(**************************************************************************)
(*                                                                        *)
(*                                 OCaml                                  *)
(*                                                                        *)
                , 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.          *)
(*                                                                        *)
(**************************************************************************)

(* Inclusion checks for the core language *)

open Asttypes
open Path
open Types
open Typedtree

(* Inclusion between value descriptions *)

exception Dont_match

let value_descriptions ~loc env name
    (vd1 : Types.value_description)
    (vd2 : Types.value_description) =
  Builtin_attributes.check_deprecated_inclusion
    ~def:vd1.val_loc
    ~use:vd2.val_loc
    loc
    vd1.val_attributes vd2.val_attributes
    name;
  if Ctype.moregeneral env true vd1.val_type vd2.val_type then begin
    match (vd1.val_kind, vd2.val_kind) with
        (Val_prim p1, Val_prim p2) ->
          if p1 = p2 then Tcoerce_none else raise Dont_match
      | (Val_prim p, _) ->
          let pc = {pc_desc = p; pc_type = vd2.Types.val_type;
                  pc_env = env; pc_loc = vd1.Types.val_loc; } in
          Tcoerce_primitive pc
      | (_, Val_prim _) -> raise Dont_match
      | (_, _) -> Tcoerce_none
  end else
    raise Dont_match

(* Inclusion between "private" annotations *)

let private_flags decl1 decl2 =
  match decl1.type_private, decl2.type_private with
  | Private, Public ->
      decl2.type_kind = Type_abstract &&
      (decl2.type_manifest = None || decl1.type_kind <> Type_abstract)
  | _, _ -> true

(* Inclusion between manifest types (particularly for private row types) *)

let is_absrow env ty =
  match ty.desc with
    Tconstr(Pident _, _, _) ->
      begin match Ctype.expand_head env ty with
        {desc=Tobject _|Tvariant _} -> true
      | _ -> false
      end
  | _ -> false

let type_manifest env ty1 params1 ty2 params2 priv2 =
  let ty1' = Ctype.expand_head env ty1 and ty2' = Ctype.expand_head env ty2 in
  match ty1'.desc, ty2'.desc with
    Tvariant row1, Tvariant row2 when is_absrow env (Btype.row_more row2) ->
      let row1 = Btype.row_repr row1 and row2 = Btype.row_repr row2 in
      Ctype.equal env true (ty1::params1) (row2.row_more::params2) &&
      begin match row1.row_more with
        {desc=Tvar _|Tconstr _|Tnil} -> true
      | _ -> false
      end &&
      let r1, r2, pairs =
        Ctype.merge_row_fields row1.row_fields row2.row_fields in
      (not row2.row_closed ||
       row1.row_closed && Ctype.filter_row_fields false r1 = []) &&
      List.for_all
        (fun (_,f) -> match Btype.row_field_repr f with
          Rabsent | Reither _ -> true | Rpresent _ -> false)
        r2 &&
      let to_equal = ref (List.combine params1 params2) in
      List.for_all
        (fun (_, f1, f2) ->
          match Btype.row_field_repr f1, Btype.row_field_repr f2 with
            Rpresent(Some t1),
            (Rpresent(Some t2) | Reither(false, [t2], _, _)) ->
              to_equal := (t1,t2) :: !to_equal; true
          | Rpresent None, (Rpresent None | Reither(true, [], _, _)) -> true
          | Reither(c1,tl1,_,_), Reither(c2,tl2,_,_)
            when List.length tl1 = List.length tl2 && c1 = c2 ->
              to_equal := List.combine tl1 tl2 @ !to_equal; true
          | Rabsent, (Reither _ | Rabsent) -> true
          | _ -> false)
        pairs &&
      let tl1, tl2 = List.split !to_equal in
      Ctype.equal env true tl1 tl2
  | Tobject (fi1, _), Tobject (fi2, _)
    when is_absrow env (snd(Ctype.flatten_fields fi2)) ->
      let (fields2,rest2) = Ctype.flatten_fields fi2 in
      Ctype.equal env true (ty1::params1) (rest2::params2) &&
      let (fields1,rest1) = Ctype.flatten_fields fi1 in
      (match rest1 with {desc=Tnil|Tvar _|Tconstr _} -> true | _ -> false) &&
      let pairs, _miss1, miss2 = Ctype.associate_fields fields1 fields2 in
      miss2 = [] &&
      let tl1, tl2 =
        List.split (List.map (fun (_,_,t1,_,t2) -> t1, t2) pairs) in
      Ctype.equal env true (params1 @ tl1) (params2 @ tl2)
  | _ ->
      let rec check_super ty1 =
        Ctype.equal env true (ty1 :: params1) (ty2 :: params2) ||
        priv2 = Private &&
        try check_super
              (Ctype.try_expand_once_opt env (Ctype.expand_head env ty1))
        with Ctype.Cannot_expand -> false
      in check_super ty1

