Clean up the cast calls

65 files changed, 392 insertions, 694 deletions

diff --git a/components/script/dom/activation.rs b/components/script/dom/activation.rs
index ba140a04269..bd843f557bb 100644
--- a/components/script/dom/activation.rs
+++ b/components/script/dom/activation.rs
@@ -45,7 +45,7 @@ pub trait Activatable {
         // Step 4
         // https://html.spec.whatwg.org/multipage/#fire-a-synthetic-mouse-event
         let win = window_from_node(element);
-        let target = element.upcast::<EventTarget>();
+        let target = element.upcast();
         let mouse = MouseEvent::new(win.r(), "click".to_owned(),
                                     EventBubbles::DoesNotBubble, EventCancelable::NotCancelable, Some(win.r()), 1,
                                     0, 0, 0, 0, ctrlKey, shiftKey, altKey, metaKey,
diff --git a/components/script/dom/attr.rs b/components/script/dom/attr.rs
index ffb2ed2ddd9..84dc04086f8 100644
--- a/components/script/dom/attr.rs
+++ b/components/script/dom/attr.rs
@@ -12,7 +12,6 @@ use dom::bindings::js::{JS, MutNullableHeap};
 use dom::bindings::js::{LayoutJS, Root, RootedReference};
 use dom::bindings::utils::{Reflector, reflect_dom_object};
 use dom::element::{AttributeMutation, Element};
-use dom::node::Node;
 use dom::values::UNSIGNED_LONG_MAX;
 use dom::virtualmethods::vtable_for;
 use dom::window::Window;
@@ -288,7 +287,7 @@ impl Attr {
         assert!(Some(owner) == self.owner().r());
         mem::swap(&mut *self.value.borrow_mut(), &mut value);
         if self.namespace == ns!("") {
-            vtable_for(owner.upcast::<Node>()).attribute_mutated(
+            vtable_for(owner.upcast()).attribute_mutated(
                 self, AttributeMutation::Set(Some(&value)));
         }
     }
diff --git a/components/script/dom/canvasrenderingcontext2d.rs b/components/script/dom/canvasrenderingcontext2d.rs
index 3166ef4c583..cbeb9a49137 100644
--- a/components/script/dom/canvasrenderingcontext2d.rs
+++ b/components/script/dom/canvasrenderingcontext2d.rs
@@ -147,9 +147,7 @@ impl CanvasRenderingContext2D {
     }
 
     fn mark_as_dirty(&self) {
-        let canvas = self.canvas.root();
-        let node = canvas.upcast::<Node>();
-        node.dirty(NodeDamage::OtherNodeDamage);
+        self.canvas.root().upcast::<Node>().dirty(NodeDamage::OtherNodeDamage);
     }
 
     fn update_transform(&self) {
diff --git a/components/script/dom/characterdata.rs b/components/script/dom/characterdata.rs
index 6c76adc7c28..8bc61288a0e 100644
--- a/components/script/dom/characterdata.rs
+++ b/components/script/dom/characterdata.rs
@@ -134,14 +134,12 @@ impl CharacterDataMethods for CharacterData {
 
     // https://dom.spec.whatwg.org/#dom-nondocumenttypechildnode-previouselementsibling
     fn GetPreviousElementSibling(&self) -> Option<Root<Element>> {
-        self.upcast::<Node>().preceding_siblings()
-                             .filter_map(Root::downcast::<Element>).next()
+        self.upcast::<Node>().preceding_siblings().filter_map(Root::downcast).next()
     }
 
     // https://dom.spec.whatwg.org/#dom-nondocumenttypechildnode-nextelementsibling
     fn GetNextElementSibling(&self) -> Option<Root<Element>> {
-        self.upcast::<Node>().following_siblings()
-                             .filter_map(Root::downcast::<Element>).next()
+        self.upcast::<Node>().following_siblings().filter_map(Root::downcast).next()
     }
 }
 
diff --git a/components/script/dom/create.rs b/components/script/dom/create.rs
index 6416c86dc37..bb7deafb747 100644
--- a/components/script/dom/create.rs
+++ b/components/script/dom/create.rs
@@ -89,11 +89,11 @@ pub fn create_element(name: QualName, prefix: Option<Atom>,
     macro_rules! make(
         ($ctor:ident) => ({
             let obj = $ctor::new((*name.local).to_owned(), prefix, document);
-            Root::upcast::<Element>(obj)
+            Root::upcast(obj)
         });
         ($ctor:ident, $($arg:expr),+) => ({
             let obj = $ctor::new((*name.local).to_owned(), prefix, document, $($arg),+);
-            Root::upcast::<Element>(obj)
+            Root::upcast(obj)
         })
     );
 
diff --git a/components/script/dom/cssstyledeclaration.rs b/components/script/dom/cssstyledeclaration.rs
index 7ad150e0cc2..03292d09a85 100644
--- a/components/script/dom/cssstyledeclaration.rs
+++ b/components/script/dom/cssstyledeclaration.rs
@@ -242,7 +242,7 @@ impl CSSStyleDeclarationMethods for CSSStyleDeclaration {
         }
 
         let document = document_from_node(element);
-        let node = element.upcast::<Node>();
+        let node = element.upcast();
         document.r().content_changed(node, NodeDamage::NodeStyleDamaged);
         Ok(())
     }
@@ -276,7 +276,7 @@ impl CSSStyleDeclarationMethods for CSSStyleDeclaration {
         }
 
         let document = document_from_node(element);
-        let node = element.upcast::<Node>();
+        let node = element.upcast();
         document.r().content_changed(node, NodeDamage::NodeStyleDamaged);
         Ok(())
     }
diff --git a/components/script/dom/dedicatedworkerglobalscope.rs b/components/script/dom/dedicatedworkerglobalscope.rs
index 6ec19c4a3e4..413a47bb526 100644
--- a/components/script/dom/dedicatedworkerglobalscope.rs
+++ b/components/script/dom/dedicatedworkerglobalscope.rs
@@ -15,7 +15,6 @@ use dom::bindings::js::{Root, RootCollection};
 use dom::bindings::refcounted::LiveDOMReferences;
 use dom::bindings::structuredclone::StructuredCloneData;
 use dom::bindings::utils::Reflectable;
-use dom::eventtarget::EventTarget;
 use dom::messageevent::MessageEvent;
 use dom::worker::{SimpleWorkerErrorHandler, TrustedWorkerAddress, WorkerMessageHandler};
 use dom::workerglobalscope::WorkerGlobalScope;
@@ -289,7 +288,7 @@ impl DedicatedWorkerGlobalScope {
         match msg {
             WorkerScriptMsg::DOMMessage(data) => {
                 let scope = self.upcast::<WorkerGlobalScope>();
-                let target = self.upcast::<EventTarget>();
+                let target = self.upcast();
                 let _ar = JSAutoRequest::new(scope.get_cx());
                 let _ac = JSAutoCompartment::new(scope.get_cx(), scope.reflector().get_jsobject().get());
                 let mut message = RootedValue::new(scope.get_cx(), UndefinedValue());
@@ -323,7 +322,7 @@ impl DedicatedWorkerGlobalScope {
     fn handle_event(&self, event: MixedMessage) {
         match event {
             MixedMessage::FromDevtools(msg) => {
-                let global_ref = GlobalRef::Worker(self.upcast::<WorkerGlobalScope>());
+                let global_ref = GlobalRef::Worker(self.upcast());
                 match msg {
                     DevtoolScriptControlMsg::EvaluateJS(_pipe_id, string, sender) =>
                         devtools::handle_evaluate_js(&global_ref, string, sender),
diff --git a/components/script/dom/document.rs b/components/script/dom/document.rs
index 2078c872978..835351cdc0d 100644
--- a/components/script/dom/document.rs
+++ b/components/script/dom/document.rs
@@ -290,8 +290,7 @@ impl Document {
         let base = self.upcast::<Node>()
             .traverse_preorder()
             .filter_map(Root::downcast::<HTMLBaseElement>)
-            .filter(|element| element.upcast::<Element>().has_attribute(&atom!("href")))
-            .next();
+            .find(|element| element.upcast::<Element>().has_attribute(&atom!("href")));
         self.base_element.set(base.r());
     }
 
@@ -379,10 +378,7 @@ impl Document {
                               element: &Element,
                               id: Atom) {
         debug!("Adding named element to document {:p}: {:p} id={}", self, element, id);
-        assert!({
-            let node = element.upcast::<Node>();
-            node.is_in_doc()
-        });
+        assert!(element.upcast::<Node>().is_in_doc());
         assert!(!id.is_empty());
 
         let mut idmap = self.idmap.borrow_mut();
@@ -401,7 +397,7 @@ impl Document {
                 let mut head: usize = 0;
                 let root = root.upcast::<Node>();
                 for node in root.traverse_preorder() {
-                    if let Some(elem) = node.downcast::<Element>() {
+                    if let Some(elem) = node.downcast() {
                         if (*elements)[head].root().r() == elem {
                             head += 1;
                         }
@@ -420,7 +416,7 @@ impl Document {
     /// https://html.spec.whatwg.org/multipage/#the-indicated-part-of-the-document
     pub fn find_fragment_node(&self, fragid: &str) -> Option<Root<Element>> {
         self.GetElementById(fragid.to_owned()).or_else(|| {
-            let check_anchor = |&node: &&HTMLAnchorElement| {
+            let check_anchor = |node: &HTMLAnchorElement| {
                 let elem = node.upcast::<Element>();
                 elem.get_attribute(&ns!(""), &atom!("name")).map_or(false, |attr| {
                     &**attr.r().value() == fragid
@@ -428,9 +424,9 @@ impl Document {
             };
             let doc_node = self.upcast::<Node>();
             doc_node.traverse_preorder()
-                    .filter_map(Root::downcast::<HTMLAnchorElement>)
-                    .find(|node| check_anchor(&node.r()))
-                    .map(Root::upcast::<Element>)
+                    .filter_map(Root::downcast)
+                    .find(|node| check_anchor(&node))
+                    .map(Root::upcast)
         })
     }
 
@@ -606,7 +602,7 @@ impl Document {
         match mouse_event_type {
             MouseEventType::Click => el.authentic_click_activation(event),
             _ =>  {
-                let target = node.upcast::<EventTarget>();
+                let target = node.upcast();
                 event.fire(target);
             },
         }
@@ -664,7 +660,7 @@ impl Document {
                 if target_ref.get_hover_state() {
                     target_ref.set_hover_state(false);
 
-                    let target = target_ref.upcast::<EventTarget>();
+                    let target = target_ref.upcast();
 
                     self.fire_mouse_event(point, &target, "mouseout".to_owned());
                 }
@@ -678,7 +674,7 @@ impl Document {
             if !target.get_hover_state() {
                 target.set_hover_state(true);
 
-                let target = target.upcast::<EventTarget>();
+                let target = target.upcast();
 
                 self.fire_mouse_event(point, target, "mouseover".to_owned());
 
@@ -690,7 +686,7 @@ impl Document {
             let top_most_node =
                 node::from_untrusted_node_address(js_runtime, mouse_over_addresses[0]);
 
-            let target = top_most_node.upcast::<EventTarget>();
+            let target = top_most_node.upcast();
             self.fire_mouse_event(point, target, "mousemove".to_owned());
         }
 
@@ -713,9 +709,9 @@ impl Document {
         let body = self.GetBody();
 
         let target = match (&focused, &body) {
-            (&Some(ref focused), _) => focused.upcast::<EventTarget>(),
-            (&None, &Some(ref body)) => body.upcast::<EventTarget>(),
-            (&None, &None) => self.window.upcast::<EventTarget>(),
+            (&Some(ref focused), _) => focused.upcast(),
+            (&None, &Some(ref body)) => body.upcast(),
+            (&None, &None) => self.window.upcast(),
         };
 
         let ctrl = modifiers.contains(CONTROL);
@@ -768,7 +764,7 @@ impl Document {
         // https://www.w3.org/Bugs/Public/show_bug.cgi?id=27337
         match key {
             Key::Space if !prevented && state == KeyState::Released => {
-                let maybe_elem: Option<&Element> = target.downcast::<Element>();
+                let maybe_elem = target.downcast::<Element>();
                 if let Some(el) = maybe_elem {
                     if let Some(a) = el.as_maybe_activatable() {
                         a.synthetic_click_activation(ctrl, alt, shift, meta);
@@ -776,7 +772,7 @@ impl Document {
                 }
             }
             Key::Enter if !prevented && state == KeyState::Released => {
-                let maybe_elem: Option<&Element> = target.downcast::<Element>();
+                let maybe_elem = target.downcast::<Element>();
                 if let Some(el) = maybe_elem {
                     if let Some(a) = el.as_maybe_activatable() {
                         a.implicit_submission(ctrl, alt, shift, meta);
@@ -797,7 +793,7 @@ impl Document {
             match nodes.into_iter().next().unwrap() {
                 NodeOrString::eNode(node) => Ok(node),
                 NodeOrString::eString(string) => {
-                    Ok(Root::upcast::<Node>(self.CreateTextNode(string)))
+                    Ok(Root::upcast(self.CreateTextNode(string)))
                 },
             }
         } else {
@@ -940,7 +936,8 @@ impl Document {
 
     /// Find an iframe element in the document.
     pub fn find_iframe(&self, subpage_id: SubpageId) -> Option<Root<HTMLIFrameElement>> {
-        self.upcast::<Node>().traverse_preorder()
+        self.upcast::<Node>()
+            .traverse_preorder()
             .filter_map(Root::downcast::<HTMLIFrameElement>)
             .find(|node| node.r().subpage_id() == Some(subpage_id))
     }
@@ -1073,10 +1070,7 @@ impl Document {
     }
 
     fn get_html_element(&self) -> Option<Root<HTMLHtmlElement>> {
-        self.GetDocumentElement()
-            .r()
-            .and_then(Castable::downcast::<HTMLHtmlElement>)
-            .map(Root::from_ref)
+        self.GetDocumentElement().and_then(Root::downcast)
     }
 
     /// https://html.spec.whatwg.org/multipage/#appropriate-template-contents-owner-document
@@ -1131,7 +1125,7 @@ impl DocumentMethods for Document {
         match self.get_focused_element() {
             Some(element) => Some(element),     // Step 3. and 4.
             None => match self.GetBody() {      // Step 5.
-                Some(body) => Some(Root::upcast::<Element>(body)),
+                Some(body) => Some(Root::upcast(body)),
                 None => self.GetDocumentElement(),
             }
         }
@@ -1186,32 +1180,28 @@ impl DocumentMethods for Document {
 
     // https://dom.spec.whatwg.org/#dom-document-doctype
     fn GetDoctype(&self) -> Option<Root<DocumentType>> {
-        let node = self.upcast::<Node>();
-        node.children()
-            .filter_map(|c| c.downcast::<DocumentType>().map(Root::from_ref))
-            .next()
+        self.upcast::<Node>().children().filter_map(Root::downcast).next()
     }
 
     // https://dom.spec.whatwg.org/#dom-document-documentelement
     fn GetDocumentElement(&self) -> Option<Root<Element>> {
-        let node = self.upcast::<Node>();
-        node.child_elements().next()
+        self.upcast::<Node>().child_elements().next()
     }
 
     // https://dom.spec.whatwg.org/#dom-document-getelementsbytagname
     fn GetElementsByTagName(&self, tag_name: DOMString) -> Root<HTMLCollection> {
-        HTMLCollection::by_tag_name(&self.window, self.upcast::<Node>(), tag_name)
+        HTMLCollection::by_tag_name(&self.window, self.upcast(), tag_name)
     }
 
     // https://dom.spec.whatwg.org/#dom-document-getelementsbytagnamens
     fn GetElementsByTagNameNS(&self, maybe_ns: Option<DOMString>, tag_name: DOMString)
                               -> Root<HTMLCollection> {
-        HTMLCollection::by_tag_name_ns(&self.window, self.upcast::<Node>(), tag_name, maybe_ns)
+        HTMLCollection::by_tag_name_ns(&self.window, self.upcast(), tag_name, maybe_ns)
     }
 
     // https://dom.spec.whatwg.org/#dom-document-getelementsbyclassname
     fn GetElementsByClassName(&self, classes: DOMString) -> Root<HTMLCollection> {
-        HTMLCollection::by_class_name(&self.window, self.upcast::<Node>(), classes)
+        HTMLCollection::by_class_name(&self.window, self.upcast(), classes)
     }
 
     // https://dom.spec.whatwg.org/#dom-nonelementparentnode-getelementbyid
@@ -1335,19 +1325,20 @@ impl DocumentMethods for Document {
     fn CreateEvent(&self, mut interface: DOMString) -> Fallible<Root<Event>> {
         interface.make_ascii_lowercase();
         match &*interface {
-            "uievents" | "uievent" => Ok(Root::upcast::<Event>(
-                UIEvent::new_uninitialized(&self.window))),
-            "mouseevents" | "mouseevent" => Ok(Root::upcast::<Event>(
-                MouseEvent::new_uninitialized(&self.window))),
-            "customevent" => Ok(Root::upcast::<Event>(
-                CustomEvent::new_uninitialized(GlobalRef::Window(&self.window)))),
-            "htmlevents" | "events" | "event" => Ok(Event::new_uninitialized(
-                GlobalRef::Window(&self.window))),
-            "keyboardevent" | "keyevents" => Ok(Root::upcast::<Event>(
-                KeyboardEvent::new_uninitialized(&self.window))),
-            "messageevent" => Ok(Root::upcast::<Event>(
-                MessageEvent::new_uninitialized(GlobalRef::Window(&self.window)))),
-            _ => Err(Error::NotSupported)
+            "uievents" | "uievent" =>
+                Ok(Root::upcast(UIEvent::new_uninitialized(&self.window))),
+            "mouseevents" | "mouseevent" =>
+                Ok(Root::upcast(MouseEvent::new_uninitialized(&self.window))),
+            "customevent" =>
+                Ok(Root::upcast(CustomEvent::new_uninitialized(GlobalRef::Window(&self.window)))),
+            "htmlevents" | "events" | "event" =>
+                Ok(Event::new_uninitialized(GlobalRef::Window(&self.window))),
+            "keyboardevent" | "keyevents" =>
+                Ok(Root::upcast(KeyboardEvent::new_uninitialized(&self.window))),
+            "messageevent" =>
+                Ok(Root::upcast(MessageEvent::new_uninitialized(GlobalRef::Window(&self.window)))),
+            _ =>
+                Err(Error::NotSupported),
         }
     }
 
@@ -1389,7 +1380,7 @@ impl DocumentMethods for Document {
                 // Step 2.
                 root.upcast::<Node>()
                     .traverse_preorder()
-                    .find(|node| node.r().is::<HTMLTitleElement>())
+                    .find(|node| node.is::<HTMLTitleElement>())
             }
         });
 
@@ -1423,7 +1414,7 @@ impl DocumentMethods for Document {
                     let elem = Element::create(name, None, self,
                                                ElementCreator::ScriptCreated);
                     root.upcast::<Node>()
-                        .AppendChild(elem.upcast::<Node>())
+                        .AppendChild(elem.upcast())
                         .unwrap()
                 }
             }
@@ -1440,7 +1431,7 @@ impl DocumentMethods for Document {
                             let elem = Element::create(name, None, self,
                                                        ElementCreator::ScriptCreated);
                             head.upcast::<Node>()
-                                .AppendChild(elem.upcast::<Node>())
+                                .AppendChild(elem.upcast())
                                 .unwrap()
                         },
                         None => return,
@@ -1457,10 +1448,7 @@ impl DocumentMethods for Document {
     // https://html.spec.whatwg.org/multipage/#dom-document-head
     fn GetHead(&self) -> Option<Root<HTMLHeadElement>> {
         self.get_html_element().and_then(|root| {
-            let node = root.upcast::<Node>();
-            node.children()
-                .filter_map(|c| c.downcast::<HTMLHeadElement>().map(Root::from_ref))
-                .next()
+            root.upcast::<Node>().children().filter_map(Root::downcast).next()
         })
     }
 
@@ -1479,9 +1467,7 @@ impl DocumentMethods for Document {
                     NodeTypeId::Element(ElementTypeId::HTMLElement(HTMLElementTypeId::HTMLFrameSetElement)) => true,
                     _ => false
                 }
-            }).map(|node| {
-                Root::from_ref(node.downcast::<HTMLElement>().unwrap())
-            })
+            }).map(|node| Root::downcast(node).unwrap())
         })
     }
 
@@ -1510,9 +1496,7 @@ impl DocumentMethods for Document {
             // Step 3.
             (Some(ref root), &Some(ref child)) => {
                 let root = root.upcast::<Node>();
-                let child = child.upcast::<Node>();
-                let new_body = new_body.upcast::<Node>();
-                assert!(root.ReplaceChild(new_body, child).is_ok())
+                root.ReplaceChild(new_body.upcast(), child.upcast()).unwrap();
             },
 
