unused;

--- a/src/Pure/PIDE/document.scala	Sun Feb 19 13:37:38 2023 +0100
+++ b/src/Pure/PIDE/document.scala	Sun Feb 19 13:43:38 2023 +0100
@@ -417,7 +417,6 @@
       } yield cmd).toList
 
     def descendants(names: List[Node.Name]): List[Node.Name] = graph.all_succs(names)
-    def requirements(names: List[Node.Name]): List[Node.Name] = graph.all_preds_rev(names)
     def topological_order: List[Node.Name] = graph.topological_order
 
     override def toString: String = topological_order.mkString("Nodes(", ",", ")")