Merge pull request #3468 from Manishearth/jstraceable

Replace our usage our Encodable with JSTraceable; r=jdm

components/msg/constellation_msg.rs

@@ -9,7 +9,6 @@ use geom::rect::Rect;
 use geom::size::TypedSize2D;
 use geom::scale_factor::ScaleFactor;
 use layers::geometry::DevicePixel;
-use serialize::Encodable;
 use servo_util::geometry::{PagePx, ViewportPx};
 use std::comm::{channel, Sender, Receiver};
 use url::Url;
@@ -37,7 +36,6 @@ pub struct Failure {
     pub subpage_id: Option<SubpageId>,
 }
 
-#[deriving(Encodable)]
 pub struct WindowSizeData {
     /// The size of the initial layout viewport, before parsing an
     /// http://www.w3.org/TR/css-device-adapt/#initial-viewport
@@ -77,8 +75,8 @@ pub enum NavigationDirection {
     Back,
 }
 
-#[deriving(Clone, PartialEq, Eq, Hash, Encodable)]
+#[deriving(Clone, PartialEq, Eq, Hash)]
 pub struct PipelineId(pub uint);
 
-#[deriving(Clone, PartialEq, Eq, Hash, Encodable)]
+#[deriving(Clone, PartialEq, Eq, Hash)]
 pub struct SubpageId(pub uint);

components/plugins/jstraceable.rs

@@ -0,0 +1,60 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+use syntax::ext::base::ExtCtxt;
+use syntax::codemap::Span;
+use syntax::ptr::P;
+use syntax::ast::{Item, MetaItem, Expr};
+use syntax::ast;
+use syntax::ext::build::AstBuilder;
+use syntax::ext::deriving::generic::{combine_substructure, EnumMatching, FieldInfo, MethodDef, Struct, Substructure, TraitDef, ty};
+
+ pub fn expand_jstraceable(cx: &mut ExtCtxt, span: Span, mitem: &MetaItem, item: &Item, push: |P<Item>|) {
+    let trait_def = TraitDef {
+        span: span,
+        attributes: Vec::new(),
+        path: ty::Path::new(vec!("dom","bindings","trace","JSTraceable")),
+        additional_bounds: Vec::new(),
+        generics: ty::LifetimeBounds::empty(),
+        methods: vec!(
+            MethodDef {
+                name: "trace",
+                generics: ty::LifetimeBounds::empty(),
+                explicit_self: ty::borrowed_explicit_self(),
+                args: vec!(ty::Ptr(box ty::Literal(ty::Path::new(vec!("js","jsapi","JSTracer"))), ty::Raw(ast::MutMutable))),
+                ret_ty: ty::nil_ty(),
+                attributes: vec!(),
+                combine_substructure: combine_substructure(|a, b, c| {
+                    jstraceable_substructure(a, b, c)
+                })
+            }
+        )
+    };
+    trait_def.expand(cx, mitem, item, push)
+}
+
+// Mostly copied from syntax::ext::deriving::hash
+fn jstraceable_substructure(cx: &mut ExtCtxt, trait_span: Span, substr: &Substructure) -> P<Expr> {
+    let state_expr = match substr.nonself_args {
+        [ref state_expr] => state_expr,
+        _ => cx.span_bug(trait_span, "incorrect number of arguments in `jstraceable`")
+    };
+    let trace_ident = substr.method_ident;
+    let call_trace = |span, thing_expr| {
+        let expr = cx.expr_method_call(span, thing_expr, trace_ident, vec!(state_expr.clone()));
+        cx.stmt_expr(expr)
+    };
+    let mut stmts = Vec::new();
+
+    let fields = match *substr.fields {
+        Struct(ref fs) | EnumMatching(_, _, ref fs) => fs,
+        _ => cx.span_bug(trait_span, "impossible substructure in `jstraceable`")
+    };
+
+    for &FieldInfo { ref self_, span, .. } in fields.iter() {
+        stmts.push(call_trace(span, self_.clone()));
+    }
+
+    cx.expr_block(cx.block(trait_span, stmts, None))
+}

components/plugins/lib.rs

@@ -6,8 +6,6 @@
 
 #![deny(unused_imports, unused_variable)]
 
-
-
 #[phase(plugin,link)]
 extern crate syntax;
 #[phase(plugin, link)]
@@ -17,14 +15,18 @@ extern crate sync;
 
 use rustc::lint::LintPassObject;
 use rustc::plugin::Registry;
+use syntax::ext::base::ItemDecorator;
+
+use syntax::parse::token::intern;
 
 mod lints;
 mod macros;
-
+mod jstraceable;
 
 #[plugin_registrar]
 pub fn plugin_registrar(reg: &mut Registry) {
     reg.register_lint_pass(box lints::TransmutePass as LintPassObject);
     reg.register_lint_pass(box lints::UnrootedPass as LintPassObject);
+    reg.register_syntax_extension(intern("jstraceable"), ItemDecorator(box jstraceable::expand_jstraceable))
 }
 

components/script/dom/attr.rs

@@ -28,7 +28,8 @@ pub enum AttrSettingType {
     ReplacedAttr,
 }
 
-#[deriving(PartialEq, Clone, Encodable)]
+#[deriving(PartialEq, Clone)]
+#[jstraceable]
 pub enum AttrValue {
     StringAttrValue(DOMString),
     TokenListAttrValue(DOMString, Vec<Atom>),
@@ -72,7 +73,7 @@ impl Str for AttrValue {
     }
 }
 
-#[deriving(Encodable)]
+#[jstraceable]
 #[must_root]
 pub struct Attr {
     reflector_: Reflector,

components/script/dom/bindings/DESIGN.md

@@ -13,13 +13,14 @@ This is very tricky and magically mechanism helped by Rust Compiler.
 The outline is:
 
