cache a bit more (again)

python/ql/lib/semmle/python/AstExtended.qll

@@ -18,7 +18,11 @@ abstract class AstNode extends AstNode_ {
    * NOTE: For some statements and other purely syntactic elements,
    * there may not be a `ControlFlowNode`
    */
-  ControlFlowNode getAFlowNode() { py_flow_bb_node(result, this, _, _) }
+  cached
+  ControlFlowNode getAFlowNode() {
+    Stages::AST::ref() and
+    py_flow_bb_node(result, this, _, _)
+  }
 
   /** Gets the location for this AST node */
   cached

python/ql/lib/semmle/python/Flow.qll

@@ -194,7 +194,9 @@ class ControlFlowNode extends @py_flow_node {
   BasicBlock getBasicBlock() { result.contains(this) }
 
   /** Gets the scope containing this flow node */
+  cached
   Scope getScope() {
+    Stages::AST::ref() and
     if this.getNode() instanceof Scope
     then
       /* Entry or exit node */

python/ql/lib/semmle/python/internal/CachedStages.qll

@@ -76,8 +76,12 @@ module Stages {
       or
       exists(any(AstExtended::AstNode n).getParentNode())
       or
+      exists(any(AstExtended::AstNode n).getAFlowNode())
+      or
       exists(any(PyFlow::BasicBlock b).getImmediateDominator())
       or
+      exists(any(PyFlow::BasicBlock b).getScope())
+      or
       any(PyFlow::BasicBlock b).strictlyDominates(_)
       or
       any(PyFlow::BasicBlock b).strictlyReaches(_)
@@ -141,7 +145,6 @@ module Stages {
     private import semmle.python.objects.TObject as TObject
     private import semmle.python.Flow as Flow
     private import semmle.python.objects.ObjectInternal as ObjectInternal
-    private import semmle.python.objects.ObjectAPI as ObjectAPI
     private import semmle.python.pointsto.PointsTo as PointsTo
 
     /**