Fix and enable specialized tuples

Author: nicolasstucki

library/src-scala3/scala/StagedTuple.scala

@@ -208,7 +208,7 @@ object StagedTuple {
           that
         case Some(1) =>
           if (thatSize.contains(0)) self
-          else stagedCons(that, self.as[Tuple1[_]], thatSize)
+          else stagedCons(that, '((~self).asInstanceOf[Tuple1[_]]._1), thatSize)
         case Some(2) =>
           val self2 = self.as[Tuple2[_, _]]
           thatSize match {

library/src-scala3/scala/Tuple.scala

@@ -26,7 +26,7 @@ object Tuple {
   inline val $MaxSpecialized = 22
   inline private val XXL = $MaxSpecialized + 1
 
-  final val specialize = false
+  final val specialize = true
 
   type Head[+X <: NonEmptyTuple] = X match {
     case x *: _ => x