Refactor array bracket access to dedicated AST node

analysis/examples/larger-project/src/TestImmutableArray.res

@@ -1,7 +1,6 @@
 @genType
 let testImmutableArrayGet = arr => {
-  open ImmutableArray
-  arr[3]
+  ImmutableArray.Array.get(arr, 3)
 }
 
 /*
@@ -10,11 +9,9 @@ let testImmutableArrayGet = arr => {
  */
 
 let testBeltArrayGet = arr => {
-  open Belt
-  arr[3]
+  Belt.Array.get(arr, 3)
 }
 
 let testBeltArraySet = arr => {
-  open Belt
-  arr[3] = 4
+  Belt.Array.set(arr, 3, 4)
 }

analysis/src/Utils.ml

@@ -95,6 +95,8 @@ let identifyPexp pexp =
   | Pexp_record _ -> "Pexp_record"
   | Pexp_field _ -> "Pexp_field"
   | Pexp_setfield _ -> "Pexp_setfield"
+  | Pexp_index _ -> "Pexp_index"
+  | Pexp_setindex _ -> "Pexp_setindex"
   | Pexp_array _ -> "Pexp_array"
   | Pexp_ifthenelse _ -> "Pexp_ifthenelse"
   | Pexp_sequence _ -> "Pexp_sequence"

compiler/frontend/bs_ast_mapper.ml

@@ -350,6 +350,10 @@ module E = struct
       field ~loc ~attrs (sub.expr sub e) (map_loc sub lid)
     | Pexp_setfield (e1, lid, e2) ->
       setfield ~loc ~attrs (sub.expr sub e1) (map_loc sub lid) (sub.expr sub e2)
+    | Pexp_index (e1, e2) ->
+      index ~loc ~attrs (sub.expr sub e1) (sub.expr sub e2)
+    | Pexp_setindex (e1, e2, e3) ->
+      setindex ~loc ~attrs (sub.expr sub e1) (sub.expr sub e2) (sub.expr sub e3)
     | Pexp_array el -> array ~loc ~attrs (List.map (sub.expr sub) el)
     | Pexp_ifthenelse (e1, e2, e3) ->
       ifthenelse ~loc ~attrs (sub.expr sub e1) (sub.expr sub e2)

compiler/ml/ast_helper.ml

@@ -174,6 +174,8 @@ module Exp = struct
   let record ?loc ?attrs a b = mk ?loc ?attrs (Pexp_record (a, b))
   let field ?loc ?attrs a b = mk ?loc ?attrs (Pexp_field (a, b))
   let setfield ?loc ?attrs a b c = mk ?loc ?attrs (Pexp_setfield (a, b, c))
+  let index ?loc ?attrs a b = mk ?loc ?attrs (Pexp_index (a, b))
+  let setindex ?loc ?attrs a b c = mk ?loc ?attrs (Pexp_setindex (a, b, c))
   let array ?loc ?attrs a = mk ?loc ?attrs (Pexp_array a)
   let ifthenelse ?loc ?attrs a b c = mk ?loc ?attrs (Pexp_ifthenelse (a, b, c))
   let sequence ?loc ?attrs a b = mk ?loc ?attrs (Pexp_sequence (a, b))

compiler/ml/ast_helper.mli

@@ -163,6 +163,14 @@ module Exp : sig
   val field : ?loc:loc -> ?attrs:attrs -> expression -> lid -> expression
   val setfield :
     ?loc:loc -> ?attrs:attrs -> expression -> lid -> expression -> expression
+  val index : ?loc:loc -> ?attrs:attrs -> expression -> expression -> expression
+  val setindex :
+    ?loc:loc ->
+    ?attrs:attrs ->
+    expression ->
+    expression ->
+    expression ->
+    expression
   val array : ?loc:loc -> ?attrs:attrs -> expression list -> expression
   val ifthenelse :
     ?loc:loc ->

