From 7e7ff873e449f55db3d14a9cc7c5775c726e6ca5 Mon Sep 17 00:00:00 2001
From: Ray Di Ciaccio <ray@appcues.com>
Date: Tue, 14 Feb 2017 19:58:38 -0500
Subject: [PATCH 1/2] Detect when Firefox is trying to use the broken,
 alternative Iterator form and don't use it. Polyfill instead.

---
 packages/regenerator-runtime/runtime.js | 10 +++++++---
 1 file changed, 7 insertions(+), 3 deletions(-)

diff --git a/packages/regenerator-runtime/runtime.js b/packages/regenerator-runtime/runtime.js
index 15fdacce8..1a0e47c6b 100644
--- a/packages/regenerator-runtime/runtime.js
+++ b/packages/regenerator-runtime/runtime.js
@@ -96,9 +96,13 @@
   if (NativeIteratorPrototype &&
       NativeIteratorPrototype !== Op &&
       hasOwn.call(NativeIteratorPrototype, iteratorSymbol)) {
-    // This environment has a native %IteratorPrototype%; use it instead
-    // of the polyfill.
-    IteratorPrototype = NativeIteratorPrototype;
+    // This environment has a native %IteratorPrototype%; use it instead of the
+    // polyfill unless it's the broken Firefox IteratorPrototype. See
+    // https://github.com/facebook/regenerator/issues/274 for more details.
+    var _n = NativeIteratorPrototype[iteratorSymbol].call(NativeIteratorPrototype);
+    if (!_n || !_n.next || _n.next.name !== 'LegacyIteratorNext') {
+      IteratorPrototype = NativeIteratorPrototype;
+    }
   }
 
   var Gp = GeneratorFunctionPrototype.prototype =

From 6480f91c2d2dba786e51c19019c113e618d5b262 Mon Sep 17 00:00:00 2001
From: Ray Di Ciaccio <ray@appcues.com>
Date: Wed, 22 Feb 2017 01:46:42 -0500
Subject: [PATCH 2/2] Fix @@iterator function call for generators, so that the
 generator itself is returned.

---
 packages/regenerator-runtime/runtime.js | 19 ++++++++++++-------
 1 file changed, 12 insertions(+), 7 deletions(-)

diff --git a/packages/regenerator-runtime/runtime.js b/packages/regenerator-runtime/runtime.js
index 1a0e47c6b..5cd995ff5 100644
--- a/packages/regenerator-runtime/runtime.js
+++ b/packages/regenerator-runtime/runtime.js
@@ -96,13 +96,9 @@
   if (NativeIteratorPrototype &&
       NativeIteratorPrototype !== Op &&
       hasOwn.call(NativeIteratorPrototype, iteratorSymbol)) {
-    // This environment has a native %IteratorPrototype%; use it instead of the
-    // polyfill unless it's the broken Firefox IteratorPrototype. See
-    // https://github.com/facebook/regenerator/issues/274 for more details.
-    var _n = NativeIteratorPrototype[iteratorSymbol].call(NativeIteratorPrototype);
-    if (!_n || !_n.next || _n.next.name !== 'LegacyIteratorNext') {
-      IteratorPrototype = NativeIteratorPrototype;
-    }
+    // This environment has a native %IteratorPrototype%; use it instead
+    // of the polyfill.
+    IteratorPrototype = NativeIteratorPrototype;
   }
 
   var Gp = GeneratorFunctionPrototype.prototype =
@@ -396,6 +392,15 @@
 
   Gp[toStringTagSymbol] = "Generator";
 
+  // A Generator should always return itself as the iterator object when the
+  // @@iterator function is called on it. Some browsers' implementations of the
+  // iterator prototype chain incorrectly implement this, causing the Generator
+  // object to not be returned from this call. This ensures that doesn't happen.
+  // See https://github.com/facebook/regenerator/issues/274 for more details.
+  Gp[iteratorSymbol] = function() {
+    return this;
+  };
+
   Gp.toString = function() {
     return "[object Generator]";
   };