src/Pure/PIDE/document.scala

--- a/src/Pure/PIDE/document.scala	Mon Feb 24 10:48:34 2014 +0100
+++ b/src/Pure/PIDE/document.scala	Mon Feb 24 11:05:02 2014 +0100
@@ -634,6 +634,10 @@
           (thy_load_commands zip other.thy_load_commands).forall(eq_commands)
         }
 
+        override def toString: String =
+          "Snapshot(node = " + node_name.node + ", version = " + version.id +
+            (if (is_outdated) ", outdated" else "") + ")"
+
 
         /* cumulate markup */