
                match decl.type_kind with
                | Type_record (lbls, Record_extension _) -> lbls
                | _ -> assert false
              in
              Types.Cstr_record lbls
        in
        args, ret_type, Text_rebind(path, lid)
  in
  let ext =
    { ext_type_path = type_path;
      ext_type_params = typext_params;
      ext_args = args;
      ext_ret_type = ret_type;
      ext_private = priv;
      Types.ext_loc = sext.pext_loc;
      Types.ext_attributes = sext.pext_attributes; }
  in
    { ext_id = id;
      ext_name = sext.pext_name;
      ext_type = ext;
      ext_kind = kind;
      Typedtree.ext_loc = sext.pext_loc;
      Typedtree.ext_attributes = sext.pext_attributes; }

let transl_extension_constructor env type_path type_params
    typext_params priv sext =
  Builtin_attributes.warning_scope sext.pext_attributes
    (fun () -> transl_extension_constructor env type_path type_params
        typext_params priv sext)

let transl_type_extension extend env loc styext =
  reset_type_variables();
  Ctype.begin_def();
  let type_path, type_decl =
    let lid = styext.ptyext_path in
    Env.lookup_type ~loc:lid.loc lid.txt env
  in
  begin
    match type_decl.type_kind with
    | Type_open -> begin
        match type_decl.type_private with
        | Private when extend -> begin
            match
              List.find
                (function {pext_kind = Pext_decl _} -> true
                        | {pext_kind = Pext_rebind _} -> false)
                styext.ptyext_constructors
            with
            | {pext_loc} ->
                raise (Error(pext_loc, Cannot_extend_private_type type_path))
            | exception Not_found -> ()
          end
        | _ -> ()
      end
    | _ ->
        raise (Error(loc, Not_extensible_type type_path))
  end;
  let type_variance =
    List.map (fun v ->
                let (co, cn) = Variance.get_upper v in
                  (not cn, not co, false))
             type_decl.type_variance
  in
  let err =
    if type_decl.type_arity <> List.length styext.ptyext_params then
      Some Includecore.Arity
    else
      if List.for_all2
           (fun (c1, n1, _) (c2, n2, _) -> (not c2 || c1) && (not n2 || n1))
           type_variance
           (Typedecl_variance.variance_of_params styext.ptyext_params)
      then None else Some Includecore.Variance
  in
  begin match err with
  | None -> ()
  | Some err -> raise (Error(loc, Extension_mismatch (type_path, err)))
  end;
  let ttype_params = make_params env styext.ptyext_params in
  let type_params = List.map (fun (cty, _) -> cty.ctyp_type) ttype_params in
  List.iter2 (Ctype.unify_var env)
    (Ctype.instance_list type_decl.type_params)
    type_params;
  let constructors =
    List.map (transl_extension_constructor env type_path
               type_decl.type_params type_params styext.ptyext_private)
      styext.ptyext_constructors
  in
  Ctype.end_def();
   types
  List.iter Ctype.generalize type_params;
  List.iter
    (fun ext ->
       Btype.iter_type_expr_cstr_args Ctype.generalize ext.ext_type.ext_args;
       Option.iter Ctype.generalize ext.ext_type.ext_ret_type)
    constructors;
  List.iter
    (fun ext ->
       match Ctype.closed_extension_constructor ext.ext_type with
         Some ty ->
           raise(Error(ext.ext_loc, Unbound_type_var_ext(ty, ext.ext_type)))
       | None -> ())
    constructors;
  List.iter
    (fun ext->
       try Typedecl_variance.check_variance_extension
             env type_decl ext (type_variance, loc)
       with Typedecl_variance.Error (loc, err) ->
         raise (Error (loc, Variance err)))
    constructors;
  let newenv =
    List.fold_left
      (fun env ext ->
         Env.add_extension ~check:true ext.ext_id ext.ext_type env)
      env constructors
  in
  let tyext =
    { tyext_path = type_path;
      tyext_txt = styext.ptyext_path;
      tyext_params = ttype_params;
      tyext_constructors = constructors;
      tyext_private = styext.ptyext_private;
      tyext_loc = styext.ptyext_loc;
      tyext_attributes = styext.ptyext_attributes; }
  in
    (tyext, newenv)

let transl_type_extension extend env loc styext =
  Builtin_attributes.warning_scope styext.ptyext_attributes
    (fun () -> transl_type_extension extend env loc styext)

