Do you mean def onModificationProhibited: Unit ?
I could do that but then it would make it abstract; I was thinking we might not always want to override it.


The parens are just convention because it's a side-effecting method. The method can still be invoked without parens but the other way around (ie. no parens here and parens at call-site) is prohibited.
​Ah. Fair enough. Carry on then. :)