From 48a682398acb48d4fe09adbf94616d1270bd1b7a Mon Sep 17 00:00:00 2001
From: Michael Sullivan <sully@msully.net>
Date: Mon, 19 Aug 2013 15:49:37 -0700
Subject: [PATCH] Don't ICE if an argument in a default method doesn't have a
 name. Closes #8417.

---
 src/librustc/middle/liveness.rs | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/librustc/middle/liveness.rs b/src/librustc/middle/liveness.rs
index edb805cfc40ae..a18fffda32e4b 100644
--- a/src/librustc/middle/liveness.rs
+++ b/src/librustc/middle/liveness.rs
@@ -1617,7 +1617,7 @@ impl Liveness {
 
     pub fn should_warn(&self, var: Variable) -> Option<@str> {
         let name = self.ir.variable_name(var);
-        if name[0] == ('_' as u8) { None } else { Some(name) }
+        if name.len() == 0 || name[0] == ('_' as u8) { None } else { Some(name) }
     }
 
     pub fn warn_about_unused_args(&self, decl: &fn_decl, entry_ln: LiveNode) {