Scala 2.12.18 release planning

This thread is for updates and discussions about the upcoming Scala 2.12.18 release.

The main motivation for the release would be to add JDK 20 support. (As usual, a new JDK version requires an ASM upgrade in order for the optimizer work.) The necessary changes, by Philippus Baalman, have already been merged. Oracle’s target release date for JDK 20 is March 21, 2023.

Timing-wise, we intend to do 2.12.18 and 2.13.11 at the same time; see the 2.13.11 release planning thread.

Our team at Lightbend has also been making some changes to help users migrate from 2.12 to 2.13, typically under the -Xsource:2.13 flag.

The 2.12.18 milestone on GitHub has lists of open and merged PRs for the release. You may wish to filter by the “release-notes” label to see only the most significant changes.

Feel free to use this thread to ask questions and share concerns about the timing and contents of the release.


We’ve just finished QAing the current 2.12 nightly on JDK 20 and all is well. Our test suite is green and will run nightly on JDK 20 from now on, and the same is true of the Scala 2.12 community build.

An update on timing: 3.3.0 is a bit delayed (not before April 17, is my understanding, since we don’t have RC4 yet), so that pushes 2.12.18 until at least April 20.