             // Step 4.
@@ -1521,8 +1505,7 @@ impl DocumentMethods for Document {
             // Step 5.
             (Some(ref root), &None) => {
                 let root = root.upcast::<Node>();
-                let new_body = new_body.upcast::<Node>();
-                assert!(root.AppendChild(new_body).is_ok());
+                root.AppendChild(new_body.upcast()).unwrap();
             }
         }
         Ok(())
@@ -1547,18 +1530,16 @@ impl DocumentMethods for Document {
     // https://html.spec.whatwg.org/multipage/#dom-document-images
     fn Images(&self) -> Root<HTMLCollection> {
         self.images.or_init(|| {
-            let root = self.upcast::<Node>();
             let filter = box ImagesFilter;
-            HTMLCollection::create(&self.window, root, filter)
+            HTMLCollection::create(&self.window, self.upcast(), filter)
         })
     }
 
     // https://html.spec.whatwg.org/multipage/#dom-document-embeds
     fn Embeds(&self) -> Root<HTMLCollection> {
         self.embeds.or_init(|| {
-            let root = self.upcast::<Node>();
             let filter = box EmbedsFilter;
-            HTMLCollection::create(&self.window, root, filter)
+            HTMLCollection::create(&self.window, self.upcast(), filter)
         })
     }
 
@@ -1570,36 +1551,32 @@ impl DocumentMethods for Document {
     // https://html.spec.whatwg.org/multipage/#dom-document-links
     fn Links(&self) -> Root<HTMLCollection> {
         self.links.or_init(|| {
-            let root = self.upcast::<Node>();
             let filter = box LinksFilter;
-            HTMLCollection::create(&self.window, root, filter)
+            HTMLCollection::create(&self.window, self.upcast(), filter)
         })
     }
 
     // https://html.spec.whatwg.org/multipage/#dom-document-forms
     fn Forms(&self) -> Root<HTMLCollection> {
         self.forms.or_init(|| {
-            let root = self.upcast::<Node>();
             let filter = box FormsFilter;
-            HTMLCollection::create(&self.window, root, filter)
+            HTMLCollection::create(&self.window, self.upcast(), filter)
         })
     }
 
     // https://html.spec.whatwg.org/multipage/#dom-document-scripts
     fn Scripts(&self) -> Root<HTMLCollection> {
         self.scripts.or_init(|| {
-            let root = self.upcast::<Node>();
             let filter = box ScriptsFilter;
-            HTMLCollection::create(&self.window, root, filter)
+            HTMLCollection::create(&self.window, self.upcast(), filter)
         })
     }
 
     // https://html.spec.whatwg.org/multipage/#dom-document-anchors
     fn Anchors(&self) -> Root<HTMLCollection> {
         self.anchors.or_init(|| {
-            let root = self.upcast::<Node>();
             let filter = box AnchorsFilter;
-            HTMLCollection::create(&self.window, root, filter)
+            HTMLCollection::create(&self.window, self.upcast(), filter)
         })
     }
 
@@ -1607,9 +1584,8 @@ impl DocumentMethods for Document {
     fn Applets(&self) -> Root<HTMLCollection> {
         // FIXME: This should be return OBJECT elements containing applets.
         self.applets.or_init(|| {
-            let root = self.upcast::<Node>();
             let filter = box AppletsFilter;
-            HTMLCollection::create(&self.window, root, filter)
+            HTMLCollection::create(&self.window, self.upcast(), filter)
         })
     }
 
@@ -1620,7 +1596,7 @@ impl DocumentMethods for Document {
 
     // https://dom.spec.whatwg.org/#dom-parentnode-children
     fn Children(&self) -> Root<HTMLCollection> {
-        HTMLCollection::children(&self.window, self.upcast::<Node>())
+        HTMLCollection::children(&self.window, self.upcast())
     }
 
     // https://dom.spec.whatwg.org/#dom-parentnode-firstelementchild
@@ -1630,7 +1606,7 @@ impl DocumentMethods for Document {
 
     // https://dom.spec.whatwg.org/#dom-parentnode-lastelementchild
     fn GetLastElementChild(&self) -> Option<Root<Element>> {
-        self.upcast::<Node>().rev_children().filter_map(Root::downcast::<Element>).next()
+        self.upcast::<Node>().rev_children().filter_map(Root::downcast).next()
     }
 
     // https://dom.spec.whatwg.org/#dom-parentnode-childelementcount
@@ -1713,7 +1689,7 @@ impl DocumentMethods for Document {
         }
         impl CollectionFilter for NamedElementFilter {
             fn filter(&self, elem: &Element, _root: &Node) -> bool {
-                filter_by_name(&self.name, elem.upcast::<Node>())
+                filter_by_name(&self.name, elem.upcast())
             }
         }
         // https://html.spec.whatwg.org/multipage/#dom-document-nameditem-filter
@@ -1866,9 +1842,8 @@ impl DocumentProgressHandler {
                                EventBubbles::DoesNotBubble,
                                EventCancelable::NotCancelable);
         let wintarget = window.upcast::<EventTarget>();
-        let doctarget = document.upcast::<EventTarget>();
         event.r().set_trusted(true);
-        let _ = wintarget.dispatch_event_with_target(doctarget, event.r());
+        let _ = wintarget.dispatch_event_with_target(document.upcast(), &event);
 
         let browsing_context = window.browsing_context();
         let browsing_context = browsing_context.as_ref().unwrap();
@@ -1878,8 +1853,7 @@ impl DocumentProgressHandler {
             let event = Event::new(GlobalRef::Window(frame_window.r()), "load".to_owned(),
                                    EventBubbles::DoesNotBubble,
                                    EventCancelable::NotCancelable);
-            let target = frame_element.upcast::<EventTarget>();
-            event.r().fire(target);
+            event.fire(frame_element.upcast());
         };
 
         document.r().notify_constellation_load();
diff --git a/components/script/dom/documentfragment.rs b/components/script/dom/documentfragment.rs
index 3a5a1800e91..26a0259fab9 100644
--- a/components/script/dom/documentfragment.rs
+++ b/components/script/dom/documentfragment.rs
@@ -48,7 +48,7 @@ impl DocumentFragmentMethods for DocumentFragment {
     // https://dom.spec.whatwg.org/#dom-parentnode-children
     fn Children(&self) -> Root<HTMLCollection> {
         let window = window_from_node(self);
-        HTMLCollection::children(window.r(), self.upcast::<Node>())
+        HTMLCollection::children(&window, self.upcast())
     }
 
     // https://dom.spec.whatwg.org/#dom-nonelementparentnode-getelementbyid
@@ -90,13 +90,11 @@ impl DocumentFragmentMethods for DocumentFragment {
 
     // https://dom.spec.whatwg.org/#dom-parentnode-queryselector
     fn QuerySelector(&self, selectors: DOMString) -> Fallible<Option<Root<Element>>> {
-        let root = self.upcast::<Node>();
-        root.query_selector(selectors)
+        self.upcast::<Node>().query_selector(selectors)
     }
 
     // https://dom.spec.whatwg.org/#dom-parentnode-queryselectorall
     fn QuerySelectorAll(&self, selectors: DOMString) -> Fallible<Root<NodeList>> {
-        let root = self.upcast::<Node>();
-        root.query_selector_all(selectors)
+        self.upcast::<Node>().query_selector_all(selectors)
     }
 }
diff --git a/components/script/dom/documenttype.rs b/components/script/dom/documenttype.rs
index 590baf4a576..1d72d783e7e 100644
--- a/components/script/dom/documenttype.rs
+++ b/components/script/dom/documenttype.rs
@@ -98,7 +98,6 @@ impl DocumentTypeMethods for DocumentType {
 
     // https://dom.spec.whatwg.org/#dom-childnode-remove
     fn Remove(&self) {
-        let node = self.upcast::<Node>();
-        node.remove_self();
+        self.upcast::<Node>().remove_self();
     }
 }
diff --git a/components/script/dom/domimplementation.rs b/components/script/dom/domimplementation.rs
index af94a32b854..02c8ad4fa84 100644
--- a/components/script/dom/domimplementation.rs
+++ b/components/script/dom/domimplementation.rs
@@ -80,20 +80,13 @@ impl DOMImplementationMethods for DOMImplementation {
             let doc_node = doc.upcast::<Node>();
 
             // Step 4.
-            match maybe_doctype {
-                None => (),
-                Some(ref doctype) => {
-                    let doc_type = doctype.upcast::<Node>();
-                    assert!(doc_node.AppendChild(doc_type).is_ok())
-                }
+            if let Some(doc_type) = maybe_doctype {
+                doc_node.AppendChild(doc_type.upcast()).unwrap();
             }
 
             // Step 5.
-            match maybe_elem {
-                None => (),
-                Some(ref elem) => {
-                    assert!(doc_node.AppendChild(elem.upcast::<Node>()).is_ok())
-                }
+            if let Some(ref elem) = maybe_elem {
+                doc_node.AppendChild(elem.upcast()).unwrap();
             }
         }
 
@@ -117,7 +110,7 @@ impl DOMImplementationMethods for DOMImplementation {
             // Step 3.
             let doc_node = doc.upcast::<Node>();
             let doc_type = DocumentType::new("html".to_owned(), None, None, doc.r());
-            assert!(doc_node.AppendChild(doc_type.upcast::<Node>()).is_ok());
+            doc_node.AppendChild(doc_type.upcast()).unwrap();
         }
 
         {
@@ -125,13 +118,13 @@ impl DOMImplementationMethods for DOMImplementation {
             let doc_node = doc.upcast::<Node>();
             let doc_html = Root::upcast::<Node>(
                 HTMLHtmlElement::new("html".to_owned(), None, doc.r()));
-            assert!(doc_node.AppendChild(doc_html.r()).is_ok());
+            doc_node.AppendChild(&doc_html).expect("Appending failed");
 
             {
                 // Step 5.
                 let doc_head = Root::upcast::<Node>(
                     HTMLHeadElement::new("head".to_owned(), None, doc.r()));
-                assert!(doc_html.r().AppendChild(doc_head.r()).is_ok());
+                doc_html.AppendChild(&doc_head).unwrap();
 
                 // Step 6.
                 match title {
@@ -140,18 +133,18 @@ impl DOMImplementationMethods for DOMImplementation {
                         // Step 6.1.
                         let doc_title = Root::upcast::<Node>(
                             HTMLTitleElement::new("title".to_owned(), None, doc.r()));
-                        assert!(doc_head.r().AppendChild(doc_title.r()).is_ok());
+                        doc_head.AppendChild(&doc_title).unwrap();
 
                         // Step 6.2.
                         let title_text = Text::new(title_str, doc.r());
-                        assert!(doc_title.r().AppendChild(title_text.upcast::<Node>()).is_ok());
+                        doc_title.AppendChild(title_text.upcast()).unwrap();
                     }
                 }
             }
 
             // Step 7.
             let doc_body = HTMLBodyElement::new("body".to_owned(), None, doc.r());
-            assert!(doc_html.r().AppendChild(doc_body.upcast::<Node>()).is_ok());
+            doc_html.AppendChild(doc_body.upcast()).unwrap();
         }
 
         // Step 8.
diff --git a/components/script/dom/element.rs b/components/script/dom/element.rs
index 52f2bbc5423..f0d078fbaf1 100644
--- a/components/script/dom/element.rs
+++ b/components/script/dom/element.rs
@@ -35,7 +35,6 @@ use dom::domrect::DOMRect;
 use dom::domrectlist::DOMRectList;
 use dom::domtokenlist::DOMTokenList;
 use dom::event::Event;
-use dom::eventtarget::EventTarget;
 use dom::htmlanchorelement::HTMLAnchorElement;
 use dom::htmlbodyelement::HTMLBodyElement;
 use dom::htmlcollection::HTMLCollection;
@@ -544,8 +543,7 @@ impl LayoutElementHelpers for LayoutJS<Element> {
         if (*self.unsafe_get()).namespace != ns!(HTML) {
             return false
         }
-        let node = self.upcast::<Node>();
-        node.owner_doc_for_layout().is_html_document_for_layout()
+        self.upcast::<Node>().owner_doc_for_layout().is_html_document_for_layout()
     }
 
     #[allow(unsafe_code)]
@@ -623,8 +621,7 @@ pub enum StylePriority {
 
 impl Element {
     pub fn html_element_in_html_document(&self) -> bool {
-        let node = self.upcast::<Node>();
-        self.namespace == ns!(HTML) && node.is_in_html_doc()
+        self.namespace == ns!(HTML) && self.upcast::<Node>().is_in_html_doc()
     }
 
     pub fn local_name(&self) -> &Atom {
@@ -784,9 +781,8 @@ impl Element {
     }
 
     pub fn serialize(&self, traversal_scope: TraversalScope) -> Fallible<DOMString> {
-        let node = self.upcast::<Node>();
         let mut writer = vec![];
-        match serialize(&mut writer, &node,
+        match serialize(&mut writer, &self.upcast::<Node>(),
                         SerializeOpts {
                             traversal_scope: traversal_scope,
                             .. Default::default()
@@ -798,10 +794,7 @@ impl Element {
 
     // https://html.spec.whatwg.org/multipage/#root-element
     pub fn get_root_element(&self) -> Root<Element> {
-        let node = self.upcast::<Node>();
-        node.inclusive_ancestors()
-            .filter_map(Root::downcast::<Element>)
-            .last()
+        self.upcast::<Node>().inclusive_ancestors().filter_map(Root::downcast).last()
             .expect("We know inclusive_ancestors will return `self` which is an element")
     }
 
@@ -889,8 +882,7 @@ impl Element {
         let attr = Attr::new(&window, local_name, value, name, namespace, prefix, Some(self));
         self.attrs.borrow_mut().push(JS::from_rooted(&attr));
         if in_empty_ns {
-            vtable_for(self.upcast::<Node>()).attribute_mutated(
-                &attr, AttributeMutation::Set(None));
+            vtable_for(self.upcast()).attribute_mutated(&attr, AttributeMutation::Set(None));
         }
     }
 
@@ -974,8 +966,7 @@ impl Element {
     pub fn parse_attribute(&self, namespace: &Namespace, local_name: &Atom,
                        value: DOMString) -> AttrValue {
         if *namespace == ns!("") {
-            vtable_for(&self.upcast::<Node>())
-                .parse_plain_attribute(local_name, value)
+            vtable_for(self.upcast()).parse_plain_attribute(local_name, value)
         } else {
             AttrValue::String(value)
         }
@@ -1001,20 +992,15 @@ impl Element {
             let attr = (*self.attrs.borrow())[idx].root();
             self.attrs.borrow_mut().remove(idx);
             attr.set_owner(None);
-            let node = self.upcast::<Node>();
             if attr.namespace() == &ns!("") {
-                vtable_for(node).attribute_mutated(&attr, AttributeMutation::Removed);
+                vtable_for(self.upcast()).attribute_mutated(&attr, AttributeMutation::Removed);
             }
             attr
         })
     }
 
     pub fn has_class(&self, name: &Atom) -> bool {
-        let quirks_mode = {
-            let node = self.upcast::<Node>();
-            let owner_doc = node.owner_doc();
-            owner_doc.r().quirks_mode()
-        };
+        let quirks_mode = document_from_node(self).quirks_mode();
         let is_equal = |lhs: &Atom, rhs: &Atom| match quirks_mode {
             NoQuirks | LimitedQuirks => lhs == rhs,
             Quirks => lhs.eq_ignore_ascii_case(&rhs)
@@ -1175,14 +1161,7 @@ impl ElementMethods for Element {
 
     // https://dom.spec.whatwg.org/#dom-element-attributes
     fn Attributes(&self) -> Root<NamedNodeMap> {
-        self.attr_list.or_init(|| {
-            let doc = {
-                let node = self.upcast::<Node>();
-                node.owner_doc()
-            };
-            let window = doc.r().window();
-            NamedNodeMap::new(window, self)
-        })
+        self.attr_list.or_init(|| NamedNodeMap::new(&window_from_node(self), self))
     }
 
     // https://dom.spec.whatwg.org/#dom-element-getattribute
@@ -1277,27 +1256,26 @@ impl ElementMethods for Element {
     // https://dom.spec.whatwg.org/#dom-element-getelementsbytagname
     fn GetElementsByTagName(&self, localname: DOMString) -> Root<HTMLCollection> {
         let window = window_from_node(self);
-        HTMLCollection::by_tag_name(window.r(), self.upcast::<Node>(), localname)
+        HTMLCollection::by_tag_name(window.r(), self.upcast(), localname)
     }
 
     // https://dom.spec.whatwg.org/#dom-element-getelementsbytagnamens
     fn GetElementsByTagNameNS(&self, maybe_ns: Option<DOMString>,
                               localname: DOMString) -> Root<HTMLCollection> {
         let window = window_from_node(self);
-        HTMLCollection::by_tag_name_ns(window.r(), self.upcast::<Node>(), localname, maybe_ns)
+        HTMLCollection::by_tag_name_ns(window.r(), self.upcast(), localname, maybe_ns)
     }
 
     // https://dom.spec.whatwg.org/#dom-element-getelementsbyclassname
     fn GetElementsByClassName(&self, classes: DOMString) -> Root<HTMLCollection> {
         let window = window_from_node(self);
-        HTMLCollection::by_class_name(window.r(), self.upcast::<Node>(), classes)
+        HTMLCollection::by_class_name(window.r(), self.upcast(), classes)
     }
 
     // https://drafts.csswg.org/cssom-view/#dom-element-getclientrects
     fn GetClientRects(&self) -> Root<DOMRectList> {
         let win = window_from_node(self);
-        let node = self.upcast::<Node>();
-        let raw_rects = node.get_content_boxes();
+        let raw_rects = self.upcast::<Node>().get_content_boxes();
         let rects = raw_rects.iter().map(|rect| {
             DOMRect::new(GlobalRef::Window(win.r()),
                          rect.origin.x.to_f64_px(),
@@ -1311,8 +1289,7 @@ impl ElementMethods for Element {
     // https://drafts.csswg.org/cssom-view/#dom-element-getboundingclientrect
     fn GetBoundingClientRect(&self) -> Root<DOMRect> {
         let win = window_from_node(self);
-        let node = self.upcast::<Node>();
-        let rect = node.get_bounding_content_box();
+        let rect = self.upcast::<Node>().get_bounding_content_box();
         DOMRect::new(GlobalRef::Window(win.r()),
                      rect.origin.x.to_f64_px(),
                      rect.origin.y.to_f64_px(),
@@ -1322,26 +1299,22 @@ impl ElementMethods for Element {
 
     // https://drafts.csswg.org/cssom-view/#dom-element-clienttop
     fn ClientTop(&self) -> i32 {
-        let node = self.upcast::<Node>();
-        node.get_client_rect().origin.y
+        self.upcast::<Node>().get_client_rect().origin.y
     }
 
     // https://drafts.csswg.org/cssom-view/#dom-element-clientleft
     fn ClientLeft(&self) -> i32 {
-        let node = self.upcast::<Node>();
-        node.get_client_rect().origin.x
+        self.upcast::<Node>().get_client_rect().origin.x
     }
 
     // https://drafts.csswg.org/cssom-view/#dom-element-clientwidth
     fn ClientWidth(&self) -> i32 {
-        let node = self.upcast::<Node>();
-        node.get_client_rect().size.width
+        self.upcast::<Node>().get_client_rect().size.width
     }
 
     // https://drafts.csswg.org/cssom-view/#dom-element-clientheight
     fn ClientHeight(&self) -> i32 {
-        let node = self.upcast::<Node>();
-        node.get_client_rect().size.height
+        self.upcast::<Node>().get_client_rect().size.height
     }
 
     /// https://w3c.github.io/DOM-Parsing/#widl-Element-innerHTML
@@ -1358,11 +1331,11 @@ impl ElementMethods for Element {
         // Step 2.
         // https://github.com/w3c/DOM-Parsing/issues/1
         let target = if let Some(template) = self.downcast::<HTMLTemplateElement>() {
-            Root::upcast::<Node>(template.Content())
+            Root::upcast(template.Content())
         } else {
             Root::from_ref(context_node)
         };
-        Node::replace_all(Some(frag.upcast::<Node>()), &target);
+        Node::replace_all(Some(frag.upcast()), &target);
         Ok(())
     }
 
@@ -1393,7 +1366,7 @@ impl ElementMethods for Element {
                 let body_elem = Element::create(QualName::new(ns!(HTML), atom!(body)),
                                                 None, context_document.r(),
                                                 ElementCreator::ScriptCreated);
-                Root::upcast::<Node>(body_elem)
+                Root::upcast(body_elem)
             },
             _ => context_node.GetParentNode().unwrap()
         };
@@ -1401,27 +1374,24 @@ impl ElementMethods for Element {
         // Step 5.
         let frag = try!(parent.r().parse_fragment(value));
         // Step 6.
-        try!(context_parent.r().ReplaceChild(frag.upcast::<Node>(),
-                                             context_node));
+        try!(context_parent.ReplaceChild(frag.upcast(), context_node));
         Ok(())
     }
 
