From 837dd14de31bd4adc92d962559047e7b449c20a6 Mon Sep 17 00:00:00 2001
From: Michael Sproul <micsproul@gmail.com>
Date: Mon, 10 Nov 2014 19:33:20 -0800
Subject: Add optional messages to the unreachable macro.

Closes #18842.
---
 src/libstd/macros.rs | 10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

(limited to 'src/libstd')

diff --git a/src/libstd/macros.rs b/src/libstd/macros.rs
index d82147947de..0c91542e5eb 100644
--- a/src/libstd/macros.rs
+++ b/src/libstd/macros.rs
@@ -211,7 +211,15 @@ macro_rules! debug_assert_eq(
 /// ```
 #[macro_export]
 macro_rules! unreachable(
-    () => (panic!("internal error: entered unreachable code"))
+    () => ({
+        panic!("internal error: entered unreachable code")
+    });
+    ($msg:expr) => ({
+        unreachable!("{}", $msg)
+    });
+    ($fmt:expr, $($arg:tt)*) => ({
+        panic!(concat!("internal error: entered unreachable code: ", $fmt), $($arg)*)
+    });
 )
 
 /// A standardised placeholder for marking unfinished code. It panics with the
-- 
cgit 1.4.1-3-g733a5