Source file engine.ml
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open Ppxlib
open! Utils
include Engine_intf
let map_lident f = function
| Lapply _ -> invalid_arg "Lident.Lapply not supported"
| Ldot (l, s) -> Ldot (l, f s)
| Lident s -> Lident (f s)
let repr_name_of_type_name = function "t" -> "t" | x -> x ^ "_t"
module Located (Attributes : Attributes.S) (A : Ast_builder.S) : S = struct
type state = {
rec_flag : rec_flag;
type_name : string;
lib : string option;
repr_name : string;
rec_detected : bool ref;
var_repr : ([ `Any | `Var of string ] -> expression option) ref;
(** Given a type variable in a type, get its corresponding typerep (if
the variable is properly bound). *)
}
let add_var_repr : type a b. (a -> b option) ref -> a * b -> unit =
fun f_ref (a, b) ->
let f_old = !f_ref in
let f_new a' = if a = a' then Some b else f_old a' in
f_ref := f_new
open Utils
open Utils.Make (A)
module Reader = Monad.Reader
module Algebraic = struct
include Algebraic
include Algebraic.Located (A) (Reader)
end
open A
open Reader.Syntax
open Reader
let all_unlabelled = List.map (fun x -> (Nolabel, x))
let recursive ~lib fparam e =
let mu = evar (match lib with Some s -> s ^ ".mu" | None -> "mu") in
[%expr [%e mu] (fun [%p pvar fparam] -> [%e e])]
type name = { typ : string; repr : string }
let mutually_recursive ~lib (e1, n1) (e2, n2) =
let mu2 = evar (match lib with Some s -> s ^ ".mu2" | None -> "mu2") in
[%expr
[%e mu2] (fun [%p pvar n1.repr] [%p pvar n2.repr] -> ([%e e1], [%e e2]))]
let in_lib ~lib x = match lib with Some lib -> lib ^ "." ^ x | None -> x
let contains_tvar tvar typ =
(object
inherit [bool] Ast_traverse.fold as super
method! core_type_desc t =
super#core_type_desc t >> fun acc ->
acc || match t with Ptyp_var v when v = tvar -> true | _ -> false
end)
#core_type
typ false
let rowfield_is_inherit = function
| { prf_desc = Rinherit _; _ } -> true
| _ -> false
let rec derive_core typ =
let* { type_name; lib; var_repr; _ } = ask in
let loc = typ.ptyp_loc in
match typ.ptyp_desc with
| Ptyp_constr ({ txt = const_name; _ }, args) -> (
match Attribute.get Attributes.repr typ with
| Some e -> return e
| None ->
let nobuiltin =
Option.to_bool (Attribute.get Attributes.nobuiltin typ)
in
let* lident = derive_lident ~nobuiltin const_name in
let+ cons_args =
args >|= derive_core |> sequence |> map all_unlabelled
in
pexp_apply (pexp_ident lident) cons_args)
| Ptyp_variant (_, Open, _) -> Raise.Unsupported.type_open_polyvar ~loc typ
| Ptyp_variant (rowfields, Closed, _labellist) ->
if List.exists rowfield_is_inherit rowfields then
Raise.Unsupported.polyvar_inherit_case ~loc typ;
derive_polyvariant type_name rowfields
| Ptyp_poly _ -> Raise.Unsupported.type_poly ~loc typ
| Ptyp_tuple args -> derive_tuple args
| Ptyp_arrow _ -> Raise.Unsupported.type_arrow ~loc typ
| Ptyp_any -> Location.raise_errorf ~loc "Unbound type variable"
| Ptyp_var v -> (
match !var_repr (`Var v) with
| Some r -> return r
| None -> Location.raise_errorf ~loc "Unbound type variable" v)
| Ptyp_package _ -> Raise.Unsupported.type_package ~loc typ
| Ptyp_extension _ -> Raise.Unsupported.type_extension ~loc typ
| Ptyp_alias (c, var) ->
if contains_tvar var c then (
add_var_repr var_repr (`Var var, evar var);
let+ inner = derive_core c in
recursive ~lib var inner)
else derive_core c
| Ptyp_object _ | Ptyp_class _ -> invalid_arg "unsupported"
and derive_tuple args =
let* { lib; _ } = ask in
match args with
| [ t ] ->
derive_core t
| _ ->
let tuple_type =
(match List.length args with
| 2 -> "pair"
| 3 -> "triple"
| 4 -> "quad"
| n -> Raise.Unsupported.tuple_size ~loc n)
|> in_lib ~lib
|> evar
in
args
>|= derive_core
|> sequence
|> map (all_unlabelled >> pexp_apply tuple_type)
and derive_record ls =
let* { type_name; lib; _ } = ask in
let subderive label_decl =
let field_name = label_decl.pld_name.txt in
let+ field_repr = derive_core label_decl.pld_type in
Algebraic.Typ.{ field_name; field_repr }
in
Algebraic.(encode Typ.Record) ~subderive ~lib ~type_name ls
