matches: special message for this case

match &e { &Pat1 => {}, &Pat2 => {}, ... }

(inspired by dogfood fixes)

tests/compile-fail/matches.rs

@@ -53,6 +53,12 @@ fn ref_pats() {
         &(v, 1) => println!("{}", v),
         _ => println!("none"),
     }
+    // special case: using & both in expr and pats
+    let w = Some(0);
+    match &w {  //~ERROR you don't need to add `&` to both
+        &Some(v) => println!("{:?}", v),
+        &None => println!("none"),
+    }
 }
 
 fn main() {