compiler/ml/ast_iterator.ml

@@ -321,6 +321,13 @@ module E = struct
       sub.expr sub e1;
       iter_loc sub lid;
       sub.expr sub e2
+    | Pexp_index (e1, e2) ->
+      sub.expr sub e1;
+      sub.expr sub e2
+    | Pexp_setindex (e1, e2, e3) ->
+      sub.expr sub e1;
+      sub.expr sub e2;
+      sub.expr sub e3
     | Pexp_array el -> List.iter (sub.expr sub) el
     | Pexp_ifthenelse (e1, e2, e3) ->
       sub.expr sub e1;

compiler/ml/ast_mapper.ml

@@ -313,6 +313,10 @@ module E = struct
       field ~loc ~attrs (sub.expr sub e) (map_loc sub lid)
     | Pexp_setfield (e1, lid, e2) ->
       setfield ~loc ~attrs (sub.expr sub e1) (map_loc sub lid) (sub.expr sub e2)
+    | Pexp_index (e1, e2) ->
+      index ~loc ~attrs (sub.expr sub e1) (sub.expr sub e2)
+    | Pexp_setindex (e1, e2, e3) ->
+      setindex ~loc ~attrs (sub.expr sub e1) (sub.expr sub e2) (sub.expr sub e3)
     | Pexp_array el -> array ~loc ~attrs (List.map (sub.expr sub) el)
     | Pexp_ifthenelse (e1, e2, e3) ->
       ifthenelse ~loc ~attrs (sub.expr sub e1) (sub.expr sub e2)

compiler/ml/ast_mapper_to0.ml

@@ -439,6 +439,24 @@ module E = struct
       field ~loc ~attrs (sub.expr sub e) (map_loc sub lid)
     | Pexp_setfield (e1, lid, e2) ->
       setfield ~loc ~attrs (sub.expr sub e1) (map_loc sub lid) (sub.expr sub e2)
+    | Pexp_index (e1, e2) ->
+      (* Map back to Array.get for parsetree0 compatibility *)
+      let container = sub.expr sub e1 in
+      let index = sub.expr sub e2 in
+      let array_get =
+        ident ~loc (mknoloc (Longident.Ldot (Longident.Lident "Array", "get")))
+      in
+      apply ~loc ~attrs array_get [(Nolabel, container); (Nolabel, index)]
+    | Pexp_setindex (e1, e2, e3) ->
+      (* Map back to Array.set for parsetree0 compatibility *)
+      let container = sub.expr sub e1 in
+      let index = sub.expr sub e2 in
+      let value_expr = sub.expr sub e3 in
+      let array_set =
+        ident ~loc (mknoloc (Longident.Ldot (Longident.Lident "Array", "set")))
+      in
+      apply ~loc ~attrs array_set
+        [(Nolabel, container); (Nolabel, index); (Nolabel, value_expr)]
     | Pexp_array el -> array ~loc ~attrs (List.map (sub.expr sub) el)
     | Pexp_ifthenelse (e1, e2, e3) ->
       ifthenelse ~loc ~attrs (sub.expr sub e1) (sub.expr sub e2)

compiler/ml/depend.ml

@@ -248,6 +248,13 @@ let rec add_expr bv exp =
     add_expr bv e1;
     add bv fld;
     add_expr bv e2
+  | Pexp_index (e1, e2) ->
+    add_expr bv e1;
+    add_expr bv e2
+  | Pexp_setindex (e1, e2, e3) ->
+    add_expr bv e1;
+    add_expr bv e2;
+    add_expr bv e3
   | Pexp_array el -> List.iter (add_expr bv) el
   | Pexp_ifthenelse (e1, e2, opte3) ->
     add_expr bv e1;

compiler/ml/parsetree.ml

@@ -279,6 +279,8 @@ and expression_desc =
     *)
   | Pexp_field of expression * Longident.t loc (* E.l *)
   | Pexp_setfield of expression * Longident.t loc * expression (* E1.l <- E2 *)
+  | Pexp_index of expression * expression (* E1[E2] *)
+  | Pexp_setindex of expression * expression * expression (* E1[E2] = E3 *)
   | Pexp_array of expression list (* [| E1; ...; En |] *)
   | Pexp_ifthenelse of expression * expression * expression option
     (* if E1 then E2 else E3 *)

