build with and test against Scala 3.6

Keep building for Scala 3.5 until the next minor version for backward
compatibility.

project/Dependencies.scala

@@ -7,8 +7,12 @@ import sbt._
 object Dependencies {
   val scala212 = sys.props.getOrElse("scala212.nightly", "2.12.20")
   val scala213 = sys.props.getOrElse("scala213.nightly", "2.13.15")
-  val scala3Next = sys.props.getOrElse("scala3.nightly", "3.5.1")
-  val scala3LTS = "3.3.4"
+  val scala36 = sys.props.getOrElse("scala3.nightly", "3.6.0")
+  val scala35 = "3.5.1"
+  val scala33 = "3.3.4"
+
+  val scala3Next = scala36
+  val scala3LTS = scala33
 
   val bijectionCoreV = "0.9.7"
   val collectionCompatV = "2.12.0"

project/ScalafixBuild.scala

@@ -33,7 +33,8 @@ object ScalafixBuild extends AutoPlugin with GhpagesKeys {
 
     // https://github.com/scalameta/scalameta/issues/2485
     lazy val coreScalaVersions = Seq(scala212, scala213)
-    lazy val cliScalaVersions = Seq(scala212, scala213, scala3LTS, scala3Next)
+    lazy val cliScalaVersions =
+      Seq(scala212, scala213, scala33, scala35, scala36)
     lazy val cliScalaVersionsWithTargets: Seq[(String, TargetAxis)] =
       cliScalaVersions.map(sv => (sv, TargetAxis(sv))) ++
         Seq(scala213, scala212).flatMap { sv =>
@@ -279,6 +280,7 @@ object ScalafixBuild extends AutoPlugin with GhpagesKeys {
     Compile / console / scalacOptions :=
       compilerOptions.value :+ "-Yrepl-class-based",
     Compile / doc / scalacOptions ++= scaladocOptions,
+    // TODO: tweak unmanagedSourceDirectories to support scala-3.3 directory
     // Don't package sources & docs when publishing locally as it adds a significant
     // overhead when testing because of publishLocalTransitive. Tweaking publishArtifact
     // would more readable, but it would also affect remote (sonatype) publishing.

scalafix-interfaces/src/main/java/scalafix/interfaces/Scalafix.java

@@ -135,6 +135,7 @@ static Scalafix fetchAndClassloadInstance(String requestedScalaVersion, List<Rep
             requestedScalaMajorMinorOrMajorVersion.equals("3.1") ||
             requestedScalaMajorMinorOrMajorVersion.equals("3.2") ||
             requestedScalaMajorMinorOrMajorVersion.equals("3.3")) {
+            // TODO: support Scala 3.5
             scalaVersionKey = "scala3LTS";
         } else if (requestedScalaMajorMinorOrMajorVersion.startsWith("3")) {
             scalaVersionKey = "scala3Next";