Remove the now unused setting -priorityclasspath.

It was previously only used in tests, and does not exist in
Scala 2.

compiler/src/dotty/tools/dotc/config/PathResolver.scala

@@ -177,7 +177,6 @@ class PathResolver(using c: Context) {
     case "extdirs"            => settings.extdirs.value
     case "classpath" | "cp"   => settings.classpath.value
     case "sourcepath"         => settings.sourcepath.value
-    case "priorityclasspath"  => settings.priorityclasspath.value
   }
 
   /** Calculated values based on any given command line options, falling back on
@@ -191,7 +190,6 @@ class PathResolver(using c: Context) {
     def javaUserClassPath: String   = if (useJavaClassPath) Defaults.javaUserClassPath else ""
     def scalaBootClassPath: String  = cmdLineOrElse("bootclasspath", Defaults.scalaBootClassPath)
     def scalaExtDirs: String        = cmdLineOrElse("extdirs", Defaults.scalaExtDirs)
-    def priorityClassPath: String   = cmdLineOrElse("priorityclasspath", "")
     /** Scaladoc doesn't need any bootstrapping, otherwise will create errors such as:
      * [scaladoc] ../scala-trunk/src/reflect/scala/reflect/macros/Reifiers.scala:89: error: object api is not a member of package reflect
      * [scaladoc] case class ReificationException(val pos: reflect.api.PositionApi, val msg: String) extends Throwable(msg)
@@ -208,9 +206,7 @@ class PathResolver(using c: Context) {
     import classPathFactory._
 
     // Assemble the elements!
-    // priority class path takes precedence
     def basis: List[Traversable[ClassPath]] = List(
-      classesInExpandedPath(priorityClassPath),     // 0. The priority class path (for testing).
       JrtClassPath.apply(),                         // 1. The Java 9 classpath (backed by the jrt:/ virtual system, if available)
       classesInPath(javaBootClassPath),             // 2. The Java bootstrap class path.
       contentsOfDirsInPath(javaExtDirs),            // 3. The Java extension class path.
@@ -226,7 +222,6 @@ class PathResolver(using c: Context) {
     override def toString: String = """
       |object Calculated {
       |  scalaHome            = %s
-      |  priorityClassPath    = %s
       |  javaBootClassPath    = %s
       |  javaExtDirs          = %s
       |  javaUserClassPath    = %s
@@ -236,7 +231,7 @@ class PathResolver(using c: Context) {
       |  userClassPath        = %s
       |  sourcePath           = %s
       |}""".trim.stripMargin.format(
-        scalaHome, ppcp(priorityClassPath),
+        scalaHome,
         ppcp(javaBootClassPath), ppcp(javaExtDirs), ppcp(javaUserClassPath),
         useJavaClassPath,
         ppcp(scalaBootClassPath), ppcp(scalaExtDirs), ppcp(userClassPath),
@@ -263,4 +258,3 @@ class PathResolver(using c: Context) {
 
   def asURLs: Seq[java.net.URL] = result.asURLs
 }
-

compiler/src/dotty/tools/dotc/config/ScalaSettings.scala

@@ -22,7 +22,6 @@ trait CommonScalaSettings { self: Settings.SettingGroup =>
   val classpath: Setting[String] = PathSetting("-classpath", "Specify where to find user class files.", defaultClasspath) withAbbreviation "-cp" withAbbreviation "--class-path"
   val outputDir: Setting[AbstractFile] = OutputSetting("-d", "directory|jar", "Destination for generated classfiles.",
     new PlainDirectory(Directory(".")))
-  val priorityclasspath: Setting[String] = PathSetting("-priorityclasspath", "Class path that takes precedence over all other paths (for testing only).", "") withAbbreviation "--priority-class-path"
   val color: Setting[String] = ChoiceSetting("-color", "mode", "Colored output", List("always", "never"/*, "auto"*/), "always"/* "auto"*/) withAbbreviation "--color"
   val verbose: Setting[Boolean] = BooleanSetting("-verbose", "Output messages about what the compiler is doing.") withAbbreviation "--verbose"
   val version: Setting[Boolean] = BooleanSetting("-version", "Print product version and exit.") withAbbreviation "--version"