title: Scala Worksheet throwing error
body: <p>I am getting an error while running my Scala Code on IntelliJ (using Scala 2.11.8):</p>
  
  <pre><code>package week4
  
  /**
    * Created by BigB on 15/08/17.
    */
  trait List[T] {
    def isEmpty: Boolean
    def head: T
    def tail: List[T]
  }
  
  class Cons[T](val head: T, val tail: List[T]) extends List[T] {
    override def isEmpty: Boolean = false
  }
  
  class Nil[T] extends List[T] {
    override def isEmpty: Boolean = true
  
    override def head: T = throw new NoSuchElementException("Nil.head")
  
    override def tail: List[T] =throw new NoSuchElementException("Nil.tail")
  }
  </code></pre>
  
  <p>My Scala Worksheet has:</p>
  
  <pre><code>import week4._
  
  object nth {
    def nth[T](n: T, l: List[T]): T = {
      if (l.isEmpty) throw new IndexOutOfBoundsException
      else if (n==0) l.head
      else nth(n-1, l.tail)
    }
  
    val l1 = new Cons(1, new Cons(2, new Cons(2, new Nil)))
  
    nth(2, l1)
  }
  </code></pre>
  
  <p><strong>Errors:</strong></p>
  
  <p>Error:(9, 20) not found: type Cons
  lazy val l1 = new Cons(1, new Cons(2, new Cons(2, new Nil)))
                    ^</p>
  
  <p>Error:(6, 16) value - is not a member of type parameter T
      else nth(n-1, l.tail)
                ^</p>