CaseClass.scala

import scala.util.Try

/**
 * Alternative to unsound construct: "sealed abstract case class"
 * see https://gist.github.com/tpolecat/a5cb0dc9adeacc93f846835ed21c92d2
 * The solution below is the summary of the comments of the above gist.
 *
 * Works as is in Scala 2.12 and higher
 * In Scala 2.11.12 you have to add -Xsource:2.12
 */
final case class NotWeird private (field: Int) {
  // if you really want one (e.g. for lenses)
  def copy(field: Int = field) = NotWeird(field)
}

object NotWeird {

  def apply(field: Int): NotWeird = {
    if (field > 0) new NotWeird(field)
    else throw new IllegalArgumentException("Only positive numbers")
  }
}

object TryItOut extends App {

  // does not compile
  // println("new NotWeird(3): " + new NotWeird(3))

  println("NotWeird(3): " + NotWeird(3))

  println("Try(NotWeird(-3)): " + Try(NotWeird(-3)))

  println("NotWeird(3).copy(field = 1): " + NotWeird(3).copy(field = 1))

  println("Try(NotWeird(3).copy(-5)): " + Try(NotWeird(3).copy(-5)))
}

SBT file for 2.11 with compiler flag:

`
name := "CaseClass"

version := "0.1"

scalaVersion := "2.11.12"

scalacOptions ++= Seq("-Xsource:2.12")
`