Since roxygen2 version 4.0.0, the @S3method tag has been deprecated in favour of using @export.
The package now t
Use @method generic class and @export instead of @S3method. Take a look at this thread:
S3 method help (roxygen2)
As Mr Flick commented, appending the full function name to the roxygen line works correctly. If I change the line to:
#' @export check.arg
then the NAMESPACE file contains:
export(check.arg)