Source file `ppx_repr.ml`

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(*
 * OCanren. PPX suntax extensions.
 * Copyright (C) 2015-2021
 * Dmitri Boulytchev, Dmitry Kosarev, Alexey Syomin, Evgeny Moiseenko
 * St.Petersburg State University, JetBrains Research
 *
 * This software is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Library General Public
 * License version 2, as published by the Free Software Foundation.
 *
 * This software 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 Library General Public License version 2 for more details
 * (enclosed in the file COPYING).
 *)

open Ppxlib

let string_of_expression e =
  Format.set_margin 1000;
  Format.set_max_indent 2000;
  let ans = Format.asprintf "%a" Pprintast.expression e in
  ans
;;

let mapper =
  object
    inherit Ast_traverse.map as super

    method! expression e =
      match e with
      | { pexp_desc = Pexp_construct ({ txt = Lident "REPR"; _ }, Some e); _ } as expr ->
        let text = string_of_expression e in
        { expr with
          pexp_desc =
            Pexp_tuple
              [ Ast_helper.Exp.constant (Pconst_string (text, e.pexp_loc, None)); e ]
        }
      | e -> super#expression e
  end
;;

let () = Ppxlib.Driver.register_transformation ~impl:(fun s -> mapper#structure s) "repr"