fix: ensure […map.keys] can be correctly transformed in loose mode (#11901)

JLHwung · web-flow · commit c41dcd045bc7 · 2020-07-31T14:26:22.000-05:00
diff --git 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
@@ -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();
+      });
     });
   },
 );
