It’s been 2 months since the new version of Scala 2.13.12 has been released. It provide exciting feature of  Quickfixes that is used for some errors and warnings, the compiler now suggests an edit that could fix the issue. scala.collection.Stepper  is a newer generation of Iterator abstraction, exposing similar semantics (hasStep instead of hasNext, nextStep instead of next). Unlike the well known Iterator, we have specialized variations of it (IntStepper, LongStepper, DoubleStepper) which enable efficient iterating over collections that hold unboxed primitives.

scala.collection.mutable.ArrayDeque double-ended queue that provides functionality similar to java.util.ArrayDeque, just with much richer API, as we are used to have in other Scala collections.