(* Inclusion between type declarations *)

type type_mismatch =
    Arity
  | Privacy
  | Kind
  | Constraint
  | Manifest
  | Variance
  | Field_type of Ident.t
  | Field_mutable of Ident.t
  | Field_arity of Ident.t
  | Field_names of int * Ident.t * Ident.t
  | Field_missing of bool * Ident.t
  true means second one is unboxed float
  true means second one is unboxed
  | Immediate

let report_type_mismatch0 first second decl ppf err =
  let pr fmt = Format.fprintf ppf fmt in
  match err with
    Arity -> pr "They have different arities"
  | Privacy -> pr "A private type would be revealed"
  | Kind -> pr "Their kinds differ"
  | Constraint -> pr "Their constraints differ"
  | Manifest -> ()
  | Variance -> pr "Their variances do not agree"
  | Field_type s ->
      pr "The types for field %s are not equal" (Ident.name s)
  | Field_mutable s ->
      pr "The mutability of field %s is different" (Ident.name s)
  | Field_arity s ->
      pr "The arities for field %s differ" (Ident.name s)
  | Field_names (n, name1, name2) ->
      pr "Fields number %i have different names, %s and %s"
        n (Ident.name name1) (Ident.name name2)
  | Field_missing (b, s) ->
      pr "The field %s is only present in %s %s"
        (Ident.name s) (if b then second else first) decl
  | Record_representation b ->
      pr "Their internal representations differ:@ %s %s %s"
        (if b then second else first) decl
        "uses unboxed float representation"
  | Unboxed_representation b ->
      pr "Their internal representations differ:@ %s %s %s"
         (if b then second else first) decl
         "uses unboxed representation"
  | Immediate -> pr "%s is not an immediate type" first

let report_type_mismatch first second decl ppf =
  List.iter
    (fun err ->
      if err = Manifest then () else
      Format.fprintf ppf "@ %a." (report_type_mismatch0 first second decl) err)

let rec compare_constructor_arguments ~loc env cstr params1 params2 arg1 arg2 =
  match arg1, arg2 with
  | Types.Cstr_tuple arg1, Types.Cstr_tuple arg2 ->
      if List.length arg1 <> List.length arg2 then [Field_arity cstr]
      else if
        (* Ctype.equal must be called on all arguments at once, cf. PR#7378 *)
        Ctype.equal env true (params1 @ arg1) (params2 @ arg2)
      then [] else [Field_type cstr]
  | Types.Cstr_record l1, Types.Cstr_record l2 ->
      compare_records env ~loc params1 params2 0 l1 l2
  | _ -> [Field_type cstr]

