[vm] Fix reading a named reference to a top-level class.

runtime/vm/snapshot.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/snapshot.h"
 
 #include "platform/assert.h"
 #include "vm/bootstrap.h"
 #include "vm/class_finalizer.h"
 #include "vm/dart.h"
@@ skipping 258 matching lines @@
          !IsObjectStoreClassId(SerializedHeaderData::decode(class_header)));
   Class& cls = Class::ZoneHandle(zone(), Class::null());
   AddBackRef(object_id, &cls, kIsDeserialized);
   // Read the library/class information and lookup the class.
   str_ ^= ReadObjectImpl(class_header, kAsInlinedObject, kInvalidPatchIndex, 0);
   library_ = Library::LookupLibrary(thread(), str_);
   if (library_.IsNull() || !library_.Loaded()) {
     SetReadException("Invalid object found in message.");
   }
   str_ ^= ReadObjectImpl(kAsInlinedObject);
-  cls = library_.LookupClassAllowPrivate(str_);
+  if (str_.raw() == Symbols::TopLevel().raw()) {
+    cls = library_.toplevel_class();
+  } else {
+    cls = library_.LookupClassAllowPrivate(str_);

[siva, 2017/06/26 20:36:45]

Would it be beneficial to add this login into LookupClassAllowPrivate itself?

[rmacnak, 2017/06/26 20:51:45]

I'm not sure. I don't think we can generally treat library-level lookups as
equivalent to lookups in the corresponding top-level class (I dimly recall that
some top-level members are only added to the library's dictionary and not the
top-level class), so I suspect they usually have to be special-cased anyway.

+  }
   if (cls.IsNull()) {
     SetReadException("Invalid object found in message.");
   }
   cls.EnsureIsFinalized(thread());
   return cls.raw();
 }
 
 
 RawFunction* SnapshotReader::ReadFunctionId(intptr_t object_id) {
   ASSERT(kind_ == Snapshot::kScript);
@@ skipping 1761 matching lines @@
       *buffer_len_ = BytesWritten();
     }
   } else {
     FreeBuffer();
     ThrowException(exception_type(), exception_msg());
   }
 }
 
 
 }  // namespace dart