From 0d97feab211c443285c4e1269964ba3ce32ce26b Mon Sep 17 00:00:00 2001
From: Marco Castelluccio <mcastelluccio@mozilla.com>
Date: Fri, 21 Jul 2023 19:24:11 +0000
Subject: [PATCH] Bug 1844115 - Part 1: Avoid creating String wrapper objects
 in Iterator.from. r=allstarschh

Update per <https://github.com/tc39/proposal-iterator-helpers/pull/281>.

Differential Revision: https://phabricator.services.mozilla.com/D183877

UltraBlame original commit: e909fbf5b324f9a1a490c634818c1fea3005f35f
---
 js/src/builtin/Iterator.js | 57 +++++++++++++++++++++++++-------------
 1 file changed, 37 insertions(+), 20 deletions(-)

diff --git a/js/src/builtin/Iterator.js b/js/src/builtin/Iterator.js
index a5f6dbd41cb67..eadf4417b3a89 100644
--- a/js/src/builtin/Iterator.js
+++ b/js/src/builtin/Iterator.js
@@ -302,8 +302,27 @@ function
 GetIteratorFlattenable
 (
 obj
+rejectStrings
 )
 {
+assert
+(
+typeof
+rejectStrings
+=
+=
+=
+"
+boolean
+"
+"
+rejectStrings
+is
+a
+boolean
+"
+)
+;
 if
 (
 !
@@ -313,6 +332,21 @@ obj
 )
 )
 {
+if
+(
+rejectStrings
+|
+|
+typeof
+obj
+!
+=
+=
+"
+string
+"
+)
+{
 ThrowTypeError
 (
 JSMSG_OBJECT_REQUIRED
@@ -331,6 +365,7 @@ obj
 )
 ;
 }
+}
 var
 method
 =
@@ -408,32 +443,13 @@ IteratorFrom
 O
 )
 {
-if
-(
-typeof
-O
-=
-=
-=
-"
-string
-"
-)
-{
-O
-=
-ToObject
-(
-O
-)
-;
-}
 var
 iterator
 =
 GetIteratorFlattenable
 (
 O
+false
 )
 ;
 var
@@ -1669,6 +1685,7 @@ innerIterator
 GetIteratorFlattenable
 (
 mapped
+true
 )
 ;
 var