[es6] Perform the IsConstructor test in GetSuperConstructor.

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 "src/runtime/runtime-utils.h"
 
 #include <stdlib.h>
 #include <limits>
 
 #include "src/arguments.h"
@@ skipping 385 matching lines @@
   RETURN_RESULT_OR_FAILURE(
       isolate,
       StoreKeyedToSuper(isolate, home_object, receiver, key, value, SLOPPY));
 }
 
 
 RUNTIME_FUNCTION(Runtime_GetSuperConstructor) {
   SealHandleScope shs(isolate);
   DCHECK_EQ(1, args.length());
   CONVERT_ARG_CHECKED(JSFunction, active_function, 0);
-  return active_function->map()->prototype();
+  Object* prototype = active_function->map()->prototype();
+  if (!prototype->IsConstructor()) {
+      return Runtime_ThrowConstructedNonConstructable(1, &prototype, isolate);

[Benedikt Meurer, 2016/11/23 04:51:00]

Please don't call other runtime functions this way. Just do the
THROW_NEW_ERROR_RETURN_FAILURE here.
Also this deserves a useful error message IMHO, i.e. something like "super
constructor <bar> of <foo> is not a constructor".

+  }
+  return prototype;
 }
 
 }  // namespace internal
 }  // namespace v8