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import language.existentials
object Test {
class Def[T]
class Exp[T]
class Contra[-T] { def head[T1 <: T] : T1 = ??? }
class Cov[+T] { }
case class ArrayApply[T](x: Exp[Array[T]], i: Exp[Int], j: Exp[_]) extends Def[T]
val IntArrayApply = ArrayApply[Int](new Exp[Array[Int]], new Exp[Int], new Exp[Int])
def f(x: Any) = x match {
case xs: Iterable[Any] => xs.head // okay
case _ => 0
}
def f2(x: Any) = x match {
case xs: Iterable[String] => xs.head // unchecked
case _ => 0
}
def f3(x: Any) = x match {
case xs: Set[Any] => xs.head // unchecked
case _ => 0
}
def f4(x: Any) = x match {
case xs: Map[Any, Any] => xs.head // unchecked
case _ => 0
}
def cf1(x: Any) = x match {
case xs: Contra[Nothing] => xs.head // okay
case _ => 0
}
def cf2(x: Any) = x match {
case xs: Contra[List[Nothing]] => xs.head // unchecked
case _ => 0
}
def co1(x: List[Cov[List[Int]]]) = x match {
case _: Seq[Cov[Seq[Any]]] => true // okay
case _ => false
}
def g[T](x: Def[T]) = x match {
case ArrayApply(x: Exp[Array[T]], i: Exp[Int], _) => x // okay
case _ => 0
}
def g2[T](x: Def[T]) = x match {
case ArrayApply(x: Exp[Array[T]], _, j: Exp[String]) => x // unchecked
case _ => 0
}
def g3[T](x: Any) = x match {
case ArrayApply(x: Exp[Array[T]], _, _) => x // unchecked
case _ => 0
}
def g4 = IntArrayApply match {
case ArrayApply(x: Exp[Array[Int]], _, _) => x // okay
case _ => ()
}
def g5[T](x: ArrayApply[Int]) = x match {
case ArrayApply(x: Exp[Array[Int]], _, _) => x // okay
case _ => 0
}
// Nope
//
// def g5 = IntArrayApply match {
// case ArrayApply(x: Exp[Array[String]], _, _) => x // nope
// case _ => ()
// }
}
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