String.prototype[Symbol.iterator] does RequireObjectCoercible(this)

src/js/string-iterator.js

Index: src/js/string-iterator.js
diff --git a/src/js/string-iterator.js b/src/js/string-iterator.js
index 3c331dd1a2da4e99dc0e84be7c9ffa091f01acad..0fbdd5273957fbee25461127319ff2f1f42e5345 100644
--- a/src/js/string-iterator.js
+++ b/src/js/string-iterator.js
@@ -32,6 +32,10 @@ function StringIterator() {}
 
 // 21.1.5.1 CreateStringIterator Abstract Operation
 function CreateStringIterator(string) {
+  if (IS_NULL_OR_UNDEFINED(string)) {

[adamk, 2016/03/09 23:31:58]

There's a macro for this:

CHECK_OBJECT_COERCIBLE(string, 'String.prototype[Symbol.iterator]');

[Dan Ehrenberg, 2016/03/09 23:53:59]

Awesome, applied

+    throw MakeTypeError(kIncompatibleMethodReceiver,
+                        'String.prototype[Symbol.iterator]');
+  }
   var s = TO_STRING(string);
   var iterator = new StringIterator;
   SET_PRIVATE(iterator, stringIteratorIteratedStringSymbol, s);