ocaml/typing/types.ml

(***********************************************************************)
(*                                                                     *)
(*                                OCaml                                *)
(*                                                                     *)
(*            Xavier Leroy, projet Cristal, INRIA Rocquencourt         *)
(*                                                                     *)
(*  Copyright 1996 Institut National de Recherche en Informatique et   *)
(*  en Automatique.  All rights reserved.  This file is distributed    *)
(*  under the terms of the Q Public License version 1.0.               *)
(*                                                                     *)
(***********************************************************************)

(* Representation of types and declarations *)

open Asttypes

(* Type expressions for the core language *)

type type_expr =
  { mutable desc: type_desc;
    mutable level: int;
    mutable id: int }

and type_desc =
    Tvar of string option
  | Tarrow of label * type_expr * type_expr * commutable
  | Ttuple of type_expr list
  | Tconstr of Path.t * type_expr list * abbrev_memo ref
  | Tobject of type_expr * (Path.t * type_expr list) option ref
  | Tfield of string * field_kind * type_expr * type_expr
  | Tnil
  | Tlink of type_expr
  | Tsubst of type_expr         (* for copying *)
  | Tvariant of row_desc
  | Tunivar of string option
  | Tpoly of type_expr * type_expr list
  | Tpackage of Path.t * Longident.t list * type_expr list

and row_desc =
    { row_fields: (label * row_field) list;
      row_more: type_expr;
      row_bound: unit;
      row_closed: bool;
      row_fixed: bool;
      row_name: (Path.t * type_expr list) option }

and row_field =
    Rpresent of type_expr option
  | Reither of bool * type_expr list * bool * row_field option ref
        (* 1st true denotes a constant constructor *)
        (* 2nd true denotes a tag in a pattern matching, and
           is erased later *)
  | Rabsent

and abbrev_memo =
    Mnil
  | Mcons of private_flag * Path.t * type_expr * type_expr * abbrev_memo
  | Mlink of abbrev_memo ref

and field_kind =
    Fvar of field_kind option ref
  | Fpresent
  | Fabsent

and commutable =
    Cok
  | Cunknown
  | Clink of commutable ref

module TypeOps = struct
  type t = type_expr
  let compare t1 t2 = t1.id - t2.id
  let hash t = t.id
  let equal t1 t2 = t1 == t2
end

(* Maps of methods and instance variables *)

module OrderedString =
  struct type t = string let compare (x:t) y = compare x y end
module Meths = Map.Make(OrderedString)
module Vars = Meths

(* Value descriptions *)

type value_description =
  { val_type: type_expr;                (* Type of the value *)
    val_kind: value_kind;
    val_loc: Location.t;
 }

and value_kind =
    Val_reg                             (* Regular value *)
  | Val_prim of Primitive.description   (* Primitive *)
  | Val_ivar of mutable_flag * string   (* Instance variable (mutable ?) *)
  | Val_self of (Ident.t * type_expr) Meths.t ref *
                (Ident.t * Asttypes.mutable_flag *
                 Asttypes.virtual_flag * type_expr) Vars.t ref *
                string * type_expr
                                        (* Self *)
  | Val_anc of (string * Ident.t) list * string
                                        (* Ancestor *)
  | Val_unbound                         (* Unbound variable *)

(* Constructor descriptions *)

type constructor_description =
  { cstr_name: string;                  (* Constructor name *)
    cstr_res: type_expr;                (* Type of the result *)
    cstr_existentials: type_expr list;  (* list of existentials *)
    cstr_args: type_expr list;          (* Type of the arguments *)
    cstr_arity: int;                    (* Number of arguments *)
    cstr_tag: constructor_tag;          (* Tag for heap blocks *)
    cstr_consts: int;                   (* Number of constant constructors *)
    cstr_nonconsts: int;                (* Number of non-const constructors *)
    cstr_normal: int;                   (* Number of non generalized constrs *)
    cstr_generalized: bool;             (* Constrained return type? *)
    cstr_private: private_flag }        (* Read-only constructor? *)

and constructor_tag =
    Cstr_constant of int                (* Constant constructor (an int) *)
  | Cstr_block of int                   (* Regular constructor (a block) *)
  | Cstr_exception of Path.t * Location.t (* Exception constructor *)