compiler/ml/pprintast.ml

@@ -691,6 +691,11 @@ and expression ctxt f x =
     | Pexp_setfield (e1, li, e2) ->
       pp f "@[<2>%a.%a@ <-@ %a@]" (simple_expr ctxt) e1 longident_loc li
         (simple_expr ctxt) e2
+    | Pexp_index (e1, e2) ->
+      pp f "%a.(%a)" (simple_expr ctxt) e1 (expression ctxt) e2
+    | Pexp_setindex (e1, e2, e3) ->
+      pp f "%a.(%a)@ <-@ %a" (simple_expr ctxt) e1 (expression ctxt) e2
+        (simple_expr ctxt) e3
     | Pexp_ifthenelse (e1, e2, eo) ->
       (* @;@[<2>else@ %a@]@] *)
       let fmt : (_, _, _) format =

compiler/ml/printast.ml

@@ -294,6 +294,18 @@ and expression i ppf x =
     expression i ppf e1;
     longident_loc i ppf li;
     expression i ppf e2
+  | Pexp_index (e1, e2) ->
+    line i ppf "Pexp_index\n";
+    expression i ppf e1;
+    line i ppf "index:\n";
+    expression i ppf e2
+  | Pexp_setindex (e1, e2, e3) ->
+    line i ppf "Pexp_setindex\n";
+    expression i ppf e1;
+    line i ppf "index:\n";
+    expression i ppf e2;
+    line i ppf "value:\n";
+    expression i ppf e3
   | Pexp_array l ->
     line i ppf "Pexp_array\n";
     list i expression ppf l

compiler/ml/printtyped.ml

@@ -329,6 +329,18 @@ and expression i ppf x =
     expression i ppf e1;
     longident i ppf li;
     expression i ppf e2
+  | Texp_index (e1, e2) ->
+    line i ppf "Texp_index\n";
+    expression i ppf e1;
+    line i ppf "index:\n";
+    expression i ppf e2
+  | Texp_setindex (e1, e2, e3) ->
+    line i ppf "Texp_setindex\n";
+    expression i ppf e1;
+    line i ppf "index:\n";
+    expression i ppf e2;
+    line i ppf "value:\n";
+    expression i ppf e3
   | Texp_array l ->
     line i ppf "Texp_array\n";
     list i expression ppf l

compiler/ml/rec_check.ml

@@ -196,8 +196,8 @@ let rec classify_expression : Typedtree.expression -> sd =
     classify_expression e
   | Texp_ident _ | Texp_for _ | Texp_constant _ | Texp_tuple _ | Texp_array _
   | Texp_construct _ | Texp_variant _ | Texp_record _ | Texp_setfield _
-  | Texp_while _ | Texp_pack _ | Texp_function _ | Texp_extension_constructor _
-    ->
+  | Texp_index _ | Texp_setindex _ | Texp_while _ | Texp_pack _
+  | Texp_function _ | Texp_extension_constructor _ ->
     Static
   | Texp_apply {funct = {exp_desc = Texp_ident (_, _, vd)}} when is_ref vd ->
     Static
@@ -273,6 +273,13 @@ let rec expression : Env.env -> Typedtree.expression -> Use.t =
         (join (expression env ifso) (option expression env ifnot)))
   | Texp_setfield (e1, _, _, e2) ->
     Use.(join (inspect (expression env e1)) (inspect (expression env e2)))
+  | Texp_index (e1, e2) ->
+    Use.(join (inspect (expression env e1)) (inspect (expression env e2)))
+  | Texp_setindex (e1, e2, e3) ->
+    Use.(
+      join
+        (join (inspect (expression env e1)) (inspect (expression env e2)))
+        (inspect (expression env e3)))
   | Texp_sequence (e1, e2) ->
     Use.(join (discard (expression env e1)) (expression env e2))
   | Texp_while (e1, e2) ->

