Add lint check for &DomRoot<T>

`&DomRoot<T> is strictly less expressive than `&T`, so using it is
pointless.

components/script/dom/bindings/serializable.rs

@@ -6,7 +6,6 @@
 //! (https://html.spec.whatwg.org/multipage/#serializable-objects).
 
 use crate::dom::bindings::reflector::DomObject;
-use crate::dom::bindings::root::DomRoot;
 use crate::dom::bindings::structuredclone::StructuredDataHolder;
 use crate::dom::globalscope::GlobalScope;
 
@@ -25,7 +24,7 @@ pub trait Serializable: DomObject {
     fn serialize(&self, sc_holder: &mut StructuredDataHolder) -> Result<StorageKey, ()>;
     /// <https://html.spec.whatwg.org/multipage/#deserialization-steps>
     fn deserialize(
-        owner: &DomRoot<GlobalScope>,
+        owner: &GlobalScope,
         sc_holder: &mut StructuredDataHolder,
         extra_data: StorageKey,
     ) -> Result<(), ()>;

components/script/dom/bindings/structuredclone.rs

@@ -56,7 +56,7 @@ enum StructuredCloneTags {
 }
 
 unsafe fn read_blob(
-    owner: &DomRoot<GlobalScope>,
+    owner: &GlobalScope,
     r: *mut JSStructuredCloneReader,
     mut sc_holder: &mut StructuredDataHolder,
 ) -> *mut JSObject {
@@ -88,7 +88,7 @@ unsafe fn read_blob(
 }
 
 unsafe fn write_blob(
-    owner: &DomRoot<GlobalScope>,
+    owner: &GlobalScope,
     blob: DomRoot<Blob>,
     w: *mut JSStructuredCloneWriter,
     sc_holder: &mut StructuredDataHolder,

components/script/dom/bindings/transferable.rs

@@ -6,7 +6,6 @@
 //! (https://html.spec.whatwg.org/multipage/#transferable-objects).
 
 use crate::dom::bindings::reflector::DomObject;
-use crate::dom::bindings::root::DomRoot;
 use crate::dom::bindings::structuredclone::StructuredDataHolder;
 use crate::dom::globalscope::GlobalScope;
 use js::jsapi::MutableHandleObject;
@@ -14,7 +13,7 @@ use js::jsapi::MutableHandleObject;
 pub trait Transferable: DomObject {
     fn transfer(&self, sc_holder: &mut StructuredDataHolder) -> Result<u64, ()>;
     fn transfer_receive(
-        owner: &DomRoot<GlobalScope>,
+        owner: &GlobalScope,
         sc_holder: &mut StructuredDataHolder,
         extra_data: u64,
         return_object: MutableHandleObject,

components/script/dom/blob.rs

@@ -125,7 +125,7 @@ impl Serializable for Blob {
 
     /// <https://w3c.github.io/FileAPI/#ref-for-deserialization-steps>
     fn deserialize(
-        owner: &DomRoot<GlobalScope>,
+        owner: &GlobalScope,
         sc_holder: &mut StructuredDataHolder,
         storage_key: StorageKey,
     ) -> Result<(), ()> {
@@ -159,7 +159,7 @@ impl Serializable for Blob {
             *blob_impls = None;
         }
 
-        let deserialized_blob = Blob::new(&**owner, blob_impl);
+        let deserialized_blob = Blob::new(&*owner, blob_impl);
 
         let blobs = blobs.get_or_insert_with(|| HashMap::new());
         blobs.insert(storage_key, deserialized_blob);

components/script/dom/globalscope.rs

@@ -892,7 +892,7 @@ impl GlobalScope {
     }
 
     /// Start tracking a blob
-    pub fn track_blob(&self, dom_blob: &DomRoot<Blob>, blob_impl: BlobImpl) {
+    pub fn track_blob(&self, dom_blob: &Blob, blob_impl: BlobImpl) {
         let blob_id = blob_impl.blob_id();
 
         let blob_info = BlobInfo {
@@ -905,7 +905,7 @@ impl GlobalScope {
     }
 
     /// Start tracking a file
-    pub fn track_file(&self, file: &DomRoot<File>, blob_impl: BlobImpl) {
+    pub fn track_file(&self, file: &File, blob_impl: BlobImpl) {
         let blob_id = blob_impl.blob_id();
 
         let blob_info = BlobInfo {

components/script/dom/messageport.rs

@@ -199,7 +199,7 @@ impl Transferable for MessagePort {
 
     /// https://html.spec.whatwg.org/multipage/#message-ports:transfer-receiving-steps
     fn transfer_receive(
-        owner: &DomRoot<GlobalScope>,
+        owner: &GlobalScope,
         sc_holder: &mut StructuredDataHolder,
         extra_data: u64,
         return_object: MutableHandleObject,
@@ -249,7 +249,7 @@ impl Transferable for MessagePort {
         };
 
         let transferred_port =
-            MessagePort::new_transferred(&**owner, id.clone(), port_impl.entangled_port_id());
+            MessagePort::new_transferred(&*owner, id.clone(), port_impl.entangled_port_id());
         owner.track_message_port(&transferred_port, Some(port_impl));
 
         return_object.set(transferred_port.reflector().rootable().get());

python/tidy/servo_tidy/tidy.py

@@ -623,6 +623,7 @@ def check_rust(file_name, lines):
             (r"DomRefCell<Heap<.+>>", "Banned type DomRefCell<Heap<T>> detected. Use MutDom<T> instead", no_filter),
             # No benefit to using &Root<T>
             (r": &Root<", "use &T instead of &Root<T>", no_filter),
+            (r": &DomRoot<", "use &T instead of &DomRoot<T>", no_filter),
             (r"^&&", "operators should go at the end of the first line", no_filter),
             # This particular pattern is not reentrant-safe in script_thread.rs
             (r"match self.documents.borrow", "use a separate variable for the match expression",

python/tidy/servo_tidy_tests/rust_tidy.rs

@@ -38,7 +38,7 @@ impl test {
         }
     }
 
-    fn test_fun2(y : &String, z : &Vec<f32>, r: &Root<isize>) -> () {
+    fn test_fun2(y : &String, z : &Vec<f32>, r: &Root<isize>, s: &DomRoot<isize>) -> () {
         let x = true;
         x
             && x;

python/tidy/servo_tidy_tests/test_tidy.py

@@ -112,6 +112,7 @@ class CheckTidiness(unittest.TestCase):
         self.assertEqual('use &[T] instead of &Vec<T>', next(errors)[2])
         self.assertEqual('use &str instead of &String', next(errors)[2])
         self.assertEqual('use &T instead of &Root<T>', next(errors)[2])
+        self.assertEqual('use &T instead of &DomRoot<T>', next(errors)[2])
         self.assertEqual('encountered function signature with -> ()', next(errors)[2])
         self.assertEqual('operators should go at the end of the first line', next(errors)[2])
         self.assertNoMoreErrors(errors)