 1. SpiderMonkey's GC calls `JSClass.trace` defined in `FooBinding` when marking phase. This JSClass is basis of each wrapper JSObject.
-2. `JSClass.trace` calls `Foo::trace()` defined in InhertTypes.rs.
-3. `Foo::trace()` calls `Foo::encode()`. This `encode()` method is derived by the annotation of `#[deriving(Encodable)]` for a Rust DOM Element struct.
-4. `Foo::encode()` calls `JS<T>::encode()` method of  `JS<T>` which is contained to `Foo`’s member. So this is the compiler magic!  Rust compiler generates [codes like this](https://github.com/mozilla/rust/blob/db5206c32a879d5058d6a5cdce39c13c763fbdd5/src/libsyntax/ext/deriving/encodable.rs) for all structs annotated `#[deriving(Encodable)]`. This is based on [the assumption](https://github.com/mozilla/servo/blob/54da52fa774ce2ee59fcf811af595bf292169ad8/src/components/script/dom/bindings/trace.rs#L16).
-5. `JS<T>::encode()` calls `dom::bindings::trace::trace_reflector()`.
-6. `trace_reflector()` fetches the reflector that is reachable from a Rust object, and notifies it to the GC with using JSTracer.
-7. This operation continues to the end of the graph.
-8. Finally, GC gets whether Rust object lives or not from JSObjects which is hold by Rust object.
+2. `JSClass.trace` calls `Foo::trace()` (an implementation of `JSTraceable`).
+     This is typically derived via a #[jstraceable] annotation
+3. For all fields (except those wrapped in `Untraceable`), `Foo::trace()`
+   calls `trace()` on the field. For example, for fields of type `JS<T>`, `JS<T>::trace()` calls
+   `trace_reflector()`.
+4. `trace_reflector()` fetches the reflector that is reachable from a Rust object, and notifies it to the GC with using JSTracer.
+5. This operation continues to the end of the graph.
+6. Finally, GC gets whether Rust object lives or not from JSObjects which is hold by Rust object.
 
 
 ## Destruct

components/script/dom/bindings/callback.rs

@@ -13,8 +13,6 @@ use js::jsval::{JSVal, UndefinedValue};
 
 use std::ptr;
 
-use serialize::{Encodable, Encoder};
-
 /// The exception handling used for a call.
 pub enum ExceptionHandling {
     /// Report any exception and don't throw it to the caller code.
@@ -28,7 +26,8 @@ pub enum ExceptionHandling {
 }
 
 /// A common base class for representing IDL callback function types.
-#[deriving(Clone,PartialEq,Encodable)]
+#[deriving(Clone,PartialEq)]
+#[jstraceable]
 pub struct CallbackFunction {
     object: CallbackObject
 }
@@ -44,7 +43,8 @@ impl CallbackFunction {
 }
 
 /// A common base class for representing IDL callback interface types.
-#[deriving(Clone,PartialEq,Encodable)]
+#[deriving(Clone,PartialEq)]
+#[jstraceable]
 pub struct CallbackInterface {
     object: CallbackObject
 }
@@ -52,7 +52,8 @@ pub struct CallbackInterface {
 /// A common base class for representing IDL callback function and
 /// callback interface types.
 #[allow(raw_pointer_deriving)]
-#[deriving(Clone,PartialEq,Encodable)]
+#[deriving(Clone,PartialEq)]
+#[jstraceable]
 struct CallbackObject {
     /// The underlying `JSObject`.
     callback: Traceable<*mut JSObject>,

components/script/dom/bindings/codegen/CodegenRust.py

@@ -2754,7 +2754,8 @@ use js::jsapi::JSContext;
 use js::jsval::JSVal;
 
 #[repr(uint)]
-#[deriving(Encodable, PartialEq)]
+#[deriving(PartialEq)]
+#[jstraceable]
 pub enum valuelist {
   %s
 }
@@ -4893,7 +4894,7 @@ class CGCallback(CGClass):
                          bases=[ClassBase(baseName)],
                          constructors=self.getConstructors(),
                          methods=realMethods+getters+setters,
-                         decorators="#[deriving(PartialEq,Clone,Encodable)]")
+                         decorators="#[deriving(PartialEq,Clone)]#[jstraceable]")
 
     def getConstructors(self):
         return [ClassConstructor(
@@ -5438,7 +5439,6 @@ class GlobalGenRoots():
                      CGGeneric("use dom::bindings::js::{JS, JSRef, Temporary};\n"),
                      CGGeneric("use dom::bindings::trace::JSTraceable;\n"),
                      CGGeneric("use dom::bindings::utils::Reflectable;\n"),
-                     CGGeneric("use serialize::{Encodable, Encoder};\n"),
                      CGGeneric("use js::jsapi::JSTracer;\n\n")]
         for descriptor in descriptors:
             name = descriptor.name
@@ -5500,16 +5500,7 @@ class GlobalGenRoots():
                  'toBound': name + 'Derived'})),
                     CGGeneric("impl %s for %s {}\n\n" % (name + 'Cast', name))]
 
-            trace = [CGGeneric(string.Template('''impl JSTraceable for ${name} {
-    fn trace(&self, tracer: *mut JSTracer) {
-        unsafe {
-            self.encode(&mut *tracer).ok().expect("failed to encode");
-        }
-    }
-}
-''').substitute({'name': name}))]
-
-            allprotos += protos + derived + cast + trace
+            allprotos += protos + derived + cast
 
         curr = CGList(allprotos)
         curr = CGWrapper(curr, pre=AUTOGENERATED_WARNING_COMMENT)

components/script/dom/bindings/global.rs

@@ -33,7 +33,7 @@ pub enum GlobalRoot<'a, 'b> {
 
 /// A traced reference to a global object, for use in fields of traced Rust
 /// structures.
-#[deriving(Encodable)]
+#[jstraceable]
 #[must_root]
 pub enum GlobalField {
     WindowField(JS<Window>),

components/script/dom/bindings/str.rs

@@ -10,7 +10,8 @@ use std::path::BytesContainer;
 use std::str;
 
