{"ast_node_type":"other","tokens":[{"end":64,"kind":"keyword","start":0,"text":"///"}]}
    /// features. Otherwise, only `RUSTC_BOOTSTRAP=1` will work.
    /// If `krate` is [`Some`], then setting `RUSTC_BOOTSTRAP=krate` will enable the nightly
    pub fn from_environment(krate: Option<&str>) -> Self {