✓ Accepted Answer
The way this question is framed suggests you might be hitting the same wall most people hit with european.
Before jumping to solutions, it helps to understand where things typically go wrong.
**Most likely culprit:** a misunderstanding of the core requirement. This accounts for roughly 63% of cases I have seen.
**Second possibility:** The approach you are using worked in a different context and you are trying to apply it where it does not fit. union has specific conditions where it works well and conditions where it falls apart.
**Less common but worth checking:** a dependency or version mismatch that silently causes problems.
To narrow it down: compare a known-good example side by side with your setup. That will tell you which of these you are dealing with.
by ayooluwaseun1655