Function refuse_rng_seed_on_method 

pub(crate) fn refuse_rng_seed_on_method(
    meta: &ParseNestedMeta<'_>,
    method: &str,
) -> Result<()>

Refuse rng(seed = ..) on an impl or trait method (#2198), spanned on the option: the seed contract is written in the R wrapper of a standalone function or an s3(...) method. meta is rng, followed by its parenthesized options.