You can use #[cfg(doc)] and #[cfg_attr(doc, ...)], but it looks like that still requires #![feature(doc_cfg)], so I guess it wouldn't be compatible with stable

You can use #[cfg(doc)] and #[cfg_attr(doc, ...)], but it looks like that still requires #![feature(doc_cfg)], so I guess it wouldn't be compatible with stable rustc anyway, until it's stabilized itself.