This isn’t simply “multiple variable assignment”, it’s fully-featured pattern matching!
So the following are all valid:
val (a, b) = (1, 2)
val Array(a, b) = Array(1, 2)
val h :: t = List(1, 2)
val List(a, Some(b)) = List(1, Option(2))
This is the way that pattern matching works, it’ll de-construct something into smaller parts, and bind those parts to new names. As specified, pattern matching won’t bind to pre-existing references, you’d have to do this yourself.
var x: Int = _
var y: Int = _
val (a, b) = (1, 2)
x = a
y = b
// or
(1,2) match {
case (a,b) => x = a; y = b
case _ =>
}