Switch lazy_static over to mutable statics instead of UnsafeCell on nightly

Author: Kimundi

src/nightly_lazy.rs

@@ -1,27 +1,28 @@
 extern crate std;
 
 use self::std::prelude::v1::*;
-use self::std::cell::UnsafeCell;
 use self::std::sync::{Once, ONCE_INIT};
 
-pub struct Lazy<T: Sync>(UnsafeCell<Option<T>>, Once);
+pub struct Lazy<T: Sync>(Option<T>, Once);
 
 impl<T: Sync> Lazy<T> {
     #[inline(always)]
     pub const fn new() -> Self {
-        Lazy(UnsafeCell::new(None), ONCE_INIT)
+        Lazy(None, ONCE_INIT)
     }
 
     #[inline(always)]
-    pub fn get<F>(&'static self, f: F) -> &T
+    pub fn get<F>(&'static mut self, f: F) -> &T
         where F: FnOnce() -> T
     {
-        unsafe {
+        {
+            let r = &mut self.0;
             self.1.call_once(|| {
-                *self.0.get() = Some(f());
+                *r = Some(f());
             });
-
-            match *self.0.get() {
+        }
+        unsafe {
+            match self.0 {
                 Some(ref x) => x,
                 None => std::intrinsics::unreachable(),
             }
@@ -35,6 +36,6 @@ unsafe impl<T: Sync> Sync for Lazy<T> {}
 #[allow_internal_unstable]
 macro_rules! __lazy_static_create {
     ($NAME:ident, $T:ty) => {
-        static $NAME: $crate::lazy::Lazy<$T> = $crate::lazy::Lazy::new();
+        static mut $NAME: $crate::lazy::Lazy<$T> = $crate::lazy::Lazy::new();
     }
 }