(diagnostic
  (schema slovo.diagnostic)
  (version 1)
  (severity error)
  (code NonExhaustiveMatch)
  (message "match is missing `none` arm(s)")
  (file "<fixture>")
  (span
    (bytes 57 105)
    (range 5 3 7 16)
  )
  (expected "some and none")
  (found "some")
)