Eng 6597 union parameters

I had written a comment here that seems to have disappeared.

I have a couple questions:
1. Does this method actually belong in ParsedUnionStmt, since it seems only to be called when "this" is a union?
2. If the goal is to have a list of all the parameters attached to the top-level union, then I would expect to be concatenating param lists from all the children up to the root of the union tree.  What am I missing here?