Type match with a match type when a match type is expected

Author: mbovel

compiler/src/dotty/tools/dotc/typer/Typer.scala

@@ -1553,7 +1553,7 @@ class Typer(@constructorOnly nestingLevel: Int = 0) extends Namer
           case otherTpe => otherTpe.widen
         /** Extractor for match types hidden behind an AppliedType/MatchAlias */
         object MatchTypeInDisguise {
-          def unapply(tp: AppliedType)(using Context): Option[MatchType] = tp match {
+          def unapply(tp: Type)(using Context): Option[MatchType] = tp match {
             case AppliedType(tycon: TypeRef, args) =>
               tycon.info match {
                 case MatchAlias(alias) =>
@@ -1563,6 +1563,7 @@ class Typer(@constructorOnly nestingLevel: Int = 0) extends Namer
                   }
                 case _ => None
               }
+            case mt: MatchType => Some(mt)
             case _ => None
           }
         }