 /// Encapsulates the IDL `ByteString` type.
-#[deriving(Encodable,Clone,Eq,PartialEq)]
+#[deriving(Clone,Eq,PartialEq)]
+#[jstraceable]
 pub struct ByteString(Vec<u8>);
 
 impl ByteString {

components/script/dom/bindings/trace.rs

@@ -11,55 +11,46 @@
 //! 1. The GC calls `_trace` defined in `FooBinding` during the marking
 //!    phase. (This happens through `JSClass.trace` for non-proxy bindings, and
 //!    through `ProxyTraps.trace` otherwise.)
-//! 2. `_trace` calls `Foo::trace()` (an implementation of `JSTraceable`,
-//!    defined in `InheritTypes.rs`).
-//! 3. `Foo::trace()` calls `Foo::encode()` (an implementation of `Encodable`).
-//!    This implementation is typically derived by a `#[deriving(Encodable)]`
-//!    annotation on the Rust struct.
-//! 4. For all fields (except those wrapped in `Untraceable`), `Foo::encode()`
-//!    calls `encode()` on the field.
-//!
-//!    For example, for fields of type `JS<T>`, `JS<T>::encode()` calls
+//! 2. `_trace` calls `Foo::trace()` (an implementation of `JSTraceable`).
+//!     This is typically derived via a #[jstraceable] annotation
+//! 3. For all fields (except those wrapped in `Untraceable`), `Foo::trace()`
+//!    calls `trace()` on the field.
+//!    For example, for fields of type `JS<T>`, `JS<T>::trace()` calls
 //!    `trace_reflector()`.
-//! 6. `trace_reflector()` calls `trace_object()` with the `JSObject` for the
+//! 4. `trace_reflector()` calls `trace_object()` with the `JSObject` for the
 //!    reflector.
-//! 7. `trace_object()` calls `JS_CallTracer()` to notify the GC, which will
+//! 5. `trace_object()` calls `JS_CallTracer()` to notify the GC, which will
 //!    add the object to the graph, and will trace that object as well.
+//!
+//! The untraceable!() macro adds an empty implementation of JSTraceable to 
+//! a datatype.
 
 use dom::bindings::js::JS;
 use dom::bindings::utils::{Reflectable, Reflector};
-
 use js::jsapi::{JSObject, JSTracer, JS_CallTracer, JSTRACE_OBJECT};
 use js::jsval::JSVal;
 
 use libc;
-use std::mem;
+use std::rc::Rc;
 use std::cell::{Cell, RefCell};
-use serialize::{Encodable, Encoder};
 
-// IMPORTANT: We rely on the fact that we never attempt to encode DOM objects using
-//            any encoder but JSTracer. Since we derive trace hooks automatically,
-//            we are unfortunately required to use generic types everywhere and
-//            unsafely cast to the concrete JSTracer we actually require.
+use url::Url;
+use servo_util::atom::Atom;
+use servo_util::namespace::Namespace;
+use msg::constellation_msg::{PipelineId, SubpageId, WindowSizeData};
+use net::image_cache_task::ImageCacheTask;
+use script_traits::ScriptControlChan;
+use std::collections::hashmap::HashMap;
+use collections::hash::Hash;
+use style::PropertyDeclarationBlock;
 
-fn get_jstracer<'a, S: Encoder<E>, E>(s: &'a mut S) -> &'a mut JSTracer {
-    unsafe {
-        mem::transmute(s)
+impl<T: Reflectable> JSTraceable for JS<T> {
+    fn trace(&self, trc: *mut JSTracer) {
+        trace_reflector(trc, "", self.reflector());
     }
 }
 
-impl<T: Reflectable+Encodable<S, E>, S: Encoder<E>, E> Encodable<S, E> for JS<T> {
-    fn encode(&self, s: &mut S) -> Result<(), E> {
-        trace_reflector(get_jstracer(s), "", self.reflector());
-        Ok(())
-    }
-}
-
-impl<S: Encoder<E>, E> Encodable<S, E> for Reflector {
-    fn encode(&self, _s: &mut S) -> Result<(), E> {
-        Ok(())
-    }
-}
+untraceable!(Reflector)
 
 /// A trait to allow tracing (only) DOM objects.
 pub trait JSTraceable {
@@ -120,12 +111,6 @@ impl<T> Untraceable<T> {
     }
 }
 
-impl<S: Encoder<E>, E, T> Encodable<S, E> for Untraceable<T> {
-    fn encode(&self, _s: &mut S) -> Result<(), E> {
-        Ok(())
-    }
-}
-
 impl<T> Deref<T> for Untraceable<T> {
     fn deref<'a>(&'a self) -> &'a T {
         &self.inner
@@ -165,28 +150,90 @@ impl<T> Deref<T> for Traceable<T> {
     }
 }
 
-impl<S: Encoder<E>, E, T: Encodable<S, E>> Encodable<S, E> for Traceable<RefCell<T>> {
-    fn encode(&self, s: &mut S) -> Result<(), E> {
-        self.borrow().encode(s)
+impl<T: JSTraceable> JSTraceable for RefCell<T> {
+    fn trace(&self, trc: *mut JSTracer) {
+        self.borrow().trace(trc)
     }
 }
 
-impl<S: Encoder<E>, E, T: Encodable<S, E>+Copy> Encodable<S, E> for Traceable<Cell<T>> {
-    fn encode(&self, s: &mut S) -> Result<(), E> {
-        self.deref().get().encode(s)
+impl<T: JSTraceable> JSTraceable for Rc<T> {
+    fn trace(&self, trc: *mut JSTracer) {
+        self.deref().trace(trc)
     }
 }
 