     // https://dom.spec.whatwg.org/#dom-nondocumenttypechildnode-previouselementsibling
     fn GetPreviousElementSibling(&self) -> Option<Root<Element>> {
-        self.upcast::<Node>().preceding_siblings()
-                             .filter_map(Root::downcast::<Element>).next()
+        self.upcast::<Node>().preceding_siblings().filter_map(Root::downcast).next()
     }
 
     // https://dom.spec.whatwg.org/#dom-nondocumenttypechildnode-nextelementsibling
     fn GetNextElementSibling(&self) -> Option<Root<Element>> {
-        self.upcast::<Node>().following_siblings()
-                             .filter_map(Root::downcast::<Element>).next()
+        self.upcast::<Node>().following_siblings().filter_map(Root::downcast).next()
     }
 
     // https://dom.spec.whatwg.org/#dom-parentnode-children
     fn Children(&self) -> Root<HTMLCollection> {
         let window = window_from_node(self);
-        HTMLCollection::children(window.r(), self.upcast::<Node>())
+        HTMLCollection::children(window.r(), self.upcast())
     }
 
     // https://dom.spec.whatwg.org/#dom-parentnode-firstelementchild
@@ -1478,8 +1448,7 @@ impl ElementMethods for Element {
 
     // https://dom.spec.whatwg.org/#dom-childnode-remove
     fn Remove(&self) {
-        let node = self.upcast::<Node>();
-        node.remove_self();
+        self.upcast::<Node>().remove_self();
     }
 
     // https://dom.spec.whatwg.org/#dom-element-matches
@@ -1513,8 +1482,7 @@ impl ElementMethods for Element {
 
 impl VirtualMethods for Element {
     fn super_type(&self) -> Option<&VirtualMethods> {
-        let node: &Node = self.upcast::<Node>();
-        Some(node as &VirtualMethods)
+        Some(self.upcast::<Node>() as &VirtualMethods)
     }
 
     fn attribute_mutated(&self, attr: &Attr, mutation: AttributeMutation) {
@@ -1620,15 +1588,15 @@ impl<'a> ::selectors::Element for Root<Element> {
     }
 
     fn last_child_element(&self) -> Option<Root<Element>> {
-        self.node.rev_children().filter_map(Root::downcast::<Element>).next()
+        self.node.rev_children().filter_map(Root::downcast).next()
     }
 
     fn prev_sibling_element(&self) -> Option<Root<Element>> {
-        self.node.preceding_siblings().filter_map(Root::downcast::<Element>).next()
+        self.node.preceding_siblings().filter_map(Root::downcast).next()
     }
 
     fn next_sibling_element(&self) -> Option<Root<Element>> {
-        self.node.following_siblings().filter_map(Root::downcast::<Element>).next()
+        self.node.following_siblings().filter_map(Root::downcast).next()
     }
 
     fn is_root(&self) -> bool {
@@ -1701,15 +1669,13 @@ impl<'a> ::selectors::Element for Root<Element> {
         Element::get_enabled_state(self)
     }
     fn get_checked_state(&self) -> bool {
-        let input_element: Option<&HTMLInputElement> = self.downcast::<HTMLInputElement>();
-        match input_element {
+        match self.downcast::<HTMLInputElement>() {
             Some(input) => input.Checked(),
             None => false,
         }
     }
     fn get_indeterminate_state(&self) -> bool {
-        let input_element: Option<&HTMLInputElement> = self.downcast::<HTMLInputElement>();
-        match input_element {
+        match self.downcast::<HTMLInputElement>() {
             Some(input) => input.get_indeterminate_state(),
             None => false,
         }
@@ -1729,8 +1695,7 @@ impl<'a> ::selectors::Element for Root<Element> {
         }
     }
     fn has_servo_nonzero_border(&self) -> bool {
-        let table_element: Option<&HTMLTableElement> = self.downcast::<HTMLTableElement>();
-        match table_element {
+        match self.downcast::<HTMLTableElement>() {
             None => false,
             Some(this) => {
                 match this.get_border() {
@@ -1774,8 +1739,7 @@ impl<'a> ::selectors::Element for Root<Element> {
 
 impl Element {
     pub fn as_maybe_activatable(&self) -> Option<&Activatable> {
-        let node = self.upcast::<Node>();
-        let element = match node.type_id() {
+        let element = match self.upcast::<Node>().type_id() {
             NodeTypeId::Element(ElementTypeId::HTMLElement(HTMLElementTypeId::HTMLInputElement)) => {
                 let element = self.downcast::<HTMLInputElement>().unwrap();
                 Some(element as &Activatable)
@@ -1798,13 +1762,11 @@ impl Element {
     }
 
     pub fn click_in_progress(&self) -> bool {
-        let node = self.upcast::<Node>();
-        node.get_flag(CLICK_IN_PROGRESS)
+        self.upcast::<Node>().get_flag(CLICK_IN_PROGRESS)
     }
 
     pub fn set_click_in_progress(&self, click: bool) {
-        let node = self.upcast::<Node>();
-        node.set_flag(CLICK_IN_PROGRESS, click)
+        self.upcast::<Node>().set_flag(CLICK_IN_PROGRESS, click)
     }
 
     // https://html.spec.whatwg.org/multipage/#nearest-activatable-element
@@ -1838,7 +1800,7 @@ impl Element {
         // the script can generate more click events from the handler)
         assert!(!self.click_in_progress());
 
-        let target = self.upcast::<EventTarget>();
+        let target = self.upcast();
         // Step 2 (requires canvas support)
         // Step 3
         self.set_click_in_progress(true);
diff --git a/components/script/dom/eventdispatcher.rs b/components/script/dom/eventdispatcher.rs
index 9df978fa589..2b0e1942843 100644
--- a/components/script/dom/eventdispatcher.rs
+++ b/components/script/dom/eventdispatcher.rs
@@ -150,8 +150,7 @@ pub fn dispatch_event(target: &EventTarget, pseudo_target: Option<&EventTarget>,
     let mut chain: RootedVec<JS<EventTarget>> = RootedVec::new();
     if let Some(target_node) = target.downcast::<Node>() {
         for ancestor in target_node.ancestors() {
-            let ancestor_target = ancestor.upcast::<EventTarget>();
-            chain.push(JS::from_ref(ancestor_target))
+            chain.push(JS::from_ref(ancestor.upcast()));
         }
     }
 
@@ -161,13 +160,9 @@ pub fn dispatch_event(target: &EventTarget, pseudo_target: Option<&EventTarget>,
     let target = event.GetTarget();
     match target {
         Some(ref target) => {
-            let node: Option<&Node> = target.downcast::<Node>();
-            match node {
-                Some(node) => {
-                    let vtable = vtable_for(&node);
-                    vtable.handle_event(event);
-                }
-                None => {}
+            if let Some(node) = target.downcast::<Node>() {
+                let vtable = vtable_for(&node);
+                vtable.handle_event(event);
             }
         }
         None => {}
diff --git a/components/script/dom/filereader.rs b/components/script/dom/filereader.rs
index 547234101d1..4e17f6dd62e 100644
--- a/components/script/dom/filereader.rs
+++ b/components/script/dom/filereader.rs
@@ -324,10 +324,7 @@ impl FileReader {
         let progressevent = ProgressEvent::new(global.r(),
             type_, EventBubbles::DoesNotBubble, EventCancelable::NotCancelable,
             total.is_some(), loaded, total.unwrap_or(0));
-
-        let target = self.upcast::<EventTarget>();
-        let event = progressevent.upcast::<Event>();
-        event.fire(target);
+        progressevent.upcast::<Event>().fire(self.upcast());
     }
 
     fn terminate_ongoing_reading(&self) {
diff --git a/components/script/dom/formdata.rs b/components/script/dom/formdata.rs
index a70387dabe1..a51e058b864 100644
--- a/components/script/dom/formdata.rs
+++ b/components/script/dom/formdata.rs
@@ -116,7 +116,7 @@ impl FormDataMethods for FormData {
 impl FormData {
     fn get_file_from_blob(&self, value: &Blob, filename: Option<DOMString>) -> Root<File> {
         let global = self.global.root();
-        let f: Option<&File> = value.downcast::<File>();
+        let f = value.downcast::<File>();
         let name = filename.unwrap_or(f.map(|inner| inner.name().clone()).unwrap_or("blob".to_owned()));
         File::new(global.r(), value, name)
     }
diff --git a/components/script/dom/htmlanchorelement.rs b/components/script/dom/htmlanchorelement.rs
index dd1c88e16e6..a269dd948fc 100644
--- a/components/script/dom/htmlanchorelement.rs
+++ b/components/script/dom/htmlanchorelement.rs
@@ -56,8 +56,7 @@ impl HTMLAnchorElement {
 
 impl VirtualMethods for HTMLAnchorElement {
     fn super_type(&self) -> Option<&VirtualMethods> {
-        let htmlelement: &HTMLElement = self.upcast::<HTMLElement>();
-        Some(htmlelement as &VirtualMethods)
+        Some(self.upcast::<HTMLElement>() as &VirtualMethods)
     }
 
     fn parse_plain_attribute(&self, name: &Atom, value: DOMString) -> AttrValue {
@@ -71,20 +70,18 @@ impl VirtualMethods for HTMLAnchorElement {
 impl HTMLAnchorElementMethods for HTMLAnchorElement {
     // https://html.spec.whatwg.org/multipage/#dom-a-text
     fn Text(&self) -> DOMString {
-        let node = self.upcast::<Node>();
-        node.GetTextContent().unwrap()
+        self.upcast::<Node>().GetTextContent().unwrap()
     }
 
     // https://html.spec.whatwg.org/multipage/#dom-a-text
     fn SetText(&self, value: DOMString) {
-        let node = self.upcast::<Node>();
-        node.SetTextContent(Some(value))
+        self.upcast::<Node>().SetTextContent(Some(value))
     }
 
     // https://html.spec.whatwg.org/multipage/#dom-a-rellist
     fn RelList(&self) -> Root<DOMTokenList> {
         self.rel_list.or_init(|| {
-            DOMTokenList::new(self.upcast::<Element>(), &atom!("rel"))
+            DOMTokenList::new(self.upcast(), &atom!("rel"))
         })
     }
 
diff --git a/components/script/dom/htmlareaelement.rs b/components/script/dom/htmlareaelement.rs
index 274d5ce89f0..c9023bdbb23 100644
--- a/components/script/dom/htmlareaelement.rs
+++ b/components/script/dom/htmlareaelement.rs
@@ -10,7 +10,6 @@ use dom::bindings::js::{JS, MutNullableHeap, Root};
 use dom::bindings::utils::Reflectable;
 use dom::document::Document;
 use dom::domtokenlist::DOMTokenList;
-use dom::element::Element;
 use dom::htmlelement::HTMLElement;
 use dom::node::Node;
 use dom::virtualmethods::VirtualMethods;
@@ -43,8 +42,7 @@ impl HTMLAreaElement {
 
 impl VirtualMethods for HTMLAreaElement {
     fn super_type(&self) -> Option<&VirtualMethods> {
-        let htmlelement: &HTMLElement = self.upcast::<HTMLElement>();
-        Some(htmlelement as &VirtualMethods)
+        Some(self.upcast::<HTMLElement>() as &VirtualMethods)
     }
 
     fn parse_plain_attribute(&self, name: &Atom, value: DOMString) -> AttrValue {
@@ -59,7 +57,7 @@ impl HTMLAreaElementMethods for HTMLAreaElement {
     // https://html.spec.whatwg.org/multipage/#dom-area-rellist
     fn RelList(&self) -> Root<DOMTokenList> {
         self.rel_list.or_init(|| {
-            DOMTokenList::new(self.upcast::<Element>(), &atom!("rel"))
+            DOMTokenList::new(self.upcast(), &atom!("rel"))
         })
     }
 }
diff --git a/components/script/dom/htmlbodyelement.rs b/components/script/dom/htmlbodyelement.rs
index 6cef068716f..4b639d0ed42 100644
--- a/components/script/dom/htmlbodyelement.rs
+++ b/components/script/dom/htmlbodyelement.rs
@@ -124,8 +124,7 @@ impl HTMLBodyElement {
 
 impl VirtualMethods for HTMLBodyElement {
     fn super_type(&self) -> Option<&VirtualMethods> {
-        let element: &HTMLElement = self.upcast::<HTMLElement>();
-        Some(element as &VirtualMethods)
+        Some(self.upcast::<HTMLElement>() as &VirtualMethods)
     }
 
     fn bind_to_tree(&self, tree_in_doc: bool) {
diff --git a/components/script/dom/htmlbuttonelement.rs b/components/script/dom/htmlbuttonelement.rs
index 8f9c2bf420e..5146c7e4888 100644
--- a/components/script/dom/htmlbuttonelement.rs
+++ b/components/script/dom/htmlbuttonelement.rs
@@ -82,8 +82,7 @@ impl HTMLButtonElementMethods for HTMLButtonElement {
 
     // https://html.spec.whatwg.org/multipage/#dom-button-type
     fn Type(&self) -> DOMString {
-        let elem = self.upcast::<Element>();
-        let mut ty = elem.get_string_attribute(&atom!("type"));
+        let mut ty = self.upcast::<Element>().get_string_attribute(&atom!("type"));
         ty.make_ascii_lowercase();
         // https://html.spec.whatwg.org/multipage/#attr-button-type
         match &*ty {
@@ -135,8 +134,7 @@ impl HTMLButtonElementMethods for HTMLButtonElement {
 
 impl VirtualMethods for HTMLButtonElement {
     fn super_type(&self) -> Option<&VirtualMethods> {
-        let htmlelement: &HTMLElement = self.upcast::<HTMLElement>();
-        Some(htmlelement as &VirtualMethods)
+        Some(self.upcast::<HTMLElement>() as &VirtualMethods)
     }
 
     fn attribute_mutated(&self, attr: &Attr, mutation: AttributeMutation) {
@@ -166,8 +164,7 @@ impl VirtualMethods for HTMLButtonElement {
             s.bind_to_tree(tree_in_doc);
         }
 
-        let el = self.upcast::<Element>();
-        el.check_ancestors_disabled_state_for_form_control();
+        self.upcast::<Element>().check_ancestors_disabled_state_for_form_control();
     }
 
     fn unbind_from_tree(&self, tree_in_doc: bool) {
@@ -189,13 +186,12 @@ impl FormControl for HTMLButtonElement {}
 
 impl<'a> Activatable for &'a HTMLButtonElement {
     fn as_element(&self) -> &Element {
-        self.upcast::<Element>()
+        self.upcast()
     }
 
     fn is_instance_activatable(&self) -> bool {
         //https://html.spec.whatwg.org/multipage/#the-button-element
-        let el = self.upcast::<Element>();
-        !(el.get_disabled_state())
+        !self.upcast::<Element>().get_disabled_state()
     }
 
     // https://html.spec.whatwg.org/multipage/#run-pre-click-activation-steps
@@ -228,8 +224,7 @@ impl<'a> Activatable for &'a HTMLButtonElement {
         let doc = document_from_node(*self);
         let node = doc.upcast::<Node>();
         let owner = self.form_owner();
-        let elem = self.upcast::<Element>();
-        if owner.is_none() || elem.click_in_progress() {
+        if owner.is_none() || self.upcast::<Element>().click_in_progress() {
             return;
         }
         node.query_selector_iter("button[type=submit]".to_owned()).unwrap()
diff --git a/components/script/dom/htmlcanvaselement.rs b/components/script/dom/htmlcanvaselement.rs
index 75d2a4151e0..38f06faf4c7 100644
--- a/components/script/dom/htmlcanvaselement.rs
+++ b/components/script/dom/htmlcanvaselement.rs
@@ -225,8 +225,7 @@ impl HTMLCanvasElementMethods for HTMLCanvasElement {
 
     // https://html.spec.whatwg.org/multipage/#dom-canvas-width
     fn SetWidth(&self, width: u32) {
-        let elem = self.upcast::<Element>();
-        elem.set_uint_attribute(&atom!("width"), width)
+        self.upcast::<Element>().set_uint_attribute(&atom!("width"), width)
     }
 
     // https://html.spec.whatwg.org/multipage/#dom-canvas-height
@@ -236,8 +235,7 @@ impl HTMLCanvasElementMethods for HTMLCanvasElement {
 
     // https://html.spec.whatwg.org/multipage/#dom-canvas-height
     fn SetHeight(&self, height: u32) {
-        let elem = self.upcast::<Element>();
-        elem.set_uint_attribute(&atom!("height"), height)
+        self.upcast::<Element>().set_uint_attribute(&atom!("height"), height)
     }
 
     // https://html.spec.whatwg.org/multipage/#dom-canvas-getcontext
@@ -264,8 +262,7 @@ impl HTMLCanvasElementMethods for HTMLCanvasElement {
 
 impl VirtualMethods for HTMLCanvasElement {
     fn super_type(&self) -> Option<&VirtualMethods> {
-        let element: &HTMLElement = self.upcast::<HTMLElement>();
-        Some(element as &VirtualMethods)
+        Some(self.upcast::<HTMLElement>() as &VirtualMethods)
     }
 
     fn attribute_mutated(&self, attr: &Attr, mutation: AttributeMutation) {
diff --git a/components/script/dom/htmlcollection.rs b/components/script/dom/htmlcollection.rs
index 7d4e217147b..dda2bd9b3b8 100644
--- a/components/script/dom/htmlcollection.rs
+++ b/components/script/dom/htmlcollection.rs
@@ -154,7 +154,7 @@ impl HTMLCollection {
         struct ElementChildFilter;
         impl CollectionFilter for ElementChildFilter {
             fn filter(&self, elem: &Element, root: &Node) -> bool {
-                root.is_parent_of(elem.upcast::<Node>())
+                root.is_parent_of(elem.upcast())
             }
         }
         HTMLCollection::create(window, root, box ElementChildFilter)
@@ -186,8 +186,8 @@ impl<'a> Iterator for HTMLCollectionElementsIter<'a> {
         let filter = self.filter;
         let root = self.root.r();
         self.node_iter.by_ref()
-                      .filter_map(Root::downcast::<Element>)
-                      .filter(|element| filter.filter(element.r(), root))
+                      .filter_map(Root::downcast)
+                      .filter(|element| filter.filter(&element, root))
                       .next()
     }
 }
diff --git a/components/script/dom/htmldatalistelement.rs b/components/script/dom/htmldatalistelement.rs
index 4b6b4cf4a12..9b262ab686f 100644
--- a/components/script/dom/htmldatalistelement.rs
+++ b/components/script/dom/htmldatalistelement.rs
@@ -48,9 +48,8 @@ impl HTMLDataListElementMethods for HTMLDataListElement {
                 elem.is::<HTMLOptionElement>()
             }
         }
-        let node = self.upcast::<Node>();
         let filter = box HTMLDataListOptionsFilter;
-        let window = window_from_node(node);
-        HTMLCollection::create(window.r(), node, filter)
+        let window = window_from_node(self);
+        HTMLCollection::create(window.r(), self.upcast(), filter)
     }
 }
diff --git a/components/script/dom/htmlelement.rs b/components/script/dom/htmlelement.rs
index f2b36bfd151..34a7847187a 100644
--- a/components/script/dom/htmlelement.rs
+++ b/components/script/dom/htmlelement.rs
@@ -162,41 +162,37 @@ impl HTMLElementMethods for HTMLElement {
             let win = window_from_node(self);
             win.r().SetOnload(listener)
         } else {
-            let target = self.upcast::<EventTarget>();
-            target.set_event_handler_common("load", listener)
+            self.upcast::<EventTarget>().set_event_handler_common("load", listener)
         }
     }
 
     // https://html.spec.whatwg.org/multipage/#dom-click
     fn Click(&self) {
-        let maybe_input: Option<&HTMLInputElement> = self.downcast::<HTMLInputElement>();
-        if let Some(i) = maybe_input {
+        if let Some(i) = self.downcast::<HTMLInputElement>() {
             if i.Disabled() {
                 return;
             }
         }
-        let element = self.upcast::<Element>();
         // https://www.w3.org/Bugs/Public/show_bug.cgi?id=27430 ?
-        element.as_maybe_activatable().map(|a| a.synthetic_click_activation(false, false, false, false));
+        self.upcast::<Element>()
+            .as_maybe_activatable()
+            .map(|a| a.synthetic_click_activation(false, false, false, false));
     }
 
     // https://html.spec.whatwg.org/multipage/#dom-focus
     fn Focus(&self) {
         // TODO: Mark the element as locked for focus and run the focusing steps.
         // https://html.spec.whatwg.org/multipage/#focusing-steps
-        let element = self.upcast::<Element>();
         let document = document_from_node(self);
-        let document = document.r();
         document.begin_focus_transaction();
-        document.request_focus(element);
+        document.request_focus(self.upcast());
         document.commit_focus_transaction(FocusType::Element);
     }
 
