rustc::lint::builtin::INACCESSIBLE_EXTERN_CRATE

pub static INACCESSIBLE_EXTERN_CRATE: &'static Lint = &::rustc::lint::Lint{name: "INACCESSIBLE_EXTERN_CRATE",
                     default_level: ::rustc::lint::Warn,
                     desc:
                         "use of inaccessible extern crate erroneously allowed",}

Unstable (rustc_private)