Test added.

src/test/ui/suggest-remove-refs.rs

@@ -0,0 +1,18 @@
+// 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.
+
+fn main() {
+    let v = vec![0, 1, 2, 3];
+
+    for (i, n) in &v.iter().enumerate() {
+        //~^ ERROR the trait bound
+        println!("{}", i);
+    }
+}

src/test/ui/suggest-remove-refs.stderr

@@ -0,0 +1,15 @@
+error[E0277]: the trait bound `&std::iter::Enumerate<std::slice::Iter<'_, {integer}>>: std::iter::Iterator` is not satisfied
+  --> $DIR/suggest-remove-refs.rs:14:19
+   |
+LL |     for (i, n) in &v.iter().enumerate() {
+   |                   ^^^^^^^^^^^^^^^^^^^^^
+   |                   |
+   |                   `&std::iter::Enumerate<std::slice::Iter<'_, {integer}>>` is not an iterator; maybe try calling `.iter()` or a similar method
+   |                   help: consider removing `&`s like: `v.iter().enumerate()`
+   |
+   = help: the trait `std::iter::Iterator` is not implemented for `&std::iter::Enumerate<std::slice::Iter<'_, {integer}>>`
+   = note: required by `std::iter::IntoIterator::into_iter`
+
+error: aborting due to previous error
+
+If you want more information on this error, try using "rustc --explain E0277"