DottyTypeBoundsAndComposition.scala

object Main {

	trait A {
	 	val age = 18 
	}

	trait B {
	  	val name = "Lucas"
	}

	def show(o: A | B): Unit = o match {
		case a: A => println(s"age ${a.age}")
		case b: B => println(s"name ${b.name}")
	}

	def show(o: A & B): Unit = {
		println(s"${o.name}, ${o.age}")
	}	

	trait TM1
	trait T0 extends TM1
	trait T1 extends T0
	trait T2 extends T1
	trait T3 extends T2	

	/*
	 * T must be upper bound of T3 and T3 must be upper bound of T0, i.e.: concrete type C is between <T> and T3,
	 * with T min of T0
 	 */
	class Box[T >: T3 <: T0] {
		def put(v: T): Unit = {}
	}

	class SpecificBox[T] {
		def put(v: T): Unit = {}
	}

	class Box2[T >: T3 <: T1] {
		def put(v: T): Unit = {}
	}

	def main(args: Array[String]): Unit = {

		val v : Int | String = 22

		show(new B{})
		show(new A with B {})

		println()

		// [T0, T3]
		val box1 = new Box[T0]()

		box1.put(new T0{})
		box1.put(new T1{})
		box1.put(new T2{})
		box1.put(new T3{})

		// [T1, T3]
		val box2 = new Box[T1]()

		//box2.put(new T0{})
		box2.put(new T1{})
		box2.put(new T2{})
		box2.put(new T3{})

		// [T2, T3]
		val box3 = new Box[T2]()

		//box3.put(new T0{})
		//box3.put(new T1{})
		box3.put(new T2{})
		box3.put(new T3{})
		
		// [T3, T3]
		val box4 = new Box[T3]()

		//box4.put(new T0{})
		//box4.put(new T1{})
		//box4.put(new T2{})
		box4.put(new T3{})

		val box5 = new SpecificBox[T1 & T3]()

		//box5.put(new T2{})
		box5.put(new T1 with T3{})

		// Compiler error! T must be at least T0 and max T3
		val box6 = new Box2[TM1]()
		
	}	

}