     // https://html.spec.whatwg.org/multipage/#dom-blur
     fn Blur(&self) {
         // TODO: Run the unfocusing steps.
-        let el = self.upcast::<Element>();
-        if !el.get_focus_state() {
+        if !self.upcast::<Element>().get_focus_state() {
             return;
         }
         // https://html.spec.whatwg.org/multipage/#unfocusing-steps
@@ -286,29 +282,25 @@ impl HTMLElement {
                .nth(1).map_or(false, |ch| ch >= 'a' && ch <= 'z') {
             return Err(Error::Syntax);
         }
-        let element = self.upcast::<Element>();
-        element.set_custom_attribute(to_snake_case(name), value)
+        self.upcast::<Element>().set_custom_attribute(to_snake_case(name), value)
     }
 
     pub fn get_custom_attr(&self, local_name: DOMString) -> Option<DOMString> {
-        let element = self.upcast::<Element>();
         let local_name = Atom::from_slice(&to_snake_case(local_name));
-        element.get_attribute(&ns!(""), &local_name).map(|attr| {
+        self.upcast::<Element>().get_attribute(&ns!(""), &local_name).map(|attr| {
             (**attr.r().value()).to_owned()
         })
     }
 
     pub fn delete_custom_attr(&self, local_name: DOMString) {
-        let element = self.upcast::<Element>();
         let local_name = Atom::from_slice(&to_snake_case(local_name));
-        element.remove_attribute(&ns!(""), &local_name);
+        self.upcast::<Element>().remove_attribute(&ns!(""), &local_name);
     }
 }
 
 impl VirtualMethods for HTMLElement {
     fn super_type(&self) -> Option<&VirtualMethods> {
-        let element: &Element = self.upcast::<Element>();
-        Some(element as &VirtualMethods)
+        Some(self.upcast::<Element>() as &VirtualMethods)
     }
 
     fn attribute_mutated(&self, attr: &Attr, mutation: AttributeMutation) {
diff --git a/components/script/dom/htmlfieldsetelement.rs b/components/script/dom/htmlfieldsetelement.rs
index b875e275c66..63c614d308f 100644
--- a/components/script/dom/htmlfieldsetelement.rs
+++ b/components/script/dom/htmlfieldsetelement.rs
@@ -56,10 +56,9 @@ impl HTMLFieldSetElementMethods for HTMLFieldSetElement {
                 TAG_NAMES.iter().any(|&tag_name| tag_name == &**elem.local_name())
             }
         }
-        let node = self.upcast::<Node>();
         let filter = box ElementsFilter;
-        let window = window_from_node(node);
-        HTMLCollection::create(window.r(), node, filter)
+        let window = window_from_node(self);
+        HTMLCollection::create(window.r(), self.upcast(), filter)
     }
 
     // https://html.spec.whatwg.org/multipage/#dom-cva-validity
@@ -82,8 +81,7 @@ impl HTMLFieldSetElementMethods for HTMLFieldSetElement {
 
 impl VirtualMethods for HTMLFieldSetElement {
     fn super_type(&self) -> Option<&VirtualMethods> {
-        let htmlelement: &HTMLElement = self.upcast::<HTMLElement>();
-        Some(htmlelement as &VirtualMethods)
+        Some(self.upcast::<HTMLElement>() as &VirtualMethods)
     }
 
     fn attribute_mutated(&self, attr: &Attr, mutation: AttributeMutation) {
diff --git a/components/script/dom/htmlfontelement.rs b/components/script/dom/htmlfontelement.rs
index ba6b586e9d3..6c54bfbc773 100644
--- a/components/script/dom/htmlfontelement.rs
+++ b/components/script/dom/htmlfontelement.rs
@@ -71,8 +71,7 @@ impl HTMLFontElementMethods for HTMLFontElement {
 
 impl VirtualMethods for HTMLFontElement {
     fn super_type(&self) -> Option<&VirtualMethods> {
-        let htmlelement = self.upcast::<HTMLElement>();
-        Some(htmlelement as &VirtualMethods)
+        Some(self.upcast::<HTMLElement>() as &VirtualMethods)
     }
 
     fn attribute_mutated(&self, attr: &Attr, mutation: AttributeMutation) {
diff --git a/components/script/dom/htmlformelement.rs b/components/script/dom/htmlformelement.rs
index 0584cd85c59..be4f092da72 100644
--- a/components/script/dom/htmlformelement.rs
+++ b/components/script/dom/htmlformelement.rs
@@ -17,7 +17,6 @@ use dom::bindings::utils::Reflectable;
 use dom::document::Document;
 use dom::element::Element;
 use dom::event::{Event, EventBubbles, EventCancelable};
-use dom::eventtarget::EventTarget;
 use dom::htmlbuttonelement::{HTMLButtonElement};
 use dom::htmldatalistelement::HTMLDataListElement;
 use dom::htmlelement::HTMLElement;
@@ -163,8 +162,7 @@ impl HTMLFormElement {
                                "submit".to_owned(),
                                EventBubbles::Bubbles,
                                EventCancelable::Cancelable);
-        let target = self.upcast::<EventTarget>();
-        event.r().fire(target);
+        event.fire(self.upcast());
         if event.r().DefaultPrevented() {
             return;
         }
@@ -316,21 +314,17 @@ impl HTMLFormElement {
                                "reset".to_owned(),
                                EventBubbles::Bubbles,
                                EventCancelable::Cancelable);
-        let target = self.upcast::<EventTarget>();
-        event.r().fire(target);
+        event.fire(self.upcast());
         if event.r().DefaultPrevented() {
             return;
         }
 
-        let node = self.upcast::<Node>();
-
         // TODO: This is an incorrect way of getting controls owned
         //       by the form, but good enough until html5ever lands
-        for child in node.traverse_preorder() {
+        for child in self.upcast::<Node>().traverse_preorder() {
             match child.r().type_id() {
                 NodeTypeId::Element(ElementTypeId::HTMLElement(HTMLElementTypeId::HTMLInputElement)) => {
-                    let input = child.downcast::<HTMLInputElement>().unwrap();
-                    input.reset()
+                    child.downcast::<HTMLInputElement>().unwrap().reset();
                 }
                 // TODO HTMLKeygenElement unimplemented
                 //NodeTypeId::Element(ElementTypeId::HTMLElement(HTMLElementTypeId::HTMLKeygenElement)) => {
@@ -342,8 +336,7 @@ impl HTMLFormElement {
                     {}
                 }
                 NodeTypeId::Element(ElementTypeId::HTMLElement(HTMLElementTypeId::HTMLTextAreaElement)) => {
-                    let textarea = child.downcast::<HTMLTextAreaElement>().unwrap();
-                    textarea.reset()
+                    child.downcast::<HTMLTextAreaElement>().unwrap().reset();
                 }
                 NodeTypeId::Element(ElementTypeId::HTMLElement(HTMLElementTypeId::HTMLOutputElement)) => {
                     // Unimplemented
@@ -484,13 +477,7 @@ pub trait FormControl: DerivedFrom<Element> + Reflectable {
                 _ => ()
             }
         }
-        let node = elem.upcast::<Node>();
-        for ancestor in node.ancestors() {
-            if let Some(ancestor) = ancestor.downcast::<HTMLFormElement>() {
-                return Some(Root::from_ref(ancestor))
-            }
-        }
-        None
+        elem.upcast::<Node>().ancestors().filter_map(Root::downcast).next()
     }
 
     fn get_form_attribute<InputFn, OwnerFn>(&self,
@@ -509,7 +496,7 @@ pub trait FormControl: DerivedFrom<Element> + Reflectable {
     }
 
     fn to_element(&self) -> &Element {
-        self.upcast::<Element>()
+        self.upcast()
     }
 }
 
diff --git a/components/script/dom/htmlheadelement.rs b/components/script/dom/htmlheadelement.rs
index 7af45e813e4..a2231a17729 100644
--- a/components/script/dom/htmlheadelement.rs
+++ b/components/script/dom/htmlheadelement.rs
@@ -37,8 +37,7 @@ impl HTMLHeadElement {
 
 impl VirtualMethods for HTMLHeadElement {
     fn super_type(&self) -> Option<&VirtualMethods> {
-        let htmlelement: &HTMLElement = self.upcast::<HTMLElement>();
-        Some(htmlelement as &VirtualMethods)
+        Some(self.upcast::<HTMLElement>() as &VirtualMethods)
     }
     fn bind_to_tree(&self, _tree_in_doc: bool) {
         load_script(self);
diff --git a/components/script/dom/htmliframeelement.rs b/components/script/dom/htmliframeelement.rs
index cbe95bc6e24..da119309bef 100644
--- a/components/script/dom/htmliframeelement.rs
+++ b/components/script/dom/htmliframeelement.rs
@@ -15,7 +15,6 @@ use dom::customevent::CustomEvent;
 use dom::document::Document;
 use dom::element::{self, AttributeMutation, Element};
 use dom::event::Event;
-use dom::eventtarget::EventTarget;
 use dom::htmlelement::HTMLElement;
 use dom::node::{Node, window_from_node};
 use dom::urlhelper::UrlHelper;
@@ -148,9 +147,7 @@ impl HTMLIFrameElement {
                                                 true,
                                                 true,
                                                 detail.handle());
-            let target = self.upcast::<EventTarget>();
-            let event = custom_event.upcast::<Event>();
-            event.fire(target);
+            custom_event.upcast::<Event>().fire(self.upcast());
         }
     }
 
@@ -161,7 +158,7 @@ impl HTMLIFrameElement {
     #[allow(unsafe_code)]
     pub fn get_width(&self) -> LengthOrPercentageOrAuto {
         unsafe {
-            element::get_attr_for_layout(self.upcast::<Element>(),
+            element::get_attr_for_layout(self.upcast(),
                                          &ns!(""),
                                          &atom!("width")).map(|attribute| {
                 str::parse_length(&**attribute.value_for_layout())
@@ -172,7 +169,7 @@ impl HTMLIFrameElement {
     #[allow(unsafe_code)]
     pub fn get_height(&self) -> LengthOrPercentageOrAuto {
         unsafe {
-            element::get_attr_for_layout(self.upcast::<Element>(),
+            element::get_attr_for_layout(self.upcast(),
                                          &ns!(""),
                                          &atom!("height")).map(|attribute| {
                 str::parse_length(&**attribute.value_for_layout())
@@ -227,8 +224,7 @@ impl HTMLIFrameElementLayoutMethods for LayoutJS<HTMLIFrameElement> {
 
 pub fn Navigate(iframe: &HTMLIFrameElement, direction: NavigationDirection) -> Fallible<()> {
     if iframe.Mozbrowser() {
-        let node = iframe.upcast::<Node>();
-        if node.is_in_doc() {
+        if iframe.upcast::<Node>().is_in_doc() {
             let window = window_from_node(iframe);
             let window = window.r();
 
@@ -249,26 +245,22 @@ pub fn Navigate(iframe: &HTMLIFrameElement, direction: NavigationDirection) -> F
 impl HTMLIFrameElementMethods for HTMLIFrameElement {
     // https://html.spec.whatwg.org/multipage/#dom-iframe-src
     fn Src(&self) -> DOMString {
-        let element = self.upcast::<Element>();
-        element.get_string_attribute(&atom!("src"))
+        self.upcast::<Element>().get_string_attribute(&atom!("src"))
     }
 
     // https://html.spec.whatwg.org/multipage/#dom-iframe-src
     fn SetSrc(&self, src: DOMString) {
-        let element = self.upcast::<Element>();
-        element.set_url_attribute(&atom!("src"), src)
+        self.upcast::<Element>().set_url_attribute(&atom!("src"), src)
     }
 
     // https://html.spec.whatwg.org/multipage/#dom-iframe-sandbox
     fn Sandbox(&self) -> DOMString {
-        let element = self.upcast::<Element>();
-        element.get_string_attribute(&atom!("sandbox"))
+        self.upcast::<Element>().get_string_attribute(&atom!("sandbox"))
     }
 
     // https://html.spec.whatwg.org/multipage/#dom-iframe-sandbox
     fn SetSandbox(&self, sandbox: DOMString) {
-        let element = self.upcast::<Element>();
-        element.set_tokenlist_attribute(&atom!("sandbox"), sandbox);
+        self.upcast::<Element>().set_tokenlist_attribute(&atom!("sandbox"), sandbox);
     }
 
     // https://html.spec.whatwg.org/multipage/#dom-iframe-contentwindow
@@ -360,8 +352,7 @@ impl HTMLIFrameElementMethods for HTMLIFrameElement {
 
 impl VirtualMethods for HTMLIFrameElement {
     fn super_type(&self) -> Option<&VirtualMethods> {
-        let htmlelement: &HTMLElement = self.upcast::<HTMLElement>();
-        Some(htmlelement as &VirtualMethods)
+        Some(self.upcast::<HTMLElement>() as &VirtualMethods)
     }
 
     fn attribute_mutated(&self, attr: &Attr, mutation: AttributeMutation) {
diff --git a/components/script/dom/htmlimageelement.rs b/components/script/dom/htmlimageelement.rs
index 865a9d05774..25b93621c02 100644
--- a/components/script/dom/htmlimageelement.rs
+++ b/components/script/dom/htmlimageelement.rs
@@ -16,7 +16,6 @@ use dom::bindings::refcounted::Trusted;
 use dom::document::Document;
 use dom::element::{AttributeMutation, Element};
 use dom::event::{Event, EventBubbles, EventCancelable};
-use dom::eventtarget::EventTarget;
 use dom::htmlelement::HTMLElement;
 use dom::node::{Node, NodeDamage, document_from_node, window_from_node};
 use dom::virtualmethods::VirtualMethods;
@@ -74,9 +73,8 @@ impl Runnable for ImageResponseHandlerRunnable {
         };
 
         // Mark the node dirty
-        let node = element.upcast::<Node>();
-        let document = document_from_node(node);
-        document.r().content_changed(node, NodeDamage::OtherNodeDamage);
+        let document = document_from_node(&*element);
+        document.content_changed(element.upcast(), NodeDamage::OtherNodeDamage);
 
         // Fire image.onload
         let window = window_from_node(document.r());
@@ -84,9 +82,7 @@ impl Runnable for ImageResponseHandlerRunnable {
                                "load".to_owned(),
                                EventBubbles::DoesNotBubble,
                                EventCancelable::NotCancelable);
-        let event = event.r();
-        let target = node.upcast::<EventTarget>();
-        event.fire(target);
+        event.fire(element.upcast());
 
         // Trigger reflow
         window.r().add_pending_reflow();
@@ -97,8 +93,7 @@ impl HTMLImageElement {
     /// Makes the local `image` member match the status of the `src` attribute and starts
     /// prefetching the image. This method must be called after `src` is changed.
     fn update_image(&self, value: Option<(DOMString, Url)>) {
-        let node = self.upcast::<Node>();
-        let document = node.owner_doc();
+        let document = document_from_node(self);
         let window = document.r().window();
         let image_cache = window.image_cache_task();
         match value {
@@ -204,8 +199,7 @@ impl HTMLImageElementMethods for HTMLImageElement {
 
     // https://html.spec.whatwg.org/multipage/#dom-img-ismap
     fn SetIsMap(&self, is_map: bool) {
-        let element = self.upcast::<Element>();
-        element.set_string_attribute(&atom!("ismap"), is_map.to_string())
+        self.upcast::<Element>().set_string_attribute(&atom!("ismap"), is_map.to_string())
     }
 
     // https://html.spec.whatwg.org/multipage/#dom-img-width
@@ -217,8 +211,7 @@ impl HTMLImageElementMethods for HTMLImageElement {
 
     // https://html.spec.whatwg.org/multipage/#dom-img-width
     fn SetWidth(&self, width: u32) {
-        let elem = self.upcast::<Element>();
-        elem.set_uint_attribute(&atom!("width"), width)
+        self.upcast::<Element>().set_uint_attribute(&atom!("width"), width)
     }
 
     // https://html.spec.whatwg.org/multipage/#dom-img-height
@@ -230,8 +223,7 @@ impl HTMLImageElementMethods for HTMLImageElement {
 
     // https://html.spec.whatwg.org/multipage/#dom-img-height
     fn SetHeight(&self, height: u32) {
-        let elem = self.upcast::<Element>();
-        elem.set_uint_attribute(&atom!("height"), height)
+        self.upcast::<Element>().set_uint_attribute(&atom!("height"), height)
     }
 
     // https://html.spec.whatwg.org/multipage/#dom-img-naturalwidth
@@ -299,8 +291,7 @@ impl HTMLImageElementMethods for HTMLImageElement {
 
 impl VirtualMethods for HTMLImageElement {
     fn super_type(&self) -> Option<&VirtualMethods> {
-        let htmlelement: &HTMLElement = self.upcast::<HTMLElement>();
-        Some(htmlelement as &VirtualMethods)
+        Some(self.upcast::<HTMLElement>() as &VirtualMethods)
     }
 
     fn attribute_mutated(&self, attr: &Attr, mutation: AttributeMutation) {
diff --git a/components/script/dom/htmlinputelement.rs b/components/script/dom/htmlinputelement.rs
index a2ad92517c0..b82f96aed63 100644
--- a/components/script/dom/htmlinputelement.rs
+++ b/components/script/dom/htmlinputelement.rs
@@ -353,7 +353,6 @@ fn broadcast_radio_checked(broadcaster: &HTMLInputElement, group: Option<&Atom>)
     //TODO: if not in document, use root ancestor instead of document
     let owner = broadcaster.form_owner();
     let doc = document_from_node(broadcaster);
-    let doc_node = doc.upcast::<Node>();
 
     // This function is a workaround for lifetime constraint difficulties.
     fn do_broadcast(doc_node: &Node, broadcaster: &HTMLInputElement,
@@ -368,7 +367,7 @@ fn broadcast_radio_checked(broadcaster: &HTMLInputElement, group: Option<&Atom>)
         }
     }
 
-    do_broadcast(doc_node, broadcaster, owner.r(), group)
+    do_broadcast(doc.upcast(), broadcaster, owner.r(), group)
 }
 
 // https://html.spec.whatwg.org/multipage/#radio-button-group
@@ -388,8 +387,7 @@ fn in_same_group(other: &HTMLInputElement, owner: Option<&HTMLFormElement>,
 impl HTMLInputElement {
     fn force_relayout(&self) {
         let doc = document_from_node(self);
-        let node = self.upcast::<Node>();
-        doc.r().content_changed(node, NodeDamage::OtherNodeDamage)
+        doc.content_changed(self.upcast(), NodeDamage::OtherNodeDamage)
     }
 
     fn radio_group_updated(&self, group: Option<&Atom>) {
@@ -439,8 +437,8 @@ impl HTMLInputElement {
     // https://html.spec.whatwg.org/multipage/#radio-button-group
     fn get_radio_group_name(&self) -> Option<Atom> {
         //TODO: determine form owner
-        let elem = self.upcast::<Element>();
-        elem.get_attribute(&ns!(""), &atom!("name"))
+        self.upcast::<Element>()
+            .get_attribute(&ns!(""), &atom!("name"))
             .map(|name| name.value().as_atom().clone())
     }
 
@@ -468,8 +466,7 @@ impl HTMLInputElement {
     fn mutable(&self) -> bool {
         // https://html.spec.whatwg.org/multipage/#the-input-element:concept-fe-mutable
         // https://html.spec.whatwg.org/multipage/#the-readonly-attribute:concept-fe-mutable
-        let el = self.upcast::<Element>();
-        !(el.get_disabled_state() || self.ReadOnly())
+        !(self.upcast::<Element>().get_disabled_state() || self.ReadOnly())
     }
 
     // https://html.spec.whatwg.org/multipage/#the-input-element:concept-form-reset-control
@@ -491,8 +488,7 @@ impl HTMLInputElement {
 
 impl VirtualMethods for HTMLInputElement {
     fn super_type(&self) -> Option<&VirtualMethods> {
-        let htmlelement: &HTMLElement = self.upcast::<HTMLElement>();
-        Some(htmlelement as &VirtualMethods)
+        Some(self.upcast::<HTMLElement>() as &VirtualMethods)
     }
 
     fn attribute_mutated(&self, attr: &Attr, mutation: AttributeMutation) {
@@ -592,8 +588,7 @@ impl VirtualMethods for HTMLInputElement {
             s.bind_to_tree(tree_in_doc);
         }
 
-        let el = self.upcast::<Element>();
-        el.check_ancestors_disabled_state_for_form_control();
+        self.upcast::<Element>().check_ancestors_disabled_state_for_form_control();
     }
 
     fn unbind_from_tree(&self, tree_in_doc: bool) {
@@ -626,13 +621,11 @@ impl VirtualMethods for HTMLInputElement {
 
