Implement for...of and for await...of loops

CHANGELOG.md

@@ -23,6 +23,7 @@
 
 - Rewatch: add `--prod` flag to `build`, `watch`, and `clean` to skip dev-dependencies and dev sources (`"type": "dev"`), enabling builds in environments where dev packages aren't installed (e.g. after `pnpm install --prod`). https://github.com/rescript-lang/rescript/pull/8347
 - Add `Dict.assignMany`, `Dict.concat`, `Dict.concatMany`, `Dict.concatAll`, `Array.concatAll` to the stdlib. https://github.com/rescript-lang/rescript/pull/8364
+- Implement `for...of` and `for await...of` loops. https://github.com/rescript-lang/rescript/pull/7887
 
 #### :bug: Bug fix
 

analysis/reanalyze/src/Arnold.ml

@@ -982,9 +982,15 @@ module Compile = struct
     | Texp_while _ ->
       notImplemented "Texp_while";
       assert false
-    | Texp_for _ ->
-      notImplemented "Texp_for";
-      assert false
+    | Texp_for (_id, _pat, e1, e2, _dir, e3) ->
+      let open Command in
+      expression ~ctx e1 +++ expression ~ctx e2 +++ expression ~ctx e3
+    | Texp_for_of (_id, _pat, e1, e2) ->
+      let open Command in
+      expression ~ctx e1 +++ expression ~ctx e2
+    | Texp_for_await_of (_id, _pat, e1, e2) ->
+      let open Command in
+      expression ~ctx e1 +++ expression ~ctx e2
     | Texp_send _ ->
       notImplemented "Texp_send";
       assert false

analysis/reanalyze/src/SideEffects.ml

@@ -62,6 +62,7 @@ let rec exprNoSideEffects (expr : Typedtree.expression) =
   | Texp_for (_id, _pat, e1, e2, _dir, e3) ->
     e1 |> exprNoSideEffects && e2 |> exprNoSideEffects
     && e3 |> exprNoSideEffects
+  | Texp_for_of _ | Texp_for_await_of _ -> false
   | Texp_send _ -> false
   | Texp_letexception (_ec, e) -> e |> exprNoSideEffects
   | Texp_pack _ -> false

analysis/src/Utils.ml

@@ -102,6 +102,8 @@ let identifyPexp pexp =
   | Pexp_continue -> "Pexp_continue"
   | Pexp_while _ -> "Pexp_while"
   | Pexp_for _ -> "Pexp_for"
+  | Pexp_for_of _ -> "Pexp_for_of"
+  | Pexp_for_await_of _ -> "Pexp_for_await_of"
   | Pexp_constraint _ -> "Pexp_constraint"
   | Pexp_coerce _ -> "Pexp_coerce"
   | Pexp_send _ -> "Pexp_send"

compiler/core/j.ml

@@ -266,6 +266,8 @@ and statement_desc =
       * for_ident
       * for_direction
       * block
+  | ForOf of label option * for_ident * expression * block
+  | ForAwaitOf of label option * for_ident * expression * block
   | Continue of label option
   | Break of label option (* only used when inline a fucntion *)
   | Return of expression

compiler/core/js_analyzer.ml

@@ -135,6 +135,7 @@ let no_side_effect_obj =
         | Throw _ | Debugger | Break _ | Variable _ | Continue _ ->
           raise_notrace Not_found
         | Exp e -> self.expression self e
+        | ForOf _ | ForAwaitOf _ -> raise_notrace Not_found
         | Int_switch _ | String_switch _ | ForRange _ | If _ | While _ | Block _
         | Return _ | Try _ ->
           super.statement self s);
@@ -255,8 +256,8 @@ and eq_statement ({statement_desc = x0} : J.statement)
     match y0 with
     | Block ys0 -> eq_block xs0 ys0
     | _ -> false)
-  | Variable _ | If _ | While _ | ForRange _ | Continue _ | Int_switch _
-  | String_switch _ | Throw _ | Try _ ->
+  | Variable _ | If _ | While _ | ForRange _ | ForOf _ | ForAwaitOf _
+  | Continue _ | Int_switch _ | String_switch _ | Throw _ | Try _ ->
     false
 
