Get types in OCaml

gettyp.ml

let _ =
  let open Typedtree in
  let open Types in
  let types_from_arrow ty =
    let rec helper ty =
      match ty.desc with
      | Tlink ty -> helper ty
      | Tarrow (_, t1, t2, _) -> helper t1 @ helper t2
      | Tconstr (Path.Pident id, _, _) -> [Ident.name id]
      | _ -> failwith "oops" in
    helper ty in
  let e = let _ = Compmisc.init_path false in
          Compmisc.initial_env () in
  let buf = Lexing.from_string "let add x y = x + y" in
  let p = Parse.implementation buf in
  let tstr, _tsig, _newe = Typemod.type_structure e p Location.none in
  (* let _ = Printtyped.implementation Format.std_formatter tstr in *)
  let {str_items} = tstr in
  let {str_desc} :: _ = str_items in
  let Typedtree.Tstr_value (_, lst) = str_desc in
  let rec helper = function
    | [] -> ()
    | ({ pat_type }, _) :: rest ->
       Printtyp.raw_type_expr Format.std_formatter pat_type;
       helper rest in
  helper lst;

Compile with ocamlbuild -pkg compiler-libs -lib ocamlcommon gettyp.ml