the Scala delimited continuations plugin and library

scala-continuations is a compiler plugin and library for Scala providing support for CPS (continuation-passing style) transformations.

It is no longer maintained. Past releases (for Scala 2.12 and earlier) remain available on Maven Central.

You might also be interested in https://github.com/scala/scala-async, which covers what was once the most common use case for the continuations plugin.