Constant syntax::codemap::SPAN_DEBUG[]

pub const SPAN_DEBUG: LocalKey<Cell<fn(Span, &mut Formatter) -> Result<(), Error>>> = {
    #[inline]
    fn __init()
     ->
         Cell<fn(: Span, : &mut fmt::Formatter)
                  -> fmt::Result> { <Cell>::new(default_span_debug) }
    unsafe fn __getit()
     ->
         ::option::Option<&'static ::cell::UnsafeCell<::option::Option<Cell<fn(:
                                                                                   Span,
                                                                               :
                                                                                   &mut fmt::Formatter)
                                                                                ->
                                                                                    fmt::Result>>>> {
                                                                                                        #[thread_local]
                                                                                                        #[cfg(all(target_thread_local,
                                                                                                                  not(target_arch
                                                                                                                          =
                                                                                                                          "wasm32")))]
                                                                                                        static __KEY:
                                                                                                               ::thread::__FastLocalKeyInner<Cell<fn(:
                                                                                                                                                         Span,
                                                                                                                                                     :
                                                                                                                                                         &mut fmt::Formatter)
                                                                                                                                                      ->
                                                                                                                                                          fmt::Result>>
                                                                                                               =
                                                                                                            <::thread::__FastLocalKeyInner>::new();
                                                                                                        __KEY.get()
                                                                                                    }
    unsafe { <::thread::LocalKey>::new(__getit, __init) }
}
🔬 This is a nightly-only experimental API. (rustc_private)

this crate is being loaded from the sysroot, an unstable location; did you mean to load this crate from crates.io via Cargo.toml instead?