diff -r 3ef6b0b6232e -r 677615cba30d src/Pure/General/path.scala
--- a/src/Pure/General/path.scala	Wed Jan 07 18:09:11 2015 +0100
+++ b/src/Pure/General/path.scala	Thu Jan 08 20:56:39 2015 +0100
@@ -118,7 +118,7 @@
 final class Path private(private val elems: List[Path.Elem]) // reversed elements
 {
   def is_current: Boolean = elems.isEmpty
-  def is_absolute: Boolean = !elems.isEmpty && elems.last.isInstanceOf[Path.Root]
+  def is_absolute: Boolean = elems.nonEmpty && elems.last.isInstanceOf[Path.Root]
   def is_basic: Boolean = elems match { case List(Path.Basic(_)) => true case _ => false }
 
   def +(other: Path): Path = new Path((other.elems :\ elems)(Path.apply_elem))