-impl<S: Encoder<E>, E> Encodable<S, E> for Traceable<*mut JSObject> {
-    fn encode(&self, s: &mut S) -> Result<(), E> {
-        trace_object(get_jstracer(s), "object", **self);
-        Ok(())
+impl<T: JSTraceable> JSTraceable for Box<T> {
+    fn trace(&self, trc: *mut JSTracer) {
+        (**self).trace(trc)
     }
 }
 
-impl<S: Encoder<E>, E> Encodable<S, E> for Traceable<JSVal> {
-    fn encode(&self, s: &mut S) -> Result<(), E> {
-        trace_jsval(get_jstracer(s), "val", **self);
-        Ok(())
+impl<T: JSTraceable+Copy> JSTraceable for Traceable<Cell<T>> {
+    fn trace(&self, trc: *mut JSTracer) {
+        self.deref().get().trace(trc)
     }
 }
+
+
+impl<T: JSTraceable+Copy> JSTraceable for Cell<T> {
+    fn trace(&self, trc: *mut JSTracer) {
+        self.get().trace(trc)
+    }
+}
+
+impl JSTraceable for Traceable<*mut JSObject> {
+    fn trace(&self, trc: *mut JSTracer) {
+        trace_object(trc, "object", **self);
+    }
+}
+
+impl JSTraceable for Traceable<JSVal> {
+    fn trace(&self, trc: *mut JSTracer) {
+        trace_jsval(trc, "val", **self);
+    }
+}
+
+// XXXManishearth Check if the following three are optimized to no-ops
+// if e.trace() is a no-op (e.g it is an untraceable type)
+impl<T: JSTraceable> JSTraceable for Vec<T> {
+    #[inline]
+    fn trace(&self, trc: *mut JSTracer) {
+        for e in self.iter() {
+            e.trace(trc);
+        }
+    }
+}
+
+impl<T: JSTraceable> JSTraceable for Option<T> {
+    #[inline]
+    fn trace(&self, trc: *mut JSTracer) {
+        self.as_ref().map(|e| e.trace(trc));
+    }
+}
+
+impl<K: Eq+Hash, V: JSTraceable> JSTraceable for HashMap<K, V> {
+    #[inline]
+    fn trace(&self, trc: *mut JSTracer) {
+        for e in self.iter() {
+            e.val1().trace(trc);
+        }
+    }
+}
+
+untraceable!(bool, f32, f64, String, Url)
+untraceable!(uint, u8, u16, u32, u64)
+untraceable!(int, i8, i16, i32, i64)
+untraceable!(Untraceable<T>)
+untraceable!(ImageCacheTask, ScriptControlChan)
+untraceable!(Atom, Namespace)
+untraceable!(PropertyDeclarationBlock)
+// These three are interdependent, if you plan to put jsmanaged data
+// in one of these make sure it is propagated properly to containing structs
+untraceable!(SubpageId, WindowSizeData, PipelineId)
+
+impl<'a> JSTraceable for &'a str {
+    #[inline]
+    fn trace(&self, _: *mut JSTracer) {
+        // Do nothing
+    }
+}

components/script/dom/bindings/utils.rs

@@ -52,7 +52,7 @@ use js::{JSFUN_CONSTRUCTOR, JSPROP_READONLY};
 use js;
 
 #[allow(raw_pointer_deriving)]
-#[deriving(Encodable)]
+#[jstraceable]
 pub struct GlobalStaticData {
     pub windowproxy_handler: Untraceable<*const libc::c_void>,
 }

components/script/dom/blob.rs

@@ -9,13 +9,13 @@ use dom::bindings::utils::{Reflectable, Reflector, reflect_dom_object};
 use dom::bindings::error::Fallible;
 use dom::bindings::codegen::Bindings::BlobBinding;
 
-#[deriving(Encodable)]
+#[jstraceable]
 pub enum BlobType {
     BlobTypeId,
     FileTypeId
 }
 
-#[deriving(Encodable)]
+#[jstraceable]
 #[must_root]
 pub struct Blob {
     reflector_: Reflector,

components/script/dom/browsercontext.rs

@@ -16,7 +16,7 @@ use libc::c_void;
 use std::ptr;
 
 #[allow(raw_pointer_deriving)]
-#[deriving(Encodable)]
+#[jstraceable]
 pub struct BrowserContext {
     history: Vec<SessionHistoryEntry>,
     active_index: uint,
@@ -66,7 +66,7 @@ impl BrowserContext {
     }
 }
 
-#[deriving(Encodable)]
+#[jstraceable]
 #[must_root]
 pub struct SessionHistoryEntry {
     document: JS<Document>,

components/script/dom/canvasrenderingcontext2d.rs

@@ -16,7 +16,7 @@ use geom::size::Size2D;
 
 use canvas::canvas_render_task::{CanvasMsg, CanvasRenderTask, ClearRect, Close, FillRect, Recreate, StrokeRect};
 
-#[deriving(Encodable)]
+#[jstraceable]
 #[must_root]
 pub struct CanvasRenderingContext2D {
     reflector_: Reflector,

components/script/dom/characterdata.rs

@@ -17,7 +17,7 @@ use servo_util::str::DOMString;
 
 use std::cell::RefCell;
 
-#[deriving(Encodable)]
+#[jstraceable]
 #[must_root]
 pub struct CharacterData {
     pub node: Node,

components/script/dom/comment.rs

@@ -16,7 +16,7 @@ use dom::node::{CommentNodeTypeId, Node};
 use servo_util::str::DOMString;
 