and compare_variants ~loc env params1 params2 n
    (cstrs1 : Types.constructor_declaration list)
    (cstrs2 : Types.constructor_declaration list) =
  match cstrs1, cstrs2 with
    [], []           -> []
  | [], c::_ -> [Field_missing (true, c.Types.cd_id)]
  | c::_, [] -> [Field_missing (false, c.Types.cd_id)]
  | cd1::rem1, cd2::rem2 ->
      if Ident.name cd1.cd_id <> Ident.name cd2.cd_id then
        [Field_names (n, cd1.cd_id, cd2.cd_id)]
      else begin
        Builtin_attributes.check_deprecated_inclusion
          ~def:cd1.cd_loc
          ~use:cd2.cd_loc
          loc
          cd1.cd_attributes cd2.cd_attributes
          (Ident.name cd1.cd_id);
        let r =
          match cd1.cd_res, cd2.cd_res with
          | Some r1, Some r2 ->
              if Ctype.equal env true [r1] [r2] then
                compare_constructor_arguments ~loc env cd1.cd_id [r1] [r2]
                  cd1.cd_args cd2.cd_args
              else [Field_type cd1.cd_id]
          | Some _, None | None, Some _ ->
              [Field_type cd1.cd_id]
          | _ ->
              compare_constructor_arguments ~loc env cd1.cd_id
                params1 params2 cd1.cd_args cd2.cd_args
        in
        if r <> [] then r
        else compare_variants ~loc env params1 params2 (n+1) rem1 rem2
      end


and compare_records ~loc env params1 params2 n
    (labels1 : Types.label_declaration list)
    (labels2 : Types.label_declaration list) =
  match labels1, labels2 with
    [], []           -> []
  | [], l::_ -> [Field_missing (true, l.Types.ld_id)]
  | l::_, [] -> [Field_missing (false, l.Types.ld_id)]
  | ld1::rem1, ld2::rem2 ->
      if Ident.name ld1.ld_id <> Ident.name ld2.ld_id
      then [Field_names (n, ld1.ld_id, ld2.ld_id)]
      else if ld1.ld_mutable <> ld2.ld_mutable then [Field_mutable ld1.ld_id] else begin
        Builtin_attributes.check_deprecated_mutable_inclusion
          ~def:ld1.ld_loc
          ~use:ld2.ld_loc
          loc
          ld1.ld_attributes ld2.ld_attributes
          (Ident.name ld1.ld_id);
        if Ctype.equal env true (ld1.ld_type::params1)(ld2.ld_type::params2)
        then (* add arguments to the parameters, cf. PR#7378 *)
          compare_records ~loc env
            (ld1.ld_type::params1) (ld2.ld_type::params2)
            (n+1)
            rem1 rem2
        else
          [Field_type ld1.ld_id]
      end

