warning I do not understand

[ghost]

Describe the bug
I have a configuration file for neovim in lua with the content

M = {}

function M.setup()
  local nls = require 'nulls-ls'
  local sources = { nls.builtins.formatting.stylua }
  nls-setup { sources=sources } W: Only has 0 variables, but you set 1 values.
end

return M

I am looking into insight into what this warning means in order to determine if it is legitimate.

[sumneko]

I cannot reproduce it, this line nls-setup { sources=sources } W: Only has 0 variables, but you set 1 values. is invalid Lua code, please provide the valid code.

[haolian9]

it seems to be a localization problem.

locale/zh-cn says:

DIAG_OVER_MAX_ARGS      =
'函数只接收 {:d} 个参数，但你传了 {:d} 个。'

while locale/en-us says:

DIAG_OVER_MAX_ARGS      =
'The function takes only {:d} parameters, but you passed {:d}.'
DIAG_OVER_MAX_ARGS      =
'Only has {} variables, but you set {} values.'