src/Pure/PIDE/session.scala

   val commands_changed = new Session.Outlet[Session.Commands_Changed](dispatcher)
   val phase_changed = new Session.Outlet[Session.Phase](dispatcher)
   val syslog_messages = new Session.Outlet[Prover.Output](dispatcher)
   val raw_output_messages = new Session.Outlet[Prover.Output](dispatcher)
   val trace_events = new Session.Outlet[Simplifier_Trace.Event.type](dispatcher)
-  val debugger_updates = new Session.Outlet[Debugger.Update](dispatcher)
+  val debugger_updates = new Session.Outlet[Debugger.Update.type](dispatcher)
 
   val all_messages = new Session.Outlet[Prover.Message](dispatcher)  // potential bottle-neck!
 
 
   /** main protocol manager **/