Prepare for change to unary panic! rejecting fmt string literals.

Author: pnkfelix

src/libcore/macros.rs

@@ -56,7 +56,8 @@ macro_rules! panic {
 macro_rules! assert {
     ($cond:expr) => (
         if !$cond {
-            panic!(concat!("assertion failed: ", stringify!($cond)))
+            const MSG: &'static str = concat!("assertion failed: ", stringify!($cond));
+            panic!(MSG)
         }
     );
     ($cond:expr, $($arg:tt)+) => (

src/libcoretest/nonzero.rs

@@ -95,6 +95,6 @@ fn test_match_option_string() {
     let five = "Five".to_string();
     match Some(five) {
         Some(s) => assert_eq!(s, "Five"),
-        None => panic!("unexpected None while matching on Some(String { ... })")
+        None => panic!("{}", "unexpected None while matching on Some(String { ... })")
     }
 }