let transl_exception env sext =
  reset_type_variables();
  Ctype.begin_def();
  let ext =
    transl_extension_constructor env
      Predef.path_exn [] [] Asttypes.Public sext
  in
  Ctype.end_def();
   types
  Btype.iter_type_expr_cstr_args Ctype.generalize ext.ext_type.ext_args;
  Option.iter Ctype.generalize ext.ext_type.ext_ret_type;
  begin match Ctype.closed_extension_constructor ext.ext_type with
    Some ty ->
      raise (Error(ext.ext_loc, Unbound_type_var_ext(ty, ext.ext_type)))
  | None -> ()
  end;
  let newenv = Env.add_extension ~check:true ext.ext_id ext.ext_type env in
  ext, newenv

let transl_type_exception env t =
  Builtin_attributes.check_no_alert t.ptyexn_attributes;
  let contructor, newenv =
    Builtin_attributes.warning_scope t.ptyexn_attributes
      (fun () ->
         transl_exception env t.ptyexn_constructor
      )
  in
  {tyexn_constructor = contructor;
   tyexn_loc = t.ptyexn_loc;
   tyexn_attributes = t.ptyexn_attributes}, newenv


let transl_effect env seff =
  reset_type_variables();
  Ctype.begin_def();
  let type_decl = Env.find_type Predef.path_eff env in
  let type_param =
    match type_decl.type_params with
    | [type_param] -> type_param
    | _ -> assert false
  in
  let typext_param = Ctype.new_global_var () in
  let id = Ident.create_local seff.peff_name.txt in
  let args, ret_type, kind =
    match seff.peff_kind with
    | Peff_decl(sargs, sret) ->
        let targs, tret_type, args, ret_type =
          make_effect_constructor env type_param sargs sret
        in
          args, ret_type, Text_decl(Cstr_tuple targs, tret_type)
    | Peff_rebind lid ->
        transl_extension_rebind env Predef.path_eff
          type_decl.type_params [typext_param] Asttypes.Public lid
  in
  let ext =
    { ext_type_path = Predef.path_eff;
      ext_type_params = [typext_param];
      ext_args = Cstr_tuple args;
      ext_ret_type = ret_type;
      ext_private = Asttypes.Public;
      Types.ext_loc = seff.peff_loc;
      Types.ext_attributes = seff.peff_attributes; }
  in
  let text =
    { ext_id = id;
      ext_name = seff.peff_name;
      ext_type = ext;
      ext_kind = kind;
      Typedtree.ext_loc = seff.peff_loc;
      Typedtree.ext_attributes = seff.peff_attributes; }
  in
  Ctype.end_def();
   types
  Btype.iter_type_expr_cstr_args Ctype.generalize ext.ext_args;
  Option.iter Ctype.generalize ext.ext_ret_type;
  begin match Ctype.closed_extension_constructor ext with
    Some ty ->
      raise (Error(ext.ext_loc, Unbound_type_var_ext(ty, ext)))
  | None -> ()
  end;
  let newenv = Env.add_extension ~check:true text.ext_id ext env in
    text, newenv

type native_repr_attribute =
  | Native_repr_attr_absent
  | Native_repr_attr_present of native_repr_kind

let get_native_repr_attribute attrs ~global_repr =
  match
    Attr_helper.get_no_payload_attribute ["unboxed"; "ocaml.unboxed"]  attrs,
    Attr_helper.get_no_payload_attribute ["untagged"; "ocaml.untagged"] attrs,
    global_repr
  with
  | None, None, None -> Native_repr_attr_absent
  | None, None, Some repr -> Native_repr_attr_present repr
  | Some _, None, None -> Native_repr_attr_present Unboxed
  | None, Some _, None -> Native_repr_attr_present Untagged
  | Some { Location.loc }, _, _
  | _, Some { Location.loc }, _ ->
    raise (Error (loc, Multiple_native_repr_attributes))

let native_repr_of_type env kind ty =
  match kind, (Ctype.expand_head_opt env ty).desc with
  | Untagged, Tconstr (path, _, _) when Path.same path Predef.path_int ->
    Some Untagged_int
  | Unboxed, Tconstr (path, _, _) when Path.same path Predef.path_float ->
    Some Unboxed_float
  | Unboxed, Tconstr (path, _, _) when Path.same path Predef.path_int32 ->
    Some (Unboxed_integer Pint32)
  | Unboxed, Tconstr (path, _, _) when Path.same path Predef.path_int64 ->
    Some (Unboxed_integer Pint64)
  | Unboxed, Tconstr (path, _, _) when Path.same path Predef.path_nativeint ->
    Some (Unboxed_integer Pnativeint)
  | _ ->
    None

