Cache AppliedType#tryNormalize

Author: mbovel

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

@@ -4177,22 +4177,25 @@ object Types {
         case nil => x
       foldArgs(op(x, tycon), args)
 
-    override def tryNormalize(using Context): Type = tycon.stripTypeVar match {
-      case tycon: TypeRef =>
-        def tryMatchAlias = tycon.info match {
-          case MatchAlias(alias) =>
-            trace(i"normalize $this", typr, show = true) {
-              MatchTypeTrace.recurseWith(this) {
-                alias.applyIfParameterized(args.map(_.normalized)).tryNormalize
-              }
-            }
+    var myTryNormalize: Type | Null = null
+    var myTryNoramlizePeriod: Period = Nowhere
+
+    override def tryNormalize(using Context): Type =
+      if myTryNoramlizePeriod != ctx.period then
+        myTryNormalize = tycon.stripTypeVar match
+          case tycon: TypeRef =>
+            def tryMatchAlias = tycon.info match
+              case MatchAlias(alias) =>
+                trace(i"normalize $this", typr, show = true) {
+                  MatchTypeTrace.recurseWith(this) {
+                    alias.applyIfParameterized(args.map(_.normalized)).tryNormalize
+                  }
+                }
+              case _ => NoType
+            tryCompiletimeConstantFold.orElse(tryMatchAlias)
           case _ =>
             NoType
-        }
-        tryCompiletimeConstantFold.orElse(tryMatchAlias)
-      case _ =>
-        NoType
-    }
+      myTryNormalize.nn
 
     /** Does this application expand to a match type? */
     def isMatchAlias(using Context): Boolean = tycon.stripTypeVar match