Use #[allow_internal_unstable] so that dependents don't have to declare feature(const_fn)

Author: Kimundi

src/lib.rs

@@ -68,7 +68,7 @@ The `Deref` implementation uses a hidden static variable that is guarded by a at
 
 */
 
-#![cfg_attr(feature="nightly", feature(const_fn, core_intrinsics))]
+#![cfg_attr(feature="nightly", feature(const_fn, allow_internal_unstable))]
 
 #[cfg(not(feature="nightly"))]
 pub mod lazy;
@@ -78,6 +78,7 @@ pub mod lazy;
 pub mod lazy;
 
 #[macro_export]
+#[cfg_attr(feature="nightly", allow_internal_unstable)]
 macro_rules! lazy_static {
     ($(#[$attr:meta])* static ref $N:ident : $T:ty = $e:expr; $($t:tt)*) => {
         lazy_static!(@PRIV, $(#[$attr])* static ref $N : $T = $e; $($t)*);

src/nightly_lazy.rs

@@ -31,6 +31,7 @@ impl<T: Sync> Lazy<T> {
 unsafe impl<T: Sync> Sync for Lazy<T> {}
 
 #[macro_export]
+#[allow_internal_unstable]
 macro_rules! __lazy_static_create {
     ($NAME:ident, $T:ty) => {
         static $NAME: $crate::lazy::Lazy<$T> = $crate::lazy::Lazy::new();