C++: Allow self-flow through indirect parameters.

Author: MathiasVP

cpp/ql/lib/semmle/code/cpp/ir/dataflow/internal/DataFlowPrivate.qll

@@ -848,7 +848,7 @@ predicate additionalLambdaFlowStep(Node nodeFrom, Node nodeTo, boolean preserves
  * One example would be to allow flow like `p.foo = p.bar;`, which is disallowed
  * by default as a heuristic.
  */
-predicate allowParameterReturnInSelf(ParameterNode p) { none() }
+predicate allowParameterReturnInSelf(ParameterNode p) { p instanceof IndirectParameterNode }
 
 private predicate fieldHasApproxName(Field f, string s) {
   s = f.getName().charAt(0) and