Cache AppliedType#tryNormalize

Author: mbovel

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

@@ -4177,22 +4177,20 @@ 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
+    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
+                }
               }
-            }
-          case _ =>
-            NoType
-        }
-        tryCompiletimeConstantFold.orElse(tryMatchAlias)
-      case _ =>
-        NoType
-    }
+            case _ => NoType
+          tryCompiletimeConstantFold.orElse(tryMatchAlias)
+        case _ =>
+          NoType
 
     /** Does this application expand to a match type? */
     def isMatchAlias(using Context): Boolean = tycon.stripTypeVar match
@@ -4212,7 +4210,16 @@ object Types {
     def isUnreducibleWild(using Context): Boolean =
       tycon.isLambdaSub && hasWildcardArg && !isMatchAlias
 
-    def tryCompiletimeConstantFold(using Context): Type = tycon match {
+    var myTryCompiletimeConstantFold: Type | Null = null
+    var myTryCompiletimeConstantFoldPeriod: Period = Nowhere
+
+    def tryCompiletimeConstantFold(using Context): Type =
+      if myTryCompiletimeConstantFoldPeriod != ctx.period then
+        myTryCompiletimeConstantFoldPeriod = ctx.period
+        myTryCompiletimeConstantFold = tryCompiletimeConstantFoldImpl
+      myTryCompiletimeConstantFold.nn
+
+    private def tryCompiletimeConstantFoldImpl(using Context): Type = tycon match {
       case tycon: TypeRef if defn.isCompiletimeAppliedType(tycon.symbol) =>
         extension (tp: Type) def fixForEvaluation: Type =
           tp.normalized.dealias match {