Add a non-regression test for issue rust-lang#8372

Author: SimonSapin

src/test/run-pass/for-loop-does-not-borrow-iterators.rs

@@ -0,0 +1,30 @@
+// 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.
+
+
+// The `for` loop use to keep a mutable borrow when executing its body,
+// making it impossible to re-use the iterator as follows.
+// https://github.com/rust-lang/rust/issues/8372
+//
+// This was fixed in https://github.com/rust-lang/rust/pull/15809
+
+pub fn main() {
+    let mut for_loop_values = Vec::new();
+    let mut explicit_next_call_values = Vec::new();
+
+    let mut iter = range(1i, 10);
+    for i in iter {
+        for_loop_values.push(i);
+        explicit_next_call_values.push(iter.next());
+    }
+
+    assert_eq!(for_loop_values, vec![1, 3, 5, 7, 9]);
+    assert_eq!(explicit_next_call_values, vec![Some(2), Some(4), Some(6), Some(8), None]);
+}