 let rev_flatten_seq (x : J.expression) =

compiler/core/js_dump.ml

@@ -1498,6 +1498,60 @@ and statement_desc top cxt f (s : J.statement_desc) : cxt =
           brace_block cxt f s)
     in
     action cxt
+  | ForOf (label, id, iterable, s) ->
+    P.vgroup f 0 (fun _ ->
+        let cxt =
+          P.group f 0 (fun _ ->
+              let cxt =
+                match label with
+                | None -> cxt
+                | Some label ->
+                  P.string f label;
+                  P.string f L.colon;
+                  P.space f;
+                  cxt
+              in
+              P.string f L.for_;
+              P.space f;
+              P.paren_group f 1 (fun _ ->
+                  P.string f L.let_;
+                  P.space f;
+                  let cxt = Ext_pp_scope.ident cxt f id in
+                  P.space f;
+                  P.string f L.of_;
+                  P.space f;
+                  expression ~level:0 cxt f iterable))
+        in
+        P.space f;
+        brace_block cxt f s)
+  | ForAwaitOf (label, id, iterable, s) ->
+    P.vgroup f 0 (fun _ ->
+        let cxt =
+          P.group f 0 (fun _ ->
+              let cxt =
+                match label with
+                | None -> cxt
+                | Some label ->
+                  P.string f label;
+                  P.string f L.colon;
+                  P.space f;
+                  cxt
+              in
+              P.string f L.for_;
+              P.space f;
+              P.string f L.await;
+              P.space f;
+              P.paren_group f 1 (fun _ ->
+                  P.string f L.let_;
+                  P.space f;
+                  let cxt = Ext_pp_scope.ident cxt f id in
+                  P.space f;
+                  P.string f L.of_;
+                  P.space f;
+                  expression ~level:0 cxt f iterable))
+        in
+        P.space f;
+        brace_block cxt f s)
   | Continue label ->
     P.string f L.continue;
     (match label with

compiler/core/js_dump_lit.ml

@@ -90,6 +90,8 @@ let if_ = "if"
 
 let for_ = "for"
 
+let of_ = "of"
+
 let try_ = "try"
 
 let finally = "finally"

compiler/core/js_fold.ml

@@ -241,6 +241,16 @@ class fold =
         let _self = _self#for_direction _x3 in
         let _self = _self#block _x4 in
         _self
+      | ForOf (_label, _x0, _x1, _x2) ->
+        let _self = _self#for_ident _x0 in
+        let _self = _self#expression _x1 in
+        let _self = _self#block _x2 in
+        _self
+      | ForAwaitOf (_label, _x0, _x1, _x2) ->
+        let _self = _self#for_ident _x0 in
+        let _self = _self#expression _x1 in
+        let _self = _self#block _x2 in
+        _self
       | Continue _ -> _self
       | Break _ -> _self
       | Return _x0 ->

compiler/core/js_pass_scope.ml

@@ -238,7 +238,9 @@ let record_scope_pass =
     statement =
       (fun self state x ->
         match x.statement_desc with
-        | ForRange (_, _, _, loop_id, _, _) ->
+        | ForRange (_, _, _, loop_id, _, _)
+        | ForOf (_, loop_id, _, _)
+        | ForAwaitOf (_, loop_id, _, _) ->
           (* TODO: simplify definition of For *)
           let {
             defined_idents = defined_idents';

compiler/core/js_record_fold.ml

@@ -245,6 +245,16 @@ let statement_desc : 'a. ('a, statement_desc) fn =
     let st = for_direction _self st _x3 in
     let st = _self.block _self st _x4 in
     st
+  | ForOf (_label, _x0, _x1, _x2) ->
+    let st = _self.for_ident _self st _x0 in
+    let st = _self.expression _self st _x1 in
+    let st = _self.block _self st _x2 in
+    st
+  | ForAwaitOf (_label, _x0, _x1, _x2) ->
+    let st = _self.for_ident _self st _x0 in
+    let st = _self.expression _self st _x1 in
+    let st = _self.block _self st _x2 in
+    st
   | Continue _ -> st
   | Break _ -> st
   | Return _x0 ->

compiler/core/js_record_iter.ml

@@ -179,6 +179,14 @@ let statement_desc : statement_desc fn =
     _self.for_ident _self _x2;
     for_direction _self _x3;
     _self.block _self _x4
+  | ForOf (_label, _x0, _x1, _x2) ->
+    _self.for_ident _self _x0;
+    _self.expression _self _x1;
+    _self.block _self _x2
+  | ForAwaitOf (_label, _x0, _x1, _x2) ->
+    _self.for_ident _self _x0;
+    _self.expression _self _x1;
+    _self.block _self _x2
   | Continue _ -> ()
   | Break _ -> ()
   | Return _x0 -> _self.expression _self _x0