             //TODO: set the editing position for text inputs
 
-            let doc = document_from_node(self);
-            doc.r().request_focus(self.upcast::<Element>());
+            document_from_node(self).request_focus(self.upcast());
         } else if &*event.Type() == "keydown" && !event.DefaultPrevented() &&
             (self.input_type.get() == InputType::InputText ||
              self.input_type.get() == InputType::InputPassword) {
-                let keyevent: Option<&KeyboardEvent> = event.downcast::<KeyboardEvent>();
-                keyevent.map(|keyevent| {
+                if let Some(keyevent) = event.downcast::<KeyboardEvent>() {
                     // This can't be inlined, as holding on to textinput.borrow_mut()
                     // during self.implicit_submission will cause a panic.
                     let action = self.textinput.borrow_mut().handle_keydown(keyevent);
@@ -653,7 +646,7 @@ impl VirtualMethods for HTMLInputElement {
                         }
                         Nothing => (),
                     }
-                });
+                }
         }
     }
 }
@@ -662,7 +655,7 @@ impl FormControl for HTMLInputElement {}
 
 impl Activatable for HTMLInputElement {
     fn as_element(&self) -> &Element {
-        self.upcast::<Element>()
+        self.upcast()
     }
 
     fn is_instance_activatable(&self) -> bool {
@@ -809,19 +802,19 @@ impl Activatable for HTMLInputElement {
                 // https://html.spec.whatwg.org/multipage/#radio-button-state-(type=radio):activation-behavior
                 if self.mutable() {
                     let win = window_from_node(self);
+                    let target = self.upcast();
+
                     let event = Event::new(GlobalRef::Window(win.r()),
                                            "input".to_owned(),
                                            EventBubbles::Bubbles,
                                            EventCancelable::NotCancelable);
-                    let target = self.upcast::<EventTarget>();
-                    event.r().fire(target);
+                    event.fire(target);
 
                     let event = Event::new(GlobalRef::Window(win.r()),
                                            "change".to_owned(),
                                            EventBubbles::Bubbles,
                                            EventCancelable::NotCancelable);
-                    let target = self.upcast::<EventTarget>();
-                    event.r().fire(target);
+                    event.fire(target);
                 }
             },
             _ => ()
@@ -839,8 +832,7 @@ impl Activatable for HTMLInputElement {
             Some(ref f) => f
         };
 
-        let elem = self.upcast::<Element>();
-        if elem.click_in_progress() {
+        if self.upcast::<Element>().click_in_progress() {
             return;
         }
         let submit_button;
diff --git a/components/script/dom/htmllinkelement.rs b/components/script/dom/htmllinkelement.rs
index f317eec0001..fc7a1818c00 100644
--- a/components/script/dom/htmllinkelement.rs
+++ b/components/script/dom/htmllinkelement.rs
@@ -89,8 +89,7 @@ fn is_favicon(value: &Option<String>) -> bool {
 
 impl VirtualMethods for HTMLLinkElement {
     fn super_type(&self) -> Option<&VirtualMethods> {
-        let htmlelement: &HTMLElement = self.upcast::<HTMLElement>();
-        Some(htmlelement as &VirtualMethods)
+        Some(self.upcast::<HTMLElement>() as &VirtualMethods)
     }
 
     fn attribute_mutated(&self, attr: &Attr, mutation: AttributeMutation) {
@@ -98,7 +97,7 @@ impl VirtualMethods for HTMLLinkElement {
         if !self.upcast::<Node>().is_in_doc() || mutation == AttributeMutation::Removed {
             return;
         }
-        let rel = get_attr(self.upcast::<Element>(), &atom!(rel));
+        let rel = get_attr(self.upcast(), &atom!(rel));
         match attr.local_name() {
             &atom!(href) => {
                 if is_stylesheet(&rel) {
@@ -129,7 +128,7 @@ impl VirtualMethods for HTMLLinkElement {
         }
 
         if tree_in_doc {
-            let element = self.upcast::<Element>();
+            let element = self.upcast();
 
             let rel = get_attr(element, &atom!("rel"));
             let href = get_attr(element, &atom!("href"));
@@ -224,9 +223,7 @@ impl HTMLLinkElementMethods for HTMLLinkElement {
 
     // https://html.spec.whatwg.org/multipage/#dom-link-rellist
     fn RelList(&self) -> Root<DOMTokenList> {
-        self.rel_list.or_init(|| {
-            DOMTokenList::new(self.upcast::<Element>(), &atom!("rel"))
-        })
+        self.rel_list.or_init(|| DOMTokenList::new(self.upcast(), &atom!("rel")))
     }
 
     // https://html.spec.whatwg.org/multipage/#dom-link-charset
@@ -267,7 +264,6 @@ impl StylesheetLoadResponder for StylesheetLoadDispatcher {
         let event = Event::new(GlobalRef::Window(window.r()), "load".to_owned(),
                                EventBubbles::DoesNotBubble,
                                EventCancelable::NotCancelable);
-        let target = elem.upcast::<EventTarget>();
-        event.r().fire(target);
+        event.fire(elem.upcast::<EventTarget>());
     }
 }
diff --git a/components/script/dom/htmlmetaelement.rs b/components/script/dom/htmlmetaelement.rs
index e1194376f31..0b0fcd4e4c8 100644
--- a/components/script/dom/htmlmetaelement.rs
+++ b/components/script/dom/htmlmetaelement.rs
@@ -57,8 +57,7 @@ impl HTMLMetaElement {
             let content = content.value();
             if !content.is_empty() {
                 if let Some(translated_rule) = ViewportRule::from_meta(&**content) {
-                    let node = self.upcast::<Node>();
-                    let win = window_from_node(node);
+                    let win = window_from_node(self);
                     let LayoutChan(ref layout_chan) = win.r().layout_chan();
 
                     layout_chan.send(Msg::AddMetaViewport(translated_rule)).unwrap();
@@ -84,8 +83,7 @@ impl HTMLMetaElementMethods for HTMLMetaElement {
 
 impl VirtualMethods for HTMLMetaElement {
     fn super_type(&self) -> Option<&VirtualMethods> {
-        let htmlelement: &HTMLElement = self.upcast::<HTMLElement>();
-        Some(htmlelement as &VirtualMethods)
+        Some(self.upcast::<HTMLElement>() as &VirtualMethods)
     }
 
     fn bind_to_tree(&self, tree_in_doc: bool) {
diff --git a/components/script/dom/htmlobjectelement.rs b/components/script/dom/htmlobjectelement.rs
index 3e11c832514..49a16688854 100644
--- a/components/script/dom/htmlobjectelement.rs
+++ b/components/script/dom/htmlobjectelement.rs
@@ -92,8 +92,7 @@ impl HTMLObjectElementMethods for HTMLObjectElement {
 
 impl VirtualMethods for HTMLObjectElement {
     fn super_type(&self) -> Option<&VirtualMethods> {
-        let htmlelement: &HTMLElement = self.upcast::<HTMLElement>();
-        Some(htmlelement as &VirtualMethods)
+        Some(self.upcast::<HTMLElement>() as &VirtualMethods)
     }
 
     fn attribute_mutated(&self, attr: &Attr, mutation: AttributeMutation) {
diff --git a/components/script/dom/htmloptgroupelement.rs b/components/script/dom/htmloptgroupelement.rs
index f1c011325bf..4d9ec9b6ca9 100644
--- a/components/script/dom/htmloptgroupelement.rs
+++ b/components/script/dom/htmloptgroupelement.rs
@@ -50,8 +50,7 @@ impl HTMLOptGroupElementMethods for HTMLOptGroupElement {
 
 impl VirtualMethods for HTMLOptGroupElement {
     fn super_type(&self) -> Option<&VirtualMethods> {
-        let htmlelement: &HTMLElement = self.upcast::<HTMLElement>();
-        Some(htmlelement as &VirtualMethods)
+        Some(self.upcast::<HTMLElement>() as &VirtualMethods)
     }
 
     fn attribute_mutated(&self, attr: &Attr, mutation: AttributeMutation) {
diff --git a/components/script/dom/htmloptionelement.rs b/components/script/dom/htmloptionelement.rs
index d60ae457203..60af71b6c2e 100644
--- a/components/script/dom/htmloptionelement.rs
+++ b/components/script/dom/htmloptionelement.rs
@@ -64,7 +64,7 @@ fn collect_text(element: &Element, value: &mut DOMString) {
         if child.is::<Text>() {
             let characterdata = child.downcast::<CharacterData>().unwrap();
             value.push_str(&characterdata.Data());
-        } else if let Some(element_child) = child.downcast::<Element>() {
+        } else if let Some(element_child) = child.downcast() {
             collect_text(element_child, value);
         }
     }
@@ -76,22 +76,19 @@ impl HTMLOptionElementMethods for HTMLOptionElement {
 
     // https://html.spec.whatwg.org/multipage/#dom-option-disabled
     fn SetDisabled(&self, disabled: bool) {
-        let elem = self.upcast::<Element>();
-        elem.set_bool_attribute(&atom!("disabled"), disabled)
+        self.upcast::<Element>().set_bool_attribute(&atom!("disabled"), disabled)
     }
 
     // https://html.spec.whatwg.org/multipage/#dom-option-text
     fn Text(&self) -> DOMString {
-        let element = self.upcast::<Element>();
         let mut content = String::new();
-        collect_text(element, &mut content);
+        collect_text(self.upcast(), &mut content);
         str_join(split_html_space_chars(&content), " ")
     }
 
     // https://html.spec.whatwg.org/multipage/#dom-option-text
     fn SetText(&self, value: DOMString) {
-        let node = self.upcast::<Node>();
-        node.SetTextContent(Some(value))
+        self.upcast::<Node>().SetTextContent(Some(value))
     }
 
     // https://html.spec.whatwg.org/multipage/#attr-option-value
@@ -144,8 +141,7 @@ impl HTMLOptionElementMethods for HTMLOptionElement {
 
 impl VirtualMethods for HTMLOptionElement {
     fn super_type(&self) -> Option<&VirtualMethods> {
-        let htmlelement: &HTMLElement = self.upcast::<HTMLElement>();
-        Some(htmlelement as &VirtualMethods)
+        Some(self.upcast::<HTMLElement>() as &VirtualMethods)
     }
 
     fn attribute_mutated(&self, attr: &Attr, mutation: AttributeMutation) {
@@ -190,8 +186,7 @@ impl VirtualMethods for HTMLOptionElement {
             s.bind_to_tree(tree_in_doc);
         }
 
-        let el = self.upcast::<Element>();
-        el.check_parent_disabled_state_for_option();
+        self.upcast::<Element>().check_parent_disabled_state_for_option();
     }
 
     fn unbind_from_tree(&self, tree_in_doc: bool) {
diff --git a/components/script/dom/htmlscriptelement.rs b/components/script/dom/htmlscriptelement.rs
index 7ae38f951bb..a32b481d252 100644
--- a/components/script/dom/htmlscriptelement.rs
+++ b/components/script/dom/htmlscriptelement.rs
@@ -19,7 +19,6 @@ use dom::bindings::trace::JSTraceable;
 use dom::document::Document;
 use dom::element::{AttributeMutation, Element, ElementCreator};
 use dom::event::{Event, EventBubbles, EventCancelable};
-use dom::eventtarget::EventTarget;
 use dom::htmlelement::HTMLElement;
 use dom::node::{ChildrenMutation, CloneChildrenFlag, Node};
 use dom::node::{document_from_node, window_from_node};
@@ -190,8 +189,7 @@ impl HTMLScriptElement {
             return NextParserState::Continue;
         }
         // Step 5.
-        let node = self.upcast::<Node>();
-        if !node.is_in_doc() {
+        if !self.upcast::<Node>().is_in_doc() {
             return NextParserState::Continue;
         }
         // Step 6, 7.
@@ -507,16 +505,13 @@ impl HTMLScriptElement {
                                type_,
                                bubbles,
                                cancelable);
-        let event = event.r();
-        let target = self.upcast::<EventTarget>();
-        event.fire(target)
+        event.fire(self.upcast())
     }
 }
 
 impl VirtualMethods for HTMLScriptElement {
     fn super_type(&self) -> Option<&VirtualMethods> {
-        let htmlelement: &HTMLElement = self.upcast::<HTMLElement>();
-        Some(htmlelement as &VirtualMethods)
+        Some(self.upcast::<HTMLElement>() as &VirtualMethods)
     }
 
     fn attribute_mutated(&self, attr: &Attr, mutation: AttributeMutation) {
@@ -537,8 +532,7 @@ impl VirtualMethods for HTMLScriptElement {
         if let Some(ref s) = self.super_type() {
             s.children_changed(mutation);
         }
-        let node = self.upcast::<Node>();
-        if !self.parser_inserted.get() && node.is_in_doc() {
+        if !self.parser_inserted.get() && self.upcast::<Node>().is_in_doc() {
             self.prepare();
         }
     }
@@ -561,8 +555,7 @@ impl VirtualMethods for HTMLScriptElement {
 
         // https://html.spec.whatwg.org/multipage/#already-started
         if self.already_started.get() {
-            let copy_elem = copy.downcast::<HTMLScriptElement>().unwrap();
-            copy_elem.mark_already_started();
+            copy.downcast::<HTMLScriptElement>().unwrap().mark_already_started();
         }
     }
 }
@@ -580,8 +573,7 @@ impl HTMLScriptElementMethods for HTMLScriptElement {
 
     // https://html.spec.whatwg.org/multipage/#dom-script-text
     fn SetText(&self, value: DOMString) {
-        let node = self.upcast::<Node>();
-        node.SetTextContent(Some(value))
+        self.upcast::<Node>().SetTextContent(Some(value))
     }
 }
 
diff --git a/components/script/dom/htmlselectelement.rs b/components/script/dom/htmlselectelement.rs
index 238d6a6f1de..f82eddf39fe 100644
--- a/components/script/dom/htmlselectelement.rs
+++ b/components/script/dom/htmlselectelement.rs
@@ -101,8 +101,7 @@ impl HTMLSelectElementMethods for HTMLSelectElement {
 
 impl VirtualMethods for HTMLSelectElement {
     fn super_type(&self) -> Option<&VirtualMethods> {
-        let htmlelement: &HTMLElement = self.upcast::<HTMLElement>();
-        Some(htmlelement as &VirtualMethods)
+        Some(self.upcast::<HTMLElement>() as &VirtualMethods)
     }
 
     fn attribute_mutated(&self, attr: &Attr, mutation: AttributeMutation) {
@@ -128,8 +127,7 @@ impl VirtualMethods for HTMLSelectElement {
             s.bind_to_tree(tree_in_doc);
         }
 
-        let el = self.upcast::<Element>();
-        el.check_ancestors_disabled_state_for_form_control();
+        self.upcast::<Element>().check_ancestors_disabled_state_for_form_control();
     }
 
     fn unbind_from_tree(&self, tree_in_doc: bool) {
diff --git a/components/script/dom/htmlstyleelement.rs b/components/script/dom/htmlstyleelement.rs
index 695e250b5c6..f33eb938f4e 100644
--- a/components/script/dom/htmlstyleelement.rs
+++ b/components/script/dom/htmlstyleelement.rs
@@ -65,16 +65,14 @@ impl HTMLStyleElement {
 
 impl VirtualMethods for HTMLStyleElement {
     fn super_type(&self) -> Option<&VirtualMethods> {
-        let htmlelement: &HTMLElement = self.upcast::<HTMLElement>();
-        Some(htmlelement as &VirtualMethods)
+        Some(self.upcast::<HTMLElement>() as &VirtualMethods)
     }
 
     fn children_changed(&self, mutation: &ChildrenMutation) {
         if let Some(ref s) = self.super_type() {
             s.children_changed(mutation);
         }
-        let node = self.upcast::<Node>();
-        if node.is_in_doc() {
+        if self.upcast::<Node>().is_in_doc() {
             self.parse_own_css();
         }
     }
diff --git a/components/script/dom/htmltablecellelement.rs b/components/script/dom/htmltablecellelement.rs
index 2cb325d4912..3f1b13633f2 100644
--- a/components/script/dom/htmltablecellelement.rs
+++ b/components/script/dom/htmltablecellelement.rs
@@ -102,8 +102,7 @@ impl HTMLTableCellElementLayoutHelpers for LayoutJS<HTMLTableCellElement> {
 
 impl VirtualMethods for HTMLTableCellElement {
     fn super_type(&self) -> Option<&VirtualMethods> {
-        let htmlelement: &HTMLElement = self.upcast::<HTMLElement>();
-        Some(htmlelement as &VirtualMethods)
+        Some(self.upcast::<HTMLElement>() as &VirtualMethods)
     }
 
     fn attribute_mutated(&self, attr: &Attr, mutation: AttributeMutation) {
diff --git a/components/script/dom/htmltableelement.rs b/components/script/dom/htmltableelement.rs
index bf22ffa429c..ddd87314587 100644
--- a/components/script/dom/htmltableelement.rs
+++ b/components/script/dom/htmltableelement.rs
@@ -52,25 +52,19 @@ impl HTMLTableElement {
 impl HTMLTableElementMethods for HTMLTableElement {
     // https://html.spec.whatwg.org/multipage/#dom-table-caption
     fn GetCaption(&self) -> Option<Root<HTMLTableCaptionElement>> {
-        let node = self.upcast::<Node>();
-        node.children()
-            .filter_map(|c| {
-                c.downcast::<HTMLTableCaptionElement>().map(Root::from_ref)
-            })
-            .next()
+        self.upcast::<Node>().children().filter_map(Root::downcast).next()
     }
 
     // https://html.spec.whatwg.org/multipage/#dom-table-caption
     fn SetCaption(&self, new_caption: Option<&HTMLTableCaptionElement>) {
-        let node = self.upcast::<Node>();
-
         if let Some(ref caption) = self.GetCaption() {
             caption.upcast::<Node>().remove_self();
         }
 
         if let Some(caption) = new_caption {
-            assert!(node.InsertBefore(caption.upcast::<Node>(),
-                                      node.GetFirstChild().as_ref().map(|n| n.r())).is_ok());
+            let node = self.upcast::<Node>();
+            node.InsertBefore(caption.upcast(), node.GetFirstChild().r())
+                .expect("Insertion failed");
         }
     }
 
@@ -86,7 +80,7 @@ impl HTMLTableElementMethods for HTMLTableElement {
                 caption
             }
         };
-        Root::upcast::<HTMLElement>(caption)
+        Root::upcast(caption)
     }
 
     // https://html.spec.whatwg.org/multipage/#dom-table-deletecaption
@@ -107,10 +101,10 @@ impl HTMLTableElementMethods for HTMLTableElement {
                 .filter_map(Root::downcast::<Element>)
                 .find(|n| n.is::<HTMLTableSectionElement>() && n.local_name() == &atom!("tbody"));
         let reference_element =
-            last_tbody.and_then(|t| Root::upcast::<Node>(t).GetNextSibling());
+            last_tbody.and_then(|t| t.upcast::<Node>().GetNextSibling());
 
-        assert!(node.InsertBefore(tbody.upcast::<Node>(),
-                                  reference_element.r()).is_ok());
+        node.InsertBefore(tbody.upcast(), reference_element.r())
+            .expect("Insertion failed");
         tbody
     }
 
@@ -142,8 +136,7 @@ impl HTMLTableElement {
 
 impl VirtualMethods for HTMLTableElement {
     fn super_type(&self) -> Option<&VirtualMethods> {
-        let htmlelement: &HTMLElement = self.upcast::<HTMLElement>();
-        Some(htmlelement as &VirtualMethods)
+        Some(self.upcast::<HTMLElement>() as &VirtualMethods)
     }
 
     fn attribute_mutated(&self, attr: &Attr, mutation: AttributeMutation) {
diff --git a/components/script/dom/htmltablerowelement.rs b/components/script/dom/htmltablerowelement.rs
index 66f3e424414..8db70bd9d2a 100644
--- a/components/script/dom/htmltablerowelement.rs
+++ b/components/script/dom/htmltablerowelement.rs
@@ -72,7 +72,7 @@ impl HTMLTableRowElementMethods for HTMLTableRowElement {
         self.cells.or_init(|| {
             let window = window_from_node(self);
             let filter = box CellsFilter;
-            HTMLCollection::create(window.r(), self.upcast::<Node>(), filter)
+            HTMLCollection::create(window.r(), self.upcast(), filter)
         })
     }
 
@@ -97,8 +97,7 @@ impl HTMLTableRowElementMethods for HTMLTableRowElement {
 
 impl VirtualMethods for HTMLTableRowElement {
     fn super_type(&self) -> Option<&VirtualMethods> {
-        let htmlelement: &HTMLElement = self.upcast::<HTMLElement>();
-        Some(htmlelement as &VirtualMethods)
+        Some(self.upcast::<HTMLElement>() as &VirtualMethods)
     }
 
     fn attribute_mutated(&self, attr: &Attr, mutation: AttributeMutation) {
diff --git a/components/script/dom/htmltablesectionelement.rs b/components/script/dom/htmltablesectionelement.rs
index b5aa3d9f675..5c6f04ef0ec 100644
--- a/components/script/dom/htmltablesectionelement.rs
+++ b/components/script/dom/htmltablesectionelement.rs
@@ -58,7 +58,7 @@ impl CollectionFilter for RowsFilter {
 impl HTMLTableSectionElementMethods for HTMLTableSectionElement {
     // https://html.spec.whatwg.org/multipage/#dom-tbody-rows
     fn Rows(&self) -> Root<HTMLCollection> {
-        HTMLCollection::create(&window_from_node(self), self.upcast::<Node>(), box RowsFilter)
+        HTMLCollection::create(&window_from_node(self), self.upcast(), box RowsFilter)
     }
 
