Mixing a trait dynamically. Copy a trait

Fantastically! I was dreaming about this for a long time. Imagine you have a trait, like

trait Dated {
 def createDate: Date
 def createAuthor: Author
}

Just some trait form db orm entity. What if you want just set nececery fields to this Dated instance, without any knowledge what case class is it, like:

def setEntityDate(entity: Dated) = entity.copy(createDate = /*now*/, createAuthor = /*currentUser*/)

This task can be accomplished by scala macroses, read about it here http://stackoverflow.com/questions/10373318/mixing-in-a-trait-dynamically and here https://gist.github.com/2559714