let type_declarations ?(equality = false) ~loc env name decl1 id decl2 =
  Builtin_attributes.check_deprecated_inclusion
    ~def:decl1.type_loc
    ~use:decl2.type_loc
    loc
    decl1.type_attributes decl2.type_attributes
    name;
  if decl1.type_arity <> decl2.type_arity then [Arity] else
  if not (private_flags decl1 decl2) then [Privacy] else
  let err = match (decl1.type_manifest, decl2.type_manifest) with
      (_, None) ->
        if Ctype.equal env true decl1.type_params decl2.type_params
        then [] else [Constraint]
    | (Some ty1, Some ty2) ->
        if type_manifest env ty1 decl1.type_params ty2 decl2.type_params
            decl2.type_private
        then [] else [Manifest]
    | (None, Some ty2) ->
        let ty1 =
          Btype.newgenty (Tconstr(Pident id, decl2.type_params, ref Mnil))
        in
        if Ctype.equal env true decl1.type_params decl2.type_params then
          if Ctype.equal env false [ty1] [ty2] then []
          else [Manifest]
        else [Constraint]
  in
  if err <> [] then err else
  let err =
    match (decl2.type_kind, decl1.type_unboxed.unboxed,
           decl2.type_unboxed.unboxed) with
    | Type_abstract, _, _ -> []
    | _, true, false -> [Unboxed_representation false]
    | _, false, true -> [Unboxed_representation true]
    | _ -> []
  in
  if err <> [] then err else
  let err = match (decl1.type_kind, decl2.type_kind) with
      (_, Type_abstract) -> []
    | (Type_variant cstrs1, Type_variant cstrs2) ->
        let mark cstrs usage name decl =
          List.iter
            (fun c ->
              Env.mark_constructor_used usage env name decl
                                        (Ident.name c.Types.cd_id))
            cstrs
        in
        let usage =
          if decl1.type_private = Private || decl2.type_private = Public
          then Env.Positive else Env.Privatize
        in
        mark cstrs1 usage name decl1;
        if equality then mark cstrs2 Env.Positive (Ident.name id) decl2;
        compare_variants ~loc env decl1.type_params decl2.type_params 1 cstrs1 cstrs2
    | (Type_record(labels1,rep1), Type_record(labels2,rep2)) ->
        let err = compare_records ~loc env decl1.type_params decl2.type_params
            1 labels1 labels2 in
        if err <> [] || rep1 = rep2 then err else
        [Record_representation (rep2 = Record_float)]
    | (Type_open, Type_open) -> []
    | (_, _) -> [Kind]
  in
  if err <> [] then err else
  let abstr = decl2.type_kind = Type_abstract && decl2.type_manifest = None in
  (* If attempt to assign a non-immediate type (e.g. string) to a type that
   * must be immediate, then we error *)
  let err =
    if abstr &&
       not decl1.type_immediate &&
       decl2.type_immediate then
      [Immediate]
    else []
  in
  if err <> [] then err else
  let need_variance =
    abstr || decl1.type_private = Private || decl1.type_kind = Type_open in
  if not need_variance then [] else
  let abstr = abstr || decl2.type_private = Private in
  let opn = decl2.type_kind = Type_open && decl2.type_manifest = None in
  let constrained ty = not (Btype.(is_Tvar (repr ty))) in
  if List.for_all2
      (fun ty (v1,v2) ->
        let open Variance in
        let imp a b = not a || b in
        let (co1,cn1) = get_upper v1 and (co2,cn2) = get_upper v2 in
        (if abstr then (imp co1 co2 && imp cn1 cn2)
         else if opn || constrained ty then (co1 = co2 && cn1 = cn2)
         else true) &&
        let (p1,n1,i1,j1) = get_lower v1 and (p2,n2,i2,j2) = get_lower v2 in
        imp abstr (imp p2 p1 && imp n2 n1 && imp i2 i1 && imp j2 j1))
      decl2.type_params (List.combine decl1.type_variance decl2.type_variance)
  then [] else [Variance]

(* Inclusion between extension constructors *)

let extension_constructors ~loc env id ext1 ext2 =
  let usage =
    if ext1.ext_private = Private || ext2.ext_private = Public
    then Env.Positive else Env.Privatize
  in
  Env.mark_extension_used usage env ext1 (Ident.name id);
  let ty1 =
    Btype.newgenty (Tconstr(ext1.ext_type_path, ext1.ext_type_params, ref Mnil))
  in
  let ty2 =
    Btype.newgenty (Tconstr(ext2.ext_type_path, ext2.ext_type_params, ref Mnil))
  in
  if Ctype.equal env true
       (ty1 :: ext1.ext_type_params)
       (ty2 :: ext2.ext_type_params)
  then
    if compare_constructor_arguments ~loc env (Ident.create "")
        ext1.ext_type_params ext2.ext_type_params
        ext1.ext_args ext2.ext_args = [] then
      if match ext1.ext_ret_type, ext2.ext_ret_type with
          Some r1, Some r2 when not (Ctype.equal env true [r1] [r2]) -> false
        | Some _, None | None, Some _ -> false
        | _ -> true
      then
        match ext1.ext_private, ext2.ext_private with
            Private, Public -> false
          | _, _ -> true
      else false
    else false
  else false