     // https://html.spec.whatwg.org/multipage/#dom-tbody-insertrow
@@ -82,8 +82,7 @@ impl HTMLTableSectionElementMethods for HTMLTableSectionElement {
 
 impl VirtualMethods for HTMLTableSectionElement {
     fn super_type(&self) -> Option<&VirtualMethods> {
-        let htmlelement: &HTMLElement = self.upcast::<HTMLElement>();
-        Some(htmlelement as &VirtualMethods)
+        Some(self.upcast::<HTMLElement>() as &VirtualMethods)
     }
 
     fn attribute_mutated(&self, attr: &Attr, mutation: AttributeMutation) {
diff --git a/components/script/dom/htmltemplateelement.rs b/components/script/dom/htmltemplateelement.rs
index 36090dfbe0a..cd2f7393614 100644
--- a/components/script/dom/htmltemplateelement.rs
+++ b/components/script/dom/htmltemplateelement.rs
@@ -64,7 +64,7 @@ impl VirtualMethods for HTMLTemplateElement {
         // Step 1.
         let doc = document_from_node(self).appropriate_template_contents_owner_document();
         // Step 2.
-        Node::adopt(self.Content().upcast::<Node>(), &doc);
+        Node::adopt(self.Content().upcast(), &doc);
     }
 
     /// https://html.spec.whatwg.org/multipage/#the-template-element:concept-node-clone-ext
@@ -79,7 +79,7 @@ impl VirtualMethods for HTMLTemplateElement {
         // Steps 2-3.
         let copy_contents = Root::upcast::<Node>(copy.Content());
         let copy_contents_doc = copy_contents.owner_doc();
-        for child in Root::upcast::<Node>(self.Content()).children() {
+        for child in self.Content().upcast::<Node>().children() {
             let copy_child = Node::clone(
                 &child, Some(&copy_contents_doc), CloneChildrenFlag::CloneChildren);
             copy_contents.AppendChild(&copy_child).unwrap();
diff --git a/components/script/dom/htmltextareaelement.rs b/components/script/dom/htmltextareaelement.rs
index a051d1d3245..d802760a308 100644
--- a/components/script/dom/htmltextareaelement.rs
+++ b/components/script/dom/htmltextareaelement.rs
@@ -169,14 +169,12 @@ impl HTMLTextAreaElementMethods for HTMLTextAreaElement {
 
     // https://html.spec.whatwg.org/multipage/#dom-textarea-defaultvalue
     fn DefaultValue(&self) -> DOMString {
-        let node = self.upcast::<Node>();
-        node.GetTextContent().unwrap()
+        self.upcast::<Node>().GetTextContent().unwrap()
     }
 
     // https://html.spec.whatwg.org/multipage/#dom-textarea-defaultvalue
     fn SetDefaultValue(&self, value: DOMString) {
-        let node = self.upcast::<Node>();
-        node.SetTextContent(Some(value));
+        self.upcast::<Node>().SetTextContent(Some(value));
 
         // if the element's dirty value flag is false, then the element's
         // raw value must be set to the value of the element's textContent IDL attribute
@@ -218,8 +216,7 @@ impl HTMLTextAreaElement {
 impl HTMLTextAreaElement {
     fn force_relayout(&self) {
         let doc = document_from_node(self);
-        let node = self.upcast::<Node>();
-        doc.r().content_changed(node, NodeDamage::OtherNodeDamage)
+        doc.content_changed(self.upcast(), NodeDamage::OtherNodeDamage)
     }
 
     fn dispatch_change_event(&self) {
@@ -230,15 +227,13 @@ impl HTMLTextAreaElement {
                                EventBubbles::DoesNotBubble,
                                EventCancelable::NotCancelable);
 
-        let target = self.upcast::<EventTarget>();
-        target.dispatch_event(event.r());
+        self.upcast::<EventTarget>().dispatch_event(&event);
     }
 }
 
 impl VirtualMethods for HTMLTextAreaElement {
     fn super_type(&self) -> Option<&VirtualMethods> {
-        let htmlelement: &HTMLElement = self.upcast::<HTMLElement>();
-        Some(htmlelement as &VirtualMethods)
+        Some(self.upcast::<HTMLElement>() as &VirtualMethods)
     }
 
     fn attribute_mutated(&self, attr: &Attr, mutation: AttributeMutation) {
@@ -279,8 +274,7 @@ impl VirtualMethods for HTMLTextAreaElement {
             s.bind_to_tree(tree_in_doc);
         }
 
-        let el = self.upcast::<Element>();
-        el.check_ancestors_disabled_state_for_form_control();
+        self.upcast::<Element>().check_ancestors_disabled_state_for_form_control();
     }
 
     fn parse_plain_attribute(&self, name: &Atom, value: DOMString) -> AttrValue {
@@ -298,7 +292,7 @@ impl VirtualMethods for HTMLTextAreaElement {
 
         let node = self.upcast::<Node>();
         let el = self.upcast::<Element>();
-        if node.ancestors().any(|ancestor| ancestor.r().is::<HTMLFieldSetElement>()) {
+        if node.ancestors().any(|ancestor| ancestor.is::<HTMLFieldSetElement>()) {
             el.check_ancestors_disabled_state_for_form_control();
         } else {
             el.check_disabled_attribute();
@@ -323,11 +317,9 @@ impl VirtualMethods for HTMLTextAreaElement {
         if &*event.Type() == "click" && !event.DefaultPrevented() {
             //TODO: set the editing position for text inputs
 
-            let doc = document_from_node(self);
-            doc.r().request_focus(self.upcast::<Element>());
+            document_from_node(self).request_focus(self.upcast());
         } else if &*event.Type() == "keydown" && !event.DefaultPrevented() {
-            let keyevent: Option<&KeyboardEvent> = event.downcast::<KeyboardEvent>();
-            keyevent.map(|kevent| {
+            if let Some(kevent) = event.downcast::<KeyboardEvent>() {
                 match self.textinput.borrow_mut().handle_keydown(kevent) {
                     KeyReaction::TriggerDefaultAction => (),
                     KeyReaction::DispatchInput => {
@@ -351,7 +343,7 @@ impl VirtualMethods for HTMLTextAreaElement {
                     }
                     KeyReaction::Nothing => (),
                 }
-            });
+            }
         }
     }
 }
diff --git a/components/script/dom/htmltitleelement.rs b/components/script/dom/htmltitleelement.rs
index 8a5f90ff14e..cb22a7bd9c2 100644
--- a/components/script/dom/htmltitleelement.rs
+++ b/components/script/dom/htmltitleelement.rs
@@ -39,13 +39,10 @@ impl HTMLTitleElement {
 impl HTMLTitleElementMethods for HTMLTitleElement {
     // https://html.spec.whatwg.org/multipage/#dom-title-text
     fn Text(&self) -> DOMString {
-        let node = self.upcast::<Node>();
         let mut content = String::new();
-        for child in node.children() {
-            let text: Option<&Text> = child.downcast::<Text>();
-            match text {
-                Some(text) => content.push_str(&text.upcast::<CharacterData>().data()),
-                None => (),
+        for child in self.upcast::<Node>().children() {
+            if let Some(text) = child.downcast::<Text>() {
+                content.push_str(&text.upcast::<CharacterData>().data());
             }
         }
         content
@@ -53,15 +50,13 @@ impl HTMLTitleElementMethods for HTMLTitleElement {
 
     // https://html.spec.whatwg.org/multipage/#dom-title-text
     fn SetText(&self, value: DOMString) {
-        let node = self.upcast::<Node>();
-        node.SetTextContent(Some(value))
+        self.upcast::<Node>().SetTextContent(Some(value))
     }
 }
 
 impl VirtualMethods for HTMLTitleElement {
     fn super_type(&self) -> Option<&VirtualMethods> {
-        let htmlelement: &HTMLElement = self.upcast::<HTMLElement>();
-        Some(htmlelement as &VirtualMethods)
+        Some(self.upcast::<HTMLElement>() as &VirtualMethods)
     }
 
     fn children_changed(&self, mutation: &ChildrenMutation) {
diff --git a/components/script/dom/keyboardevent.rs b/components/script/dom/keyboardevent.rs
index e877ea95fbc..e3d2bf4f657 100644
--- a/components/script/dom/keyboardevent.rs
+++ b/components/script/dom/keyboardevent.rs
@@ -762,13 +762,12 @@ impl KeyboardEventMethods for KeyboardEvent {
                          _modifiersListArg: DOMString,
                          repeat: bool,
                          _locale: DOMString) {
-        let event = self.upcast::<Event>();
-        if event.dispatching() {
+        if self.upcast::<Event>().dispatching() {
             return;
         }
 
-        let uievent = self.upcast::<UIEvent>();
-        uievent.InitUIEvent(typeArg, canBubbleArg, cancelableArg, viewArg, 0);
+        self.upcast::<UIEvent>()
+            .InitUIEvent(typeArg, canBubbleArg, cancelableArg, viewArg, 0);
         *self.key_string.borrow_mut() = keyArg;
         self.location.set(locationArg);
         self.repeat.set(repeat);
diff --git a/components/script/dom/messageevent.rs b/components/script/dom/messageevent.rs
index 88ff10e4a55..4af83b3af7d 100644
--- a/components/script/dom/messageevent.rs
+++ b/components/script/dom/messageevent.rs
@@ -78,8 +78,7 @@ impl MessageEvent {
         let messageevent = MessageEvent::new(
             scope, "message".to_owned(), false, false, message,
             "".to_owned(), "".to_owned());
-        let event = messageevent.upcast::<Event>();
-        event.fire(target);
+        messageevent.upcast::<Event>().fire(target);
     }
 }
 
diff --git a/components/script/dom/mod.rs b/components/script/dom/mod.rs
index 6ae697ab19d..a61ddd76c2c 100644
--- a/components/script/dom/mod.rs
+++ b/components/script/dom/mod.rs
@@ -151,8 +151,8 @@
 //! # use script::dom::node::Node;
 //! # use script::dom::htmlelement::HTMLElement;
 //! fn f(element: &Element) {
-//!     let base: &Node = element.upcast::<Node>();
-//!     let derived: Option<&HTMLElement> = element.downcast::<HTMLElement>();
+//!     let base = element.upcast::<Node>();
+//!     let derived = element.downcast::<HTMLElement>();
 //! }
 //! ```
 //!
diff --git a/components/script/dom/mouseevent.rs b/components/script/dom/mouseevent.rs
index 63c4e5ba8bd..a81d54f0b9b 100644
--- a/components/script/dom/mouseevent.rs
+++ b/components/script/dom/mouseevent.rs
@@ -189,13 +189,12 @@ impl MouseEventMethods for MouseEvent {
                       metaKeyArg: bool,
                       buttonArg: i16,
                       relatedTargetArg: Option<&EventTarget>) {
-        let event: &Event = self.upcast::<Event>();
-        if event.dispatching() {
+        if self.upcast::<Event>().dispatching() {
             return;
         }
 
-        let uievent: &UIEvent = self.upcast::<UIEvent>();
-        uievent.InitUIEvent(typeArg, canBubbleArg, cancelableArg, viewArg, detailArg);
+        self.upcast::<UIEvent>()
+            .InitUIEvent(typeArg, canBubbleArg, cancelableArg, viewArg, detailArg);
         self.screen_x.set(screenXArg);
         self.screen_y.set(screenYArg);
         self.client_x.set(clientXArg);
diff --git a/components/script/dom/node.rs b/components/script/dom/node.rs
index 92389b127aa..1eb4240f307 100644
--- a/components/script/dom/node.rs
+++ b/components/script/dom/node.rs
@@ -355,9 +355,9 @@ impl<'a> Iterator for QuerySelectorIterator {
         // TODO(cgaebel): Is it worth it to build a bloom filter here
         // (instead of passing `None`)? Probably.
         self.iterator.by_ref().filter_map(|node| {
-            if let Some(element) = Root::downcast::<Element>(node) {
+            if let Some(element) = Root::downcast(node) {
                 if matches(selectors, &element, None) {
-                    return Some(Root::upcast::<Node>(element))
+                    return Some(Root::upcast(element));
                 }
             }
             None
@@ -718,7 +718,7 @@ impl Node {
             Err(()) => Err(Error::Syntax),
             // Step 3.
             Ok(ref selectors) => {
-                Ok(self.traverse_preorder().filter_map(Root::downcast::<Element>).find(|element| {
+                Ok(self.traverse_preorder().filter_map(Root::downcast).find(|element| {
                     matches(selectors, element, None)
                 }))
             }
@@ -787,12 +787,7 @@ impl Node {
     }
 
     pub fn child_elements(&self) -> ChildElementIterator {
-        fn to_temporary(node: Root<Node>) -> Option<Root<Element>> {
-            Root::downcast::<Element>(node)
-        }
-        self.children()
-            .filter_map(to_temporary as fn(_) -> _)
-            .peekable()
+        self.children().filter_map(Root::downcast as fn(_) -> _).peekable()
     }
 
     pub fn remove_self(&self) {
@@ -823,18 +818,10 @@ impl Node {
             name: "".to_owned(),
             publicId: "".to_owned(),
             systemId: "".to_owned(),
-
-            attrs: {
-                let e: Option<&Element> = self.downcast::<Element>();
-                match e {
-                    Some(element) => element.summarize(),
-                    None => vec!(),
-                }
-            },
+            attrs: self.downcast().map(Element::summarize).unwrap_or(vec![]),
 
             isDocumentElement:
                 self.owner_doc()
-                    .r()
                     .GetDocumentElement()
                     .map(|elem| elem.upcast::<Node>() == self)
                     .unwrap_or(false),
@@ -846,12 +833,10 @@ impl Node {
 
     // https://dvcs.w3.org/hg/innerhtml/raw-file/tip/index.html#dfn-concept-parse-fragment
     pub fn parse_fragment(&self, markup: DOMString) -> Fallible<Root<DocumentFragment>> {
-        let context_node: &Node = self.upcast::<Node>();
         let context_document = document_from_node(self);
         let fragment = DocumentFragment::new(context_document.r());
         if context_document.r().is_html_document() {
-            let fragment_node = fragment.upcast::<Node>();
-            parse_html_fragment(context_node, markup, fragment_node);
+            parse_html_fragment(self.upcast(), markup, fragment.upcast());
         } else {
             // FIXME: XML case
             unimplemented!();
@@ -1619,7 +1604,7 @@ impl Node {
         // XXXabinader: clone() for each node as trait?
         let copy: Root<Node> = match node.type_id() {
             NodeTypeId::DocumentType => {
-                let doctype: &DocumentType = node.downcast::<DocumentType>().unwrap();
+                let doctype = node.downcast::<DocumentType>().unwrap();
                 let doctype = DocumentType::new(doctype.name().clone(),
                                                 Some(doctype.public_id().clone()),
                                                 Some(doctype.system_id().clone()), document.r());
@@ -1720,8 +1705,7 @@ impl Node {
     pub fn collect_text_contents<T: Iterator<Item=Root<Node>>>(iterator: T) -> String {
         let mut content = String::new();
         for node in iterator {
-            let text = node.downcast::<Text>();
-            match text {
+            match node.downcast::<Text>() {
                 Some(text) => content.push_str(&text.upcast::<CharacterData>().Data()),
                 None => (),
             }
@@ -1778,7 +1762,7 @@ impl Node {
                     // Step 3.
                     None => ns!(""),
                     // Step 4.
-                    Some(parent) => Node::locate_namespace(parent.upcast::<Node>(), prefix)
+                    Some(parent) => Node::locate_namespace(parent.upcast(), prefix)
                 }
             },
             NodeTypeId::Document => {
@@ -1787,7 +1771,7 @@ impl Node {
                     None => ns!(""),
                     // Step 2.
                     Some(document_element) => {
-                        Node::locate_namespace(document_element.upcast::<Node>(), prefix)
+                        Node::locate_namespace(document_element.upcast(), prefix)
                     }
                 }
             },
@@ -1797,7 +1781,7 @@ impl Node {
                      // Step 1.
                      None => ns!(""),
                      // Step 2.
-                     Some(parent) => Node::locate_namespace(parent.upcast::<Node>(), prefix)
+                     Some(parent) => Node::locate_namespace(parent.upcast(), prefix)
                  }
         }
     }
@@ -1828,19 +1812,15 @@ impl NodeMethods for Node {
     fn NodeName(&self) -> DOMString {
         match self.type_id() {
             NodeTypeId::Element(..) => {
-                let elem: &Element = self.downcast::<Element>().unwrap();
-                elem.TagName()
+                self.downcast::<Element>().unwrap().TagName()
             }
             NodeTypeId::CharacterData(CharacterDataTypeId::Text) => "#text".to_owned(),
             NodeTypeId::CharacterData(CharacterDataTypeId::ProcessingInstruction) => {
-                let processing_instruction: &ProcessingInstruction =
-                    self.downcast::<ProcessingInstruction>().unwrap();
-                processing_instruction.Target()
+                self.downcast::<ProcessingInstruction>().unwrap().Target()
             }
             NodeTypeId::CharacterData(CharacterDataTypeId::Comment) => "#comment".to_owned(),
             NodeTypeId::DocumentType => {
-                let doctype: &DocumentType = self.downcast::<DocumentType>().unwrap();
-                doctype.name().clone()
+                self.downcast::<DocumentType>().unwrap().name().clone()
             },
             NodeTypeId::DocumentFragment => "#document-fragment".to_owned(),
             NodeTypeId::Document => "#document".to_owned()
@@ -1870,7 +1850,7 @@ impl NodeMethods for Node {
 
     // https://dom.spec.whatwg.org/#dom-node-parentelement
     fn GetParentElement(&self) -> Option<Root<Element>> {
-        self.GetParentNode().and_then(Root::downcast::<Element>)
+        self.GetParentNode().and_then(Root::downcast)
     }
 
     // https://dom.spec.whatwg.org/#dom-node-haschildnodes
@@ -1911,7 +1891,7 @@ impl NodeMethods for Node {
     fn GetNodeValue(&self) -> Option<DOMString> {
         match self.type_id() {
             NodeTypeId::CharacterData(..) => {
-                let chardata: &CharacterData = self.downcast::<CharacterData>().unwrap();
+                let chardata = self.downcast::<CharacterData>().unwrap();
                 Some(chardata.Data())
             }
             _ => {
@@ -1939,7 +1919,7 @@ impl NodeMethods for Node {
                 Some(content)
             }
             NodeTypeId::CharacterData(..) => {
-                let characterdata: &CharacterData = self.downcast::<CharacterData>().unwrap();
+                let characterdata = self.downcast::<CharacterData>().unwrap();
                 Some(characterdata.Data())
             }
             NodeTypeId::DocumentType |
@@ -1959,15 +1939,14 @@ impl NodeMethods for Node {
                 let node = if value.is_empty() {
                     None
                 } else {
-                    let document = self.owner_doc();
-                    Some(Root::upcast::<Node>(document.r().CreateTextNode(value)))
+                    Some(Root::upcast(self.owner_doc().CreateTextNode(value)))
                 };
 
                 // Step 3.
                 Node::replace_all(node.r(), self);
             }
             NodeTypeId::CharacterData(..) => {
-                let characterdata: &CharacterData = self.downcast::<CharacterData>().unwrap();
+                let characterdata = self.downcast::<CharacterData>().unwrap();
                 characterdata.SetData(value);
 