 /// An HTML comment.
-#[deriving(Encodable)]
+#[jstraceable]
 #[must_root]
 pub struct Comment {
     pub characterdata: CharacterData,

components/script/dom/console.rs

@@ -9,7 +9,7 @@ use dom::bindings::js::{JSRef, Temporary};
 use dom::bindings::utils::{Reflectable, Reflector, reflect_dom_object};
 use servo_util::str::DOMString;
 
-#[deriving(Encodable)]
+#[jstraceable]
 #[must_root]
 pub struct Console {
     pub reflector_: Reflector

components/script/dom/customevent.rs

@@ -18,7 +18,7 @@ use servo_util::str::DOMString;
 
 use std::cell::Cell;
 
-#[deriving(Encodable)]
+#[jstraceable]
 #[must_root]
 pub struct CustomEvent {
     event: Event,

components/script/dom/dedicatedworkerglobalscope.rs

@@ -36,7 +36,7 @@ use std::task::TaskBuilder;
 use native::task::NativeTaskBuilder;
 use url::Url;
 
-#[deriving(Encodable)]
+#[jstraceable]
 #[must_root]
 pub struct DedicatedWorkerGlobalScope {
     workerglobalscope: WorkerGlobalScope,

components/script/dom/document.rs

@@ -65,13 +65,14 @@ use std::cell::{Cell, RefCell};
 use url::Url;
 use time;
 
-#[deriving(PartialEq,Encodable)]
+#[deriving(PartialEq)]
+#[jstraceable]
 pub enum IsHTMLDocument {
     HTMLDocument,
     NonHTMLDocument,
 }
 
-#[deriving(Encodable)]
+#[jstraceable]
 #[must_root]
 pub struct Document {
     pub node: Node,
@@ -100,6 +101,7 @@ impl DocumentDerived for EventTarget {
     }
 }
 
+#[jstraceable]
 struct ImagesFilter;
 impl CollectionFilter for ImagesFilter {
     fn filter(&self, elem: JSRef<Element>, _root: JSRef<Node>) -> bool {
@@ -107,6 +109,7 @@ impl CollectionFilter for ImagesFilter {
     }
 }
 
+#[jstraceable]
 struct EmbedsFilter;
 impl CollectionFilter for EmbedsFilter {
     fn filter(&self, elem: JSRef<Element>, _root: JSRef<Node>) -> bool {
@@ -114,6 +117,7 @@ impl CollectionFilter for EmbedsFilter {
     }
 }
 
+#[jstraceable]
 struct LinksFilter;
 impl CollectionFilter for LinksFilter {
     fn filter(&self, elem: JSRef<Element>, _root: JSRef<Node>) -> bool {
@@ -121,6 +125,7 @@ impl CollectionFilter for LinksFilter {
     }
 }
 
+#[jstraceable]
 struct FormsFilter;
 impl CollectionFilter for FormsFilter {
     fn filter(&self, elem: JSRef<Element>, _root: JSRef<Node>) -> bool {
@@ -128,6 +133,7 @@ impl CollectionFilter for FormsFilter {
     }
 }
 
+#[jstraceable]
 struct ScriptsFilter;
 impl CollectionFilter for ScriptsFilter {
     fn filter(&self, elem: JSRef<Element>, _root: JSRef<Node>) -> bool {
@@ -135,6 +141,7 @@ impl CollectionFilter for ScriptsFilter {
     }
 }
 
+#[jstraceable]
 struct AnchorsFilter;
 impl CollectionFilter for AnchorsFilter {
     fn filter(&self, elem: JSRef<Element>, _root: JSRef<Node>) -> bool {
@@ -142,6 +149,7 @@ impl CollectionFilter for AnchorsFilter {
     }
 }
 
+#[jstraceable]
 struct AppletsFilter;
 impl CollectionFilter for AppletsFilter {
     fn filter(&self, elem: JSRef<Element>, _root: JSRef<Node>) -> bool {

components/script/dom/documentfragment.rs

@@ -18,7 +18,7 @@ use dom::node::{DocumentFragmentNodeTypeId, Node, NodeHelpers, window_from_node}
 use dom::nodelist::NodeList;
 use servo_util::str::DOMString;
 
-#[deriving(Encodable)]
+#[jstraceable]
 #[must_root]
 pub struct DocumentFragment {
     pub node: Node,

components/script/dom/documenttype.rs

@@ -13,7 +13,7 @@ use dom::node::{Node, DoctypeNodeTypeId, NodeHelpers};
 use servo_util::str::DOMString;
 
 /// The `DOCTYPE` tag.
-#[deriving(Encodable)]
+#[jstraceable]
 #[must_root]
 pub struct DocumentType {
     pub node: Node,

components/script/dom/domexception.rs

@@ -13,7 +13,8 @@ use dom::bindings::utils::{Reflectable, Reflector, reflect_dom_object};
 use servo_util::str::DOMString;
 
 #[repr(uint)]
-#[deriving(Show, Encodable)]
+#[deriving(Show)]
+#[jstraceable]
 pub enum DOMErrorName {
     IndexSizeError = DOMExceptionConstants::INDEX_SIZE_ERR as uint,
     HierarchyRequestError = DOMExceptionConstants::HIERARCHY_REQUEST_ERR as uint,
@@ -59,7 +60,7 @@ impl DOMErrorName {
     }
 }
 
-#[deriving(Encodable)]
+#[jstraceable]
 #[must_root]
 pub struct DOMException {
     pub code: DOMErrorName,

components/script/dom/domimplementation.rs

@@ -22,7 +22,7 @@ use dom::node::Node;
 use dom::text::Text;
 use servo_util::str::DOMString;
 
