Guard recognizing the filters this pass is about: the ones whose top level conjunction says something about at least one variable, and the contradictory ones, which are the empty operation.
The transformation context
The operation to check
whether it is such a filter; anything else is left where it is, and the traversal keeps descending into it looking for the filters deeper down
Guard recognizing the filters this pass is about: the ones whose top level conjunction says something about at least one variable, and the contradictory ones, which are the empty operation.