Calling a generator function returns a generator object

src/factory.cc

Index: src/factory.cc
diff --git a/src/factory.cc b/src/factory.cc
index a2e91e64a5acfd3dc90469963aa195411bdc2ee8..bdffa29c2e4ab982f29cc68b5e1a1b7aec4aa651 100644
--- a/src/factory.cc
+++ b/src/factory.cc
@@ -614,8 +614,8 @@ Handle<JSFunction> Factory::NewFunctionFromSharedFunctionInfo(
   if (function_info->is_generator()) {
     // Generator functions have specialized prototypes and instance types, so
     // they need their prototypes to be created eagerly.
-    // TODO(wingo): Use JS_GENERATOR_TYPE.
-    Handle<Map> instance_map = NewMap(JS_OBJECT_TYPE, JSObject::kHeaderSize);
+    Handle<Map> instance_map =
+      NewMap(JS_GENERATOR_ITERATOR_TYPE, JSGeneratorIterator::kSize);
     Handle<JSObject> iterator_prototype = NewFunctionPrototype(result);
     instance_map->set_prototype(*iterator_prototype);
     result->set_initial_map(*instance_map);
@@ -978,6 +978,15 @@ Handle<JSObject> Factory::NewJSObject(Handle<JSFunction> constructor,
 }
 
 
+Handle<JSGeneratorIterator> Factory::NewJSGeneratorIterator(
+    Handle<JSFunction> function) {
+  CALL_HEAP_FUNCTION(
+      isolate(),
+      isolate()->heap()->AllocateJSGeneratorIterator(*function),
+      JSGeneratorIterator);
+}
+
+
 Handle<JSModule> Factory::NewJSModule(Handle<Context> context,
                                       Handle<ScopeInfo> scope_info) {
   CALL_HEAP_FUNCTION(