Enum members and union types

[felixmulder]

enum ParseResult {
  case Trees(xs: List[Int])
  case Errors(xs: List[String])
  case Incomplete
  case Exit
}

import ParseResult._

type Fine     = Trees | Errors
type NotFine0 = Trees | Incomplete
type NotFine1 = Trees | Errors | Incomplete
type NotFine2 = Trees | Errors | Exit

I'm assuming this is due to Incomplete and Exit getting desugared into:

final case val Exit: Test.ParseResult = Test.ParseResult.$new(3, "Exit")

ping @odersky

[sjrd]

What's wrong? You should write

type Fine     = Trees | Errors
type NotFine0 = Trees | Incomplete.type
type NotFine1 = Trees | Errors | Incomplete.type
type NotFine2 = Trees | Errors | Exit.type

[felixmulder]

@sjrd - singleton types are not allowed in union types currently

[japgolly]

singleton types are not allowed in union types currently

oh god... please tell me that's going to change at some point.

[felixmulder]

@japgolly - there was some breakage a while back, where at the time, we decided that fixing the breakage was more important than allowing singleton types in unions.

I'm hoping that we can get back to enabling this again, but so far other things have taken priority. If you're interested in helping out on this, we're more than happy to help you get started :)

[smarter]

This appears to be a special case of #1551 so closing this one in favor of the other.