************************************************************************
                                                                        
                                 OCaml                                  
                                                                        
                                                                        
     en Automatique.                                                    
                                                                        
   All rights reserved.  This file is distributed under the terms of    
   special exception on linking described in the file LICENSE.          
                                                                        
************************************************************************
 Inclusion checks for the core language 
 Inclusion between value descriptions 
 Inclusion between "private" annotations 
 Inclusion between manifest types (particularly for private row types) 
 Inclusion between type declarations 
 Ctype.equal must be called on all arguments at once, cf. PR#7378 
 add arguments to the parameters, cf. PR#7378 
 If attempt to assign a non-immediate type (e.g. string) to a type that
   * must be immediate, then we error 
 Inclusion between extension constructors 
                , 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 Asttypes
open Path
open Types
open Typedtree


exception Dont_match

let value_descriptions ~loc env name
    (vd1 : Types.value_description)
    (vd2 : Types.value_description) =
  Builtin_attributes.check_deprecated_inclusion
    ~def:vd1.val_loc
    ~use:vd2.val_loc
    loc
    vd1.val_attributes vd2.val_attributes
    name;
  if Ctype.moregeneral env true vd1.val_type vd2.val_type then begin
    match (vd1.val_kind, vd2.val_kind) with
        (Val_prim p1, Val_prim p2) ->
          if p1 = p2 then Tcoerce_none else raise Dont_match
      | (Val_prim p, _) ->
          let pc = {pc_desc = p; pc_type = vd2.Types.val_type;
                  pc_env = env; pc_loc = vd1.Types.val_loc; } in
          Tcoerce_primitive pc
      | (_, Val_prim _) -> raise Dont_match
      | (_, _) -> Tcoerce_none
  end else
    raise Dont_match


let private_flags decl1 decl2 =
  match decl1.type_private, decl2.type_private with
  | Private, Public ->
      decl2.type_kind = Type_abstract &&
      (decl2.type_manifest = None || decl1.type_kind <> Type_abstract)
  | _, _ -> true


let is_absrow env ty =
  match ty.desc with
    Tconstr(Pident _, _, _) ->
      begin match Ctype.expand_head env ty with
        {desc=Tobject _|Tvariant _} -> true
      | _ -> false
      end
  | _ -> false

let type_manifest env ty1 params1 ty2 params2 priv2 =
  let ty1' = Ctype.expand_head env ty1 and ty2' = Ctype.expand_head env ty2 in
  match ty1'.desc, ty2'.desc with
    Tvariant row1, Tvariant row2 when is_absrow env (Btype.row_more row2) ->
      let row1 = Btype.row_repr row1 and row2 = Btype.row_repr row2 in
      Ctype.equal env true (ty1::params1) (row2.row_more::params2) &&
      begin match row1.row_more with
        {desc=Tvar _|Tconstr _|Tnil} -> true
      | _ -> false
      end &&
      let r1, r2, pairs =
        Ctype.merge_row_fields row1.row_fields row2.row_fields in
      (not row2.row_closed ||
       row1.row_closed && Ctype.filter_row_fields false r1 = []) &&
      List.for_all
        (fun (_,f) -> match Btype.row_field_repr f with
          Rabsent | Reither _ -> true | Rpresent _ -> false)
        r2 &&
      let to_equal = ref (List.combine params1 params2) in
      List.for_all
        (fun (_, f1, f2) ->
          match Btype.row_field_repr f1, Btype.row_field_repr f2 with
            Rpresent(Some t1),
            (Rpresent(Some t2) | Reither(false, [t2], _, _)) ->
              to_equal := (t1,t2) :: !to_equal; true
          | Rpresent None, (Rpresent None | Reither(true, [], _, _)) -> true
          | Reither(c1,tl1,_,_), Reither(c2,tl2,_,_)
            when List.length tl1 = List.length tl2 && c1 = c2 ->
              to_equal := List.combine tl1 tl2 @ !to_equal; true
          | Rabsent, (Reither _ | Rabsent) -> true
          | _ -> false)
        pairs &&
      let tl1, tl2 = List.split !to_equal in
      Ctype.equal env true tl1 tl2
  | Tobject (fi1, _), Tobject (fi2, _)
    when is_absrow env (snd(Ctype.flatten_fields fi2)) ->
      let (fields2,rest2) = Ctype.flatten_fields fi2 in
      Ctype.equal env true (ty1::params1) (rest2::params2) &&
      let (fields1,rest1) = Ctype.flatten_fields fi1 in
      (match rest1 with {desc=Tnil|Tvar _|Tconstr _} -> true | _ -> false) &&
      let pairs, _miss1, miss2 = Ctype.associate_fields fields1 fields2 in
      miss2 = [] &&
      let tl1, tl2 =
        List.split (List.map (fun (_,_,t1,_,t2) -> t1, t2) pairs) in
      Ctype.equal env true (params1 @ tl1) (params2 @ tl2)
  | _ ->
      let rec check_super ty1 =
        Ctype.equal env true (ty1 :: params1) (ty2 :: params2) ||
        priv2 = Private &&
        try check_super
              (Ctype.try_expand_once_opt env (Ctype.expand_head env ty1))
        with Ctype.Cannot_expand -> false
      in check_super ty1


