src/Pure/PIDE/document.scala

   class Snapshot private[Document](
     val state: State,
     val version: Version,
     val node_name: Node.Name,
     edits: List[Text.Edit],
-    snippet_command: Option[Command])
+    val snippet_command: Option[Command])
   {
     override def toString: String =
       "Snapshot(node = " + node_name.node + ", version = " + version.id +
         (if (is_outdated) ", outdated" else "") + ")"