Scala Dotty 联合类型 DaysOfTheWeek 示例

Question

Scala Dotty 官方团队展示了来自 ( https://d-d.me/talks/scalaworld2015/#/12 ) 的这个例子

object DaysOfTheWeek {
  object Mon
  object Tue
  object Wed
  object Thu
  object Fri
  object Sat
  object Sun

  type Weekend = Sat.type | Sun.type
  type Workweek = Mon.type | Tue.type | Wed.type | Thu.type | Fri.type
  type All = Weekend | Workweek
}

如果我使用最新的 Dotty nightly build，截至本文发布时为“0.1.1-20170322-5fd7a95-NIGHTLY”，该示例会导致以下错误:

Error:(13, 18) Singleton type DaysOfTheWeek.Sat.type is not allowed in a union type
Error:(13, 29) Singleton type DaysOfTheWeek.Sun.type is not allowed in a union type
Error:(14, 19) Singleton type DaysOfTheWeek.Mon.type is not allowed in a union type
Error:(14, 30) Singleton type DaysOfTheWeek.Tue.type is not allowed in a union type
Error:(14, 41) Singleton type DaysOfTheWeek.Wed.type is not allowed in a union type
Error:(14, 52) Singleton type DaysOfTheWeek.Thu.type is not allowed in a union type
Error:(14, 63) Singleton type DaysOfTheWeek.Fri.type is not allowed in a union type

有什么办法可以使这个官方示例正常工作吗？

Answer 1

这现在有效:

enum DaysOfTheWeek {
case Mon
case Tue
case Wed
case Thu
case Fri
case Sat
case Sun
  type Weekend = Sat.type | Sun.type
  type Workweek = Mon.type | Tue.type | Wed.type | Thu.type | Fri.type
  type All = Weekend | Workweek
}

链接到 Scastie