src/Pure/Tools/print_operation.scala

--- a/src/Pure/Tools/print_operation.scala	Sat Apr 09 15:40:29 2022 +0200
+++ b/src/Pure/Tools/print_operation.scala	Thu Apr 21 10:03:38 2022 +0200
@@ -34,6 +34,7 @@
       true
     }
 
-    override val functions = List(Markup.PRINT_OPERATIONS -> put)
+    override val functions: Session.Protocol_Functions =
+      List(Markup.PRINT_OPERATIONS -> put)
   }
 }