Refine lookupRefined for Wildcard prefixes

lookupRefined used to fall back to unbounded Wildcard, given a Wildcard prefix.
But that loses bounds when called from wildApprox, which in turn loses companion
objects in the implicit scope of a type.

In `i553-shuffle.scala` this happened because we projected with #Apply on a type that
approximated to a bounded wildcard.

The fix keeps the bounds, projecting in turn on them.

Author: odersky

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

@@ -869,7 +869,13 @@ object Types {
         case SkolemType(tp) =>
           tp.lookupRefined(name)
         case pre: WildcardType =>
-          WildcardType
+          pre.optBounds match {
+            case TypeBounds(lo, hi) if name.isTypeName =>
+              // for term names, forming a Termref with just the name risks losing overloaded instance
+              WildcardType(TypeBounds(NamedType(lo, name), NamedType(hi, name)))
+            case _ =>
+              WildcardType
+          }
         case pre: TypeRef =>
           pre.info match {
             case TypeAlias(alias) => loop(alias, resolved)

tests/pos/i553-shuffle.scala

@@ -1,8 +1,7 @@
 import scala.util.Random
-import scala.collection.immutable.List._
 object Test {
   def test = {
     val rand = new Random
-    rand.shuffle(List(1,2))//(List.canBuildFrom[Int]) // fails
+    rand.shuffle(List(1,2))// infers implicit argument list (List.canBuildFrom[Int]) 
   }
 }