src/Tools/jEdit/src/debugger_dockable.scala

 
   /* pretty text area */
 
   val pretty_text_area = new Pretty_Text_Area(view)
 
-  override def detach_operation = pretty_text_area.detach_operation
+  override def detach_operation: Option[() => Unit] = pretty_text_area.detach_operation
 
   private def handle_resize()
   {
     GUI_Thread.require {}
 

     reactions += { case ButtonClicked(_) => debugger.set_break(selected) }
   }
 
   private val continue_button = new Button("Continue") {
     tooltip = "Continue program on current thread, until next breakpoint"
-    reactions += { case ButtonClicked(_) => thread_selection().map(debugger.continue(_)) }
+    reactions += { case ButtonClicked(_) => thread_selection().map(debugger.continue) }
   }
 
   private val step_button = new Button("Step") {
     tooltip = "Single-step in depth-first order"
-    reactions += { case ButtonClicked(_) => thread_selection().map(debugger.step(_)) }
+    reactions += { case ButtonClicked(_) => thread_selection().map(debugger.step) }
   }
 
   private val step_over_button = new Button("Step over") {
     tooltip = "Single-step within this function"
-    reactions += { case ButtonClicked(_) => thread_selection().map(debugger.step_over(_)) }
+    reactions += { case ButtonClicked(_) => thread_selection().map(debugger.step_over) }
   }
 
   private val step_out_button = new Button("Step out") {
     tooltip = "Single-step outside this function"
-    reactions += { case ButtonClicked(_) => thread_selection().map(debugger.step_out(_)) }
+    reactions += { case ButtonClicked(_) => thread_selection().map(debugger.step_out) }
   }
 
   private val context_label = new Label("Context:") {
     tooltip = "Isabelle/ML context: type theory, Proof.context, Context.generic"
   }

   }
 
 
   /* main panel */
 
-  val main_panel = new SplitPane(Orientation.Vertical) {
+  val main_panel: SplitPane = new SplitPane(Orientation.Vertical) {
     oneTouchExpandable = true
     leftComponent = tree_pane
     rightComponent = Component.wrap(pretty_text_area)
   }
   set_content(main_panel)