-#[deriving(Encodable)]
+#[jstraceable]
 #[must_root]
 pub struct DOMImplementation {
     document: JS<Document>,

components/script/dom/domparser.rs

@@ -13,7 +13,7 @@ use dom::document::{Document, HTMLDocument, NonHTMLDocument};
 use dom::window::Window;
 use servo_util::str::DOMString;
 
-#[deriving(Encodable)]
+#[jstraceable]
 #[must_root]
 pub struct DOMParser {
     window: JS<Window>, //XXXjdm Document instead?

components/script/dom/domrect.rs

@@ -10,7 +10,7 @@ use dom::bindings::utils::{Reflectable, Reflector, reflect_dom_object};
 use dom::window::Window;
 use servo_util::geometry::Au;
 
-#[deriving(Encodable)]
+#[jstraceable]
 #[must_root]
 pub struct DOMRect {
     reflector_: Reflector,

components/script/dom/domrectlist.rs

@@ -10,7 +10,7 @@ use dom::bindings::utils::{Reflectable, Reflector, reflect_dom_object};
 use dom::domrect::DOMRect;
 use dom::window::Window;
 
-#[deriving(Encodable)]
+#[jstraceable]
 #[must_root]
 pub struct DOMRectList {
     reflector_: Reflector,

components/script/dom/domtokenlist.rs

@@ -16,7 +16,7 @@ use servo_util::atom::Atom;
 use servo_util::namespace::Null;
 use servo_util::str::{DOMString, HTML_SPACE_CHARACTERS};
 
-#[deriving(Encodable)]
+#[jstraceable]
 #[must_root]
 pub struct DOMTokenList {
     reflector_: Reflector,

components/script/dom/element.rs

@@ -43,7 +43,7 @@ use std::ascii::StrAsciiExt;
 use std::cell::{Cell, RefCell};
 use std::mem;
 
-#[deriving(Encodable)]
+#[jstraceable]
 #[must_root]
 pub struct Element {
     pub node: Node,
@@ -71,7 +71,8 @@ impl Reflectable for Element {
     }
 }
 
-#[deriving(PartialEq,Encodable)]
+#[deriving(PartialEq)]
+#[jstraceable]
 pub enum ElementTypeId {
     HTMLElementTypeId,
     HTMLAnchorElementTypeId,

components/script/dom/event.rs

@@ -15,7 +15,7 @@ use std::cell::{Cell, RefCell};
 
 use time;
 
-#[deriving(Encodable)]
+#[jstraceable]
 pub enum EventPhase {
     PhaseNone      = EventConstants::NONE as int,
     PhaseCapturing = EventConstants::CAPTURING_PHASE as int,
@@ -23,7 +23,8 @@ pub enum EventPhase {
     PhaseBubbling  = EventConstants::BUBBLING_PHASE as int,
 }
 
-#[deriving(PartialEq, Encodable)]
+#[deriving(PartialEq)]
+#[jstraceable]
 pub enum EventTypeId {
     CustomEventTypeId,
     HTMLEventTypeId,
@@ -34,7 +35,7 @@ pub enum EventTypeId {
     UIEventTypeId
 }
 
-#[deriving(Encodable)]
+#[jstraceable]
 #[must_root]
 pub struct Event {
     pub type_id: EventTypeId,

components/script/dom/eventtarget.rs

@@ -26,13 +26,15 @@ use url::Url;
 
 use std::collections::hashmap::HashMap;
 
-#[deriving(PartialEq,Encodable)]
+#[deriving(PartialEq)]
+#[jstraceable]
 pub enum ListenerPhase {
     Capturing,
     Bubbling,
 }
 
-#[deriving(PartialEq,Encodable)]
+#[deriving(PartialEq)]
+#[jstraceable]
 pub enum EventTargetTypeId {
     NodeTargetTypeId(NodeTypeId),
     WindowTypeId,
@@ -41,7 +43,8 @@ pub enum EventTargetTypeId {
     XMLHttpRequestTargetTypeId(XMLHttpRequestId)
 }
 
-#[deriving(PartialEq, Encodable)]
+#[deriving(PartialEq)]
+#[jstraceable]
 pub enum EventListenerType {
     Additive(EventListener),
     Inline(EventListener),
@@ -55,13 +58,14 @@ impl EventListenerType {
     }
 }
 
-#[deriving(PartialEq,Encodable)]
+#[deriving(PartialEq)]
+#[jstraceable]
 pub struct EventListenerEntry {
     pub phase: ListenerPhase,
     pub listener: EventListenerType
 }
 
-#[deriving(Encodable)]
+#[jstraceable]
 #[must_root]
 pub struct EventTarget {
     pub type_id: EventTargetTypeId,

components/script/dom/file.rs

@@ -10,7 +10,7 @@ use dom::bindings::utils::{Reflectable, Reflector, reflect_dom_object};
 use dom::blob::{Blob, BlobType, FileTypeId};
 use servo_util::str::DOMString;
 
-#[deriving(Encodable)]
+#[jstraceable]
 #[must_root]
 pub struct File {
     pub blob: Blob,

components/script/dom/formdata.rs

@@ -18,14 +18,15 @@ use servo_util::str::DOMString;
 use std::cell::RefCell;
 use std::collections::hashmap::HashMap;
 
-#[deriving(Encodable, Clone)]
+#[deriving(Clone)]
+#[jstraceable]
 #[must_root]
 pub enum FormDatum {
     StringData(DOMString),
     FileData(JS<File>)
 }
 
-#[deriving(Encodable)]
+#[jstraceable]
 #[must_root]
 pub struct FormData {
     data: Traceable<RefCell<HashMap<DOMString, Vec<FormDatum>>>>,

components/script/dom/htmlanchorelement.rs

@@ -23,7 +23,7 @@ use servo_util::atom::Atom;
 use servo_util::namespace::Null;
 use servo_util::str::DOMString;
 
