feature: ExplicitResultTypes for Scala 3

build.sbt

@@ -119,7 +119,11 @@ lazy val rules = projectMatrix
           semanticdbScalacCore,
           collectionCompat
         )
-      else Nil
+      else
+        Seq(
+          "org.scala-lang" %% "scala3-presentation-compiler" % scalaVersion.value,
+          coursierInterfaces
+        )
     },
     // companion of `.dependsOn(core)`
     // issue reported in https://github.com/sbt/sbt/issues/7405

docs/rules/ExplicitResultTypes.md

@@ -4,8 +4,7 @@ id: ExplicitResultTypes
 title: ExplicitResultTypes
 ---
 
-This rewrite inserts type annotations for inferred public members. Only compatible with 
-scala 2.12 & 2.13.
+This rewrite inserts type annotations for inferred public members.
 
 Example:
 
@@ -35,6 +34,9 @@ This rule has several known limitations, which are most likely fixable with some
 effort. At the time of this writing, there are no short-term plans to address
 these issues however.
 
+Scala 3 support is recent and therefore not widely tested. Expect annotations
+to be be less precise than the ones added to sources compiled with Scala 2.x.
+
 ### Imports ordering
 
 The rewrite inserts imports at the bottom of the global import list. Users are
@@ -43,8 +45,8 @@ expected to organize the imports according to the conventions of their codebase.
 For example, the rewrite may produce the following diff.
 
 ```diff
-import java.io.File
-import scala.collection.mutable
+  import java.io.File
+  import scala.collection.mutable
 + import java.util.UUID
 ```
 

project/ScalafixBuild.scala

@@ -58,7 +58,10 @@ object ScalafixBuild extends AutoPlugin with GhpagesKeys {
           val xsource3 = TargetAxis(sv, xsource3 = true)
 
           (prevVersions :+ xsource3).map((sv, _))
-        } :+ (scala3Next, TargetAxis(scala213))
+        } ++ Seq(
+          (scala3Next, TargetAxis(scala213)),
+          (scala3Next, TargetAxis(scala3LTS))
+        )
 
     lazy val publishLocalTransitive =
       taskKey[Unit]("Run publishLocal on this project and its dependencies")
@@ -280,13 +283,6 @@ object ScalafixBuild extends AutoPlugin with GhpagesKeys {
     Compile / console / scalacOptions :=
       compilerOptions.value :+ "-Yrepl-class-based",
     Compile / doc / scalacOptions ++= scaladocOptions,
-    Compile / unmanagedResourceDirectories ++= {
-      val resourceParentDir = (Compile / resourceDirectory).value.getParentFile
-      CrossVersion.partialVersion(scalaVersion.value) match {
-        case Some((major, _)) => Seq(resourceParentDir / s"resources-${major}")
-        case _ => Seq()
-      }
-    },
     // 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.
@@ -316,13 +312,7 @@ object ScalafixBuild extends AutoPlugin with GhpagesKeys {
       if (scalaVersion.value.startsWith("3")) Set.empty
       else Set.empty
     },
-    mimaBinaryIssueFilters ++= Mima.ignoredABIProblems,
-    scalafixConfig := {
-      if (scalaBinaryVersion.value.startsWith("2"))
-        Some(file(".scalafix-scala2.conf"))
-      else
-        Some(file(".scalafix-scala3.conf"))
-    }
+    mimaBinaryIssueFilters ++= Mima.ignoredABIProblems
   )
 
   /**

scalafix-core/src/main/scala/scalafix/internal/util/DocConstants.scala

@@ -2,24 +2,24 @@ package scalafix.internal.util
 import org.typelevel.paiges.Doc
 
 object DocConstants {
-  val `|` = Doc.char('|')
-  val `&` = Doc.char('&')
-  val `.` = Doc.char('.')
-  val `#` = Doc.char('#')
-  val `(` = Doc.char('(')
-  val `)` = Doc.char(')')
-  val `[` = Doc.char('[')
-  val `]` = Doc.char(']')
-  val `{` = Doc.char('{')
-  val `}` = Doc.char('}')
-  val `=>` = Doc.text("=>")
-  val `=>>` = Doc.text("=>>")
-  val `()` = Doc.text("()")
-  val `*` = Doc.char('*')
+  val `|`: Doc = Doc.char('|')
+  val `&`: Doc = Doc.char('&')
+  val `.`: Doc = Doc.char('.')
+  val `#`: Doc = Doc.char('#')
+  val `(`: Doc = Doc.char('(')
+  val `)`: Doc = Doc.char(')')
+  val `[`: Doc = Doc.char('[')
+  val `]`: Doc = Doc.char(']')
+  val `{`: Doc = Doc.char('{')
+  val `}`: Doc = Doc.char('}')
+  val `=>`: Doc = Doc.text("=>")
+  val `=>>`: Doc = Doc.text("=>>")
+  val `()`: Doc = Doc.text("()")
+  val `*`: Doc = Doc.char('*')
   val L: Doc = Doc.char('L')
   val f: Doc = Doc.char('f')
-  val `:` = Doc.char(':')
-  val `@` = Doc.char('@')
+  val `:`: Doc = Doc.char(':')
+  val `@`: Doc = Doc.char('@')
   val `val`: Doc = Doc.text("val")
   val `var`: Doc = Doc.text("var")
   val `def`: Doc = Doc.text("def")

scalafix-core/src/main/scala/scalafix/v0/Symbol.scala

@@ -53,9 +53,9 @@ object Symbol {
   // https://github.com/scalameta/scalameta/pull/1241.
   def apply(s: String): Symbol = {
     object naiveParser {
-      val EOL = System.lineSeparator()
+      val EOL: String = System.lineSeparator()
       var i = 0
-      def fail(message: String = "invalid symbol format") = {
+      def fail(message: String = "invalid symbol format"): Nothing = {
         val caret = " " * (i - 1) + "^"
         throw new IllegalArgumentException(s"$message$EOL$s$EOL$caret")
       }