Implement for...of and for await...of loops (#7887)

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

* fixes

* CHANGELOG

# Conflicts:
#	CHANGELOG.md

Author: cknitt

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';