Remove the -Xno-value-classes setting.

This setting is not tested, and forks the binary ecosystem.

Author: sjrd

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

@@ -118,7 +118,6 @@ class ScalaSettings extends Settings.SettingGroup with CommonScalaSettings {
   val XprintSuspension: Setting[Boolean] = BooleanSetting("-Xprint-suspension", "Show when code is suspended until macros are compiled.")
   val Xprompt: Setting[Boolean] = BooleanSetting("-Xprompt", "Display a prompt after each error (debugging option).")
   val XshowPhases: Setting[Boolean] = BooleanSetting("-Xshow-phases", "Print all compiler phases.")
-  val XnoValueClasses: Setting[Boolean] = BooleanSetting("-Xno-value-classes", "Do not use value classes. Helps debugging.")
   val XreplLineWidth: Setting[Int] = IntSetting("-Xrepl-line-width", "Maximal number of columns per line for REPL output.", 390)
   val XreplDisableDisplay: Setting[Boolean] = BooleanSetting("-Xrepl-disable-display", "Do not display definitions in REPL.")
   val XfatalWarnings: Setting[Boolean] = BooleanSetting("-Xfatal-warnings", "Fail the compilation if there are any warnings.")

compiler/src/dotty/tools/dotc/transform/ValueClasses.scala

@@ -15,7 +15,6 @@ object ValueClasses {
 
   def isDerivedValueClass(sym: Symbol)(using Context): Boolean = {
     val d = sym.denot
-    !ctx.settings.XnoValueClasses.value &&
     !d.isRefinementClass &&
     d.isValueClass &&
     (d.initial.symbol ne defn.AnyValClass) && // Compare the initial symbol because AnyVal does not exist after erasure