Consider the following code:
object MatchTest {
val a: Array[Long] = Array(1L)
def test(x: Any) = x match {
case Array(i: Long) => println("Success!")
case _ => println("Failure!") }
def main(args: Array[String]): Unit = test(a) }
When run under Scala 2.13.8 this produces Success whereas under Scala 3.1.1 it produces Failure. For the latter it does not matter if the compiler option -source:3.0-migration is used.
If the change is intended, this should at least produce a big fat warning that the match will possibly fail. If it is not intended, well … it’s even worse, for this significantly changes runtime behaviour after migration. I could not find a page in the migration documentation discussing this (the matchable trait page is related, but addresses a different problem).
Btw, if you replace the relevant Array by IArray the result is again Success, but gives other warnings.