compiler/ml/tast_iterator.ml

@@ -176,6 +176,13 @@ let expr sub {exp_extra; exp_desc; exp_env; _} =
   | Texp_setfield (exp1, _, _, exp2) ->
     sub.expr sub exp1;
     sub.expr sub exp2
+  | Texp_index (exp1, exp2) ->
+    sub.expr sub exp1;
+    sub.expr sub exp2
+  | Texp_setindex (exp1, exp2, exp3) ->
+    sub.expr sub exp1;
+    sub.expr sub exp2;
+    sub.expr sub exp3
   | Texp_array list -> List.iter (sub.expr sub) list
   | Texp_ifthenelse (exp1, exp2, expo) ->
     sub.expr sub exp1;

compiler/ml/tast_mapper.ml

@@ -232,6 +232,16 @@ let expr sub x =
     | Texp_field (exp, lid, ld) -> Texp_field (sub.expr sub exp, lid, ld)
     | Texp_setfield (exp1, lid, ld, exp2) ->
       Texp_setfield (sub.expr sub exp1, lid, ld, sub.expr sub exp2)
+    | Texp_index (exp1, exp2) ->
+      (* Use let bindings to ensure left-to-right evaluation order *)
+      let exp1 = sub.expr sub exp1 in
+      let exp2 = sub.expr sub exp2 in
+      Texp_index (exp1, exp2)
+    | Texp_setindex (exp1, exp2, exp3) ->
+      let exp1 = sub.expr sub exp1 in
+      let exp2 = sub.expr sub exp2 in
+      let exp3 = sub.expr sub exp3 in
+      Texp_setindex (exp1, exp2, exp3)
     | Texp_array list -> Texp_array (List.map (sub.expr sub) list)
     | Texp_ifthenelse (exp1, exp2, expo) ->
       Texp_ifthenelse

compiler/ml/translcore.ml

@@ -891,6 +891,17 @@ and transl_exp0 (e : Typedtree.expression) : Lambda.lambda =
         Psetfield (lbl.lbl_pos + 1, Lambda.fld_record_extension_set lbl)
     in
     Lprim (access, [transl_exp arg; transl_exp newval], e.exp_loc)
+  | Texp_index (container, index) ->
+    (* Read: translate to Parrayrefu primitive (unsafe array get) *)
+    let container_lambda = transl_exp container in
+    let index_lambda = transl_exp index in
+    Lprim (Parrayrefu, [container_lambda; index_lambda], e.exp_loc)
+  | Texp_setindex (container, index, value) ->
+    (* Write: translate to Parraysetu primitive (unsafe array set) *)
+    let container_lambda = transl_exp container in
+    let index_lambda = transl_exp index in
+    let value_lambda = transl_exp value in
+    Lprim (Parraysetu, [container_lambda; index_lambda; value_lambda], e.exp_loc)
   | Texp_array expr_list ->
     let ll = transl_list expr_list in
     Lprim (Pmakearray Mutable, ll, e.exp_loc)

