You'd need a pretty hefty support library to add the JVM-provided features Scala relies on. Garbage collection is obviously a major one, but there are also the

You'd need a pretty hefty support library to add the JVM-provided features Scala relies on. Garbage collection is obviously a major one, but there are also the pieces of the standard Java libraries that Scala builds on top of (though I'm not sure how deep those dependencies run). GCJ attempted to do this for straight Java; I don't believe many people consider it a success.