dotty build

[giabao]

• Some akka modules, ex akka-testkit can not be used with dotty even if using .withDottyCompat(scalaVersion.value).
• dotty is now feature complete, less break changes.
• We can make many changes in akka now that is full akka-backward-compatible and dotty-compatible, ex: Remove procedure syntax, make implicit val/def type explicit, dont use auto application,...
• If things go well, we can even provide a experiment akka build for dotty.

[patriknw]

Sounds great if you can help making those changes. Note that Akka is required to be binary backwards compatible, and we currently support Scala 2.12 and 2.13 builds.

The binary compatibility is for public (user) APIs, so internals can be changed.

If there are things that can’t be done in source compatible ways 2.12, 2.13, 3 we might have the option to use separate source directories for some classes, but that should be minimized to avoid having to maintain copies.

[He-Pin]

@ohze Any update for this?

[SethTisue]

there is a WIP PR at #29929 (and @smarter has suggested there that the effort be merged with @ohze's)

[SethTisue]

as for using Akka with withDottyCompat, I don't think there is any centralized discussion of how much does or doesn't work, but apparently core functionality is there — @eloots did a proof-of-concept at https://github.com/eloots/akka-typed-on-scala-3 . it's on a now rather outdated Dotty version — someone might like to try to update it to Scala 3.0.0-M3?

[Sciss]

is there any path to Akka Stream on Scala 3?

[SethTisue]

there is some WIP at #30174

[raboof]

Futher work in this is ongoing and tracked under the t:scala-3 label - I think this issue can be closed since there are more specific issues for the remaining issues - feel free to open more if things are missing!