(diagnostic
  (schema slovo.diagnostic)
  (version 1)
  (severity error)
  (code UnknownStructType)
  (message "function return type `Missing` is not a declared struct")
  (file "<fixture>")
  (span
    (bytes 31 38)
    (range 4 16 4 23)
  )
  (expected "known struct")
  (found "Missing")
  (hint "declare the struct before using it as a type")
)