1 files changed, 36 insertions, 0 deletions
diff --git a/third_party/rust/new_debug_unreachable/src/lib.rs b/third_party/rust/new_debug_unreachable/src/lib.rs
new file mode 100644
index 0000000000..db0f968f0a
--- /dev/null
+++ b/third_party/rust/new_debug_unreachable/src/lib.rs
@@ -0,0 +1,36 @@
+#![deny(missing_docs, warnings)]
+
+#![no_std]
+
+//! `panic!()` in debug builds, optimization hint in release.
+
+#[doc(hidden)] pub mod _internal { pub use core::hint::unreachable_unchecked; }
+
+#[macro_export]
+/// `panic!()` in debug builds, optimization hint in release.
+///
+/// Example:
+///
+/// ```
+/// use debug_unreachable::debug_unreachable;
+///
+/// fn main() {
+///     if 0 > 100 {
+///         // Can't happen!
+///         unsafe { debug_unreachable!() }
+///     } else {
+///         println!("Good, 0 <= 100.");
+///     }
+/// }
+/// ```
+macro_rules! debug_unreachable {
+    () => { debug_unreachable!("entered unreachable code") };
+    ($e:expr) => {
+        if cfg!(debug_assertions) {
+            panic!($e)
+        } else {
+            $crate::_internal::unreachable_unchecked()
+        }
+    }
+}
+