determine whether a borrow is active based solely on the location

src/test/compile-fail/borrowck/two-phase-across-loop.rs

@@ -0,0 +1,34 @@
+// Copyright 2016 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 a borrow which starts as a 2-phase borrow and gets
+// carried around a loop winds up conflicting with itself.
+
+#![feature(nll)]
+
+struct Foo { x: String }
+
+impl Foo {
+    fn get_string(&mut self) -> &str {
+        &self.x
+    }
+}
+
+fn main() {
+    let mut foo = Foo { x: format!("Hello, world") };
+    let mut strings = vec![];
+
+    loop {
+        strings.push(foo.get_string()); //~ ERROR cannot borrow `foo` as mutable
+        if strings.len() > 2 { break; }
+    }
+
+    println!("{:?}", strings);
+}