[modules] Detect and throw exceptions for cyclic dependencies

src/objects-debug.cc

 // Copyright 2012 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/objects.h"
 
 #include "src/bootstrapper.h"
 #include "src/disasm.h"
 #include "src/disassembler.h"
 #include "src/field-type.h"
@@ skipping 910 matching lines @@
 }
 
 void Module::ModuleVerify() {
   CHECK(IsModule());
   CHECK(code()->IsSharedFunctionInfo() || code()->IsJSFunction());
   code()->ObjectVerify();
   exports()->ObjectVerify();
   requested_modules()->ObjectVerify();
   VerifySmiField(kFlagsOffset);
   embedder_data()->ObjectVerify();
+  CHECK(shared()->name()->IsSymbol());
   // TODO(neis): Check more.
 }
 
 void PrototypeInfo::PrototypeInfoVerify() {
   CHECK(IsPrototypeInfo());
   if (prototype_users()->IsWeakFixedArray()) {
     WeakFixedArray::cast(prototype_users())->FixedArrayVerify();
   } else {
     CHECK(prototype_users()->IsSmi());
   }
@@ skipping 421 matching lines @@
 
   // Both are done at the same time.
   CHECK_EQ(new_it.done(), old_it.done());
 }
 
 
 #endif  // DEBUG
 
 }  // namespace internal
 }  // namespace v8