src/Pure/Concurrent/consumer_thread.scala

--- a/src/Pure/Concurrent/consumer_thread.scala	Tue Sep 07 15:05:57 2021 +0200
+++ b/src/Pure/Concurrent/consumer_thread.scala	Tue Sep 07 15:10:53 2021 +0200
@@ -48,7 +48,7 @@
   private val mailbox = Mailbox[Option[Request]]
 
   private val thread = Isabelle_Thread.fork(name = name, daemon = daemon) { main_loop(Nil) }
-  def is_active: Boolean = active && thread.isAlive
+  def is_active(): Boolean = active && thread.isAlive
   def check_thread: Boolean = Thread.currentThread == thread
 
   private def failure(exn: Throwable): Unit =
@@ -77,7 +77,7 @@
   private def request(req: Request): Unit =
   {
     synchronized {
-      if (is_active) mailbox.send(Some(req))
+      if (is_active()) mailbox.send(Some(req))
       else error("Consumer thread not active: " + quote(thread.getName))
     }
     req.await()
@@ -111,14 +111,14 @@
 
   /* main methods */
 
-  assert(is_active)
+  assert(is_active())
 
   def send(arg: A): Unit = request(new Request(arg))
   def send_wait(arg: A): Unit = request(new Request(arg, acknowledge = true))
 
   def shutdown(): Unit =
   {
-    synchronized { if (is_active) { active = false; mailbox.send(None) } }
+    synchronized { if (is_active()) { active = false; mailbox.send(None) } }
     thread.join()
   }
 }