Avoid reading RawObject::class_ directly in the runtime.

runtime/vm/object.cc

 // Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 #include "vm/object.h"
 
 #include "platform/assert.h"
 #include "vm/assembler.h"
 #include "vm/bigint_operations.h"
 #include "vm/bootstrap.h"
@@ skipping 260 matching lines @@
   {
     intptr_t size = Class::InstanceSize();
     uword address = heap->Allocate(size, Heap::kOld);
     class_class_ = reinterpret_cast<RawClass*>(address + kHeapObjectTag);
     InitializeObject(address, Class::kInstanceKind, size);
     // Make the class_ field point to itself.
     class_class_->ptr()->class_ = class_class_;
 
     Class fake;
     // Initialization from Class::New<Class>.
-    cls = class_class_;
+    // Directly set raw_ to break a circular dependency: SetRaw will attempt
+    // to lookup class class in the class table where it is not registered yet.
+    cls.raw_ = class_class_;
     cls.set_handle_vtable(fake.vtable());
     cls.set_instance_size(Class::InstanceSize());
     cls.set_next_field_offset(Class::InstanceSize());
     cls.set_instance_kind(Class::kInstanceKind);
     cls.set_index(Class::kInstanceKind);
     cls.raw_ptr()->is_const_ = false;
     cls.raw_ptr()->is_interface_ = false;
     cls.set_is_finalized();
     cls.raw_ptr()->type_arguments_instance_field_offset_ =
         Class::kNoTypeArguments;
@@ skipping 9820 matching lines @@
   const String& str = String::Handle(pattern());
   const char* format = "JSRegExp: pattern=%s flags=%s";
   intptr_t len = OS::SNPrint(NULL, 0, format, str.ToCString(), Flags());
   char* chars = reinterpret_cast<char*>(
       Isolate::Current()->current_zone()->Allocate(len + 1));
   OS::SNPrint(chars, (len + 1), format, str.ToCString(), Flags());
   return chars;
 }
 
 }  // namespace dart