src/Pure/Tools/simplifier_trace.scala

--- a/src/Pure/Tools/simplifier_trace.scala	Fri Apr 01 17:06:10 2022 +0200
+++ b/src/Pure/Tools/simplifier_trace.scala	Fri Apr 01 23:19:12 2022 +0200
@@ -162,7 +162,7 @@
     }
 
     Consumer_Thread.fork[Any]("Simplifier_Trace.manager", daemon = true)(
-      consume = (arg: Any) => {
+      consume = { (arg: Any) =>
         arg match {
           case Handle_Results(session, id, results, slot) =>
             var new_context = contexts.getOrElse(id, Context())