The first two given use cases are #[rustc::since(1.26)] for u128 and #[rustc::attr(since(1.27), must_use)]. That seems fine, except select-rustc is a 2018 edition crate, so the fact that you can use this at all implies that your rustc is at least 1.31 already.
It would be nicer to see examples with newer things you might check for, and perhaps state the 1.31 requirement clearly somewhere.
The first two given use cases are
#[rustc::since(1.26)]foru128and#[rustc::attr(since(1.27), must_use)]. That seems fine, exceptselect-rustcis a 2018 edition crate, so the fact that you can use this at all implies that your rustc is at least 1.31 already.It would be nicer to see examples with newer things you might check for, and perhaps state the 1.31 requirement clearly somewhere.
Anyway, it's a cool crate, thanks!