type type_mismatch =
    Arity
  | Privacy
  | Kind
  | Constraint
  | Manifest
  | Variance
  | Field_type of Ident.t
  | Field_mutable of Ident.t
  | Field_arity of Ident.t
  | Field_names of int * Ident.t * Ident.t
  | Field_missing of bool * Ident.t
  true means second one is unboxed float
  true means second one is unboxed
  | Immediate

let report_type_mismatch0 first second decl ppf err =
  let pr fmt = Format.fprintf ppf fmt in
  match err with
    Arity -> pr "They have different arities"
  | Privacy -> pr "A private type would be revealed"
  | Kind -> pr "Their kinds differ"
  | Constraint -> pr "Their constraints differ"
  | Manifest -> ()
  | Variance -> pr "Their variances do not agree"
  | Field_type s ->
      pr "The types for field %s are not equal" (Ident.name s)
  | Field_mutable s ->
      pr "The mutability of field %s is different" (Ident.name s)
  | Field_arity s ->
      pr "The arities for field %s differ" (Ident.name s)
  | Field_names (n, name1, name2) ->
      pr "Fields number %i have different names, %s and %s"
        n (Ident.name name1) (Ident.name name2)
  | Field_missing (b, s) ->
      pr "The field %s is only present in %s %s"
        (Ident.name s) (if b then second else first) decl
  | Record_representation b ->
      pr "Their internal representations differ:@ %s %s %s"
        (if b then second else first) decl
        "uses unboxed float representation"
  | Unboxed_representation b ->
      pr "Their internal representations differ:@ %s %s %s"
         (if b then second else first) decl
         "uses unboxed representation"
  | Immediate -> pr "%s is not an immediate type" first

let report_type_mismatch first second decl ppf =
  List.iter
    (fun err ->
      if err = Manifest then () else
      Format.fprintf ppf "@ %a." (report_type_mismatch0 first second decl) err)

let rec compare_constructor_arguments ~loc env cstr params1 params2 arg1 arg2 =
  match arg1, arg2 with
  | Types.Cstr_tuple arg1, Types.Cstr_tuple arg2 ->
      if List.length arg1 <> List.length arg2 then [Field_arity cstr]
      else if
        Ctype.equal env true (params1 @ arg1) (params2 @ arg2)
      then [] else [Field_type cstr]
  | Types.Cstr_record l1, Types.Cstr_record l2 ->
      compare_records env ~loc params1 params2 0 l1 l2
  | _ -> [Field_type cstr]

