From e382267cfb9133ef12d59b66a2935ee45b546a61 Mon Sep 17 00:00:00 2001
From: Nicholas Nethercote <nnethercote@mozilla.com>
Date: Fri, 21 Oct 2016 10:42:30 +1100
Subject: [PATCH] Avoid an unnecessary clone in `generic_extensions`.

This avoids ~800,000 allocations in html5ever.
---
 src/libsyntax/ext/tt/macro_rules.rs | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/src/libsyntax/ext/tt/macro_rules.rs b/src/libsyntax/ext/tt/macro_rules.rs
index a74d335d6046d..c585c66f9a228 100644
--- a/src/libsyntax/ext/tt/macro_rules.rs
+++ b/src/libsyntax/ext/tt/macro_rules.rs
@@ -139,9 +139,9 @@ fn generic_extension<'cx>(cx: &'cx ExtCtxt,
                     macro_ident: name
                 })
             }
-            Failure(sp, ref msg) => if sp.lo >= best_fail_spot.lo {
+            Failure(sp, msg) => if sp.lo >= best_fail_spot.lo {
                 best_fail_spot = sp;
-                best_fail_msg = (*msg).clone();
+                best_fail_msg = msg;
             },
             Error(err_sp, ref msg) => {
                 cx.span_fatal(err_sp.substitute_dummy(sp), &msg[..])