  Raises an error when [ core_type ] contains an [ @unboxed ] or [ @untagged ] 
    attribute in a strict sub - term .
   attribute in a strict sub-term. *)
let error_if_has_deep_native_repr_attributes core_type =
  let open Ast_iterator in
  let this_iterator =
    { default_iterator with typ = fun iterator core_type ->
      begin
        match
          get_native_repr_attribute core_type.ptyp_attributes ~global_repr:None
        with
        | Native_repr_attr_present kind ->
           raise (Error (core_type.ptyp_loc,
                         Deep_unbox_or_untag_attribute kind))
        | Native_repr_attr_absent -> ()
      end;
      default_iterator.typ iterator core_type }
  in
  default_iterator.typ this_iterator core_type

let make_native_repr env core_type ty ~global_repr =
  error_if_has_deep_native_repr_attributes core_type;
  match get_native_repr_attribute core_type.ptyp_attributes ~global_repr with
  | Native_repr_attr_absent ->
    Same_as_ocaml_repr
  | Native_repr_attr_present kind ->
    begin match native_repr_of_type env kind ty with
    | None ->
      raise (Error (core_type.ptyp_loc, Cannot_unbox_or_untag_type kind))
    | Some repr -> repr
    end

let rec parse_native_repr_attributes env core_type ty ~global_repr =
  match core_type.ptyp_desc, (Ctype.repr ty).desc,
    get_native_repr_attribute core_type.ptyp_attributes ~global_repr:None
  with
  | Ptyp_arrow _, Tarrow _, Native_repr_attr_present kind  ->
    raise (Error (core_type.ptyp_loc, Cannot_unbox_or_untag_type kind))
  | Ptyp_arrow (_, ct1, ct2), Tarrow (_, t1, t2, _), _ ->
    let repr_arg = make_native_repr env ct1 t1 ~global_repr in
    let repr_args, repr_res =
      parse_native_repr_attributes env ct2 t2 ~global_repr
    in
    (repr_arg :: repr_args, repr_res)
  | Ptyp_arrow _, _, _ | _, Tarrow _, _ -> assert false
  | _ -> ([], make_native_repr env core_type ty ~global_repr)


let check_unboxable env loc ty =
  let check_type acc ty : Path.Set.t =
    let ty = Ctype.repr (Ctype.expand_head_opt env ty) in
    try match ty.desc with
      | Tconstr (p, _, _) ->
        let tydecl = Env.find_type p env in
        if tydecl.type_unboxed.default then
          Path.Set.add p acc
        else acc
      | _ -> acc
    with Not_found -> acc
  in
  let all_unboxable_types = Btype.fold_type_expr check_type Path.Set.empty ty in
  Path.Set.fold
    (fun p () ->
       Location.prerr_warning loc
         (Warnings.Unboxable_type_in_prim_decl (Path.name p))
    )
    all_unboxable_types
    ()

let transl_value_decl env loc valdecl =
  let cty = Typetexp.transl_type_scheme env valdecl.pval_type in
  let ty = cty.ctyp_type in
  let v =
  match valdecl.pval_prim with
    [] when Env.is_in_signature env ->
      { val_type = ty; val_kind = Val_reg; Types.val_loc = loc;
        val_attributes = valdecl.pval_attributes }
  | [] ->
      raise (Error(valdecl.pval_loc, Val_in_structure))
  | _ ->
      let global_repr =
        match
          get_native_repr_attribute valdecl.pval_attributes ~global_repr:None
        with
        | Native_repr_attr_present repr -> Some repr
        | Native_repr_attr_absent -> None
      in
      let native_repr_args, native_repr_res =
        parse_native_repr_attributes env valdecl.pval_type ty ~global_repr
      in
      let prim =
        Primitive.parse_declaration valdecl
          ~native_repr_args
          ~native_repr_res
      in
      if prim.prim_arity = 0 &&
         (prim.prim_name = "" || prim.prim_name.[0] <> '%') then
        raise(Error(valdecl.pval_type.ptyp_loc, Null_arity_external));
      if !Clflags.native_code
      && prim.prim_arity > 5
      && prim.prim_native_name = ""
      then raise(Error(valdecl.pval_type.ptyp_loc, Missing_native_external));
      check_unboxable env loc ty;
      { val_type = ty; val_kind = Val_prim prim; Types.val_loc = loc;
        val_attributes = valdecl.pval_attributes }
  in
  let (id, newenv) =
    Env.enter_value valdecl.pval_name.txt v env
      ~check:(fun s -> Warnings.Unused_value_declaration s)
  in
  let desc =
    {
     val_id = id;
     val_name = valdecl.pval_name;
     val_desc = cty; val_val = v;
     val_prim = valdecl.pval_prim;
     val_loc = valdecl.pval_loc;
     val_attributes = valdecl.pval_attributes;
    }
  in
  desc, newenv