compiler/core/js_record_map.ml

@@ -243,6 +243,16 @@ let statement_desc : statement_desc fn =
     let _x3 = for_direction _self _x3 in
     let _x4 = _self.block _self _x4 in
     ForRange (_label, _x0, _x1, _x2, _x3, _x4)
+  | ForOf (_label, _x0, _x1, _x2) ->
+    let _x0 = _self.for_ident _self _x0 in
+    let _x1 = _self.expression _self _x1 in
+    let _x2 = _self.block _self _x2 in
+    ForOf (_label, _x0, _x1, _x2)
+  | ForAwaitOf (_label, _x0, _x1, _x2) ->
+    let _x0 = _self.for_ident _self _x0 in
+    let _x1 = _self.expression _self _x1 in
+    let _x2 = _self.block _self _x2 in
+    ForAwaitOf (_label, _x0, _x1, _x2)
   | Continue _ as v -> v
   | Break _ as v -> v
   | Return _x0 ->

compiler/core/js_stmt_make.ml

@@ -326,6 +326,12 @@ let for_ ?comment ?label for_ident_expression finish_ident_expression id
     comment;
   }
 
+let for_of ?comment ?label iterable_expression id (b : J.block) : t =
+  {statement_desc = ForOf (label, id, iterable_expression, b); comment}
+
+let for_await_of ?comment ?label iterable_expression id (b : J.block) : t =
+  {statement_desc = ForAwaitOf (label, id, iterable_expression, b); comment}
+
 let try_ ?comment ?with_ ?finally body : t =
   {statement_desc = Try (body, with_, finally); comment}
 

compiler/core/js_stmt_make.mli

@@ -142,6 +142,12 @@ val for_ :
   J.block ->
   t
 
+val for_of :
+  ?comment:string -> ?label:J.label -> J.expression -> J.ident -> J.block -> t
+
+val for_await_of :
+  ?comment:string -> ?label:J.label -> J.expression -> J.ident -> J.block -> t
+
 val try_ :
   ?comment:string ->
   ?with_:J.ident * J.block ->

compiler/core/lam.ml

@@ -108,6 +108,8 @@ module Types = struct
     | Lcontinue
     | Lwhile of t * t
     | Lfor of ident * t * t * Asttypes.direction_flag * t
+    | Lfor_of of ident * t * t
+    | Lfor_await_of of ident * t * t
     | Lassign of ident * t
   (* | Lsend of Lam_compat.meth_kind * t * t * t list * Location.t *)
 end
@@ -162,6 +164,8 @@ module X = struct
     | Lcontinue
     | Lwhile of t * t
     | Lfor of ident * t * t * Asttypes.direction_flag * t
+    | Lfor_of of ident * t * t
+    | Lfor_await_of of ident * t * t
     | Lassign of ident * t
   (* | Lsend of Lam_compat.meth_kind * t * t * t list * Location.t *)
 end
@@ -252,6 +256,14 @@ let inner_map (l : t) (f : t -> X.t) : X.t =
     let e2 = f e2 in
     let e3 = f e3 in
     Lfor (v, e1, e2, dir, e3)
+  | Lfor_of (v, e1, e2) ->
+    let e1 = f e1 in
+    let e2 = f e2 in
+    Lfor_of (v, e1, e2)
+  | Lfor_await_of (v, e1, e2) ->
+    let e1 = f e1 in
+    let e2 = f e2 in
+    Lfor_await_of (v, e1, e2)
   | Lassign (id, e) ->
     let e = f e in
     Lassign (id, e)
@@ -409,7 +421,9 @@ let rec eq_approx (l1 : t) (l2 : t) =
   | Lfunction _
   | Llet (_, _, _, _)
   | Lletrec _ | Lswitch _ | Lstaticcatch _ | Ltrywith _
-  | Lfor (_, _, _, _, _) ->
+  | Lfor (_, _, _, _, _)
+  | Lfor_of (_, _, _)
+  | Lfor_await_of (_, _, _) ->
     false
 
 and eq_option l1 l2 =
@@ -469,6 +483,8 @@ let letrec bindings body : t = Lletrec (bindings, body)
 let while_ a b : t = Lwhile (a, b)
 let try_ body id handler : t = Ltrywith (body, id, handler)
 let for_ v e1 e2 dir e3 : t = Lfor (v, e1, e2, dir, e3)
+let for_of v e1 e2 : t = Lfor_of (v, e1, e2)
+let for_await_of v e1 e2 : t = Lfor_await_of (v, e1, e2)
 let assign v l : t = Lassign (v, l)
 let staticcatch a b c : t = Lstaticcatch (a, b, c)
 let staticraise a b : t = Lstaticraise (a, b)

compiler/core/lam.mli

@@ -81,6 +81,8 @@ and t = private
   | Lcontinue
   | Lwhile of t * t
   | Lfor of ident * t * t * Asttypes.direction_flag * t
+  | Lfor_of of ident * t * t
+  | Lfor_await_of of ident * t * t
   | Lassign of ident * t
 
