error: Found `ENDU` outside of a `UNION` construct
    at invalid-union.asm(1)
error: Found `NEXTU` outside of a `UNION` construct
    at invalid-union.asm(2)
error: `UNION`s must be inside a `SECTION`
    at invalid-union.asm(3)
error: Unterminated `UNION` construct
    at invalid-union.asm(7)
Assembly aborted with 4 errors!