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Use extension node for encoding labeled tuples #2387

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merged 2 commits into from
May 9, 2024
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Use extension node for encoding labeled tuples #2387

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Use extension node for encoding labeled tuples rather than merely an …
ncik-roberts Mar 22, 2024
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ncik-roberts Mar 22, 2024
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17 changes: 15 additions & 2 deletions ocaml/parsing/jane_syntax.ml
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Original file line number Diff line number Diff line change
Expand Up @@ -1354,6 +1354,13 @@ module Labeled_tuples = struct
labeled_components, ptyp_attributes
| _ -> Desugaring_error.raise typ.ptyp_loc Malformed

(* We wrap labeled tuple expressions in an additional extension node
so that tools that inspect the OCaml syntax tree are less likely
to treat a labeled tuple as a regular tuple.
*)
let labeled_tuple_extension_node_name =
Embedded_name.of_feature feature [] |> Embedded_name.to_string

let expr_of ~loc el =
match check_for_any_label el with
| No_labels el -> Ast_helper.Exp.tuple ~loc el
Expand All @@ -1362,15 +1369,21 @@ module Labeled_tuples = struct
Expression.make_entire_jane_syntax ~loc feature (fun () ->
let names = List.map (fun (label, _) -> string_of_label label) el in
Expression.make_jane_syntax feature names
@@ Ast_helper.Exp.tuple (List.map snd el))
@@ Ast_helper.Exp.apply
(Ast_helper.Exp.extension
(Location.mknoloc labeled_tuple_extension_node_name, PStr []))
[Nolabel, Ast_helper.Exp.tuple (List.map snd el)])

(* Returns remaining unconsumed attributes *)
let of_expr expr =
let labels, pexp_attributes =
expand_labeled_tuple_extension expr.pexp_loc expr.pexp_attributes
in
match expr.pexp_desc with
| Pexp_tuple components ->
| Pexp_apply
( { pexp_desc = Pexp_extension (name, PStr []) },
[(Nolabel, { pexp_desc = Pexp_tuple components; _ })] )
when String.equal name.txt labeled_tuple_extension_node_name ->
if List.length labels <> List.length components
then Desugaring_error.raise expr.pexp_loc Malformed;
let labeled_components =
Expand Down