Improve needless_borrowed_ref and update its stderr.

clippy_tests/examples/needless_borrowed_ref.rs

@@ -8,13 +8,24 @@ fn main() {
     let _ = v.iter_mut().filter(|&ref a| a.is_empty());
     //                            ^ should be linted
 
-    let mut var = 5;
-    let thingy = Some(&mut var);
-    if let Some(&mut ref v) = thingy {
+    let var = 3;
+    let thingy = Some(&var);
+    if let Some(&ref v) = thingy {
+        //          ^ should be linted
+    }
+
+    let mut var2 = 5;
+    let thingy2 = Some(&mut var2);
+    if let Some(&mut ref mut v) = thingy2 {
         //          ^ should *not* be linted
-        // here, var is borrowed as immutable.
+        // v is borrowed as mutable.
+        *v = 10;
+    }
+    if let Some(&mut ref v) = thingy2 {
+        //          ^ should *not* be linted
+        // here, v is borrowed as immutable.
         // can't do that:
-        //*v = 10;
+        //*v = 15;
     }
 }
 

clippy_tests/examples/needless_borrowed_ref.stderr

@@ -1,8 +1,41 @@
-warning: this pattern takes a reference on something that is being de-referenced
- --> needless_borrowed_ref.rs:7:35
+error: this pattern takes a reference on something that is being de-referenced
+ --> examples/needless_borrowed_ref.rs:8:34
   |
-7 |     let _ = v.iter_mut().filter(|&ref a| a.is_empty());
-  |                                   ^^^^^
+8 |     let _ = v.iter_mut().filter(|&ref a| a.is_empty());
+  |                                  ^^^^^^ help: try removing the `&ref` part and just keep `a`
   |
-  = note: #[warn(needless_borrowed_reference)] on by default
+  = note: `-D needless-borrowed-reference` implied by `-D warnings`
   = help: for further information visit https://github.com/Manishearth/rust-clippy/wiki#needless_borrowed_reference
+
+error: this pattern takes a reference on something that is being de-referenced
+  --> examples/needless_borrowed_ref.rs:13:17
+   |
+13 |     if let Some(&ref v) = thingy {
+   |                 ^^^^^^ help: try removing the `&ref` part and just keep `v`
+   |
+   = note: `-D needless-borrowed-reference` implied by `-D warnings`
+   = help: for further information visit https://github.com/Manishearth/rust-clippy/wiki#needless_borrowed_reference
+
+error: this pattern takes a reference on something that is being de-referenced
+  --> examples/needless_borrowed_ref.rs:42:27
+   |
+42 |         (&Animal::Cat(v), &ref k) | (&ref k, &Animal::Cat(v)) => (), // lifetime mismatch error if there is no '&ref'
+   |                           ^^^^^^ help: try removing the `&ref` part and just keep `k`
+   |
+   = note: `-D needless-borrowed-reference` implied by `-D warnings`
+   = help: for further information visit https://github.com/Manishearth/rust-clippy/wiki#needless_borrowed_reference
+
+error: this pattern takes a reference on something that is being de-referenced
+  --> examples/needless_borrowed_ref.rs:42:38
+   |
+42 |         (&Animal::Cat(v), &ref k) | (&ref k, &Animal::Cat(v)) => (), // lifetime mismatch error if there is no '&ref'
+   |                                      ^^^^^^ help: try removing the `&ref` part and just keep `k`
+   |
+   = note: `-D needless-borrowed-reference` implied by `-D warnings`
+   = help: for further information visit https://github.com/Manishearth/rust-clippy/wiki#needless_borrowed_reference
+
+error: aborting due to previous error(s)
+
+error: Could not compile `clippy_tests`.
+
+To learn more, run the command again with --verbose.