let transl_value_decl env loc valdecl =
  Builtin_attributes.warning_scope valdecl.pval_attributes
    (fun () -> transl_value_decl env loc valdecl)

  Translate a " with " constraint -- much simplified version of 
     transl_type_decl .
    transl_type_decl. *)
let transl_with_constraint env id row_path orig_decl sdecl =
  Env.mark_type_used (Ident.name id) orig_decl;
  reset_type_variables();
  Ctype.begin_def();
  let tparams = make_params env sdecl.ptype_params in
  let params = List.map (fun (cty, _) -> cty.ctyp_type) tparams in
  let orig_decl = Ctype.instance_declaration orig_decl in
  let arity_ok = List.length params = orig_decl.type_arity in
  if arity_ok then
    List.iter2 (Ctype.unify_var env) params orig_decl.type_params;
  let constraints = List.map
    (function (ty, ty', loc) ->
       try
         let cty = transl_simple_type env false ty in
         let cty' = transl_simple_type env false ty' in
         let ty = cty.ctyp_type in
         let ty' = cty'.ctyp_type in
         Ctype.unify env ty ty';
         (cty, cty', loc)
       with Ctype.Unify tr ->
         raise(Error(loc, Inconsistent_constraint (env, tr))))
    sdecl.ptype_cstrs
  in
  let no_row = not (is_fixed_type sdecl) in
  let (tman, man) =  match sdecl.ptype_manifest with
      None -> None, None
    | Some sty ->
        let cty = transl_simple_type env no_row sty in
        Some cty, Some cty.ctyp_type
  in
  let priv =
    if sdecl.ptype_private = Private then Private else
    if arity_ok && orig_decl.type_kind <> Type_abstract
    then orig_decl.type_private else sdecl.ptype_private
  in
  if arity_ok && orig_decl.type_kind <> Type_abstract
  && sdecl.ptype_private = Private then
    Location.deprecated sdecl.ptype_loc "spurious use of private";
  let type_kind, type_unboxed =
    if arity_ok && man <> None then
      orig_decl.type_kind, orig_decl.type_unboxed
    else
      Type_abstract, unboxed_false_default_false
  in
  let decl =
    { type_params = params;
      type_arity = List.length params;
      type_kind;
      type_private = priv;
      type_manifest = man;
      type_variance = [];
      type_is_newtype = false;
      type_expansion_scope = Btype.lowest_level;
      type_loc = sdecl.ptype_loc;
      type_attributes = sdecl.ptype_attributes;
      type_immediate = Unknown;
      type_unboxed;
    }
  in
  begin match row_path with None -> ()
  | Some p -> set_fixed_row env sdecl.ptype_loc p decl
  end;
  begin match Ctype.closed_type_decl decl with None -> ()
  | Some ty -> raise(Error(sdecl.ptype_loc, Unbound_type_var(ty,decl)))
  end;
  let decl = name_recursion sdecl id decl in
  let type_variance =
    try Typedecl_variance.compute_decl
          env ~check:true decl (Typedecl_variance.variance_of_sdecl sdecl)
    with Typedecl_variance.Error (loc, err) ->
      raise (Error (loc, Variance err)) in
  let type_immediate =
    Typedecl_immediacy.compute_decl env decl in
  let decl = {decl with type_variance; type_immediate} in
  Ctype.end_def();
  generalize_decl decl;
  {
    typ_id = id;
    typ_name = sdecl.ptype_name;
    typ_params = tparams;
    typ_type = decl;
    typ_cstrs = constraints;
    typ_loc = sdecl.ptype_loc;
    typ_manifest = tman;
    typ_kind = Ttype_abstract;
    typ_private = sdecl.ptype_private;
    typ_attributes = sdecl.ptype_attributes;
  }


