Coming Soon: Scala 2.12.13

This is a thread to discuss plans and share progress on Scala 2.12.13 .

I’ve set the target date on the 2.12.13 milestone to October 29 .

This is primarily a bug fix release. It will also include some performance improvements to certain collections, most notably to immutable.{TreeSet, TreeMap}(#8794.)

Links helpful for seeing how 2.12.13 is shaping up:

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It would be cool if this could be fixed

A few issues and PRs are still in flight. Current target date is Mon Nov 16 :crossed_fingers:

I’m trying to fix

It is 2020-11-17 already. What is the target date now?

It seems it is a bug from Spark. See

@sadhen Thanks for looking into that issue. I would suggest fixing it by catching the exception and falling back to a mode where the backend doesn’t inline from that JAR.

Testing of 2.12.x found some regressions due to changes since 2.12.12 which I’ve been working through. I believe its is stabilized now and we’re planning to release soon. A fix for that bug would need to be merged after the release given that it is not a regression and has a workaround.


Please review:

Catched the exceptions with proper logging.

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The candidate build is 2.12.13-bin-ade1bbc (available from https/

I’ll run this through our internal testing (including the community build). I’d appreciate any feedback from folks who try this build out in their project.

@sadhen I decided to included your fix to be tolerant of mal-formed classfiles in the optimizer. Thanks for your contribution!

Assuming we find no further issues we should release later this week.


2.12.13-bin-ade1bbc is green in the community build.


The issue I pointed above is fixed.


The new release candidate is 2.12.13-bin-5c9699d. This includes a performance regression fix for ClassTag creation.

Is there an update on when 2.12.13 will be released? It looks like there are currently no open PRs or bugs left targeting this milestone.

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Update: we are performing some additional regression testing in partnership with a customer with a large 2.12.x codebase. I’m expecting results tomorrow, if they are okay we’ll go ahead with the release on Friday.


The good news is, the release candidate has passed QA.

The bad news is, we weren’t able to release on Friday.

And we now feel that releasing this week or next would inappropriately intrude on the holiday season, since Scala releases make work downstream (for authors of compiler plugins, tooling, etc). So, Jason will pull the release levers in early January.


Do you have a new estimate when this release will be cut? Thanks for everyone’s work on this!

We had an unexpected setback internally last week. With any luck, we’ll be pulling release levers tomorrow.


2.12.13 JARs are now on Maven Central. We’re working pulling the rest of the levers.

Levers pulled, announcements made.

Macro paradise isn’t available yet but will follow soon.

Scala.js 1.x (all versions 1.0.0->1.4.0) and 0.6.33 support for Scala 2.12.13 is on its way to Maven Central.

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Macro paradise is available:

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