Simplistic reproduction of https://github.com/scala/scala/blob/v2.13.3/src/library/scala/collection/immutable/List.scala

QList.scala

{

  trait QList[+A]{
    def ::[B >: A](head: B): QList[B] = new ::(head, this)
  }

  case class ::[+A](head: A, tail: QList[A]) extends QList[A]

  object QNil extends QList[Nothing]

  }

// defined trait QList
// defined class ::
// defined object QNil

1 :: QNil
// res9: QList[Int] = 1 :: ammonite.$sess.cmd8$QNil$@f2d890c

1 :: QNil  match {
  case QNil => 1
  case _ => 0
  }
// res10: Int = 0

QNil  match {
  case QNil => 1
  case _ => 0
  }
// res11: Int = 1

2 :: QNil  match {
  case a::_ => a
  case _ => 0
  }
// res12: Int = 2

1::2::3::QNil
// res13: QList[Int] = 1 :: 2 :: 3 :: ammonite.$sess.cmd8$QNil$@f2d890c

"1"::"2"::"3"::QNil
// res14: QList[String] = "1" :: "2" :: "3" :: ammonite.$sess.cmd8$QNil$@f2d890c

To try it yourself there is a so called one-click Scala install option to consider:
https://www.scala-lang.org/2020/06/29/one-click-install.html

... will install all the following software, if not yet installed:

a JDK
the build tools sbt and mill
the Ammonite enhanced REPL
scalafmt, the Scala formatter
the coursier CLI, to install further Scala-based applications
the scala and scalac command-line tools
With all those installed, we are ready to go! Later, cs update can be used to update the installation.

For power users, the cs setup command offers more configuration options, such as a non-interactive mode.

If you need one or more very simple VM for your experiment(s) you may try:
https://multipass.run