let abstract_type_decl arity =
  let rec make_params n =
    if n <= 0 then [] else Ctype.newvar() :: make_params (n-1) in
  Ctype.begin_def();
  let decl =
    { type_params = make_params arity;
      type_arity = arity;
      type_kind = Type_abstract;
      type_private = Public;
      type_manifest = None;
      type_variance = replicate_list Variance.full arity;
      type_is_newtype = false;
      type_expansion_scope = Btype.lowest_level;
      type_loc = Location.none;
      type_attributes = [];
      type_immediate = Unknown;
      type_unboxed = unboxed_false_default_false;
     } in
  Ctype.end_def();
  generalize_decl decl;
  decl

let approx_type_decl sdecl_list =
  let scope = Ctype.create_scope () in
  List.map
    (fun sdecl ->
      (Ident.create_scoped ~scope sdecl.ptype_name.txt,
       abstract_type_decl (List.length sdecl.ptype_params)))
    sdecl_list


let check_recmod_typedecl env loc recmod_ids path decl =
  recmod_ids is the list of recursively - defined module idents . 
      ( path ,  ) is the type declaration to be checked .
     (path, decl) is the type declaration to be checked. *)
  let to_check path = Path.exists_free recmod_ids path in
  check_well_founded_decl env loc path decl to_check;
  check_recursion env loc path decl to_check;
  check_coherence env loc path decl



open Format

let explain_unbound_gen ppf tv tl typ kwd pr =
  try
    let ti = List.find (fun ti -> Ctype.deep_occur tv (typ ti)) tl in
      Btype.newgenty (Tobject(tv, ref None)) in
    Printtyp.reset_and_mark_loops_list [typ ti; ty0];
    fprintf ppf
      ".@.@[<hov2>In %s@ %a@;<1 -2>the variable %a is unbound@]"
      kwd pr ti Printtyp.marked_type_expr tv
  with Not_found -> ()

let explain_unbound ppf tv tl typ kwd lab =
  explain_unbound_gen ppf tv tl typ kwd
    (fun ppf ti ->
       fprintf ppf "%s%a" (lab ti) Printtyp.marked_type_expr (typ ti)
    )

let explain_unbound_single ppf tv ty =
  let trivial ty =
    explain_unbound ppf tv [ty] (fun t -> t) "type" (fun _ -> "") in
  match (Ctype.repr ty).desc with
    Tobject(fi,_) ->
      let (tl, rv) = Ctype.flatten_fields fi in
      if rv == tv then trivial ty else
      explain_unbound ppf tv tl (fun (_,_,t) -> t)
        "method" (fun (lab,_,_) -> lab ^ ": ")
  | Tvariant row ->
      let row = Btype.row_repr row in
      if row.row_more == tv then trivial ty else
      explain_unbound ppf tv row.row_fields
        (fun (_l,f) -> match Btype.row_field_repr f with
          Rpresent (Some t) -> t
        | Reither (_,[t],_,_) -> t
        | Reither (_,tl,_,_) -> Btype.newgenty (Ttuple tl)
        | _ -> Btype.newgenty (Ttuple[]))
        "case" (fun (lab,_) -> "`" ^ lab ^ " of ")
  | _ -> trivial ty


let tys_of_constr_args = function
  | Types.Cstr_tuple tl -> tl
  | Types.Cstr_record lbls -> List.map (fun l -> l.Types.ld_type) lbls