and compare_variants ~loc env params1 params2 n
    (cstrs1 : Types.constructor_declaration list)
    (cstrs2 : Types.constructor_declaration list) =
  match cstrs1, cstrs2 with
    [], []           -> []
  | [], c::_ -> [Field_missing (true, c.Types.cd_id)]
  | c::_, [] -> [Field_missing (false, c.Types.cd_id)]
  | cd1::rem1, cd2::rem2 ->
      if Ident.name cd1.cd_id <> Ident.name cd2.cd_id then
        [Field_names (n, cd1.cd_id, cd2.cd_id)]
      else begin
        Builtin_attributes.check_deprecated_inclusion
          ~def:cd1.cd_loc
          ~use:cd2.cd_loc
          loc
          cd1.cd_attributes cd2.cd_attributes
          (Ident.name cd1.cd_id);
        let r =
          match cd1.cd_res, cd2.cd_res with
          | Some r1, Some r2 ->
              if Ctype.equal env true [r1] [r2] then
                compare_constructor_arguments ~loc env cd1.cd_id [r1] [r2]
                  cd1.cd_args cd2.cd_args
              else [Field_type cd1.cd_id]
          | Some _, None | None, Some _ ->
              [Field_type cd1.cd_id]
          | _ ->
              compare_constructor_arguments ~loc env cd1.cd_id
                params1 params2 cd1.cd_args cd2.cd_args
        in
        if r <> [] then r
        else compare_variants ~loc env params1 params2 (n+1) rem1 rem2
      end


and compare_records ~loc env params1 params2 n
    (labels1 : Types.label_declaration list)
    (labels2 : Types.label_declaration list) =
  match labels1, labels2 with
    [], []           -> []
  | [], l::_ -> [Field_missing (true, l.Types.ld_id)]
  | l::_, [] -> [Field_missing (false, l.Types.ld_id)]
  | ld1::rem1, ld2::rem2 ->
      if Ident.name ld1.ld_id <> Ident.name ld2.ld_id
      then [Field_names (n, ld1.ld_id, ld2.ld_id)]
      else if ld1.ld_mutable <> ld2.ld_mutable then [Field_mutable ld1.ld_id] else begin
        Builtin_attributes.check_deprecated_mutable_inclusion
          ~def:ld1.ld_loc
          ~use:ld2.ld_loc
          loc
          ld1.ld_attributes ld2.ld_attributes
          (Ident.name ld1.ld_id);
        if Ctype.equal env true (ld1.ld_type::params1)(ld2.ld_type::params2)
          compare_records ~loc env
            (ld1.ld_type::params1) (ld2.ld_type::params2)
            (n+1)
            rem1 rem2
        else
          [Field_type ld1.ld_id]
      end

