1 files changed, 4 insertions, 1 deletions
diff --git a/src/libsyntax/ext/tt/macro_parser.rs b/src/libsyntax/ext/tt/macro_parser.rs
index 89e8d48425f..54308536ab2 100644
--- a/src/libsyntax/ext/tt/macro_parser.rs
+++ b/src/libsyntax/ext/tt/macro_parser.rs
@@ -455,6 +455,9 @@ pub fn parse_nt(p: &mut Parser, name: &str) -> Nonterminal {
         res
       }
       "matchers" => token::NtMatchers(p.parse_matchers()),
-      _ => p.fatal("unsupported builtin nonterminal parser: ".to_owned() + name)
+      _ => {
+          p.fatal(format!("unsupported builtin nonterminal parser: {}",
+                          name).as_slice())
+      }
     }
 }