Python: Move hack from CastNode into flowCheckNodeSpecific

Author: owen-mc

python/ql/lib/semmle/python/dataflow/new/internal/DataFlowPrivate.qll

@@ -486,6 +486,13 @@ class DataFlowType extends TDataFlowType {
 
 /** A node that performs a type cast. */
 class CastNode extends Node {
+  CastNode() { none() }
+}
+
+/**
+ * Holds if `n` should be a FlowCheckNode, which will appear in path summaries.
+ */
+predicate flowCheckNodeSpecific(Node n) {
   // We include read- and store steps here to force them to be
   // shown in path explanations.
   // This hack is necessary, because we have included some of these
@@ -494,14 +501,9 @@ class CastNode extends Node {
   // We should revert this once, we can remove this steps from the
   // default taint steps; this should be possible once we have
   // implemented flow summaries and recursive content.
-  CastNode() { readStep(_, _, this) or storeStep(_, _, this) }
+  readStep(_, _, n) or storeStep(_, _, n)
 }
 
-/**
- * Holds if `n` should be a FlowCheckNode, which will appear in path summaries.
- */
-predicate flowCheckNodeSpecific(Node n) { none() }
-
 /**
  * Holds if `t1` and `t2` are compatible, that is, whether data can flow from
  * a node of type `t1` to a node of type `t2`.