--- /dev/null
+#![feature(plugin)]
+#![plugin(clippy)]
+
+#[warn(needless_borrowed_reference)]
+fn main() {
+ let mut v = Vec::<String>::new();
+ let _ = v.iter_mut().filter(|&ref a| a.is_empty());
+}
+
--- /dev/null
+warning: this pattern takes a reference on something that is being de-referenced
+ --> needless_borrowed_ref.rs:7:35
+ |
+7 | let _ = v.iter_mut().filter(|&ref a| a.is_empty());
+ | ^^^^^
+ |
+ = note: #[warn(needless_borrowed_reference)] on by default
+ = help: for further information visit https://github.com/Manishearth/rust-clippy/wiki#needless_borrowed_reference