 (* | Lsend of Lambda.meth_kind * t * t * t list * Location.t *)
@@ -170,6 +172,10 @@ val staticraise : int -> t list -> t
 
 val for_ : ident -> t -> t -> Asttypes.direction_flag -> t -> t
 
+val for_of : ident -> t -> t -> t
+
+val for_await_of : ident -> t -> t -> t
+
 (**************************************************************)
 
 val eq_approx : t -> t -> bool

compiler/core/lam_analysis.ml

@@ -120,6 +120,7 @@ let rec no_side_effects (lam : Lam.t) : bool =
   | Lwhile _ ->
     false (* conservative here, non-terminating loop does have side effect *)
   | Lfor _ -> false
+  | Lfor_of _ | Lfor_await_of _ -> false
   | Lassign _ -> false (* actually it depends ... *)
   (* | Lsend _ -> false  *)
   | Lapply
@@ -181,6 +182,7 @@ let rec size (lam : Lam.t) =
     | Lbreak | Lcontinue -> 1
     | Lwhile _ -> really_big ()
     | Lfor _ -> really_big ()
+    | Lfor_of _ | Lfor_await_of _ -> really_big ()
     | Lassign (_, v) -> 1 + size v
     (* This is side effectful,  be careful *)
     (* | Lsend _  ->  really_big () *)

compiler/core/lam_arity_analysis.ml

@@ -130,7 +130,8 @@ let rec get_arity (meta : Lam_stats.t) (lam : Lam.t) : Lam_arity.t =
   | Lsequence (_, l2) -> get_arity meta l2
   | Lstaticraise _ (* since it will not be in tail position *) -> Lam_arity.na
   | Lbreak | Lcontinue -> Lam_arity.non_function_arity_info
-  | Lwhile _ | Lfor _ | Lassign _ -> Lam_arity.non_function_arity_info
+  | Lwhile _ | Lfor _ | Lfor_of _ | Lfor_await_of _ | Lassign _ ->
+    Lam_arity.non_function_arity_info
 
 and all_lambdas meta (xs : Lam.t list) =
   match xs with

compiler/core/lam_bounded_vars.ml

@@ -103,6 +103,16 @@ let rewrite (map : _ Hash_ident.t) (lam : Lam.t) : Lam.t =
       let l2 = aux l2 in
       let l3 = aux l3 in
       Lam.for_ ident (aux l1) l2 dir l3
+    | Lfor_of (ident, l1, l2) ->
+      let ident = rebind ident in
+      let l1 = aux l1 in
+      let l2 = aux l2 in
+      Lam.for_of ident l1 l2
+    | Lfor_await_of (ident, l1, l2) ->
+      let ident = rebind ident in
+      let l1 = aux l1 in
+      let l2 = aux l2 in
+      Lam.for_await_of ident l1 l2
     | Lconst _ -> lam
     | Lprim {primitive; args; loc} ->
       (* here it makes sure that global vars are not rebound *)

compiler/core/lam_check.ml

@@ -62,6 +62,12 @@ let check file lam =
       check_staticfails e1 cxt;
       check_staticfails e2 cxt;
       check_staticfails e3 Set_int.empty
+    | Lfor_of (_v, e1, e2) ->
+      check_staticfails e1 cxt;
+      check_staticfails e2 Set_int.empty
+    | Lfor_await_of (_v, e1, e2) ->
+      check_staticfails e1 cxt;
+      check_staticfails e2 Set_int.empty
     | Lbreak | Lcontinue -> ()
     | Llet (_str, _id, arg, body) -> check_list [arg; body] cxt
     | Lletrec (decl, body) ->
@@ -148,6 +154,14 @@ let check file lam =
       iter e2;
       def v;
       iter e3
+    | Lfor_of (v, e1, e2) ->
+      iter e1;
+      def v;
+      iter e2
+    | Lfor_await_of (v, e1, e2) ->
+      iter e1;
+      def v;
+      iter e2
     | Lassign (id, e) ->
       use id;
       iter e