List of shapes infers to List[Shape] but list of boxed shapes infers to List[Box[Square | Circle]]
scala> sealed trait Shape
| case class Square() extends Shape
| case class Circle() extends Shape
| case class Box[+T <: Shape](t: T)
| List(Square(), Circle())
| List(Box(Square()), Box(Circle()))
val res0: List[Shape & Product & Serializable] = List(Square(), Circle())
val res1: List[Box[Square | Circle]] = List(Box(Square()), Box(Circle()))
Why is res0 not typed to List[Square | Circle] in symmetry with List[Box[Square | Circle]], or vice-versa?
Dotty defines least upper bound in terms of union types
the least upper bound (lub) of a set of types is the union of these types. This replaces the definition of least upper bound in the Scala 2 specification.
What are the rules now for unification relative to this change?