Remove temporary flag

Author: OlivierBlanvillain

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

@@ -215,7 +215,6 @@ class ScalaSettings extends Settings.SettingGroup with CommonScalaSettings {
   val YerasedTerms: Setting[Boolean] = BooleanSetting("-Yerased-terms", "Allows the use of erased terms.")
   val YcheckInit: Setting[Boolean] = BooleanSetting("-Ycheck-init", "Check initialization of objects")
   val YrequireTargetName: Setting[Boolean] = BooleanSetting("-Yrequire-targetName", "Warn if an operator is defined without a @targetName annotation")
-  val YunsoundMatchTypes: Setting[Boolean] = BooleanSetting("-Yunsound-match-types", "Use unsound match type reduction algorithm.")
 
   /** Area-specific debug output */
   val YexplainLowlevel: Setting[Boolean] = BooleanSetting("-Yexplain-lowlevel", "When explaining type errors, show types at a lower level.")

compiler/src/dotty/tools/dotc/core/TypeComparer.scala

@@ -2523,20 +2523,16 @@ class TypeComparer(@constructorOnly initctx: Context) extends ConstraintHandling
       case (tp1: TermRef, tp2: TermRef) if isEnumValueOrModule(tp1) && isEnumValueOrModule(tp2) =>
         tp1.termSymbol != tp2.termSymbol
       case (tp1: TypeProxy, tp2: TypeProxy) =>
-        provablyDisjoint(matchTypeSuperType(tp1), tp2) || provablyDisjoint(tp1, matchTypeSuperType(tp2))
+        provablyDisjoint(tp1.superType, tp2) || provablyDisjoint(tp1, tp2.superType)
       case (tp1: TypeProxy, _) =>
-        provablyDisjoint(matchTypeSuperType(tp1), tp2)
+        provablyDisjoint(tp1.superType, tp2)
       case (_, tp2: TypeProxy) =>
-        provablyDisjoint(tp1, matchTypeSuperType(tp2))
+        provablyDisjoint(tp1, tp2.superType)
       case _ =>
         false
     }
   }
 
-  /** Restores the buggy match type reduction under -Yunsound-match-types. */
-  private def matchTypeSuperType(tp: TypeProxy): Type =
-    if ctx.settings.YunsoundMatchTypes.value then tp.underlying else tp.superType
-
   protected def explainingTypeComparer = ExplainingTypeComparer(comparerContext)
   protected def trackingTypeComparer = TrackingTypeComparer(comparerContext)