Add support for Scala 3

[Flowdalic]

It appears mill-scalafix 0.2.2 does not yet support Scala 3. At least, as soon as I change the scalaVersion to 3, I get

Resolution failed for 1 modules:
--------------------------------------------
  org.scalameta:semanticdb-scalac_3.0.0:4.4.10

when running mill on my project. Commenting out mill-scalafix makes the issue disappear.

[joan38]

Thanks for the ticket but for now not even scalafix supports Scala 3 scalacenter/scalafix#1316 and I don't think semanticdb supports Scala 3 yet.

Scala Steward will automatically update these once they are published.

[olafurpg]

The semanticdb-scalac compiler plugin does not exist for Scala 3 because the Scala 3 compiler has built-in SemanticDB support. You can remove the dependency on semanticdb-scalac and add -Xsemanticdb compiler option instead. The latest release of Scalafix supports Scala 3 https://contributors.scala-lang.org/t/scalafix-0-9-28-with-support-for-scala-3/5091 However, note that Scalafix rules that depend on compiler diagnostics (for example, RemoveUnused) don't work with Scala 3 because the compiler doesn't report warnings about unused code.

[joan38]

Ah I see, thanks @olafurpg for the info.
I just created this PR: #47

[joan38]

Released in 0.2.3