and derive_variant cs =
let* { type_name; lib; _ } = ask in
let subderive c =
let case_name = c.pcd_name.txt in
let+ case_cons =
match c.pcd_args with
| Pcstr_record _ -> invalid_arg "Inline record types unsupported"
| Pcstr_tuple [] -> return None
| Pcstr_tuple cs ->
let+ tuple_typ = derive_tuple cs in
Some (tuple_typ, List.length cs)
in
Algebraic.Typ.{ case_name; case_cons }
in
Algebraic.(encode Variant) ~subderive ~lib ~type_name cs
and derive_polyvariant name rowfields =
let* { lib; _ } = ask in
let subderive f =
let+ case_name, case_cons =
match f.prf_desc with
| Rtag (label, _, []) -> return (label.txt, None)
| Rtag (label, _, typs) ->
let+ tuple_typ = derive_tuple typs in
(label.txt, Some (tuple_typ, List.length typs))
| Rinherit _ -> assert false
in
Algebraic.Typ.{ case_name; case_cons }
in
Algebraic.(encode Polyvariant) ~subderive ~lib ~type_name:name rowfields
and derive_lident :
nobuiltin:bool -> longident -> (longident loc, state) Reader.t =
fun ~nobuiltin txt ->
let+ { lib; type_name; rec_flag; rec_detected; repr_name; _ } = ask in
match (rec_flag, txt) with
| Recursive, Lident const_name when String.equal const_name type_name ->
rec_detected := true;
Located.lident repr_name
| _ -> (
match (nobuiltin, Dsl.type_to_combinator_name txt) with
| true, (Some _ | None) | false, None ->
map_lident repr_name_of_type_name txt |> Located.mk
| false, Some combinator_name ->
in_lib ~lib combinator_name |> Located.lident)
let derive_type_decl : type_declaration -> (expression, state) Reader.t =
fun typ ->
match typ.ptype_kind with
| Ptype_abstract -> (
match typ.ptype_manifest with
| None -> invalid_arg "No manifest"
| Some c -> (
match c.ptyp_desc with
| Ptyp_constr ({ txt; loc = _ }, []) -> (
match Attribute.get Attributes.repr c with
| Some repr -> return repr
| None ->
let nobuiltin =
match Attribute.get Attributes.nobuiltin c with
| Some () -> true
| None -> false
in
let+ name = derive_lident ~nobuiltin txt in
pexp_ident name)
| _ -> derive_core c))
| Ptype_variant cs -> derive_variant cs
| Ptype_record ls -> derive_record ls
| Ptype_open -> Raise.Unsupported.type_open ~loc
let parse_lib expr =
let pattern =
let open Ast_pattern in
let none = map0 ~f:None @@ pexp_construct (lident (string "None")) none in
let some =
map1 ~f:Option.some
@@ pexp_construct (lident (string "Some")) (some (estring __))
in
none ||| some
in
Ast_pattern.parse pattern loc expr
(fun k -> k)
~on_error:(fun () ->
Location.raise_errorf ~loc:expr.pexp_loc
"Could not process `lib' argument: must be either `Some \"Lib\"' or \
`None'")
let list_uniq_stable =
let rec inner ~seen acc = function
| [] -> List.rev acc
| x :: xs when not (List.mem x seen) ->
inner ~seen:(x :: seen) (x :: acc) xs
| _ :: xs -> inner ~seen acc xs
in
inner ~seen:[] []
module Unbound_tvars = struct
type acc = { free : string list; ctx_bound : string list }
let find typ =
(object
inherit [acc] Ast_traverse.fold_map as super
method! core_type_desc t acc =
match t with
| Ptyp_var v when not (List.mem v acc.ctx_bound) ->
(t, { acc with free = v :: acc.free })
| Ptyp_any ->
let name = gen_symbol () in
(Ptyp_var name, { acc with free = name :: acc.free })
| Ptyp_alias (c, v) ->
let c, acc =
super#core_type c { acc with ctx_bound = v :: acc.ctx_bound }
in
let ctx_bound =
match acc.ctx_bound with
| v' :: ctx_bound when v = v' -> ctx_bound
| _ -> assert false
in
(Ptyp_alias (c, v), { acc with ctx_bound })
| _ -> super#core_type_desc t acc
end)
#core_type
typ
{ free = []; ctx_bound = [] }
end
let expand_typ ?lib typ =
let typ, Unbound_tvars.{ free = tvars; _ } = Unbound_tvars.find typ in
let tvars = List.rev tvars |> list_uniq_stable in
let env =
{
rec_flag = Nonrecursive;
type_name = "t";
repr_name = "t";
rec_detected = ref false;
lib;
var_repr =
ref (function
| `Any ->
assert false
| `Var x -> Some (evar x));
}
in
run (derive_core typ) env |> lambda tvars
let derive_sig ~plugins ~name ~lib (_rec_flag, type_declarations) =
List.concat_map type_declarations ~f:(fun typ ->
