Proposal for Opaque Type Aliases

Scala Improvement Process
96

Nope, as mentioned before, outside of their definition they behave exactly like abstract type aliases do. You can already make opaques like this:

object Permission {
  type Permission
  def apply(i: Int): Permission = i.asInstanceOf[Permission]
  private[this] def unwrap(p: Permission) = p.asInstanceOf[Int]
  
  def (i: Permission) | (other: Permission): Permission = Permission(unwrap(i) | unwrap(other))
  def (i: Permission) isOneOf (permission: Permission): Boolean = (unwrap(i) & unwrap(permission)) != 0
}

And various tagging libraries like GitHub - estatico/scala-newtype: NewTypes for Scala with no runtime overhead let you do the same with less boilerplate.

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