support RemoveUnused on Scala 3

build.sbt

@@ -180,8 +180,7 @@ lazy val input = projectMatrix
     noPublishAndNoMima,
     scalacOptions ~= (_.filterNot(_ == "-Yno-adapted-args")),
     scalacOptions ++= warnAdaptedArgs.value, // For NoAutoTupling
-    scalacOptions ++= warnUnusedImports.value, // For RemoveUnused
-    scalacOptions ++= warnUnused.value, // For RemoveUnusedTerms
+    scalacOptions += "Wunused", // For RemoveUnusedTerms
     logLevel := Level.Error, // avoid flood of compiler warnings
     libraryDependencies ++= testsDependencies.value,
     coverageEnabled := false

docs/rules/RemoveUnused.md

@@ -14,15 +14,12 @@ example diff from running `sbt "scalafix RemoveUnused"`.
 
 To use this rule:
 
-- Enable the Scala compiler option `-Ywarn-unused` (or `-Wunused` in 2.13). In
-  sbt, this is done with `scalacOptions += "-Ywarn-unused"`.
+- Enable the Scala compiler option `-Wunused`. In sbt, this is done with
+  `scalacOptions += "-Wunused"`.
 - Disable `-Xfatal-warnings` if you have it enabled. This is required so the
   compiler warnings do not fail the build before running Scalafix. If you are
   running 2.13.2 or later, you may keep `-Xfatal-warnings` by modifying how
   specific warnings are handled via `scalacOptions += "-Wconf:cat=unused:info"`.
-- This rule **can't work** yet on Scala 3 projects since the compiler option `warn-unused`
-  is not yet available in Scala 3. You need to remove `RemoveUnused` 
-  from `.scalafix.conf` for Scala 3 projects.
 
 ## Examples
 
@@ -146,4 +143,4 @@ Enable or disable specific `unused' warnings
   params     Enable -Ywarn-unused:explicits,implicits.
   linted     -Xlint:unused.
 Default: All choices are enabled by default.
-```
+```

project/ScalafixBuild.scala

@@ -47,14 +47,9 @@ object ScalafixBuild extends AutoPlugin with GhpagesKeys {
       scalaVersion.value.startsWith("2.12")
     }
     lazy val warnUnusedImports = Def.setting {
-      if (isScala3.value) Nil
-      else if (isScala213.value) Seq("-Wunused:imports")
+      if (isScala213.value || isScala3.value) Seq("-Wunused:imports")
       else Seq("-Ywarn-unused-import")
     }
-    lazy val warnUnused = Def.setting {
-      if (isScala2.value) Seq("-Ywarn-unused")
-      else Nil
-    }
     lazy val targetJvm = Def.setting {
       if (isScala3.value) Seq("-Xtarget:8")
       else if (isScala213.value) Seq("-release", "8")

scalafix-rules/src/main/scala/scalafix/internal/rule/RemoveUnused.scala

@@ -26,7 +26,7 @@ class RemoveUnused(config: RemoveUnusedConfig)
   def this() = this(RemoveUnusedConfig.default)
 
   override def description: String =
-    "Removes unused imports and terms that reported by the compiler under -Ywarn-unused"
+    "Removes unused imports and terms that reported by the compiler under -Yunused"
   override def isRewrite: Boolean = true
 
   private def warnUnusedPrefix = List("-Wunused", "-Ywarn-unused")
@@ -36,17 +36,19 @@ class RemoveUnused(config: RemoveUnusedConfig)
       warnUnusedPrefix.exists(prefix => option.startsWith(prefix)) ||
         warnUnusedString.contains(option)
     )
-    if (config.scalaVersion.startsWith("3"))
-      Configured.error(
-        "This rule is specific to Scala 2, because the compiler option `-Ywarn-unused` is not available yet in scala 3 " +
-          "To fix this error, remove RemoveUnused from .scalafix.conf"
-      )
-    else if (!hasWarnUnused) {
-      Configured.error(
-        s"""|The Scala compiler option "-Ywarn-unused" is required to use RemoveUnused.
-          |To fix this problem, update your build to use at least one Scala compiler
-          |option like -Ywarn-unused, -Xlint:unused (2.12.2 or above), or -Wunused (2.13 only)""".stripMargin
-      )
+    if (!hasWarnUnused) {
+      if (config.scalaVersion.startsWith("3"))
+        Configured.error(
+          """|The Scala compiler option "-Ywarn-unused" (available from Scala 3.3.0) is
+            |required to use RemoveUnused. To fix this problem, update your build to add
+            |it.""".stripMargin
+        )
+      else
+        Configured.error(
+          """|A Scala compiler option is required to use RemoveUnused. To fix this problem,
+            |update your build to add either -Ywarn-unused, -Xlint:unused (2.12.2 or above),
+            |or -Wunused (2.13).""".stripMargin
+        )
     } else {
       config.conf
         .getOrElse("RemoveUnused")(this.config)

scalafix-tests/input/src/main/scala-2/test/removeUnused/RemoveUnusedTerms.scala → scalafix-tests/input/src/main/scala/test/removeUnused/RemoveUnusedTerms.scala

@@ -5,7 +5,7 @@ package test.removeUnused
 
 object RemoveUnusedTerms {
 
-  def foo {
+  def foo = {
     val a = "unused"
     val aa = println(5)
     var b = 0

scalafix-tests/integration/src/test/scala-2/scalafix/tests/cli/BaseCliSuite.scala

@@ -43,7 +43,7 @@ trait BaseCliSuite extends AnyFunSuite with DiffAssertions {
   val ps = new PrintStream(new ByteArrayOutputStream())
 
   val removeImportsPath: RelativePath =
-    RelativePath("scala-2/test/removeUnused/RemoveUnusedImports.scala")
+    RelativePath("scala/test/removeUnused/RemoveUnusedImports.scala")
   val explicitResultTypesPath: RelativePath =
     RelativePath(
       "scala-2/test/explicitResultTypes/ExplicitResultTypesBase.scala"

scalafix-tests/integration/src/test/scala-2/scalafix/tests/cli/CliSemanticSuite.scala

@@ -245,15 +245,4 @@ class CliSemanticSuite extends BaseCliSuite {
     assert(exit.is(ExitStatus.MissingSemanticdbError))
   }
 
-  checkSemantic(
-    name = "ScalaVersion Scala3",
-    args = Array(
-      "--classpath",
-      defaultClasspath,
-      "--scalaVersion",
-      "3.0.0-RC3"
-    ),
-    expectedExit = ExitStatus.CommandLineError
-  )
-
 }

scalafix-tests/output/src/main/scala-2/test/removeUnused/RemoveUnusedTerms.scala → scalafix-tests/output/src/main/scala/test/removeUnused/RemoveUnusedTerms.scala

@@ -2,7 +2,7 @@ package test.removeUnused
 
 object RemoveUnusedTerms {
 
-  def foo {
+  def foo = {
 
     println(5)