Python: Remove points-to to from ControlFlowNode

Moves the existing points-to predicates to the newly added class
`ControlFlowNodeWithPointsTo` which resides in the `LegacyPointsTo`
module.

(Existing code that uses these predicates should import this module, and
references to `ControlFlowNode` should be changed to
`ControlFlowNodeWithPointsTo`.)

Also updates all existing points-to based code to do just this.

python/ql/src/Statements/IterableStringOrSequence.ql

@@ -12,6 +12,7 @@
  */
 
 import python
+private import LegacyPointsTo
 import semmle.python.filters.Tests
 
 predicate has_string_type(Value v) {
@@ -21,7 +22,7 @@ predicate has_string_type(Value v) {
 }
 
 from
-  For loop, ControlFlowNode iter, Value str, Value seq, ControlFlowNode seq_origin,
+  For loop, ControlFlowNodeWithPointsTo iter, Value str, Value seq, ControlFlowNode seq_origin,
   ControlFlowNode str_origin
 where
   loop.getIter().getAFlowNode() = iter and

python/ql/src/Statements/ModificationOfLocals.ql

@@ -12,8 +12,11 @@
  */
 
 import python
+private import LegacyPointsTo
 
-predicate originIsLocals(ControlFlowNode n) { n.pointsTo(_, _, Value::named("locals").getACall()) }
+predicate originIsLocals(ControlFlowNodeWithPointsTo n) {
+  n.pointsTo(_, _, Value::named("locals").getACall())
+}
 
 predicate modification_of_locals(ControlFlowNode f) {
   originIsLocals(f.(SubscriptNode).getObject()) and

python/ql/src/Statements/NonIteratorInForLoop.ql

@@ -12,8 +12,9 @@
  */
 
 import python
+private import LegacyPointsTo
 
-from For loop, ControlFlowNode iter, Value v, ClassValue t, ControlFlowNode origin
+from For loop, ControlFlowNodeWithPointsTo iter, Value v, ClassValue t, ControlFlowNode origin
 where
   loop.getIter().getAFlowNode() = iter and
   iter.pointsTo(_, v, origin) and

python/ql/src/Statements/ShouldUseWithStatement.ql

@@ -13,6 +13,7 @@
  */
 
 import python
+private import LegacyPointsTo
 
 predicate calls_close(Call c) { exists(Attribute a | c.getFunc() = a and a.getName() = "close") }
 
@@ -22,7 +23,7 @@ predicate only_stmt_in_finally(Try t, Call c) {
   )
 }
 
-predicate points_to_context_manager(ControlFlowNode f, ClassValue cls) {
+predicate points_to_context_manager(ControlFlowNodeWithPointsTo f, ClassValue cls) {
   forex(Value v | f.pointsTo(v) | v.getClass() = cls) and
   cls.isContextManager()
 }

python/ql/src/Statements/StringConcatenationInLoop.ql

@@ -11,6 +11,7 @@
  */
 
 import python
+private import LegacyPointsTo
 
 predicate string_concat_in_loop(BinaryExpr b) {
   b.getOp() instanceof Add and
@@ -19,7 +20,7 @@ predicate string_concat_in_loop(BinaryExpr b) {
   |
     d.getDefinition().(DefinitionNode).getValue() = add and
     u.getAUse() = add.getAnOperand() and
-    add.getAnOperand().pointsTo().getClass() = ClassValue::str()
+    add.getAnOperand().(ControlFlowNodeWithPointsTo).pointsTo().getClass() = ClassValue::str()
   )
 }
 

python/ql/src/Statements/UseOfExit.ql

@@ -12,9 +12,10 @@
  */
 
 import python
+private import LegacyPointsTo
 
 from CallNode call, string name
-where call.getFunction().pointsTo(Value::siteQuitter(name))
+where call.getFunction().(ControlFlowNodeWithPointsTo).pointsTo(Value::siteQuitter(name))
 select call,
   "The '" + name +
     "' site.Quitter object may not exist if the 'site' module is not loaded or is modified."