bind.lua

function utils.bind(fn, self, ...)
  local argsLength = select("#", ...)
  if argsLength == 0 then
    return function (...)
      return fn(self, ...)
    end
  else
    -- This table will get mutated on every call, but it's async safe and the
    -- unpack fence will only use the fresh data so it's ok.
    local args = {...}
    return function (...)
      local extraLength = select("#", ...)
      local extra = {...}
      for i = 1, extraLength do
        args[i + argsLength] = extra[i]
      end
      return fn(self, unpack(args, 1, argsLength + extraLength))
    end
  end
end