Calling a generator function returns a generator object

src/objects-inl.h

Index: src/objects-inl.h
diff --git a/src/objects-inl.h b/src/objects-inl.h
index 5cde67d7e97e17560c8e22553a0909eb20f38532..bffe4144d791b5e7bab0ffa78df44e4f9543f754 100644
--- a/src/objects-inl.h
+++ b/src/objects-inl.h
@@ -653,6 +653,7 @@ TYPE_CHECKER(Code, CODE_TYPE)
 TYPE_CHECKER(Oddball, ODDBALL_TYPE)
 TYPE_CHECKER(JSGlobalPropertyCell, JS_GLOBAL_PROPERTY_CELL_TYPE)
 TYPE_CHECKER(SharedFunctionInfo, SHARED_FUNCTION_INFO_TYPE)
+TYPE_CHECKER(JSGeneratorObject, JS_GENERATOR_OBJECT_TYPE)
 TYPE_CHECKER(JSModule, JS_MODULE_TYPE)
 TYPE_CHECKER(JSValue, JS_VALUE_TYPE)
 TYPE_CHECKER(JSDate, JS_DATE_TYPE)
@@ -1584,6 +1585,8 @@ int JSObject::GetHeaderSize() {
   // field operations considerably on average.
   if (type == JS_OBJECT_TYPE) return JSObject::kHeaderSize;
   switch (type) {
+    case JS_GENERATOR_OBJECT_TYPE:
+      return JSGeneratorObject::kSize;
     case JS_MODULE_TYPE:
       return JSModule::kSize;
     case JS_GLOBAL_PROXY_TYPE:
@@ -5010,6 +5013,19 @@ void Foreign::set_foreign_address(Address value) {
 }
 
 
+ACCESSORS(JSGeneratorObject, function, JSFunction, kFunctionOffset)
+ACCESSORS(JSGeneratorObject, context, Object, kContextOffset)
+SMI_ACCESSORS(JSGeneratorObject, continuation, kContinuationOffset)
+ACCESSORS(JSGeneratorObject, operand_stack, FixedArray, kOperandStackOffset)
+
+
+JSGeneratorObject* JSGeneratorObject::cast(Object* obj) {
+  ASSERT(obj->IsJSGeneratorObject());
+  ASSERT(HeapObject::cast(obj)->Size() == JSGeneratorObject::kSize);
+  return reinterpret_cast<JSGeneratorObject*>(obj);
+}
+
+
 ACCESSORS(JSModule, context, Object, kContextOffset)
 ACCESSORS(JSModule, scope_info, ScopeInfo, kScopeInfoOffset)