From f53c145ef18db6543e8e5420e172e04b6054db2e Mon Sep 17 00:00:00 2001
From: Esteban Küber <esteban@kuber.com.ar>
Date: Sat, 14 Jul 2018 20:50:30 -0700
Subject: Improve suggestion for missing fmt str in println

Avoid using `concat!(fmt, "\n")` to improve the diagnostics being
emitted when the first `println!()` argument isn't a formatting string
literal.
---
 src/libstd/macros.rs | 10 ++++++++--
 1 file changed, 8 insertions(+), 2 deletions(-)

(limited to 'src/libstd')

diff --git a/src/libstd/macros.rs b/src/libstd/macros.rs
index 75f038407c1..a4a6ed73c61 100644
--- a/src/libstd/macros.rs
+++ b/src/libstd/macros.rs
@@ -155,8 +155,14 @@ macro_rules! print {
 #[stable(feature = "rust1", since = "1.0.0")]
 macro_rules! println {
     () => (print!("\n"));
-    ($fmt:expr) => (print!(concat!($fmt, "\n")));
-    ($fmt:expr, $($arg:tt)*) => (print!(concat!($fmt, "\n"), $($arg)*));
+    ($fmt:expr) => ({
+        print!($fmt);
+        print!("\n");
+    });
+    ($fmt:expr, $($arg:tt)*) => ({
+        print!($fmt, $($arg)*);
+        print!("\n");
+    });
 }
 
 /// Macro for printing to the standard error.
-- 
cgit 1.4.1-3-g733a5