* `AnyVal` (can be used as a new type on Scala 2/3)
* `opaque type` (can be used as a new type on Scala 3)
* `@@` type from [Scalaz](https://github.com/scalaz/scalaz) (tagged type)
* `@@` type from [MacWire](https://github.com/softwaremill/macwire) (tagged type)
* `@newtype` macro from [NewType (`estatico/scala-newtype`)](https://github.com/estatico/scala-newtype) (newtype, Scala 2-only)
* `Newtype` from [Newtypes (`monix/newtypes`)](https://newtypes.monix.io/) (newtype, Scala 2/3)
* `NewType` type from [neotype (`kitlangton/neotype`)](https://github.com/kitlangton/neotype) (newtype, Scala 3-only)