Make named repeated parameters discoverable during PatMat.

They used to be discoverable using repeatedType, but ElimRepeated eliminates it.
Instead I'm using internal synthetic Typed nodes name, similar to how it's done for non-star Wildcards.
This makes handling Wildcards and Wildacard_Star more symmetric in patmat.

Author: DarkDimius

src/dotty/tools/dotc/ast/TreeInfo.scala

@@ -189,7 +189,8 @@ trait TreeInfo[T >: Untyped <: Type] { self: Trees.Instance[T] =>
 
   /** Is this argument node of the form <expr> : _* ?
    */
-  def isWildcardStarArg(tree: untpd.Tree)(implicit ctx: Context): Boolean = unsplice(tree) match {
+  def isWildcardStarArg(tree: Tree)(implicit ctx: Context): Boolean = unbind(tree) match {
+    case Typed(Ident(nme.WILDCARD_STAR), _) => true
     case Typed(_, Ident(tpnme.WILDCARD_STAR)) => true
     case Typed(_, tpt: TypeTree) => tpt.hasType && tpt.tpe.isRepeatedParam
     case _ => false

src/dotty/tools/dotc/typer/Typer.scala

@@ -377,10 +377,11 @@ class Typer extends Namer with TypeAssigner with Applications with Implicits wit
     }
     tree.expr match {
       case id: untpd.Ident if (ctx.mode is Mode.Pattern) && isVarPattern(id) =>
-        if (id.name == nme.WILDCARD) regularTyped(isWildcard = true)
+        if (id.name == nme.WILDCARD || id.name == nme.WILDCARD_STAR) regularTyped(isWildcard = true)
         else {
           import untpd._
-          typed(Bind(id.name, Typed(Ident(nme.WILDCARD), tree.tpt)).withPos(id.pos), pt)
+          val name = if (untpd.isWildcardStarArg(tree)) nme.WILDCARD_STAR else nme.WILDCARD
+          typed(Bind(id.name, Typed(Ident(name), tree.tpt)).withPos(id.pos), pt)
         }
       case _ =>
         if (untpd.isWildcardStarArg(tree))