From 8e48572bd41554f9c7123928349c9a0a2b68f233 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Hu=C3=A1ng=20J=C3=B9nli=C3=A0ng?= <jlhwung@gmail.com>
Date: Fri, 31 Jul 2020 13:34:47 -0400
Subject: [PATCH] =?UTF-8?q?fix:=20ensure=20[=E2=80=A6map.keys]=20is=20corr?=
 =?UTF-8?q?ectly=20transformed=20in=20loose=20mode?=
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---
 packages/babel-plugin-transform-block-scoping/src/index.js | 2 +-
 packages/babel-standalone/test/babel.js                    | 7 +++++++
 2 files changed, 8 insertions(+), 1 deletion(-)

diff --git a/packages/babel-plugin-transform-block-scoping/src/index.js b/packages/babel-plugin-transform-block-scoping/src/index.js
index c6a7fe26f48e..3a9576a525fe 100644
--- a/packages/babel-plugin-transform-block-scoping/src/index.js
+++ b/packages/babel-plugin-transform-block-scoping/src/index.js
@@ -518,7 +518,7 @@ class BlockScoping {
     // remap loop heads with colliding variables
     if (this.loop) {
       // nb: clone outsideRefs keys since the map is modified within the loop
-      for (const name of [...outsideRefs.keys()]) {
+      for (const name of Array.from(outsideRefs.keys())) {
         const id = outsideRefs.get(name);
 
         if (
diff --git a/packages/babel-standalone/test/babel.js b/packages/babel-standalone/test/babel.js
index 44b08166abcd..c6a450328491 100644
--- a/packages/babel-standalone/test/babel.js
+++ b/packages/babel-standalone/test/babel.js
@@ -210,6 +210,13 @@
           }),
         ).not.toThrow();
       });
+      it("#11897 - [...map.keys()] in Babel source should be transformed correctly", () => {
+        expect(() =>
+          Babel.transform("for (let el of []) { s => el }", {
+            plugins: ["transform-block-scoping"],
+          }),
+        ).not.toThrow();
+      });
     });
   },
 );