Don't ICE if an argument in a default method doesn't have a name. Closes #8417.

msullivan · msullivan · commit 48a682398acb · 2013-08-22T10:14:10.000-07:00
diff --git 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) {

Original file line number	Diff line number	Diff line change
`@@ -1617,7 +1617,7 @@ impl Liveness {`
`1617`	`1617`
`1618`	`1618`	`pub fn should_warn(&self, var: Variable) -> Option<@str> {`
`1619`	`1619`	`let name = self.ir.variable_name(var);`
`1620`		`- if name[0] == ('_' as u8) { None } else { Some(name) }`
	`1620`	`+ if name.len() == 0 \|\| name[0] == ('_' as u8) { None } else { Some(name) }`
`1621`	`1621`	`}`
`1622`	`1622`
`1623`	`1623`	`pub fn warn_about_unused_args(&self, decl: &fn_decl, entry_ln: LiveNode) {`