From 5ba2e6254b43be5a0b14e797c3e2b311c87dd557 Mon Sep 17 00:00:00 2001
From: Sebastian McKenzie <sebmck@gmail.com>
Date: Sat, 21 Feb 2015 18:00:43 +1100
Subject: [PATCH] check if iterator has a return method before calling it when
 breaking in a for...of - #838

---
 lib/babel/transformation/transformers/es6/for-of.js | 13 +++++++++++--
 .../es6-for-of-loose/break/expected.js              |  6 +++---
 .../transformation/es6-for-of/break/expected.js     |  8 +++-----
 3 files changed, 17 insertions(+), 10 deletions(-)

diff --git a/lib/babel/transformation/transformers/es6/for-of.js b/lib/babel/transformation/transformers/es6/for-of.js
index 2343a57e09..935d1dcc19 100644
--- a/lib/babel/transformation/transformers/es6/for-of.js
+++ b/lib/babel/transformation/transformers/es6/for-of.js
@@ -53,7 +53,7 @@ var breakVisitor = {
       var ret = t.expressionStatement(
         t.callExpression(t.memberExpression(state.iteratorKey, t.identifier("return")), [])
       );
-      if (state.wrapReturn) ret = state.wrapReturn(ret);
+      ret = state.wrapReturn(ret);
 
       this.skip();
       return [ret, node];
@@ -100,7 +100,13 @@ var loose = function (node, parent, scope, file) {
   scope.traverse(node, breakVisitor, {
     iteratorKey: iteratorKey,
     wrapReturn:  function (node) {
-      return t.ifStatement(t.unaryExpression("!", isArrayKey, true), node);
+      return t.ifStatement(
+        t.logicalExpression(
+          "&&",
+          t.unaryExpression("!", isArrayKey, true),
+          t.memberExpression(iteratorKey, t.identifier("return")
+        )
+      ), node);
     },
     label:       t.isLabeledStatement(parent) && parent.label.name
   });
@@ -146,6 +152,9 @@ var spec = function (node, parent, scope, file) {
 
   scope.traverse(node, breakVisitor, {
     iteratorKey: iteratorKey,
+    wrapReturn:  function (node) {
+      return t.ifStatement(t.memberExpression(iteratorKey, t.identifier("return")), node);
+    },
     label:       t.isLabeledStatement(parent) && parent.label.name
   });
 
diff --git a/test/fixtures/transformation/es6-for-of-loose/break/expected.js b/test/fixtures/transformation/es6-for-of-loose/break/expected.js
index 8a0183d098..c83887fadf 100644
--- a/test/fixtures/transformation/es6-for-of-loose/break/expected.js
+++ b/test/fixtures/transformation/es6-for-of-loose/break/expected.js
@@ -17,7 +17,7 @@ foo: for (var _iterator = foo(), _isArray = Array.isArray(_iterator), _i = 0, _i
   var x = _ref;
 
   while (true) {
-    if (!_isArray) _iterator["return"]();
+    if (!_isArray && _iterator["return"]) _iterator["return"]();
 
     break foo;
   }
@@ -55,7 +55,7 @@ foo: for (var _iterator3 = foo(), _isArray3 = Array.isArray(_iterator3), _i3 = 0
   }
 
   var x = _ref3;
-  if (!_isArray3) _iterator3["return"]();
+  if (!_isArray3 && _iterator3["return"]) _iterator3["return"]();
 
   break foo;
 }
@@ -75,7 +75,7 @@ for (var _iterator4 = foo(), _isArray4 = Array.isArray(_iterator4), _i4 = 0, _it
   }
 
   var x = _ref4;
-  if (!_isArray4) _iterator4["return"]();
+  if (!_isArray4 && _iterator4["return"]) _iterator4["return"]();
 
   break;
 }
diff --git a/test/fixtures/transformation/es6-for-of/break/expected.js b/test/fixtures/transformation/es6-for-of/break/expected.js
index 20a7d2f79f..fe7b0f9d20 100644
--- a/test/fixtures/transformation/es6-for-of/break/expected.js
+++ b/test/fixtures/transformation/es6-for-of/break/expected.js
@@ -6,7 +6,7 @@ foo: for (var _iterator = foo()[Symbol.iterator](), _step; !(_step = _iterator.n
   var x = _step.value;
 
   while (true) {
-    _iterator["return"]();
+    if (_iterator["return"]) _iterator["return"]();
 
     break foo;
   }
@@ -22,8 +22,7 @@ foo: for (var _iterator2 = foo()[Symbol.iterator](), _step2; !(_step2 = _iterato
 
 foo: for (var _iterator3 = foo()[Symbol.iterator](), _step3; !(_step3 = _iterator3.next()).done;) {
   var x = _step3.value;
-
-  _iterator3["return"]();
+  if (_iterator3["return"]) _iterator3["return"]();
 
   break foo;
 }
@@ -32,8 +31,7 @@ foo: for (var _iterator3 = foo()[Symbol.iterator](), _step3; !(_step3 = _iterato
 
 for (var _iterator4 = foo()[Symbol.iterator](), _step4; !(_step4 = _iterator4.next()).done;) {
   var x = _step4.value;
-
-  _iterator4["return"]();
+  if (_iterator4["return"]) _iterator4["return"]();
 
   break;
 }