Check for ident length. Fixes rust-lang#13105

Author: Aatch

src/librustc/middle/lint.rs

@@ -1204,11 +1204,13 @@ fn check_pat_uppercase_variable(cx: &Context, p: &ast::Pat) {
                     // last identifier alone is right choice for this lint.
                     let ident = path.segments.last().unwrap().identifier;
                     let s = token::get_ident(ident);
-                    if s.get().char_at(0).is_uppercase() {
-                        cx.span_lint(
-                            UppercaseVariables,
-                            path.span,
-                            "variable names should start with a lowercase character");
+                    if s.get().len() > 0 {
+                        if s.get().char_at(0).is_uppercase() {
+                            cx.span_lint(
+                                UppercaseVariables,
+                                path.span,
+                                "variable names should start with a lowercase character");
+                        }
                     }
                 }
                 _ => {}

src/test/run-pass/13105-unnamed-argument-lint.rs

@@ -0,0 +1,36 @@
+// Copyright 2012 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+
+// Regression test for issue #13105
+
+#[deny(uppercase_variables)];
+
+trait Foo {
+    // Good
+    fn foo(&self);
+
+    // Good
+    fn bar(u8);
+
+    // Good
+    fn baz(&self) {
+
+    }
+
+    // ICE
+    fn quux(u8) {
+
+    }
+}
+
+fn main() {
+
+}