let report_error ppf = function
  | Repeated_parameter ->
      fprintf ppf "A type parameter occurs several times"
  | Duplicate_constructor s ->
      fprintf ppf "Two constructors are named %s" s
  | Too_many_constructors ->
      fprintf ppf
        "@[Too many non-constant constructors@ -- maximum is %i %s@]"
        (Config.max_tag + 1) "non-constant constructors"
  | Duplicate_label s ->
      fprintf ppf "Two labels are named %s" s
  | Recursive_abbrev s ->
      fprintf ppf "The type abbreviation %s is cyclic" s
  | Cycle_in_def (s, ty) ->
      fprintf ppf "@[<v>The definition of %s contains a cycle:@ %a@]"
        s Printtyp.type_expr ty
  | Definition_mismatch (ty, None) ->
      fprintf ppf "@[<v>@[<hov>%s@ %s@;<1 2>%a@]@]"
        "This variant or record definition" "does not match that of type"
        Printtyp.type_expr ty
  | Definition_mismatch (ty, Some err) ->
      fprintf ppf "@[<v>@[<hov>%s@ %s@;<1 2>%a@]%a@]"
        "This variant or record definition" "does not match that of type"
        Printtyp.type_expr ty
        (Includecore.report_type_mismatch "the original" "this" "definition")
        err
  | Constraint_failed (ty, ty') ->
      Printtyp.reset_and_mark_loops ty;
      Printtyp.mark_loops ty';
      Printtyp.Naming_context.reset ();
      fprintf ppf "@[%s@ @[<hv>Type@ %a@ should be an instance of@ %a@]@]"
        "Constraints are not satisfied in this type."
        !Oprint.out_type (Printtyp.tree_of_typexp false ty)
        !Oprint.out_type (Printtyp.tree_of_typexp false ty')
  | Parameters_differ (path, ty, ty') ->
      Printtyp.reset_and_mark_loops ty;
      Printtyp.mark_loops ty';
      Printtyp.Naming_context.reset ();
      fprintf ppf
        "@[<hv>In the definition of %s, type@ %a@ should be@ %a@]"
        (Path.name path)
        !Oprint.out_type (Printtyp.tree_of_typexp false ty)
        !Oprint.out_type (Printtyp.tree_of_typexp false ty')
  | Inconsistent_constraint (env, trace) ->
      fprintf ppf "The type constraints are not consistent.@.";
      Printtyp.report_unification_error ppf env trace
        (fun ppf -> fprintf ppf "Type")
        (fun ppf -> fprintf ppf "is not compatible with type")
  | Type_clash (env, trace) ->
      Printtyp.report_unification_error ppf env trace
        (function ppf ->
           fprintf ppf "This type constructor expands to type")
        (function ppf ->
           fprintf ppf "but is used here with type")
  | Null_arity_external ->
      fprintf ppf "External identifiers must be functions"
  | Missing_native_external ->
      fprintf ppf "@[<hv>An external function with more than 5 arguments \
                   requires a second stub function@ \
                   for native-code compilation@]"
  | Unbound_type_var (ty, decl) ->
      fprintf ppf "A type variable is unbound in this type declaration";
      let ty = Ctype.repr ty in
      begin match decl.type_kind, decl.type_manifest with
      | Type_variant tl, _ ->
          explain_unbound_gen ppf ty tl (fun c ->
              let tl = tys_of_constr_args c.Types.cd_args in
              Btype.newgenty (Ttuple tl)
            )
            "case" (fun ppf c ->
                fprintf ppf
                  "%a of %a" Printtyp.ident c.Types.cd_id
                  Printtyp.constructor_arguments c.Types.cd_args)
      | Type_record (tl, _), _ ->
          explain_unbound ppf ty tl (fun l -> l.Types.ld_type)
            "field" (fun l -> Ident.name l.Types.ld_id ^ ": ")
      | Type_abstract, Some ty' ->
          explain_unbound_single ppf ty ty'
      | _ -> ()
      end
  | Unbound_type_var_ext (ty, ext) ->
      fprintf ppf "A type variable is unbound in this extension constructor";
      let args = tys_of_constr_args ext.ext_args in
      explain_unbound ppf ty args (fun c -> c) "type" (fun _ -> "")
  | Cannot_extend_private_type path ->
      fprintf ppf "@[%s@ %a@]"
        "Cannot extend private type definition"
        Printtyp.path path
  | Not_extensible_type path ->
      fprintf ppf "@[%s@ %a@ %s@]"
        "Type definition"
        Printtyp.path path
        "is not extensible"
  | Extension_mismatch (path, err) ->
      fprintf ppf "@[<v>@[<hov>%s@ %s@;<1 2>%s@]%a@]"
        "This extension" "does not match the definition of type"
        (Path.name path)
        (Includecore.report_type_mismatch
           "the type" "this extension" "definition")
        err
  | Rebind_wrong_type (lid, env, trace) ->
      Printtyp.report_unification_error ppf env trace
        (function ppf ->
           fprintf ppf "The constructor %a@ has type"
