Add compile-fail test of DST rvalues resulting from overloaded index

Author: bkoropoff

src/test/compile-fail/dst-index.rs

@@ -0,0 +1,40 @@
+// Copyright 2014 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.
+
+// Test that overloaded index expressions with DST result types
+// can't be used as rvalues
+
+use std::ops::Index;
+use std::fmt::Show;
+
+struct S;
+
+impl Index<uint, str> for S {
+    fn index<'a>(&'a self, _: &uint) -> &'a str {
+        "hello"
+    }
+}
+
+struct T;
+
+impl Index<uint, Show + 'static> for T {
+    fn index<'a>(&'a self, idx: &uint) -> &'a Show + 'static {
+        static x: uint = 42;
+        &x
+    }
+}
+
+fn main() {
+    S[0];
+    //~^ ERROR E0161
+    T[0];
+    //~^ ERROR cannot move out of dereference
+    //~^^ ERROR E0161
+}