> - Can this reuse existing Scala code?
I think that's the plan. Would be a pretty pointless exercise without that, right? :-)
> - How does it compare against Rust/GO/Swift? Why use this over them?
Rust: Scala and Rust have different niches. Rust is more focused on low runtime overhead, while Scala is more focused on low development overhead. This means Rust can be potentially faster to run, but Scala is faster to develop.
Go: Go is utter shit that only survives due to the devs name-dropping "Google" every 5 minutes.
Swift: Scala is more mature, simpler, better designed. Not a knock against Swift, but there is a difference between a language where changes have been tried experimentally for years before either adopting or removing them, and Swift where things get added at a frightening rate.
> - How about libraries?
Libraries without Java dependencies should work, libraries with Java dependencies depend on whether their Java dependency is provided by Scala-Native (just like on Scala.js).