             Printtyp.longident lid)
        (function ppf ->
           fprintf ppf "but was expected to be of type")
  | Rebind_mismatch (lid, p, p') ->
      fprintf ppf
        "@[%s@ %a@ %s@ %s@ %s@ %s@ %s@]"
        "The constructor" Printtyp.longident lid
        "extends type" (Path.name p)
        "whose declaration does not match"
        "the declaration of type" (Path.name p')
  | Rebind_private lid ->
      fprintf ppf "@[%s@ %a@ %s@]"
        "The constructor"
        Printtyp.longident lid
        "is private"
  | Variance (Typedecl_variance.Bad_variance (n, v1, v2)) ->
      let variance (p,n,i) =
        let inj = if i then "injective " else "" in
        match p, n with
          true,  true  -> inj ^ "invariant"
        | true,  false -> inj ^ "covariant"
        | false, true  -> inj ^ "contravariant"
        | false, false -> if inj = "" then "unrestricted" else inj
      in
      let suffix n =
        let teen = (n mod 100)/10 = 1 in
        match n mod 10 with
        | 1 when not teen -> "st"
        | 2 when not teen -> "nd"
        | 3 when not teen -> "rd"
        | _ -> "th"
      in
      (match n with
       | Variance_not_reflected ->
           fprintf ppf "@[%s@ %s@ It"
             "In this definition, a type variable has a variance that"
             "is not reflected by its occurrence in type parameters."
       | No_variable ->
           fprintf ppf "@[%s@ %s@]"
             "In this definition, a type variable cannot be deduced"
             "from the type parameters."
       | Variance_not_deducible ->
           fprintf ppf "@[%s@ %s@ It"
             "In this definition, a type variable has a variance that"
             "cannot be deduced from the type parameters."
       | Variance_not_satisfied n ->
           fprintf ppf "@[%s@ %s@ The %d%s type parameter"
             "In this definition, expected parameter"
             "variances are not satisfied."
             n (suffix n));
      (match n with
       | No_variable -> ()
       | _ ->
           fprintf ppf " was expected to be %s,@ but it is %s.@]"
             (variance v2) (variance v1))
  | Unavailable_type_constructor p ->
      fprintf ppf "The definition of type %a@ is unavailable" Printtyp.path p
  | Bad_fixed_type r ->
      fprintf ppf "This fixed type %s" r
  | Variance Typedecl_variance.Varying_anonymous ->
      fprintf ppf "@[%s@ %s@ %s@]"
        "In this GADT definition," "the variance of some parameter"
        "cannot be checked"
  | Val_in_structure ->
      fprintf ppf "Value declarations are only allowed in signatures"
  | Multiple_native_repr_attributes ->
      fprintf ppf "Too many [@@unboxed]/[@@untagged] attributes"
  | Cannot_unbox_or_untag_type Unboxed ->
      fprintf ppf "@[Don't know how to unbox this type.@ \
                   Only float, int32, int64 and nativeint can be unboxed.@]"
  | Cannot_unbox_or_untag_type Untagged ->
      fprintf ppf "@[Don't know how to untag this type.@ \
                   Only int can be untagged.@]"
  | Deep_unbox_or_untag_attribute kind ->
      fprintf ppf
        "@[The attribute '%s' should be attached to@ \
         a direct argument or result of the primitive,@ \
         it should not occur deeply into its type.@]"
        (match kind with Unboxed -> "@unboxed" | Untagged -> "@untagged")
  | Immediacy (Typedecl_immediacy.Bad_immediacy_attribute violation) ->
      fprintf ppf "@[%a@]" Format.pp_print_text
        (match violation with
         | Type_immediacy.Violation.Not_always_immediate ->
             "Types marked with the immediate attribute must be \
              non-pointer types like int or bool."
         | Type_immediacy.Violation.Not_always_immediate_on_64bits ->
             "Types marked with the immediate64 attribute must be \
              produced using the Stdlib.Sys.Immediate64.Make functor.")
  | Bad_unboxed_attribute msg ->
      fprintf ppf "@[This type cannot be unboxed because@ %s.@]" msg
  | Wrong_unboxed_type_float ->
      fprintf ppf "@[This type cannot be unboxed because@ \
                   it might contain both float and non-float values.@ \
                   You should annotate it with [%@%@ocaml.boxed].@]"
  | Boxed_and_unboxed ->
      fprintf ppf "@[A type cannot be boxed and unboxed at the same time.@]"
  | Nonrec_gadt ->
      fprintf ppf
        "@[GADT case syntax cannot be used in a 'nonrec' block.@]"

let () =
  Location.register_error_of_exn
    (function
      | Error (loc, err) ->
        Some (Location.error_of_printer ~loc report_error err)
      | _ ->
        None
    )
