add &Root<T> checker

update rust_tidy tests

update rust_tidy.rs and test_tidy.py

python/tidy/servo_tidy/tidy.py

@@ -387,6 +387,8 @@ def check_rust(file_name, lines):
             (r": &Vec<", "use &[T] instead of &Vec<T>", no_filter),
             # No benefit over using &str
             (r": &String", "use &str instead of &String", no_filter),
+            # No benefit to using &Root<T>
+            (r": &Root<", "use &T instead of &Root<T>", no_filter),
             (r"^&&", "operators should go at the end of the first line", no_filter),
         ]
 

python/tidy/servo_tidy_tests/rust_tidy.rs

@@ -35,7 +35,7 @@ impl test {
         }
     }
 
-    fn test_fun2(y : &String, z : &Vec<f32>) -> f32 {
+    fn test_fun2(y : &String, z : &Vec<f32>, r: &Root<isize>) -> f32 {
         let x = true;
         x
             && x;

python/tidy/servo_tidy_tests/test_tidy.py

@@ -72,6 +72,7 @@ class CheckTidiness(unittest.TestCase):
         self.assertEqual('extra space before :', errors.next()[2])
         self.assertEqual('use &[T] instead of &Vec<T>', errors.next()[2])
         self.assertEqual('use &str instead of &String', errors.next()[2])
+        self.assertEqual('use &T instead of &Root<T>', errors.next()[2])
         self.assertEqual('operators should go at the end of the first line', errors.next()[2])
         self.assertNoMoreErrors(errors)