(typename $union
  (enum u8
    $self
    $power
  )
)

(typename $self
  (union $union
    ;; A union variant that will expand to a strict keyword `Self`.
    (field $self (@witx pointer f32))
    ;; Oh it's true, that there's power in a union!
    (field $power (@witx pointer f32))
  )
)