While Kotlin 1.0.X releases keep delivering incremental updates and tooling features, we are working on the new language features in Kotlin 1.1. Today we are presenting the first preview version of 1.1, it's far from Beta, but the brave and curious ones can play with new exciting things (and hopefully give us their invaluable feedback).
Compatibility
This is not a stable version of Kotlin, and no compatibility guarantees are given here: in the future previews of 1.1, syntax, APIs, command-line switches and anything else may be changed. If you need a stable version of Kotlin, please stay on