(diagnostic
  (schema slovo.diagnostic)
  (version 1)
  (severity error)
  (code UnsupportedGenericFunction)
  (message "generic function declarations are reserved but not supported in beta.9")
  (file "<fixture>")
  (span
    (bytes 23 38)
    (range 4 8 4 23)
  )
  (expected "(fn name ((arg ConcreteType) ...) -> ConcreteType body...)")
  (found "(type_params ...)")
  (hint "write a concrete function for each currently supported type family")
)