From 76c313ceb15228a8683ca1dd03ce277ed0b69d4c Mon Sep 17 00:00:00 2001
From: Alex Crichton <alex@alexcrichton.com>
Date: Thu, 13 Feb 2014 04:31:19 -0800
Subject: Lift $dst outside the closure in write!

If you were writing to something along the lines of `self.foo` then with the new
closure rules it meant that you were borrowing `self` for the entirety of the
closure, meaning that you couldn't format other fields of `self` at the same
time as writing to a buffer contained in `self`.

By lifting the borrow outside of the closure the borrow checker can better
understand that you're only borrowing one of the fields at a time. This had to
use type ascription as well in order to preserve trait object coercions.
---
 src/libstd/macros.rs | 14 ++++++++------
 1 file changed, 8 insertions(+), 6 deletions(-)

(limited to 'src/libstd')

diff --git a/src/libstd/macros.rs b/src/libstd/macros.rs
index be1fdc4594d..14ae7c9900c 100644
--- a/src/libstd/macros.rs
+++ b/src/libstd/macros.rs
@@ -145,16 +145,18 @@ macro_rules! format(
 
 #[macro_export]
 macro_rules! write(
-    ($dst:expr, $($arg:tt)*) => (
-        format_args!(|args| { ::std::fmt::write($dst, args) }, $($arg)*)
-    )
+    ($dst:expr, $($arg:tt)*) => ({
+        let dst: &mut ::std::io::Writer = $dst;
+        format_args!(|args| { ::std::fmt::write(dst, args) }, $($arg)*)
+    })
 )
 
 #[macro_export]
 macro_rules! writeln(
-    ($dst:expr, $($arg:tt)*) => (
-        format_args!(|args| { ::std::fmt::writeln($dst, args) }, $($arg)*)
-    )
+    ($dst:expr, $($arg:tt)*) => ({
+        let dst: &mut ::std::io::Writer = $dst;
+        format_args!(|args| { ::std::fmt::writeln(dst, args) }, $($arg)*)
+    })
 )
 
 #[macro_export]
-- 
cgit 1.4.1-3-g733a5