Add optional messages to the unreachable macro.

Closes #18842.
2014-11-10 19:33:20 -08:00
parent 40fb87d40f
commit 837dd14de3
4 changed files with 35 additions and 1 deletions
--- 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