1 files changed, 65 insertions, 0 deletions
diff --git a/lazy-static/src/inline_lazy.rs b/lazy-static/src/inline_lazy.rs
new file mode 100644
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+++ b/lazy-static/src/inline_lazy.rs
@@ -0,0 +1,65 @@
+// Copyright 2016 lazy-static.rs Developers
+//
+// Licensed under the Apache License, Version 2.0, <LICENSE-APACHE or
+// http://apache.org/licenses/LICENSE-2.0> or the MIT license <LICENSE-MIT or
+// http://opensource.org/licenses/MIT>, at your option. This file may not be
+// copied, modified, or distributed except according to those terms.
+
+extern crate core;
+extern crate std;
+
+use self::std::prelude::v1::*;
+use self::std::cell::Cell;
+use self::std::sync::Once;
+pub use self::std::sync::ONCE_INIT;
+
+// FIXME: Replace Option<T> with MaybeInitialized<T>
+pub struct Lazy<T: Sync>(Cell<Option<T>>, Once);
+
+impl<T: Sync> Lazy<T> {
+    pub const INIT: Self = Lazy(Cell::new(None), ONCE_INIT);
+
+    #[inline(always)]
+    pub fn get<F>(&'static self, f: F) -> &T
+    where
+        F: FnOnce() -> T,
+    {
+        self.1.call_once(|| {
+            self.0.set(Some(f()));
+        });
+
+        // `self.0` is guaranteed to be `Some` by this point
+        // The `Once` will catch and propegate panics
+        unsafe {
+            match *self.0.as_ptr() {
+                Some(ref x) => x,
+                None => {
+                    debug_assert!(false, "attempted to derefence an uninitialized lazy static. This is a bug");
+
+                    unreachable_unchecked()
+                },
+            }
+        }
+    }
+}
+
+unsafe impl<T: Sync> Sync for Lazy<T> {}
+
+#[macro_export]
+#[doc(hidden)]
+macro_rules! __lazy_static_create {
+    ($NAME:ident, $T:ty) => {
+        static $NAME: $crate::lazy::Lazy<$T> = $crate::lazy::Lazy::INIT;
+    };
+}
+
+/// Polyfill for std::hint::unreachable_unchecked. There currently exists a
+/// [crate](https://docs.rs/unreachable) for an equivalent to std::hint::unreachable_unchecked, but
+/// lazy_static currently doesn't include any runtime dependencies and we've chosen to include this
+/// short polyfill rather than include a new crate in every consumer's build.
+///
+/// This should be replaced by std's version when lazy_static starts to require at least Rust 1.27.
+unsafe fn unreachable_unchecked() -> ! {
+    enum Void {}
+    match std::mem::uninitialized::<Void>() {}
+}