[es6] Class extends may not be a generator function

src/runtime/runtime-classes.cc

 // Copyright 2014 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include <stdlib.h>
 #include <limits>
 
 #include "src/v8.h"
 
 #include "src/arguments.h"
@@ skipping 101 matching lines @@
 
   Handle<Object> prototype_parent;
   Handle<Object> constructor_parent;
 
   if (super_class->IsTheHole()) {
     prototype_parent = isolate->initial_object_prototype();
   } else {
     if (super_class->IsNull()) {
       prototype_parent = isolate->factory()->null_value();
     } else if (super_class->IsSpecFunction()) {
+      if (Handle<JSFunction>::cast(super_class)->shared()->is_generator()) {
+        Handle<Object> args[1] = {super_class};
+        THROW_NEW_ERROR_RETURN_FAILURE(
+            isolate,
+            NewTypeError("extends_value_generator", HandleVector(args, 1)));
+      }
       ASSIGN_RETURN_FAILURE_ON_EXCEPTION(
           isolate, prototype_parent,
           Runtime::GetObjectProperty(isolate, super_class,
                                      isolate->factory()->prototype_string()));
       if (!prototype_parent->IsNull() && !prototype_parent->IsSpecObject()) {
         Handle<Object> args[1] = {prototype_parent};
         THROW_NEW_ERROR_RETURN_FAILURE(
             isolate, NewTypeError("prototype_parent_not_an_object",
                                   HandleVector(args, 1)));
       }
@@ skipping 327 matching lines @@
   return nullptr;
 }
 
 
 RUNTIME_FUNCTION(Runtime_CallSuperWithSpread) {
   UNIMPLEMENTED();
   return nullptr;
 }
 }
 }  // namespace v8::internal