Ruby: Ensure Node::{toString,getLocation} are computed in data flow stage

ruby/ql/lib/codeql/ruby/dataflow/internal/DataFlowPrivate.qll

@@ -340,6 +340,12 @@ private module Cached {
     p.(KeywordParameter).getDefaultValue() = e.getExprNode().getExpr()
   }
 
+  cached
+  Location getLocation(NodeImpl n) { result = n.getLocationImpl() }
+
+  cached
+  string toString(NodeImpl n) { result = n.toStringImpl() }
+
   /**
    * This is the local flow predicate that is used as a building block in global
    * data flow.

ruby/ql/lib/codeql/ruby/dataflow/internal/DataFlowPublic.qll

@@ -19,12 +19,10 @@ class Node extends TNode {
   Parameter asParameter() { result = this.(ParameterNode).getParameter() }
 
   /** Gets a textual representation of this node. */
-  cached
-  final string toString() { result = this.(NodeImpl).toStringImpl() }
+  final string toString() { result = toString(this) }
 
   /** Gets the location of this node. */
-  cached
-  final Location getLocation() { result = this.(NodeImpl).getLocationImpl() }
+  final Location getLocation() { result = getLocation(this) }
 
   /**
    * Holds if this element is at the specified location.