(* Record label descriptions *)

type label_description =
  { lbl_name: string;                   (* Short name *)
    lbl_res: type_expr;                 (* Type of the result *)
    lbl_arg: type_expr;                 (* Type of the argument *)
    lbl_mut: mutable_flag;              (* Is this a mutable field? *)
    lbl_pos: int;                       (* Position in block *)
    lbl_all: label_description array;   (* All the labels in this type *)
    lbl_repres: record_representation;  (* Representation for this record *)
    lbl_private: private_flag }         (* Read-only field? *)

and record_representation =
    Record_regular                      (* All fields are boxed / tagged *)
  | Record_float                        (* All fields are floats *)

(* Variance *)

module Variance = struct
  type t = int
  type f = May_pos | May_neg | May_weak | Inj | Pos | Neg | Inv
  let single = function
    | May_pos -> 1
    | May_neg -> 2
    | May_weak -> 4
    | Inj -> 8
    | Pos -> 16
    | Neg -> 32
    | Inv -> 64
  let union v1 v2 = v1 lor v2
  let inter v1 v2 = v1 land v2
  let subset v1 v2 = (v1 land v2 = v1)
  let set x b v =
    if b then v lor single x else  v land (lnot (single x))
  let mem x = subset (single x)
  let null = 0
  let may_inv = 7
  let full = 127
  let covariant = single May_pos lor single Pos lor single Inj
  let swap f1 f2 v =
    let v' = set f1 (mem f2 v) v in set f2 (mem f1 v) v'
  let conjugate v = swap May_pos May_neg (swap Pos Neg v)
  let get_upper v = (mem May_pos v, mem May_neg v)
  let get_lower v = (mem Pos v, mem Neg v, mem Inv v, mem Inj v)
end 

(* Type definitions *)

type type_declaration =
  { type_params: type_expr list;
    type_arity: int;
    type_kind: type_kind;
    type_private: private_flag;
    type_manifest: type_expr option;
    type_variance: Variance.t list;
    type_newtype_level: (int * int) option;
    type_loc: Location.t }

and type_kind =
    Type_abstract
  | Type_record of
      (Ident.t * mutable_flag * type_expr) list * record_representation
  | Type_variant of (Ident.t * type_expr list * type_expr option) list

and type_transparence =
    Type_public      (* unrestricted expansion *)
  | Type_new         (* "new" type *)
  | Type_private     (* private type *)

type exception_declaration =
    { exn_args: type_expr list;
      exn_loc: Location.t }

(* Type expressions for the class language *)

module Concr = Set.Make(OrderedString)

type class_type =
    Cty_constr of Path.t * type_expr list * class_type
  | Cty_signature of class_signature
  | Cty_fun of label * type_expr * class_type

and class_signature =
  { cty_self: type_expr;
    cty_vars:
      (Asttypes.mutable_flag * Asttypes.virtual_flag * type_expr) Vars.t;
    cty_concr: Concr.t;
    cty_inher: (Path.t * type_expr list) list }

type class_declaration =
  { cty_params: type_expr list;
    mutable cty_type: class_type;
    cty_path: Path.t;
    cty_new: type_expr option;
    cty_variance: Variance.t list }

type class_type_declaration =
  { clty_params: type_expr list;
    clty_type: class_type;
    clty_path: Path.t;
    clty_variance: Variance.t list }

(* Type expressions for the module language *)

type module_type =
    Mty_ident of Path.t
  | Mty_signature of signature
  | Mty_functor of Ident.t * module_type * module_type

and signature = signature_item list

and signature_item =
    Sig_value of Ident.t * value_description
  | Sig_type of Ident.t * type_declaration * rec_status
  | Sig_exception of Ident.t * exception_declaration
  | Sig_module of Ident.t * module_type * rec_status
  | Sig_modtype of Ident.t * modtype_declaration
  | Sig_class of Ident.t * class_declaration * rec_status
  | Sig_class_type of Ident.t * class_type_declaration * rec_status

and modtype_declaration =
    Modtype_abstract
  | Modtype_manifest of module_type

and rec_status =
    Trec_not                            (* not recursive *)
  | Trec_first                          (* first in a recursive group *)
  | Trec_next                           (* not first in a recursive group *)