upgrade to Scala 3.3.0 and enable unused warnings (#516)

Author: SethTisue

build.sbt

@@ -3,8 +3,10 @@ ThisBuild / startYear := Some(2004)
 
 val commonSettings = Seq(
   versionScheme := Some("early-semver"),
-  versionPolicyIntention := Compatibility.BinaryAndSourceCompatible,
-  crossScalaVersions := Seq("2.13.10", "2.12.17", "3.2.2"),
+  // change back to BinaryAndSourceCompatible after next minor release;
+  // the Scala 3.2 -> 3.3 upgrade requires a minor version bump
+  versionPolicyIntention := Compatibility.BinaryCompatible,
+  crossScalaVersions := Seq("2.13.10", "2.12.17", "3.3.0"),
   scalaVersion := crossScalaVersions.value.head,
 )
 
@@ -39,6 +41,7 @@ lazy val parserCombinators = crossProject(JVMPlatform, JSPlatform, NativePlatfor
         // not sure what resolving this would look like? didn't think about it too hard
         "-Wconf:site=scala.util.parsing.combinator.lexical.StdLexical.*&cat=other-match-analysis:i",
       )
+      case Some((3, _)) => Seq("Wunused:all")
       case _ => Seq()
     }),
     Compile / doc / scalacOptions ++= (CrossVersion.partialVersion(scalaVersion.value) match {

shared/src/test/scala/scala/util/parsing/combinator/LongestMatchTest.scala

@@ -2,7 +2,6 @@ package scala.util.parsing.combinator
 
 import java.io.StringReader
 
-import scala.util.parsing.combinator.Parsers
 import scala.util.parsing.input.StreamReader
 
 import org.junit.Test