let type_declarations ?(equality = false) ~loc env name decl1 id decl2 =
  Builtin_attributes.check_deprecated_inclusion
    ~def:decl1.type_loc
    ~use:decl2.type_loc
    loc
    decl1.type_attributes decl2.type_attributes
    name;
  if decl1.type_arity <> decl2.type_arity then [Arity] else
  if not (private_flags decl1 decl2) then [Privacy] else
  let err = match (decl1.type_manifest, decl2.type_manifest) with
      (_, None) ->
        if Ctype.equal env true decl1.type_params decl2.type_params
        then [] else [Constraint]
    | (Some ty1, Some ty2) ->
        if type_manifest env ty1 decl1.type_params ty2 decl2.type_params
            decl2.type_private
        then [] else [Manifest]
    | (None, Some ty2) ->
        let ty1 =
          Btype.newgenty (Tconstr(Pident id, decl2.type_params, ref Mnil))
        in
        if Ctype.equal env true decl1.type_params decl2.type_params then
          if Ctype.equal env false [ty1] [ty2] then []
          else [Manifest]
        else [Constraint]
  in
  if err <> [] then err else
  let err =
    match (decl2.type_kind, decl1.type_unboxed.unboxed,
           decl2.type_unboxed.unboxed) with
    | Type_abstract, _, _ -> []
    | _, true, false -> [Unboxed_representation false]
    | _, false, true -> [Unboxed_representation true]
    | _ -> []
  in
  if err <> [] then err else
  let err = match (decl1.type_kind, decl2.type_kind) with
      (_, Type_abstract) -> []
    | (Type_variant cstrs1, Type_variant cstrs2) ->
        let mark cstrs usage name decl =
          List.iter
            (fun c ->
              Env.mark_constructor_used usage env name decl
                                        (Ident.name c.Types.cd_id))
            cstrs
        in
        let usage =
          if decl1.type_private = Private || decl2.type_private = Public
          then Env.Positive else Env.Privatize
        in
        mark cstrs1 usage name decl1;
        if equality then mark cstrs2 Env.Positive (Ident.name id) decl2;
        compare_variants ~loc env decl1.type_params decl2.type_params 1 cstrs1 cstrs2
    | (Type_record(labels1,rep1), Type_record(labels2,rep2)) ->
        let err = compare_records ~loc env decl1.type_params decl2.type_params
            1 labels1 labels2 in
        if err <> [] || rep1 = rep2 then err else
        [Record_representation (rep2 = Record_float)]
    | (Type_open, Type_open) -> []
    | (_, _) -> [Kind]
  in
  if err <> [] then err else
  let abstr = decl2.type_kind = Type_abstract && decl2.type_manifest = None in
  let err =
    if abstr &&
       not decl1.type_immediate &&
       decl2.type_immediate then
      [Immediate]
    else []
  in
  if err <> [] then err else
  let need_variance =
    abstr || decl1.type_private = Private || decl1.type_kind = Type_open in
  if not need_variance then [] else
  let abstr = abstr || decl2.type_private = Private in
  let opn = decl2.type_kind = Type_open && decl2.type_manifest = None in
  let constrained ty = not (Btype.(is_Tvar (repr ty))) in
  if List.for_all2
      (fun ty (v1,v2) ->
        let open Variance in
        let imp a b = not a || b in
        let (co1,cn1) = get_upper v1 and (co2,cn2) = get_upper v2 in
        (if abstr then (imp co1 co2 && imp cn1 cn2)
         else if opn || constrained ty then (co1 = co2 && cn1 = cn2)
         else true) &&
        let (p1,n1,i1,j1) = get_lower v1 and (p2,n2,i2,j2) = get_lower v2 in
        imp abstr (imp p2 p1 && imp n2 n1 && imp i2 i1 && imp j2 j1))
      decl2.type_params (List.combine decl1.type_variance decl2.type_variance)
  then [] else [Variance]


let extension_constructors ~loc env id ext1 ext2 =
  let usage =
    if ext1.ext_private = Private || ext2.ext_private = Public
    then Env.Positive else Env.Privatize
  in
  Env.mark_extension_used usage env ext1 (Ident.name id);
  let ty1 =
    Btype.newgenty (Tconstr(ext1.ext_type_path, ext1.ext_type_params, ref Mnil))
  in
  let ty2 =
    Btype.newgenty (Tconstr(ext2.ext_type_path, ext2.ext_type_params, ref Mnil))
  in
  if Ctype.equal env true
       (ty1 :: ext1.ext_type_params)
       (ty2 :: ext2.ext_type_params)
  then
    if compare_constructor_arguments ~loc env (Ident.create "")
        ext1.ext_type_params ext2.ext_type_params
        ext1.ext_args ext2.ext_args = [] then
      if match ext1.ext_ret_type, ext2.ext_ret_type with
          Some r1, Some r2 when not (Ctype.equal env true [r1] [r2]) -> false
        | Some _, None | None, Some _ -> false
        | _ -> true
      then
        match ext1.ext_private, ext2.ext_private with
            Private, Public -> false
          | _, _ -> true
      else false
    else false
  else false