let type_name = typ.ptype_name.txt in
let name =
Located.mk
(match name with
| Some n -> n
| None -> repr_name_of_type_name type_name)
in
let ty_lident =
(match lib with
| Some _ -> in_lib ~lib "t"
| None -> (
match name.txt with "t" -> "ty" | _ -> "t"))
|> Located.lident
in
let type_ =
combinator_type_of_type_declaration typ ~f:(fun ~loc:_ t ->
ptyp_constr ty_lident [ t ])
in
let plugin_derivations =
let td = name_type_params_in_td typ in
let params =
ListLabels.map td.ptype_params ~f:(function v, _ ->
ptyp_constr ty_lident [ v ])
in
let ctyp = core_type_of_type_declaration td in
ListLabels.map plugins
~f:(Meta_deriving.Plugin.derive_sig ~loc ~type_name ~params ~ctyp)
in
psig_value (value_description ~name ~type_ ~prim:[])
:: plugin_derivations)
module Typerep_derivation = struct
type t = { params : string list; body : expression }
(** A typerep derivation is an expression defined in terms of combinators,
potentially scoped inside a list of parameters (if the corresponding
type has type parameters). *)
let to_expr ?(transform_body = Fun.id) t =
lambda t.params (transform_body t.body)
end
let repr_of_type_decl ~(handle_recursion : bool) ~(lib : string option)
~rec_flag typ repr_name :
pattern * Typerep_derivation.t * [ `Param_required of bool ] =
let tparams =
typ.ptype_params
|> List.map (function
| { ptyp_desc = Ptyp_var v; _ }, _ -> v
| { ptyp_desc = Ptyp_any; _ }, _ -> "_"
| _ -> assert false)
in
let env =
let type_name = typ.ptype_name.txt in
let rec_detected = ref false in
let var_repr =
ref (function
| `Any -> Raise.Unsupported.type_any ~loc
| `Var v -> if List.mem v tparams then Some (evar v) else None)
in
{ rec_flag; type_name; repr_name; rec_detected; lib; var_repr }
in
let expr = run (derive_type_decl typ) env in
let expr =
if handle_recursion && !(env.rec_detected) then
recursive ~lib:env.lib env.repr_name expr
else expr
in
let expr = Typerep_derivation.{ params = tparams; body = expr } in
let pat = pvar env.repr_name in
(pat, expr, `Param_required (List.length tparams > 0))
let derive_str ~plugins ~name ~lib = function
| Recursive, [] -> assert false
| Recursive, tds when List.length tds > 2 ->
Raise.Unsupported.recursive_groups ~loc
(List.map (fun x -> x.ptype_name.txt) tds)
| rec_flag, type_declarations ->
let multiple_tds = List.length type_declarations > 1 in
let repr_names =
match (name, type_declarations) with
| _, [] -> assert false
| Some _, _ :: _ :: _ ->
failwith "Cannot specify name of mutually-recursive group"
| Some repr, [ typ ] -> [ { repr; typ = typ.ptype_name.txt } ]
| None, _ ->
ListLabels.map type_declarations ~f:(fun typ ->
let typ = typ.ptype_name.txt in
let repr = repr_name_of_type_name typ in
{ typ; repr })
in
let pats, named_treps =
let handle_recursion = rec_flag = Recursive && not multiple_tds in
ListLabels.map2 type_declarations repr_names ~f:(fun typ name ->
let pat, expr, `Param_required pr =
repr_of_type_decl ~rec_flag ~handle_recursion ~lib typ name.repr
in
if pr && multiple_tds then
Raise.Unsupported.recursive_type_with_type_paramets ~loc
typ.ptype_name.txt;
(pat, (expr, name)))
|> List.split
in
let pat, expr =
match (pats, named_treps) with
| [ p1 ], [ (e1, _) ] -> (p1, Typerep_derivation.to_expr e1)
| ps, es ->
let pat =
List.reduce_exn ps ~f:(fun p1 p2 -> [%pat? [%p p1], [%p p2]])
in
let expr =
if rec_flag = Recursive then
match (es : (Typerep_derivation.t * name) list) with
| [ (e1, n1); (e2, n2) ] ->
assert (e1.params = []);
assert (e2.params = []);
mutually_recursive ~lib (e1.body, n1) (e2.body, n2)
| _ ->
assert false
else
List.map (fst >> Typerep_derivation.to_expr) es
|> List.reduce_exn ~f:(fun e1 e2 -> [%expr [%e e1], [%e e2]])
in
(pat, expr)
in
let plugin_derivations =
List.concat_map named_treps ~f:(fun (typerep, name) ->
ListLabels.map plugins ~f:(fun plugin ->
Meta_deriving.Plugin.derive_str ~loc ~type_name:name.typ
~params:typerep.Typerep_derivation.params
~expr:typerep.Typerep_derivation.body plugin))
in
pstr_value Nonrecursive [ value_binding ~pat ~expr ]
:: plugin_derivations
end