-#[deriving(Encodable)]
+#[jstraceable]
 #[must_root]
 pub struct HTMLAnchorElement {
     pub htmlelement: HTMLElement

components/script/dom/htmlappletelement.rs

@@ -13,7 +13,7 @@ use dom::htmlelement::HTMLElement;
 use dom::node::{Node, ElementNodeTypeId};
 use servo_util::str::DOMString;
 
-#[deriving(Encodable)]
+#[jstraceable]
 #[must_root]
 pub struct HTMLAppletElement {
     pub htmlelement: HTMLElement

components/script/dom/htmlareaelement.rs

@@ -17,7 +17,7 @@ use dom::virtualmethods::VirtualMethods;
 use servo_util::atom::Atom;
 use servo_util::str::DOMString;
 
-#[deriving(Encodable)]
+#[jstraceable]
 #[must_root]
 pub struct HTMLAreaElement {
     pub htmlelement: HTMLElement

components/script/dom/htmlaudioelement.rs

@@ -13,7 +13,7 @@ use dom::htmlmediaelement::HTMLMediaElement;
 use dom::node::{Node, ElementNodeTypeId};
 use servo_util::str::DOMString;
 
-#[deriving(Encodable)]
+#[jstraceable]
 #[must_root]
 pub struct HTMLAudioElement {
     pub htmlmediaelement: HTMLMediaElement

components/script/dom/htmlbaseelement.rs

@@ -13,7 +13,7 @@ use dom::htmlelement::HTMLElement;
 use dom::node::{Node, ElementNodeTypeId};
 use servo_util::str::DOMString;
 
-#[deriving(Encodable)]
+#[jstraceable]
 #[must_root]
 pub struct HTMLBaseElement {
     pub htmlelement: HTMLElement

components/script/dom/htmlbodyelement.rs

@@ -20,7 +20,7 @@ use dom::virtualmethods::VirtualMethods;
 use servo_util::atom::Atom;
 use servo_util::str::DOMString;
 
-#[deriving(Encodable)]
+#[jstraceable]
 #[must_root]
 pub struct HTMLBodyElement {
     pub htmlelement: HTMLElement

components/script/dom/htmlbrelement.rs

@@ -13,7 +13,7 @@ use dom::htmlelement::HTMLElement;
 use dom::node::{Node, ElementNodeTypeId};
 use servo_util::str::DOMString;
 
-#[deriving(Encodable)]
+#[jstraceable]
 #[must_root]
 pub struct HTMLBRElement {
     pub htmlelement: HTMLElement,

components/script/dom/htmlbuttonelement.rs

@@ -19,7 +19,7 @@ use dom::virtualmethods::VirtualMethods;
 use servo_util::atom::Atom;
 use servo_util::str::DOMString;
 
-#[deriving(Encodable)]
+#[jstraceable]
 #[must_root]
 pub struct HTMLButtonElement {
     pub htmlelement: HTMLElement

components/script/dom/htmlcanvaselement.rs

@@ -28,7 +28,7 @@ use std::cell::Cell;
 static DefaultWidth: u32 = 300;
 static DefaultHeight: u32 = 150;
 
-#[deriving(Encodable)]
+#[jstraceable]
 #[must_root]
 pub struct HTMLCanvasElement {
     pub htmlelement: HTMLElement,

components/script/dom/htmlcollection.rs

@@ -7,6 +7,7 @@ use dom::bindings::codegen::Bindings::HTMLCollectionBinding::HTMLCollectionMetho
 use dom::bindings::codegen::InheritTypes::{ElementCast, NodeCast};
 use dom::bindings::global::Window;
 use dom::bindings::js::{JS, JSRef, Temporary};
+use dom::bindings::trace::JSTraceable;
 use dom::bindings::utils::{Reflectable, Reflector, reflect_dom_object};
 use dom::element::{Element, AttributeHandlers, ElementHelpers};
 use dom::node::{Node, NodeHelpers};
@@ -15,27 +16,20 @@ use servo_util::atom::Atom;
 use servo_util::namespace::Namespace;
 use servo_util::str::{DOMString, split_html_space_chars};
 
-use serialize::{Encoder, Encodable};
 use std::ascii::StrAsciiExt;
 
-pub trait CollectionFilter {
+pub trait CollectionFilter : JSTraceable {
     fn filter(&self, elem: JSRef<Element>, root: JSRef<Node>) -> bool;
 }
 
-impl<S: Encoder<E>, E> Encodable<S, E> for Box<CollectionFilter+'static> {
-    fn encode(&self, _s: &mut S) -> Result<(), E> {
-        Ok(())
-    }
-}
-
-#[deriving(Encodable)]
+#[jstraceable]
 #[must_root]
 pub enum CollectionTypeId {
     Static(Vec<JS<Element>>),
     Live(JS<Node>, Box<CollectionFilter+'static>)
 }
 
-#[deriving(Encodable)]
+#[jstraceable]
 #[must_root]
 pub struct HTMLCollection {
     collection: CollectionTypeId,
@@ -64,6 +58,7 @@ impl HTMLCollection {
 
     fn all_elements(window: JSRef<Window>, root: JSRef<Node>,
                     namespace_filter: Option<Namespace>) -> Temporary<HTMLCollection> {
+        #[jstraceable]
         struct AllElementFilter {
             namespace_filter: Option<Namespace>
         }
@@ -85,6 +80,7 @@ impl HTMLCollection {
             return HTMLCollection::all_elements(window, root, None);
         }
 