                 // Notify the document that the content of this node is different
@@ -2034,8 +2013,7 @@ impl NodeMethods for Node {
                         0 => (),
                         // Step 6.1.2
                         1 => {
-                            if self.child_elements()
-                                   .any(|c| c.upcast::<Node>() != child) {
+                            if self.child_elements().any(|c| c.upcast::<Node>() != child) {
                                 return Err(Error::HierarchyRequest);
                             }
                             if child.following_siblings()
@@ -2137,14 +2115,13 @@ impl NodeMethods for Node {
         for child in self.children() {
             match child.downcast::<Text>() {
                 Some(text) => {
-                    let characterdata: &CharacterData = text.upcast::<CharacterData>();
+                    let characterdata = text.upcast::<CharacterData>();
                     if characterdata.Length() == 0 {
                         Node::remove(&*child, self, SuppressObserver::Unsuppressed);
                     } else {
                         match prev_text {
                             Some(ref text_node) => {
-                                let prev_characterdata =
-                                    text_node.upcast::<CharacterData>();
+                                let prev_characterdata = text_node.upcast::<CharacterData>();
                                 prev_characterdata.append_data(&**characterdata.data());
                                 Node::remove(&*child, self, SuppressObserver::Unsuppressed);
                             },
@@ -2172,34 +2149,34 @@ impl NodeMethods for Node {
     // https://dom.spec.whatwg.org/#dom-node-isequalnode
     fn IsEqualNode(&self, maybe_node: Option<&Node>) -> bool {
         fn is_equal_doctype(node: &Node, other: &Node) -> bool {
-            let doctype: &DocumentType = node.downcast::<DocumentType>().unwrap();
-            let other_doctype: &DocumentType = other.downcast::<DocumentType>().unwrap();
+            let doctype = node.downcast::<DocumentType>().unwrap();
+            let other_doctype = other.downcast::<DocumentType>().unwrap();
             (*doctype.name() == *other_doctype.name()) &&
             (*doctype.public_id() == *other_doctype.public_id()) &&
             (*doctype.system_id() == *other_doctype.system_id())
         }
         fn is_equal_element(node: &Node, other: &Node) -> bool {
-            let element: &Element = node.downcast::<Element>().unwrap();
-            let other_element: &Element = other.downcast::<Element>().unwrap();
+            let element = node.downcast::<Element>().unwrap();
+            let other_element = other.downcast::<Element>().unwrap();
             (*element.namespace() == *other_element.namespace()) &&
             (*element.prefix() == *other_element.prefix()) &&
             (*element.local_name() == *other_element.local_name()) &&
             (element.attrs().len() == other_element.attrs().len())
         }
         fn is_equal_processinginstruction(node: &Node, other: &Node) -> bool {
-            let pi: &ProcessingInstruction = node.downcast::<ProcessingInstruction>().unwrap();
-            let other_pi: &ProcessingInstruction = other.downcast::<ProcessingInstruction>().unwrap();
+            let pi = node.downcast::<ProcessingInstruction>().unwrap();
+            let other_pi = other.downcast::<ProcessingInstruction>().unwrap();
             (*pi.target() == *other_pi.target()) &&
             (*pi.upcast::<CharacterData>().data() == *other_pi.upcast::<CharacterData>().data())
         }
         fn is_equal_characterdata(node: &Node, other: &Node) -> bool {
-            let characterdata: &CharacterData = node.downcast::<CharacterData>().unwrap();
-            let other_characterdata: &CharacterData = other.downcast::<CharacterData>().unwrap();
+            let characterdata = node.downcast::<CharacterData>().unwrap();
+            let other_characterdata = other.downcast::<CharacterData>().unwrap();
             *characterdata.data() == *other_characterdata.data()
         }
         fn is_equal_element_attrs(node: &Node, other: &Node) -> bool {
-            let element: &Element = node.downcast::<Element>().unwrap();
-            let other_element: &Element = other.downcast::<Element>().unwrap();
+            let element = node.downcast::<Element>().unwrap();
+            let other_element = other.downcast::<Element>().unwrap();
             assert!(element.attrs().len() == other_element.attrs().len());
             // FIXME(https://github.com/rust-lang/rust/issues/23338)
             let attrs = element.attrs();
@@ -2327,7 +2304,9 @@ impl NodeMethods for Node {
 
         // Step 2.
         match self.type_id() {
-            NodeTypeId::Element(..) => self.downcast::<Element>().unwrap().lookup_prefix(namespace),
+            NodeTypeId::Element(..) => {
+                self.downcast::<Element>().unwrap().lookup_prefix(namespace)
+            },
             NodeTypeId::Document => {
                 self.downcast::<Document>().unwrap().GetDocumentElement().and_then(|element| {
                     element.r().lookup_prefix(namespace)
@@ -2376,8 +2355,7 @@ pub struct TrustedNodeAddress(pub *const c_void);
 unsafe impl Send for TrustedNodeAddress {}
 
 pub fn document_from_node<T: DerivedFrom<Node> + Reflectable>(derived: &T) -> Root<Document> {
-    let node: &Node = derived.upcast::<Node>();
-    node.owner_doc()
+    derived.upcast().owner_doc()
 }
 
 pub fn window_from_node<T: DerivedFrom<Node> + Reflectable>(derived: &T) -> Root<Window> {
@@ -2387,8 +2365,7 @@ pub fn window_from_node<T: DerivedFrom<Node> + Reflectable>(derived: &T) -> Root
 
 impl VirtualMethods for Node {
     fn super_type(&self) -> Option<&VirtualMethods> {
-        let eventtarget: &EventTarget = self.upcast::<EventTarget>();
-        Some(eventtarget as &VirtualMethods)
+        Some(self.upcast::<EventTarget>() as &VirtualMethods)
     }
 
     fn children_changed(&self, mutation: &ChildrenMutation) {
diff --git a/components/script/dom/range.rs b/components/script/dom/range.rs
index 725bce6de50..a67140db970 100644
--- a/components/script/dom/range.rs
+++ b/components/script/dom/range.rs
@@ -43,7 +43,7 @@ impl Range {
     }
 
     pub fn new_with_doc(document: &Document) -> Root<Range> {
-        let root = document.upcast::<Node>();
+        let root = document.upcast();
         Range::new(document, root, 0, root, 0)
     }
 
@@ -369,7 +369,7 @@ impl RangeMethods for Range {
                 let text = text.SubstringData(start_offset, end_offset - start_offset);
                 clone.downcast::<CharacterData>().unwrap().SetData(text.unwrap());
                 // Step 4.3.
-                try!(fragment.upcast::<Node>().AppendChild(clone.r()));
+                try!(fragment.upcast::<Node>().AppendChild(&clone));
                 // Step 4.4
                 return Ok(fragment);
             }
@@ -389,12 +389,12 @@ impl RangeMethods for Range {
                 let text = text.SubstringData(start_offset, start_node.len() - start_offset);
                 clone.downcast::<CharacterData>().unwrap().SetData(text.unwrap());
                 // Step 13.3.
-                try!(fragment.upcast::<Node>().AppendChild(clone.r()));
+                try!(fragment.upcast::<Node>().AppendChild(&clone));
             } else {
                 // Step 14.1.
                 let clone = child.CloneNode(false);
                 // Step 14.2.
-                try!(fragment.upcast::<Node>().AppendChild(clone.r()));
+                try!(fragment.upcast::<Node>().AppendChild(&clone));
                 // Step 14.3.
                 let subrange = Range::new(clone.owner_doc().r(),
                                           start_node.r(),
@@ -404,7 +404,7 @@ impl RangeMethods for Range {
                 // Step 14.4.
                 let subfragment = try!(subrange.CloneContents());
                 // Step 14.5.
-                try!(clone.AppendChild(subfragment.upcast::<Node>()));
+                try!(clone.AppendChild(subfragment.upcast()));
             }
         }
 
@@ -413,7 +413,7 @@ impl RangeMethods for Range {
             // Step 15.1.
             let clone = child.CloneNode(true);
             // Step 15.2.
-            try!(fragment.upcast::<Node>().AppendChild(clone.r()));
+            try!(fragment.upcast::<Node>().AppendChild(&clone));
         }
 
         if let Some(child) = last_contained_child {
@@ -426,12 +426,12 @@ impl RangeMethods for Range {
                 let text = text.SubstringData(0, end_offset);
                 clone.downcast::<CharacterData>().unwrap().SetData(text.unwrap());
                 // Step 16.3.
-                try!(fragment.upcast::<Node>().AppendChild(clone.r()));
+                try!(fragment.upcast::<Node>().AppendChild(&clone));
             } else {
                 // Step 17.1.
                 let clone = child.CloneNode(false);
                 // Step 17.2.
-                try!(fragment.upcast::<Node>().AppendChild(clone.r()));
+                try!(fragment.upcast::<Node>().AppendChild(&clone));
                 // Step 17.3.
                 let subrange = Range::new(clone.owner_doc().r(),
                                           child.r(),
@@ -441,7 +441,7 @@ impl RangeMethods for Range {
                 // Step 17.4.
                 let subfragment = try!(subrange.CloneContents());
                 // Step 17.5.
-                try!(clone.AppendChild(subfragment.upcast::<Node>()));
+                try!(clone.AppendChild(subfragment.upcast()));
             }
         }
 
@@ -477,7 +477,7 @@ impl RangeMethods for Range {
                 let text = end_data.SubstringData(start_offset, end_offset - start_offset);
                 clone.downcast::<CharacterData>().unwrap().SetData(text.unwrap());
                 // Step 4.3.
-                try!(fragment.upcast::<Node>().AppendChild(clone.r()));
+                try!(fragment.upcast::<Node>().AppendChild(&clone));
                 // Step 4.4.
                 try!(end_data.ReplaceData(start_offset,
                                           end_offset - start_offset,
@@ -513,7 +513,7 @@ impl RangeMethods for Range {
                                                     start_node.len() - start_offset);
                 clone.downcast::<CharacterData>().unwrap().SetData(text.unwrap());
                 // Step 15.3.
-                try!(fragment.upcast::<Node>().AppendChild(clone.r()));
+                try!(fragment.upcast::<Node>().AppendChild(&clone));
                 // Step 15.4.
                 try!(start_data.ReplaceData(start_offset,
                                             start_node.len() - start_offset,
@@ -522,7 +522,7 @@ impl RangeMethods for Range {
                 // Step 16.1.
                 let clone = child.CloneNode(false);
                 // Step 16.2.
-                try!(fragment.upcast::<Node>().AppendChild(clone.r()));
+                try!(fragment.upcast::<Node>().AppendChild(&clone));
                 // Step 16.3.
                 let subrange = Range::new(clone.owner_doc().r(),
                                           start_node.r(),
@@ -532,13 +532,13 @@ impl RangeMethods for Range {
                 // Step 16.4.
                 let subfragment = try!(subrange.ExtractContents());
                 // Step 16.5.
-                try!(clone.AppendChild(subfragment.upcast::<Node>()));
+                try!(clone.AppendChild(subfragment.upcast()));
             }
         }
 
         // Step 17.
         for child in contained_children {
-            try!(fragment.upcast::<Node>().AppendChild(child.r()));
+            try!(fragment.upcast::<Node>().AppendChild(&child));
         }
 
         if let Some(child) = last_contained_child {
@@ -550,14 +550,14 @@ impl RangeMethods for Range {
                 let text = end_data.SubstringData(0, end_offset);
                 clone.downcast::<CharacterData>().unwrap().SetData(text.unwrap());
                 // Step 18.3.
-                try!(fragment.upcast::<Node>().AppendChild(clone.r()));
+                try!(fragment.upcast::<Node>().AppendChild(&clone));
                 // Step 18.4.
                 try!(end_data.ReplaceData(0, end_offset, "".to_owned()));
             } else {
                 // Step 19.1.
                 let clone = child.CloneNode(false);
                 // Step 19.2.
-                try!(fragment.upcast::<Node>().AppendChild(clone.r()));
+                try!(fragment.upcast::<Node>().AppendChild(&clone));
                 // Step 19.3.
                 let subrange = Range::new(clone.owner_doc().r(),
                                           child.r(),
@@ -567,7 +567,7 @@ impl RangeMethods for Range {
                 // Step 19.4.
                 let subfragment = try!(subrange.ExtractContents());
                 // Step 19.5.
-                try!(clone.AppendChild(subfragment.upcast::<Node>()));
+                try!(clone.AppendChild(subfragment.upcast()));
             }
         }
 
@@ -697,7 +697,7 @@ impl RangeMethods for Range {
         try!(self.InsertNode(new_parent));
 
         // Step 6.
-        let _ = try!(new_parent.AppendChild(fragment.upcast::<Node>()));
+        try!(new_parent.AppendChild(fragment.upcast()));
 
         // Step 7.
         self.SelectNode(new_parent)
diff --git a/components/script/dom/servohtmlparser.rs b/components/script/dom/servohtmlparser.rs
index 061cdd533c7..4999d600a20 100644
--- a/components/script/dom/servohtmlparser.rs
+++ b/components/script/dom/servohtmlparser.rs
@@ -48,7 +48,7 @@ impl Sink {
             NodeOrText::AppendNode(n) => n.root(),
             NodeOrText::AppendText(t) => {
                 let text = Text::new(t.into(), &self.document);
-                Root::upcast::<Node>(text)
+                Root::upcast(text)
             }
         }
     }
diff --git a/components/script/dom/storage.rs b/components/script/dom/storage.rs
index 926848e66c7..8d0377b30ee 100644
--- a/components/script/dom/storage.rs
+++ b/components/script/dom/storage.rs
@@ -11,7 +11,6 @@ use dom::bindings::js::{Root, RootedReference};
 use dom::bindings::refcounted::Trusted;
 use dom::bindings::utils::{Reflector, reflect_dom_object};
 use dom::event::{Event, EventBubbles, EventCancelable};
-use dom::eventtarget::EventTarget;
 use dom::storageevent::StorageEvent;
 use dom::urlhelper::UrlHelper;
 use ipc_channel::ipc;
@@ -193,7 +192,6 @@ impl MainThreadRunnable for StorageEventRunnable {
             ev_url.to_string(),
             Some(storage)
         );
-        let event = storage_event.upcast::<Event>();
 
         let root_page = script_task.root_page();
         for it_page in root_page.iter() {
@@ -203,8 +201,7 @@ impl MainThreadRunnable for StorageEventRunnable {
             // TODO: Such a Document object is not necessarily fully active, but events fired on such
             // objects are ignored by the event loop until the Document becomes fully active again.
             if ev_window.pipeline() != it_window.pipeline() {
-                let target = it_window.upcast::<EventTarget>();
-                event.fire(target);
+                storage_event.upcast::<Event>().fire(it_window.upcast());
             }
         }
     }
diff --git a/components/script/dom/text.rs b/components/script/dom/text.rs
index 6f6e713ef27..d7c21cfa78d 100644
--- a/components/script/dom/text.rs
+++ b/components/script/dom/text.rs
@@ -63,9 +63,7 @@ impl TextMethods for Text {
         let parent = node.GetParentNode();
         if let Some(ref parent) = parent {
             // Step 7.
-            parent.r().InsertBefore(new_node.upcast::<Node>(),
-                                    node.GetNextSibling().r())
-                  .unwrap();
+            parent.InsertBefore(new_node.upcast(), node.GetNextSibling().r()).unwrap();
             // TODO: Ranges.
         }
         // Step 8.
diff --git a/components/script/dom/uievent.rs b/components/script/dom/uievent.rs
index 45b3aa07a7c..343d9f31620 100644
--- a/components/script/dom/uievent.rs
+++ b/components/script/dom/uievent.rs
@@ -86,7 +86,7 @@ impl UIEventMethods for UIEvent {
                    cancelable: bool,
                    view: Option<&Window>,
                    detail: i32) {
-        let event: &Event = self.upcast::<Event>();
+        let event = self.upcast::<Event>();
         if event.dispatching() {
             return;
         }
diff --git a/components/script/dom/userscripts.rs b/components/script/dom/userscripts.rs
index b7546ad4b27..35b1c2333a5 100644
--- a/components/script/dom/userscripts.rs
+++ b/components/script/dom/userscripts.rs
@@ -44,8 +44,7 @@ pub fn load_script(head: &HTMLHeadElement) {
             let new_script = doc.CreateElement("script".to_owned()).unwrap();
             let new_script = new_script.r();
             new_script.set_string_attribute(&atom!("src"), name);
-            let new_script_node = new_script.upcast::<Node>();
-            node.InsertBefore(new_script_node, first_child.r()).unwrap();
+            node.InsertBefore(new_script.upcast(), first_child.r()).unwrap();
         }
     }
 }
diff --git a/components/script/dom/virtualmethods.rs b/components/script/dom/virtualmethods.rs
index 95a40df6f6c..da80f414da4 100644
--- a/components/script/dom/virtualmethods.rs
+++ b/components/script/dom/virtualmethods.rs
@@ -123,131 +123,97 @@ pub trait VirtualMethods {
 pub fn vtable_for(node: &Node) -> &VirtualMethods {
     match node.type_id() {
         NodeTypeId::Element(ElementTypeId::HTMLElement(HTMLElementTypeId::HTMLAnchorElement)) => {
-            let element = node.downcast::<HTMLAnchorElement>().unwrap();
-            element as &VirtualMethods
+            node.downcast::<HTMLAnchorElement>().unwrap() as &VirtualMethods
         }
         NodeTypeId::Element(ElementTypeId::HTMLElement(HTMLElementTypeId::HTMLAppletElement)) => {
             node.downcast::<HTMLAppletElement>().unwrap() as &VirtualMethods
         }
         NodeTypeId::Element(ElementTypeId::HTMLElement(HTMLElementTypeId::HTMLAreaElement)) => {
-            let element = node.downcast::<HTMLAreaElement>().unwrap();
-            element as &VirtualMethods
+            node.downcast::<HTMLAreaElement>().unwrap() as &VirtualMethods
         }
         NodeTypeId::Element(ElementTypeId::HTMLElement(HTMLElementTypeId::HTMLBaseElement)) => {
-            let element = node.downcast::<HTMLBaseElement>().unwrap();
-            element as &VirtualMethods
+            node.downcast::<HTMLBaseElement>().unwrap() as &VirtualMethods
         }
         NodeTypeId::Element(ElementTypeId::HTMLElement(HTMLElementTypeId::HTMLBodyElement)) => {
-            let element = node.downcast::<HTMLBodyElement>().unwrap();
-            element as &VirtualMethods
+            node.downcast::<HTMLBodyElement>().unwrap() as &VirtualMethods
         }
         NodeTypeId::Element(ElementTypeId::HTMLElement(HTMLElementTypeId::HTMLButtonElement)) => {
-            let element = node.downcast::<HTMLButtonElement>().unwrap();
-            element as &VirtualMethods
+            node.downcast::<HTMLButtonElement>().unwrap() as &VirtualMethods
         }
         NodeTypeId::Element(ElementTypeId::HTMLElement(HTMLElementTypeId::HTMLCanvasElement)) => {
-            let element = node.downcast::<HTMLCanvasElement>().unwrap();
-            element as &VirtualMethods
+            node.downcast::<HTMLCanvasElement>().unwrap() as &VirtualMethods
         }
         NodeTypeId::Element(ElementTypeId::HTMLElement(HTMLElementTypeId::HTMLFieldSetElement)) => {
-            let element = node.downcast::<HTMLFieldSetElement>().unwrap();
-            element as &VirtualMethods
+            node.downcast::<HTMLFieldSetElement>().unwrap() as &VirtualMethods
         }
         NodeTypeId::Element(ElementTypeId::HTMLElement(HTMLElementTypeId::HTMLFontElement)) => {
-            let element = node.downcast::<HTMLFontElement>().unwrap();
-            element as &VirtualMethods
+            node.downcast::<HTMLFontElement>().unwrap() as &VirtualMethods
         }
         NodeTypeId::Element(ElementTypeId::HTMLElement(HTMLElementTypeId::HTMLFormElement)) => {
-            let element = node.downcast::<HTMLFormElement>().unwrap();
-            element as &VirtualMethods
+            node.downcast::<HTMLFormElement>().unwrap() as &VirtualMethods
         }
         NodeTypeId::Element(ElementTypeId::HTMLElement(HTMLElementTypeId::HTMLHeadElement)) => {
-            let element = node.downcast::<HTMLHeadElement>().unwrap();
-            element as &VirtualMethods
+            node.downcast::<HTMLHeadElement>().unwrap() as &VirtualMethods
         }
         NodeTypeId::Element(ElementTypeId::HTMLElement(HTMLElementTypeId::HTMLImageElement)) => {
-            let element = node.downcast::<HTMLImageElement>().unwrap();
-            element as &VirtualMethods
+            node.downcast::<HTMLImageElement>().unwrap() as &VirtualMethods
         }
         NodeTypeId::Element(ElementTypeId::HTMLElement(HTMLElementTypeId::HTMLIFrameElement)) => {
-            let element = node.downcast::<HTMLIFrameElement>().unwrap();
-            element as &VirtualMethods
+            node.downcast::<HTMLIFrameElement>().unwrap() as &VirtualMethods
         }
         NodeTypeId::Element(ElementTypeId::HTMLElement(HTMLElementTypeId::HTMLInputElement)) => {
-            let element = node.downcast::<HTMLInputElement>().unwrap();
-            element as &VirtualMethods
+            node.downcast::<HTMLInputElement>().unwrap() as &VirtualMethods
         }
         NodeTypeId::Element(ElementTypeId::HTMLElement(HTMLElementTypeId::HTMLLinkElement)) => {
-            let element = node.downcast::<HTMLLinkElement>().unwrap();
-            element as &VirtualMethods
+            node.downcast::<HTMLLinkElement>().unwrap() as &VirtualMethods
         }
         NodeTypeId::Element(ElementTypeId::HTMLElement(HTMLElementTypeId::HTMLMetaElement)) => {
-            let element = node.downcast::<HTMLMetaElement>().unwrap();
-            element as &VirtualMethods
+            node.downcast::<HTMLMetaElement>().unwrap() as &VirtualMethods
         }
         NodeTypeId::Element(ElementTypeId::HTMLElement(HTMLElementTypeId::HTMLObjectElement)) => {
-            let element = node.downcast::<HTMLObjectElement>().unwrap();
-            element as &VirtualMethods
+            node.downcast::<HTMLObjectElement>().unwrap() as &VirtualMethods
         }
         NodeTypeId::Element(ElementTypeId::HTMLElement(HTMLElementTypeId::HTMLOptGroupElement)) => {
-            let element = node.downcast::<HTMLOptGroupElement>().unwrap();
-            element as &VirtualMethods
+            node.downcast::<HTMLOptGroupElement>().unwrap() as &VirtualMethods
         }
         NodeTypeId::Element(ElementTypeId::HTMLElement(HTMLElementTypeId::HTMLOptionElement)) => {
-            let element = node.downcast::<HTMLOptionElement>().unwrap();
-            element as &VirtualMethods
+            node.downcast::<HTMLOptionElement>().unwrap() as &VirtualMethods
         }
         NodeTypeId::Element(ElementTypeId::HTMLElement(HTMLElementTypeId::HTMLScriptElement)) => {
-            let element = node.downcast::<HTMLScriptElement>().unwrap();
-            element as &VirtualMethods
+            node.downcast::<HTMLScriptElement>().unwrap() as &VirtualMethods
         }
         NodeTypeId::Element(ElementTypeId::HTMLElement(HTMLElementTypeId::HTMLSelectElement)) => {
-            let element = node.downcast::<HTMLSelectElement>().unwrap();
-            element as &VirtualMethods
+            node.downcast::<HTMLSelectElement>().unwrap() as &VirtualMethods
         }
         NodeTypeId::Element(ElementTypeId::HTMLElement(HTMLElementTypeId::HTMLStyleElement)) => {
-            let element = node.downcast::<HTMLStyleElement>().unwrap();
-            element as &VirtualMethods
+            node.downcast::<HTMLStyleElement>().unwrap() as &VirtualMethods
         }
         NodeTypeId::Element(ElementTypeId::HTMLElement(HTMLElementTypeId::HTMLTableElement)) => {
-            let element =
-                node.downcast::<HTMLTableElement>().unwrap();
-            element as &VirtualMethods
+            node.downcast::<HTMLTableElement>().unwrap() as &VirtualMethods
         }
         NodeTypeId::Element(ElementTypeId::HTMLElement(HTMLElementTypeId::HTMLTableCellElement(_))) => {
-            let element =
-                node.downcast::<HTMLTableCellElement>().unwrap();
-            element as &VirtualMethods
+            node.downcast::<HTMLTableCellElement>().unwrap() as &VirtualMethods
         }
         NodeTypeId::Element(ElementTypeId::HTMLElement(HTMLElementTypeId::HTMLTableRowElement)) => {
-            let element =
-                node.downcast::<HTMLTableRowElement>().unwrap();
-            element as &VirtualMethods
+            node.downcast::<HTMLTableRowElement>().unwrap() as &VirtualMethods
         }
         NodeTypeId::Element(ElementTypeId::HTMLElement(HTMLElementTypeId::HTMLTableSectionElement)) => {
-            let element =
-                node.downcast::<HTMLTableSectionElement>().unwrap();
-            element as &VirtualMethods
+            node.downcast::<HTMLTableSectionElement>().unwrap() as &VirtualMethods
         }
         NodeTypeId::Element(ElementTypeId::HTMLElement(HTMLElementTypeId::HTMLTemplateElement)) => {
             node.downcast::<HTMLTemplateElement>().unwrap() as &VirtualMethods
         }
         NodeTypeId::Element(ElementTypeId::HTMLElement(HTMLElementTypeId::HTMLTextAreaElement)) => {
-            let element = node.downcast::<HTMLTextAreaElement>().unwrap();
-            element as &VirtualMethods
+            node.downcast::<HTMLTextAreaElement>().unwrap() as &VirtualMethods
         }
         NodeTypeId::Element(ElementTypeId::HTMLElement(HTMLElementTypeId::HTMLTitleElement)) => {
-            let element =
-                node.downcast::<HTMLTitleElement>().unwrap();
-            element as &VirtualMethods
+            node.downcast::<HTMLTitleElement>().unwrap() as &VirtualMethods
         }
         NodeTypeId::Element(ElementTypeId::Element) => {
-            let element = node.downcast::<Element>().unwrap();
-            element as &VirtualMethods
+            node.downcast::<Element>().unwrap() as &VirtualMethods
         }
         NodeTypeId::Element(_) => {
-            let element = node.downcast::<HTMLElement>().unwrap();
-            element as &VirtualMethods
+            node.downcast::<HTMLElement>().unwrap() as &VirtualMethods
         }
         _ => {
             node as &VirtualMethods
diff --git a/components/script/dom/webglrenderingcontext.rs b/components/script/dom/webglrenderingcontext.rs
index cc4f4579dd9..c7011c8e056 100644
--- a/components/script/dom/webglrenderingcontext.rs
+++ b/components/script/dom/webglrenderingcontext.rs
@@ -14,7 +14,6 @@ use dom::bindings::global::{GlobalField, GlobalRef};
 use dom::bindings::js::{JS, LayoutJS, MutNullableHeap, Root};
 use dom::bindings::utils::{Reflector, reflect_dom_object};
 use dom::event::{Event, EventBubbles, EventCancelable};
-use dom::eventtarget::EventTarget;
 use dom::htmlcanvaselement::HTMLCanvasElement;
 use dom::htmlcanvaselement::utils as canvas_utils;
 use dom::node::{Node, NodeDamage, window_from_node};
@@ -121,7 +120,7 @@ impl WebGLRenderingContext {
                                                    EventBubbles::DoesNotBubble,
                                                    EventCancelable::Cancelable,
                                                    msg);
-                event.upcast::<Event>().fire(canvas.upcast::<EventTarget>());
+                event.upcast::<Event>().fire(canvas.upcast());
                 None
             }
         }
@@ -153,9 +152,7 @@ impl WebGLRenderingContext {
     }
 
