Use underlyingMatchType for tryNormalize

Author: EugeneFlesselle

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

@@ -1527,16 +1527,15 @@ object Types extends TypeUtils {
     /** The result of normalization using `tryNormalize`, or the type itself if
      *  tryNormlize yields NoType
      */
-    final def normalized(using Context): Type = {
-      val normed = tryNormalize
-      if (normed.exists) normed else this
-    }
+    final def normalized(using Context): Type = tryNormalize.orElse(this)
 
     /** If this type can be normalized at the top-level by rewriting match types
      *  of S[n] types, the result after applying all toplevel normalizations,
      *  otherwise NoType
      */
-    def tryNormalize(using Context): Type = NoType
+    def tryNormalize(using Context): Type =
+      if isMatchAlias then underlyingMatchType.tryNormalize
+      else NoType
 
     private def widenDealias1(keep: AnnotatedType => Context ?=> Boolean)(using Context): Type = {
       val res = this.widen.dealias1(keep, keepOpaques = false)

compiler/test/dotc/pos-test-pickling.blacklist

@@ -66,6 +66,7 @@ tuple-fold.scala
 mt-redux-norm.perspective.scala
 i18211.scala
 10867.scala
+matchtype.scala
 
 # Opaque type
 i5720.scala

compiler/test/dotc/run-test-pickling.blacklist

@@ -46,3 +46,6 @@ i12656.scala
 trait-static-forwarder
 i17255
 
+# Match types
+i13332a.scala
+anon-mirror-gen-local.scala