src/Pure/Concurrent/event_timer.scala

--- a/src/Pure/Concurrent/event_timer.scala	Thu Mar 04 19:55:52 2021 +0100
+++ b/src/Pure/Concurrent/event_timer.scala	Thu Mar 04 21:04:27 2021 +0100
@@ -19,7 +19,7 @@
 
   final class Request private[Event_Timer](val time: Time, val repeat: Option[Time], task: TimerTask)
   {
-    def cancel: Boolean = task.cancel
+    def cancel(): Boolean = task.cancel()
   }
 
   def request(time: Time, repeat: Option[Time] = None)(event: => Unit): Request =