Python: start on local flow

python/ql/src/semmle/code/python/dataflow/internal/DataFlowPrivate.qll

@@ -1,6 +1,11 @@
 private import python
 private import DataFlowPublic
 
+// Data flow graph
+
+// Nodes
+
+
 class DataFlowCall extends Call {
   /** Gets the enclosing callable of this call. */
   abstract DataFlowCallable getEnclosingCallable();
@@ -92,7 +97,16 @@ predicate compatibleTypes(DataFlowType t1, DataFlowType t2) {
  * excludes SSA flow through instance fields.
  */
 predicate simpleLocalFlowStep(Node nodeFrom, Node nodeTo) {
-  none()
+
+  exists(EssaEdgeRefinement r |
+    nodeTo.asEssaNode() = r.getVariable() and
+    nodeFrom.asEssaNode() = r.getInput()
+  )
+  or
+  exists(EssaNodeRefinement r |
+    nodeTo.asEssaNode() = r.getVariable() and
+    nodeFrom.asEssaNode() = r.getInput()
+  )
 }
 
 /**

python/ql/src/semmle/code/python/dataflow/internal/DataFlowPublic.qll

@@ -5,11 +5,19 @@
 import python
 private import DataFlowPrivate
 
+newtype TNode =
+  TEssaNode(EssaVariable var)
+
 /**
  * An element, viewed as a node in a data flow graph. Either an expression
  * (`ExprNode`) or a parameter (`ParameterNode`).
  */
-class Node extends ControlFlowNode {
+class Node extends TNode {
+
+  EssaVariable asEssaNode() { this = TEssaNode(result) }
+
+  string toString() { result = this.asEssaNode().toString() }
+
   /** Gets the enclosing callable of this node. */
   final DataFlowCallable getEnclosingCallable() {
     none()
@@ -32,9 +40,10 @@ class Node extends ControlFlowNode {
   predicate hasLocationInfo(
     string filepath, int startline, int startcolumn, int endline, int endcolumn
   ) {
-    getLocation().hasLocationInfo(filepath, startline, startcolumn, endline, endcolumn)
+    this.asEssaNode().getDefinition().getLocation().hasLocationInfo(filepath, startline, startcolumn, endline, endcolumn)
   }
 
+
 }
 
 /**