Self-defined Classes in one cell cannot be invoked in another cell about spylon-kernel HOT 10 CLOSED

sealed trait List[+A]
case object Nil extends List[Nothing]
case class Cons[+A](head: A, tail: List[A]) extends List[A]
object List {
def sum(ints: List[Int]): Int = ints match {
case Nil => 0
case Cons(x,xs) => x + sum(xs)
}
def product(ds: List[Double]): Double = ds match {
case Nil => 1.0
case Cons(0.0, _) => 0.0
case Cons(x,xs) => x * product(xs)
}
def apply[A](as: A*): List[A] =
if (as.isEmpty) Nil
else Cons(as.head, apply(as.tail: _*))
}

def sum(ints: List[Int]): Int = ints match {
case Nil => 0
case Cons(x,xs) => x + sum(xs)
}

val x = List(1,2,3,4,5) match {
case Cons(x, Cons(2, Cons(4, _))) => x
case Nil => 42
case Cons(x, Cons(y, Cons(3, Cons(4, _)))) => x + y
case Cons(h, t) => h + sum(t)
case _ => 101
}

val x = List(1,2,3,4,5) match {
case Cons(x, Cons(2, Cons(4, _))) => x
case Nil => 42
case Cons(x, Cons(y, Cons(3, Cons(4, _)))) => x + y
case Cons(h, t) => h + sum(t)
case _ => 101
}


Output:
<console>:40: error: reference to List is ambiguous;
it is imported twice in the same scope by
import $line16$read.List
and import INSTANCE.List
       val x = List(1,2,3,4,5) match {
               ^
<console>:43: error: type mismatch;
 found   : Any
 required: String
       case Cons(x, Cons(y, Cons(3, Cons(4, _)))) => x + y
                                                         ^
<console>:44: error: type mismatch;
 found   : List[Any]
 required: List[Int]
       case Cons(h, t) => h + sum(t)
                                  ^