     fn mark_as_dirty(&self) {
-        let canvas = self.canvas.root();
-        let node = canvas.upcast::<Node>();
-        node.dirty(NodeDamage::OtherNodeDamage);
+        self.canvas.root().upcast::<Node>().dirty(NodeDamage::OtherNodeDamage);
     }
 }
 
diff --git a/components/script/dom/websocket.rs b/components/script/dom/websocket.rs
index 149f4ba32e3..88f3c6a2f8e 100644
--- a/components/script/dom/websocket.rs
+++ b/components/script/dom/websocket.rs
@@ -454,7 +454,7 @@ impl Runnable for ConnectionEstablishedTask {
         let event = Event::new(global.r(), "open".to_owned(),
                                EventBubbles::DoesNotBubble,
                                EventCancelable::NotCancelable);
-        event.fire(ws.upcast::<EventTarget>());
+        event.fire(ws.upcast());
     }
 }
 
@@ -496,8 +496,7 @@ impl Runnable for CloseTask {
                                    "error".to_owned(),
                                    EventBubbles::DoesNotBubble,
                                    EventCancelable::Cancelable);
-            let target = ws.upcast::<EventTarget>();
-            event.r().fire(target);
+            event.fire(ws.upcast());
         }
         let rsn = ws.reason.borrow();
         let rsn_clone = rsn.clone();
@@ -511,9 +510,7 @@ impl Runnable for CloseTask {
                                           ws.clean_close.get(),
                                           ws.code.get(),
                                           rsn_clone);
-        let target = ws.upcast::<EventTarget>();
-        let event = close_event.upcast::<Event>();
-        event.fire(target);
+        close_event.upcast::<Event>().fire(ws.upcast());
     }
 }
 
@@ -562,7 +559,6 @@ impl Runnable for MessageReceivedTask {
             },
         }
 
-        let target = ws.upcast::<EventTarget>();
-        MessageEvent::dispatch_jsval(target, global.r(), message.handle());
+        MessageEvent::dispatch_jsval(ws.upcast(), global.r(), message.handle());
     }
 }
diff --git a/components/script/dom/window.rs b/components/script/dom/window.rs
index 9ca6713991d..5a9233319c1 100644
--- a/components/script/dom/window.rs
+++ b/components/script/dom/window.rs
@@ -793,8 +793,7 @@ impl<'a, T: Reflectable> ScriptHelpers for &'a T {
 
 impl Window {
     pub fn clear_js_runtime(&self) {
-        let document = self.Document();
-        document.upcast::<Node>().teardown();
+        self.Document().upcast::<Node>().teardown();
 
         // The above code may not catch all DOM objects
         // (e.g. DOM objects removed from the tree that haven't
@@ -835,9 +834,7 @@ impl Window {
         let body = self.Document().GetBody();
         let (x, y) = match body {
             Some(e) => {
-                let node = e.upcast::<Node>();
-                let content_size = node.get_bounding_content_box();
-
+                let content_size = e.upcast::<Node>().get_bounding_content_box();
                 let content_height = content_size.size.height.to_f64_px();
                 let content_width = content_size.size.width.to_f64_px();
                 (xfinite.max(0.0f64).min(content_width - width),
@@ -1055,7 +1052,7 @@ impl Window {
         let js_runtime = js_runtime.as_ref().unwrap();
         let element = response.node_address.and_then(|parent_node_address| {
             let node = from_untrusted_node_address(js_runtime.rt(), parent_node_address);
-            Root::downcast::<Element>(node)
+            Root::downcast(node)
         });
         (element, response.rect)
     }
diff --git a/components/script/dom/worker.rs b/components/script/dom/worker.rs
index 6d890f1a14e..e3fc2a202e5 100644
--- a/components/script/dom/worker.rs
+++ b/components/script/dom/worker.rs
@@ -115,7 +115,7 @@ impl Worker {
         let worker = address.root();
 
         let global = worker.r().global.root();
-        let target = worker.upcast::<EventTarget>();
+        let target = worker.upcast();
         let _ar = JSAutoRequest::new(global.r().get_cx());
         let _ac = JSAutoCompartment::new(global.r().get_cx(), target.reflector().get_jsobject().get());
         let mut message = RootedValue::new(global.r().get_cx(), UndefinedValue());
@@ -126,13 +126,11 @@ impl Worker {
     pub fn dispatch_simple_error(address: TrustedWorkerAddress) {
         let worker = address.root();
         let global = worker.r().global.root();
-        let target = worker.upcast::<EventTarget>();
-
         let event = Event::new(global.r(),
                                "error".to_owned(),
                                EventBubbles::DoesNotBubble,
                                EventCancelable::NotCancelable);
-        event.r().fire(target);
+        event.fire(worker.upcast());
     }
 
     pub fn handle_error_message(address: TrustedWorkerAddress, message: DOMString,
@@ -140,12 +138,10 @@ impl Worker {
         let worker = address.root();
         let global = worker.r().global.root();
         let error = RootedValue::new(global.r().get_cx(), UndefinedValue());
-        let target = worker.upcast::<EventTarget>();
         let errorevent = ErrorEvent::new(global.r(), "error".to_owned(),
                                          EventBubbles::Bubbles, EventCancelable::Cancelable,
                                          message, filename, lineno, colno, error.handle());
-        let event = errorevent.upcast::<Event>();
-        event.fire(target);
+        errorevent.upcast::<Event>().fire(worker.upcast());
     }
 }
 
diff --git a/components/script/dom/xmlhttprequest.rs b/components/script/dom/xmlhttprequest.rs
index e84a4781bab..067ba1019ed 100644
--- a/components/script/dom/xmlhttprequest.rs
+++ b/components/script/dom/xmlhttprequest.rs
@@ -737,8 +737,7 @@ impl XMLHttpRequest {
                                "readystatechange".to_owned(),
                                EventBubbles::DoesNotBubble,
                                EventCancelable::Cancelable);
-        let target = self.upcast::<EventTarget>();
-        event.r().fire(target);
+        event.fire(self.upcast());
     }
 
     fn process_headers_available(&self, cors_request: Option<CORSRequest>,
@@ -921,12 +920,11 @@ impl XMLHttpRequest {
                                                total.is_some(), loaded,
                                                total.unwrap_or(0));
         let target = if upload {
-            self.upload.upcast::<EventTarget>()
+            self.upload.upcast()
         } else {
-            self.upcast::<EventTarget>()
+            self.upcast()
         };
-        let event = progressevent.upcast::<Event>();
-        event.fire(target);
+        progressevent.upcast::<Event>().fire(target);
     }
 
     fn dispatch_upload_progress_event(&self, type_: DOMString, partial_load: Option<u64>) {
diff --git a/components/script/parse/html.rs b/components/script/parse/html.rs
index 36955322d6c..4943fecdb5f 100644
--- a/components/script/parse/html.rs
+++ b/components/script/parse/html.rs
@@ -45,16 +45,14 @@ impl<'a> TreeSink for servohtmlparser::Sink {
     type Handle = JS<Node>;
 
     fn get_document(&mut self) -> JS<Node> {
-        let doc = self.document.root();
-        let node = doc.upcast::<Node>();
-        JS::from_ref(node)
+        JS::from_ref(self.document.root().upcast())
     }
 
     fn get_template_contents(&self, target: JS<Node>) -> JS<Node> {
         let target = target.root();
         let template = target.downcast::<HTMLTemplateElement>()
             .expect("tried to get template contents of non-HTMLTemplateElement in HTML parsing");
-        JS::from_ref(template.Content().upcast::<Node>())
+        JS::from_ref(template.Content().upcast())
     }
 
     fn same_node(&self, x: JS<Node>, y: JS<Node>) -> bool {
@@ -81,15 +79,13 @@ impl<'a> TreeSink for servohtmlparser::Sink {
             elem.r().set_attribute_from_parser(attr.name, attr.value.into(), None);
         }
 
-        let node = elem.upcast::<Node>();
-        JS::from_ref(node)
+        JS::from_ref(elem.upcast())
     }
 
     fn create_comment(&mut self, text: StrTendril) -> JS<Node> {
         let doc = self.document.root();
         let comment = Comment::new(text.into(), doc.r());
-        let node = Root::upcast::<Node>(comment);
-        JS::from_rooted(&node)
+        JS::from_ref(comment.upcast())
     }
 
     fn append_before_sibling(&mut self,
@@ -127,12 +123,9 @@ impl<'a> TreeSink for servohtmlparser::Sink {
     fn append_doctype_to_document(&mut self, name: StrTendril, public_id: StrTendril,
                                   system_id: StrTendril) {
         let doc = self.document.root();
-        let doc_node = doc.upcast::<Node>();
         let doctype = DocumentType::new(
             name.into(), Some(public_id.into()), Some(system_id.into()), doc.r());
-        let node: Root<Node> = Root::upcast::<Node>(doctype);
-
-        assert!(doc_node.AppendChild(node.r()).is_ok());
+        doc.upcast::<Node>().AppendChild(doctype.upcast()).expect("Appending failed");
     }
 
     fn add_attrs_if_missing(&mut self, target: JS<Node>, attrs: Vec<Attribute>) {
@@ -153,13 +146,13 @@ impl<'a> TreeSink for servohtmlparser::Sink {
 
     fn mark_script_already_started(&mut self, node: JS<Node>) {
         let node: Root<Node> = node.root();
-        let script: Option<&HTMLScriptElement> = node.downcast::<HTMLScriptElement>();
+        let script = node.downcast::<HTMLScriptElement>();
         script.map(|script| script.mark_already_started());
     }
 
     fn complete_script(&mut self, node: JS<Node>) -> NextParserState {
         let node: Root<Node> = node.root();
-        let script: Option<&HTMLScriptElement> = node.downcast::<HTMLScriptElement>();
+        let script = node.downcast::<HTMLScriptElement>();
         if let Some(script) = script {
             return script.prepare();
         }
@@ -305,8 +298,7 @@ pub fn parse_html_fragment(context_node: &Node,
 
     // Step 14.
     let root_element = document.r().GetDocumentElement().expect("no document element");
-    let root_node = root_element.upcast::<Node>();
-    for child in root_node.children() {
+    for child in root_element.upcast::<Node>().children() {
         output.AppendChild(child.r()).unwrap();
     }
 }
diff --git a/components/script/script_task.rs b/components/script/script_task.rs
index c52bcd66f4c..79e749b82d6 100644
--- a/components/script/script_task.rs
+++ b/components/script/script_task.rs
@@ -34,7 +34,6 @@ use dom::document::{Document, DocumentProgressHandler, IsHTMLDocument};
 use dom::document::{DocumentProgressTask, DocumentSource, MouseEventType};
 use dom::element::Element;
 use dom::event::{Event, EventBubbles, EventCancelable};
-use dom::eventtarget::EventTarget;
 use dom::node::{Node, NodeDamage, window_from_node};
 use dom::servohtmlparser::{ParserContext, ServoHTMLParser};
 use dom::uievent::UIEvent;
@@ -1256,12 +1255,10 @@ impl ScriptTask {
                 urls.push(current_url.clone());
 
                 for child in it_page.document().upcast::<Node>().traverse_preorder() {
-                    let target = child.upcast::<EventTarget>();
-                    dom_tree_size += heap_size_of_self_and_children(target);
+                    dom_tree_size += heap_size_of_self_and_children(&*child);
                 }
                 let window = it_page.window();
-                let target = window.upcast::<EventTarget>();
-                dom_tree_size += heap_size_of_self_and_children(target);
+                dom_tree_size += heap_size_of_self_and_children(&*window);
 
                 reports.push(Report {
                     path: path![format!("url({})", current_url), "dom-tree"],
@@ -1323,9 +1320,8 @@ impl ScriptTask {
         let frame_element = doc.find_iframe(subpage_id);
 
         if let Some(ref frame_element) = frame_element {
-            let element = frame_element.upcast::<Element>();
             doc.r().begin_focus_transaction();
-            doc.r().request_focus(element);
+            doc.r().request_focus(frame_element.upcast());
             doc.r().commit_focus_transaction(FocusType::Parent);
         }
     }
@@ -1625,7 +1621,7 @@ impl ScriptTask {
                                      DocumentSource::FromParser,
                                      loader);
 
-        let frame_element = frame_element.r().map(Castable::upcast::<Element>);
+        let frame_element = frame_element.r().map(Castable::upcast);
         window.r().init_browsing_context(document.r(), frame_element);
 
         // Create the root frame
@@ -1671,9 +1667,8 @@ impl ScriptTask {
         }
     }
 
-    fn scroll_fragment_point(&self, pipeline_id: PipelineId, node: &Element) {
-        let node = node.upcast::<Node>();
-        let rect = node.get_bounding_content_box();
+    fn scroll_fragment_point(&self, pipeline_id: PipelineId, element: &Element) {
+        let rect = element.upcast::<Node>().get_bounding_content_box();
         let point = Point2D::new(rect.origin.x.to_f32_px(), rect.origin.y.to_f32_px());
         // FIXME(#2003, pcwalton): This is pretty bogus when multiple layers are involved.
         // Really what needs to happen is that this needs to go through layout to ask which
@@ -1844,10 +1839,7 @@ impl ScriptTask {
                                    "resize".to_owned(), EventBubbles::DoesNotBubble,
                                    EventCancelable::NotCancelable, Some(window.r()),
                                    0i32);
-        let event = uievent.upcast::<Event>();
-
-        let wintarget = window.upcast::<EventTarget>();
-        event.fire(wintarget);
+        uievent.upcast::<Event>().fire(window.upcast());
     }
 
     /// Initiate a non-blocking fetch for a specified resource. Stores the InProgressLoad
@@ -1905,7 +1897,7 @@ impl ScriptTask {
         // Kick off the initial reflow of the page.
         debug!("kicking off initial reflow of {:?}", final_url);
         document.r().disarm_reflow_timeout();
-        document.r().content_changed(document.upcast::<Node>(),
+        document.r().content_changed(document.upcast(),
                                      NodeDamage::OtherNodeDamage);
         let window = window_from_node(document.r());
         window.r().reflow(ReflowGoal::ForDisplay, ReflowQueryType::NoQuery, ReflowReason::FirstLoad);
diff --git a/components/script/webdriver_handlers.rs b/components/script/webdriver_handlers.rs
index 1812f16b802..5e9b87be23a 100644
--- a/components/script/webdriver_handlers.rs
+++ b/components/script/webdriver_handlers.rs
@@ -116,8 +116,7 @@ pub fn handle_find_element_css(page: &Rc<Page>, _pipeline: PipelineId, selector:
                                reply: IpcSender<Result<Option<String>, ()>>) {
     reply.send(match page.document().r().QuerySelector(selector.clone()) {
         Ok(node) => {
-            let result = node.map(|x| x.upcast::<Node>().get_unique_id());
-            Ok(result)
+            Ok(node.map(|x| x.upcast::<Node>().get_unique_id()))
         }
         Err(_) => Err(())
     }).unwrap();
@@ -172,8 +171,7 @@ pub fn handle_get_name(page: &Rc<Page>,
                        reply: IpcSender<Result<String, ()>>) {
     reply.send(match find_node_by_unique_id(&*page, pipeline, node_id) {
         Some(node) => {
-            let element = node.downcast::<Element>().unwrap();
-            Ok(element.TagName())
+            Ok(node.downcast::<Element>().unwrap().TagName())
         },
         None => Err(())
     }).unwrap();