Peformance test for WIP

Use these changes to compile the stdlib. You need to comment out AnyVal.scala and then
use the following command on community-projects/stdLib213:

    sc -Ydetailed-stats *.scala */*.scala */*/*.scala */*/*/*.scala

What I see is:

Calls to `translucentSuperType` 53152:

    try norm KO -> 53086
    try norm OK -> 66

The only computationally relevant part of this are calls to tryMatchAlias

    try match alias -> 528

Those calls suceed in 66 cases

    try norm OK -> 66

The successful normalizations all return types like this:

    try norm OK F[T1] *: scala.Tuple.Map[(T2, T3, T4, T5, T6, T7, T8), F] -> 3

Now it could be that trying the normalizations is costly, or that the normalized types
cause exhaustivity checking to explode. Tht remains to be found out.

Author: odersky

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

@@ -4019,7 +4019,14 @@ object Types {
       case tycon: TypeRef if tycon.symbol.isOpaqueAlias =>
         tycon.translucentSuperType.applyIfParameterized(args)
       case _ =>
-        tryNormalize.orElse(superType)
+        val x = tryNormalize
+        if x.exists then
+          record("try norm OK")
+          record(i"try norm OK $x")
+          x
+        else
+          record("try norm KO")
+          superType
     }
 
     inline def map(inline op: Type => Type)(using Context) =
@@ -4038,6 +4045,9 @@ object Types {
       case tycon: TypeRef =>
         def tryMatchAlias = tycon.info match {
           case MatchAlias(alias) =>
+            record(i"try match alias")
+            record(i"try match alias $this in ${ctx.owner.ownersIterator.toList}%, %")
+            //new Error().printStackTrace()
             trace(i"normalize $this", typr, show = true) {
               MatchTypeTrace.recurseWith(this) {
                 alias.applyIfParameterized(args).tryNormalize

compiler/src/dotty/tools/dotc/util/Stats.scala

@@ -9,7 +9,7 @@ import collection.mutable
 
 @sharable object Stats {
 
-  final val enabled = false
+  final val enabled = true
 
   var monitored: Boolean = false