unapplySeq allows arrays

[lrytz]

class SQ {
  val isEmpty = false
  val get = Array(1)
}
object A {
  def unapplySeq(a: Int): SQ = new SQ
}

object Main {
  def main(args: Array[String]): Unit = {
    val seq: Seq[Int] = 2 match {
      case A(xs: _*) => xs
    }
  }
}

➜  sandbox git:(typo) dotc Test.scala
undefined: x3.<none> # 814: TermRef(TermRef(NoPrefix,val x3),<none>) at pruneErasedDefs
one error found

https://github.com/lampepfl/dotty/blob/652092b07c4058201909effc4a8ffde469e37a75/compiler/src/dotty/tools/dotc/typer/Applications.scala#L105

.elemType works for Seqs but also arrays. there's no check that the getTp is a Seq.