A condition in If CodeQL formulas that requires comparison of different types

[Sim4n6]

I have this verification to be done using the CodeQL formulas If.
I need to check whether arg is equal to None or [] (empty list) or C (random stuff).

from DataFlow::Node sink, DataFlow::Node arg
where
    if 
          arg instanceof None
          or
          arg instanceof ListObject and arg.(ListObject).getLength() = 0
          or
          arg = C
    then sink = A
    else sink = B
  )
select sink, "sink" + sink.getLocation()

I wonder how to guess a common CodeQL type that would fit arg? how to fix this, please?

Sorry guys if I ask too many questions in here, but I love CodeQL and I'm a bit lost...

[Sim4n6]

To be more precise arg can take values as such:

• None
• []
• [Obj1,Obj1,...]
• f(Obj1)

any help is a welcome ?

[yoff]

Could you describe what you are trying to achieve overall? It looks like you might want one data flow query for the case sink = A with sources being None and the empty list, and another for the case sink = B. But I am not sure when the case sink = B is supposed to kick in, since the first case also includes C (random stuff).

If it is all purely syntactic, you could use AstNode as the common type...

[Sim4n6]

I figure it out 👍🏾

if
        arg.asCfgNode() instanceof NameConstantNode or
        arg.asCfgNode() instanceof ListNode
      then sink = A
      else sink = B

Now how to check arg is an empty list ... please?

[tausbn]

To check whether a ListNode l corresponds to an empty list, you can use not exists(l.getAnElement()).

[Sim4n6]

very simple and elegant, thank you 👍🏾