What does `:_*` (colon underscore star) do in Scala?

Question

I have the following piece of code from this question:

def addChild(n: Node, newChild: Node) = n match {
  case Elem(prefix, label, attribs, scope, child @ _         


        

Answer 1

• child ++ newChild - sequence
• : - type ascription, a hint that helps compiler to understand, what type does that expression have
• _* - placeholder accepting any value + vararg operator

child ++ newChild : _* expands Seq[Node] to Node* (tells the compiler that we're rather working with a varargs, than a sequence). Particularly useful for the methods that can accept only varargs.