And Scala (via Dotty) is being re-worked to have sum types with a cleaner "enum"...

sixbrx on Feb 16, 2018 | parent | context | favorite | on: Sum Types Are Coming (2015)

And Scala (via Dotty) is being re-worked to have sum types with a cleaner "enum" syntax soon too: https://github.com/lampepfl/dotty/issues/1970 (merged)