Borrow checking for overloaded indexing

Closes #15525

src/test/compile-fail/borrowck-overloaded-index-2.rs

@@ -0,0 +1,26 @@
+// 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.
+
+struct MyVec<T> {
+    data: Vec<T>,
+}
+
+impl<T> Index<uint, T> for MyVec<T> {
+    fn index<'a>(&'a self, &i: &uint) -> &'a T {
+        self.data.get(i)
+    }
+}
+
+fn main() {
+    let v = MyVec { data: vec!(box 1i, box 2, box 3) };
+    let good = &v[0]; // Shouldn't fail here
+    let bad = v[0];
+    //~^ ERROR cannot move out of dereference (dereference is implicit, due to indexing)
+}

src/test/compile-fail/borrowck-overloaded-index.rs

@@ -58,7 +58,7 @@ fn main() {
         x: 1,
     };
     s[2] = 20;
-    //~^ ERROR cannot assign to immutable indexed content
+    //~^ ERROR cannot assign to immutable dereference (dereference is implicit, due to indexing)
 }