Kotlin 2.3.0 is now generally available, with the language update offering capabilities such as an unused return value checker and support for Java 25. The release has a variety of experimental-stage features including the value checker, Swift interoperability, and a new syntax for explicit backing fields.
JetBrains released the language update on December 16. Installation instructions can be found at blog.jetbrains.com. This general release of the Java rival follows a release candidate introduced November 18.
With Kotlin 2.3.0, a new checker for unused values helps prevent ignored results. It warns whenever an expression returns a value other than Unit or Nothing and is not passed to a function, checked in a condition, or otherwise used. The checker helps catch bugs where a function call produces a meaningful result that was silently dropped, which can lead to unexpected behavior or hard-to-trace issues. This feature is currently experimental.
