ast_typ_uncurry.ml

(* Copyright (C) 2020 Hongbo Zhang, Authors of ReScript
 * 
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU Lesser General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * In addition to the permissions granted to you by the LGPL, you may combine
 * or link a "work that uses the Library" with a publicly distributed version
 * of this file to produce a combined library or application, then distribute
 * that combined work under the terms of your choosing, with no requirement
 * to comply with the obligations normally placed on you by section 4 of the
 * LGPL version 3 (or the corresponding section of a later version of the LGPL
 * should you choose to use a later version).
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU Lesser General Public License for more details.
 * 
 * You should have received a copy of the GNU Lesser General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA. *)

type typ = Parsetree.core_type

type 'a cxt = Ast_helper.loc -> Bs_ast_mapper.mapper -> 'a

type uncurry_type_gen = (Asttypes.arg_label -> typ -> typ -> typ) cxt

module Typ = Ast_helper.Typ

let to_method_callback_type loc (mapper : Bs_ast_mapper.mapper)
    (label : Asttypes.arg_label) (first_arg : Parsetree.core_type)
    (typ : Parsetree.core_type) =
  let first_arg = mapper.typ mapper first_arg in
  let typ = mapper.typ mapper typ in
  let meth_type = Typ.arrow ~loc label first_arg typ in
  let arity = Ast_core_type.get_uncurry_arity meth_type in
  match arity with
  | Some n ->
      Typ.constr
        {
          txt =
            Ldot (Ast_literal.Lid.js_meth_callback, "arity" ^ string_of_int n);
          loc;
        }
        [ meth_type ]
  | None -> assert false

let self_type_lit = "self_type"

let generate_method_type loc (mapper : Bs_ast_mapper.mapper) ?alias_type
    method_name lbl pat e : Parsetree.core_type =
  let arity = Ast_pat.arity_of_fun pat e in
  let result = Typ.var ~loc method_name in
  let self_type loc = Typ.var ~loc self_type_lit in

  let self_type =
    let v = self_type loc in
    match alias_type with
    | None -> v
    | Some ty -> Typ.alias ~loc ty self_type_lit
  in
  if arity = 0 then to_method_callback_type loc mapper Nolabel self_type result
  else
    let tyvars =
      Ext_list.mapi (lbl :: Ast_pat.labels_of_fun e) (fun i x ->
          (x, Typ.var ~loc (method_name ^ string_of_int i)))
      (* Ext_list.init arity (fun i -> Typ.var ~loc (method_name ^ string_of_int i)) *)
    in
    match tyvars with
    | (label, x) :: rest ->
        let method_rest =
          Ext_list.fold_right rest result (fun (label, v) acc ->
              Typ.arrow ~loc label v acc)
        in
        to_method_callback_type loc mapper Nolabel self_type
          (Typ.arrow ~loc label x method_rest)
    | _ -> assert false

let to_method_type loc (mapper : Bs_ast_mapper.mapper)
    (label : Asttypes.arg_label) (first_arg : Parsetree.core_type)
    (typ : Parsetree.core_type) =
  let first_arg = mapper.typ mapper first_arg in
  let typ = mapper.typ mapper typ in
  let meth_type = Typ.arrow ~loc label first_arg typ in
  let arity = Ast_core_type.get_uncurry_arity meth_type in
  match arity with
  | Some 0 ->
      Typ.constr { txt = Ldot (Ast_literal.Lid.js_meth, "arity0"); loc } [ typ ]
  | Some n ->
      Typ.constr
        { txt = Ldot (Ast_literal.Lid.js_meth, "arity" ^ string_of_int n); loc }
        [ meth_type ]
  | None -> assert false

let generate_arg_type loc (mapper : Bs_ast_mapper.mapper) method_name label pat
    body : Ast_core_type.t =
  let arity = Ast_pat.arity_of_fun pat body in
  let result = Typ.var ~loc method_name in
  if arity = 0 then
    to_method_type loc mapper Nolabel (Ast_literal.type_unit ~loc ()) result
  else
    let tyvars =
      Ext_list.mapi (label :: Ast_pat.labels_of_fun body) (fun i x ->
          (x, Typ.var ~loc (method_name ^ string_of_int i)))
    in
    match tyvars with
    | (label, x) :: rest ->
        let method_rest =
          Ext_list.fold_right rest result (fun (label, v) acc ->
              Typ.arrow ~loc label v acc)
        in
        to_method_type loc mapper label x method_rest
    | _ -> assert false

let to_uncurry_type loc (mapper : Bs_ast_mapper.mapper)
    (label : Asttypes.arg_label) (first_arg : Parsetree.core_type)
    (typ : Parsetree.core_type) =
  (* no need to error for optional here,
     since we can not make it
     TODO: still error out for external?
     Maybe no need to error on optional at all
     it just does not make sense
  *)
  let first_arg = mapper.typ mapper first_arg in
  let typ = mapper.typ mapper typ in

  let fn_type = Typ.arrow ~loc label first_arg typ in
  let arity = Ast_core_type.get_uncurry_arity fn_type in
  match arity with
  | Some 0 ->
      Typ.constr { txt = Ldot (Ast_literal.Lid.js_fn, "arity0"); loc } [ typ ]
  | Some n ->
      Typ.constr
        { txt = Ldot (Ast_literal.Lid.js_fn, "arity" ^ string_of_int n); loc }
        [ fn_type ]
  | None -> assert false