Scalar is a Scala language provider for Cleanroom. It provides Scala 3 library for new Cleanroom mods.

Yes, you can develop with Scala 3 + Java 21 in 1.12.2!

If you want the Scalar providing Scala 2.11 which compats with legacy Forge mods, please use Scalar Legacy.

To run new Cleanroom mods developed in Scala 3 (like OpenComputers Rescaled), this mod is necessary.

FAQ:

Q: What is Cleanroom?
A: Cleanroom is a 1.12.2 Forge fork, providing newer toolchain, new APIs and 99% compatibility. Our plan is to make 1.12.2 up-to-date with latest toolchain while adding more feature to Forge & vanilla, so we don't need to care about higher versions' X point release * Y Mod API headache.
Q: How to install Cleanroom?
A: Please follow the instructions in README.
Q: Can I include this in my Forge modpack? Will it crash my Forge pack?
A: Yes, you can, and it is safe! This mod won't be loaded or crash anything in a Forge environment.
Q: Why make another project?
A: Putting Scala 3 provider and Scala 2 provider in same project keep producing confusion and unnecessary crash reports. So Scala 2 provider now belong to a new project.
Q: Why not just include Scala in the loader?
A: Scala 2.11 is deprecated and can't be compiled against under Java 21+. Our goal is not only providing a runtime but also latest development toolchain, so switching to Scala 3 is important. Make Scala become standalone mods is the only solution here.

Note: mod files marked as "Forge" because CurseForge doesn't support Cleanroom yet.