compiler/ml/typecore.ml

@@ -178,10 +178,16 @@ let iter_expression f e =
     | Pexp_letexception (_, e)
     | Pexp_field (e, _) ->
       expr e
-    | Pexp_while (e1, e2) | Pexp_sequence (e1, e2) | Pexp_setfield (e1, _, e2)
-      ->
+    | Pexp_while (e1, e2)
+    | Pexp_sequence (e1, e2)
+    | Pexp_setfield (e1, _, e2)
+    | Pexp_index (e1, e2) ->
       expr e1;
       expr e2
+    | Pexp_setindex (e1, e2, e3) ->
+      expr e1;
+      expr e2;
+      expr e3
     | Pexp_ifthenelse (e1, e2, eo) ->
       expr e1;
       expr e2;
@@ -2834,6 +2840,53 @@ and type_expect_ ?deprecated_context ~context ?in_function ?(recarg = Rejected)
         exp_attributes = sexp.pexp_attributes;
         exp_env = env;
       }
+  | Pexp_index (scontainer, sindex) ->
+    (* Read access: arr[i] -> array<'a> -> int -> option<'a>
+       Returns option because JS bracket access returns undefined for
+       out-of-bounds indices, which maps to None in ReScript's option type. *)
+    let container = type_exp ~context:None env scontainer in
+    let index =
+      type_expect ~context:None env sindex (instance_def Predef.type_int)
+    in
+    let element_type = newvar () in
+    let array_type = Predef.type_array element_type in
+    unify_exp ~context:None env container array_type;
+    rue
+      {
+        exp_desc = Texp_index (container, index);
+        exp_loc = loc;
+        exp_extra = [];
+        exp_type = type_option element_type;
+        exp_attributes = sexp.pexp_attributes;
+        exp_env = env;
+      }
+  | Pexp_setindex (scontainer, sindex, svalue) ->
+    (* Write access: arr[i] = v -> array<'a> -> int -> 'a -> unit *)
+    let container = type_exp ~context:None env scontainer in
+    let index =
+      type_expect ~context:None env sindex (instance_def Predef.type_int)
+    in
+    (* Extract element type from container to preserve arity information *)
+    let element_type =
+      match (expand_head env container.exp_type).desc with
+      | Tconstr (Pident {name = "array"}, [element_ty], _) -> element_ty
+      | _ ->
+        (* Fallback: create fresh type variable and unify *)
+        let element_type = newgenvar () in
+        let array_type = instance_def (Predef.type_array element_type) in
+        unify_exp ~context:None env container array_type;
+        element_type
+    in
+    let value = type_expect ~context:None env svalue element_type in
+    rue
+      {
+        exp_desc = Texp_setindex (container, index, value);
+        exp_loc = loc;
+        exp_extra = [];
+        exp_type = instance_def Predef.type_unit;
+        exp_attributes = sexp.pexp_attributes;
+        exp_env = env;
+      }
   | Pexp_array sargl ->
     let ty = newgenvar () in
     let to_unify = Predef.type_array ty in

compiler/ml/typedtree.ml

@@ -106,6 +106,8 @@ and expression_desc =
   | Texp_field of expression * Longident.t loc * label_description
   | Texp_setfield of
       expression * Longident.t loc * label_description * expression
+  | Texp_index of expression * expression
+  | Texp_setindex of expression * expression * expression
   | Texp_array of expression list
   | Texp_ifthenelse of expression * expression * expression option
   | Texp_sequence of expression * expression

compiler/ml/typedtree.mli

@@ -207,6 +207,8 @@ and expression_desc =
   | Texp_field of expression * Longident.t loc * label_description
   | Texp_setfield of
       expression * Longident.t loc * label_description * expression
+  | Texp_index of expression * expression
+  | Texp_setindex of expression * expression * expression
   | Texp_array of expression list
   | Texp_ifthenelse of expression * expression * expression option
   | Texp_sequence of expression * expression

compiler/ml/typedtreeIter.ml

@@ -261,6 +261,13 @@ end = struct
     | Texp_setfield (exp1, _, _label, exp2) ->
       iter_expression exp1;
       iter_expression exp2
+    | Texp_index (exp1, exp2) ->
+      iter_expression exp1;
+      iter_expression exp2
+    | Texp_setindex (exp1, exp2, exp3) ->
+      iter_expression exp1;
+      iter_expression exp2;
+      iter_expression exp3
     | Texp_array list -> List.iter iter_expression list
     | Texp_ifthenelse (exp1, exp2, expo) -> (
       iter_expression exp1;

compiler/syntax/src/res_ast_debugger.ml

@@ -641,6 +641,16 @@ module SexpAst = struct
             longident longident_loc.Asttypes.txt;
             expression expr2;
           ]
+      | Pexp_index (e1, e2) ->
+        Sexp.list [Sexp.atom "Pexp_index"; expression e1; expression e2]
+      | Pexp_setindex (e1, e2, e3) ->
+        Sexp.list
+          [
+            Sexp.atom "Pexp_setindex";
+            expression e1;
+            expression e2;
+            expression e3;
+          ]
       | Pexp_array exprs ->
         Sexp.list
           [Sexp.atom "Pexp_array"; Sexp.list (map_empty ~f:expression exprs)]