[es6] Perform the IsConstructor test in GetSuperConstructor.

src/runtime/runtime-classes.cc

Index: src/runtime/runtime-classes.cc
diff --git a/src/runtime/runtime-classes.cc b/src/runtime/runtime-classes.cc
index 323604ffdec47047d31e14cd4600fa9e0f78e068..fb1b34f5ba4bb5970497577118786ea2b9986802 100644
--- a/src/runtime/runtime-classes.cc
+++ b/src/runtime/runtime-classes.cc
@@ -403,7 +403,11 @@ 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