Incorporated feedback on a couple recent commits. No review.

git-svn-id: http://lampsvn.epfl.ch/svn-repos/scala/scala/trunk@24060 5e8d7ff9-d8ef-0310-90f0-a4852d11357a

src/compiler/scala/tools/nsc/transform/Erasure.scala

@@ -966,7 +966,7 @@ abstract class Erasure extends AddInterfaces with typechecker.Analyzer with ast.
           // This must be because some earlier transformation is being skipped on ##, but so
           // far I don't know what.  We also crash on null.## but unless we want to implement
           // my good idea that null.## works (like null == "abc" works) we have to NPE.
-          val arg = qual.tpe.typeSymbol match {
+          val arg = qual.tpe.typeSymbolDirect match {
             case UnitClass  => BLOCK(qual, REF(BoxedUnit_UNIT))       // ({ expr; UNIT }).##
             case NullClass  => Typed(qual, TypeTree(ObjectClass.tpe)) // (null: Object).##
             case _          => qual

src/library/scala/collection/SetLike.scala

@@ -212,12 +212,13 @@ self =>
   def subsetOf(that: Set[A]) = this forall that
   
   /** An iterator over all subsets of this set of the given size.
+   *  If the requested size is impossible, an empty iterator is returned.
    *
    *  @param len  the size of the subsets.
    *  @return     the iterator.
    */
   def subsets(len: Int): Iterator[This] = {
-    if (len < 0 || len > size) throw new IllegalArgumentException(len.toString)
+    if (len < 0 || len > size) Iterator.empty
     else new SubsetsItr(self.toIndexedSeq, len)
   }