Calling a generator function returns a generator object

src/runtime.cc

Index: src/runtime.cc
diff --git a/src/runtime.cc b/src/runtime.cc
index 7288f38171eb75f6c4e15106817249b4b0b950fe..843b8d701cbcb3cf2b09d3eedf80bc2cb65c1852 100644
--- a/src/runtime.cc
+++ b/src/runtime.cc
@@ -2292,6 +2292,31 @@ RUNTIME_FUNCTION(MaybeObject*, Runtime_SetExpectedNumberOfProperties) {
 }
 
 
+RUNTIME_FUNCTION(MaybeObject*, Runtime_CreateJSGeneratorObject) {
+  NoHandleAllocation ha(isolate);
+  ASSERT(args.length() == 0);
+  JavaScriptFrameIterator it(isolate);
+  JavaScriptFrame* frame = it.frame();
+  JSFunction* function = JSFunction::cast(frame->function());
+  RUNTIME_ASSERT(function->shared()->is_generator());
+
+  JSGeneratorObject* generator;
+  if (frame->IsConstructor()) {
+    generator = JSGeneratorObject::cast(frame->receiver());
+  } else {
+    MaybeObject* maybe_generator =
+        isolate->heap()->AllocateJSGeneratorObject(function);
+    if (!maybe_generator->To(&generator)) return maybe_generator;
+  }
+  generator->set_function(function);
+  generator->set_context(isolate->heap()->undefined_value());
+  generator->set_continuation(0);
+  generator->set_operand_stack(isolate->heap()->empty_fixed_array());
+
+  return generator;
+}
+
+
 MUST_USE_RESULT static MaybeObject* CharFromCode(Isolate* isolate,
                                                  Object* char_code) {
   uint32_t code;