Use of synchronized in scala.Iterator.duplicate?

I was a little bit surprised to see synchronization used in the 
implementation of scala.Iterator.duplicate, particularly seeing as only 
the explicitly synchronized collections in scala.collections.mutable 
make use any synchronization at all.

Granted there's state here, but given that the underlying collection 
isn't in general thread-safe it looks like the sync in duplicate is 
giving a false sense of security ...

Cheers,


Miles