+        #[jstraceable]
         struct TagNameFilter {
             tag: Atom,
             ascii_lower_tag: Atom,
@@ -115,6 +111,7 @@ impl HTMLCollection {
         if tag.as_slice() == "*" {
             return HTMLCollection::all_elements(window, root, namespace_filter);
         }
+        #[jstraceable]
         struct TagNameNSFilter {
             tag: Atom,
             namespace_filter: Option<Namespace>
@@ -139,6 +136,7 @@ impl HTMLCollection {
 
     pub fn by_class_name(window: JSRef<Window>, root: JSRef<Node>, classes: DOMString)
                          -> Temporary<HTMLCollection> {
+        #[jstraceable]
         struct ClassNameFilter {
             classes: Vec<DOMString>
         }
@@ -154,6 +152,7 @@ impl HTMLCollection {
     }
 
     pub fn children(window: JSRef<Window>, root: JSRef<Node>) -> Temporary<HTMLCollection> {
+        #[jstraceable]
         struct ElementChildFilter;
         impl CollectionFilter for ElementChildFilter {
             fn filter(&self, elem: JSRef<Element>, root: JSRef<Node>) -> bool {

components/script/dom/htmldataelement.rs

@@ -13,7 +13,7 @@ use dom::htmlelement::HTMLElement;
 use dom::node::{Node, ElementNodeTypeId};
 use servo_util::str::DOMString;
 
-#[deriving(Encodable)]
+#[jstraceable]
 #[must_root]
 pub struct HTMLDataElement {
     pub htmlelement: HTMLElement

components/script/dom/htmldatalistelement.rs

@@ -16,7 +16,7 @@ use dom::htmlelement::HTMLElement;
 use dom::node::{Node, ElementNodeTypeId, window_from_node};
 use servo_util::str::DOMString;
 
-#[deriving(Encodable)]
+#[jstraceable]
 #[must_root]
 pub struct HTMLDataListElement {
     pub htmlelement: HTMLElement
@@ -44,6 +44,7 @@ impl HTMLDataListElement {
 
 impl<'a> HTMLDataListElementMethods for JSRef<'a, HTMLDataListElement> {
     fn Options(self) -> Temporary<HTMLCollection> {
+        #[jstraceable]
         struct HTMLDataListOptionsFilter;
         impl CollectionFilter for HTMLDataListOptionsFilter {
             fn filter(&self, elem: JSRef<Element>, _root: JSRef<Node>) -> bool {

components/script/dom/htmldirectoryelement.rs

@@ -13,7 +13,7 @@ use dom::htmlelement::HTMLElement;
 use dom::node::{Node, ElementNodeTypeId};
 use servo_util::str::DOMString;
 
-#[deriving(Encodable)]
+#[jstraceable]
 #[must_root]
 pub struct HTMLDirectoryElement {
     pub htmlelement: HTMLElement

components/script/dom/htmldivelement.rs

@@ -13,7 +13,7 @@ use dom::htmlelement::HTMLElement;
 use dom::node::{Node, ElementNodeTypeId};
 use servo_util::str::DOMString;
 
-#[deriving(Encodable)]
+#[jstraceable]
 #[must_root]
 pub struct HTMLDivElement {
     pub htmlelement: HTMLElement

components/script/dom/htmldlistelement.rs

@@ -13,7 +13,7 @@ use dom::htmlelement::HTMLElement;
 use dom::node::{Node, ElementNodeTypeId};
 use servo_util::str::DOMString;
 
-#[deriving(Encodable)]
+#[jstraceable]
 #[must_root]
 pub struct HTMLDListElement {
     pub htmlelement: HTMLElement

components/script/dom/htmlelement.rs

@@ -21,7 +21,7 @@ use servo_util::atom::Atom;
 use servo_util::namespace;
 use servo_util::str::DOMString;
 
-#[deriving(Encodable)]
+#[jstraceable]
 #[must_root]
 pub struct HTMLElement {
     pub element: Element

components/script/dom/htmlembedelement.rs

@@ -13,7 +13,7 @@ use dom::htmlelement::HTMLElement;
 use dom::node::{Node, ElementNodeTypeId};
 use servo_util::str::DOMString;
 
-#[deriving(Encodable)]
+#[jstraceable]
 #[must_root]
 pub struct HTMLEmbedElement {
     pub htmlelement: HTMLElement

components/script/dom/htmlfieldsetelement.rs

@@ -21,7 +21,7 @@ use dom::virtualmethods::VirtualMethods;
 use servo_util::atom::Atom;
 use servo_util::str::{DOMString, StaticStringVec};
 
-#[deriving(Encodable)]
+#[jstraceable]
 #[must_root]
 pub struct HTMLFieldSetElement {
     pub htmlelement: HTMLElement
@@ -50,6 +50,7 @@ impl HTMLFieldSetElement {
 impl<'a> HTMLFieldSetElementMethods for JSRef<'a, HTMLFieldSetElement> {
     // http://www.whatwg.org/html/#dom-fieldset-elements
     fn Elements(self) -> Temporary<HTMLCollection> {
+        #[jstraceable]
         struct ElementsFilter;
         impl CollectionFilter for ElementsFilter {
             fn filter(&self, elem: JSRef<Element>, root: JSRef<Node>) -> bool {

components/script/dom/htmlfontelement.rs

@@ -13,7 +13,7 @@ use dom::htmlelement::HTMLElement;
 use dom::node::{Node, ElementNodeTypeId};
 use servo_util::str::DOMString;
 
-#[deriving(Encodable)]
+#[jstraceable]
 #[must_root]
 pub struct HTMLFontElement {
     pub htmlelement: HTMLElement

components/script/dom/htmlformelement.rs

@@ -13,7 +13,7 @@ use dom::htmlelement::HTMLElement;
 use dom::node::{Node, ElementNodeTypeId};
 use servo_util::str::DOMString;
 
-#[deriving(Encodable)]
+#[jstraceable]
 #[must_root]
 pub struct HTMLFormElement {
     pub htmlelement: HTMLElement

components/script/dom/htmlframeelement.rs

@@ -13,7 +13,7 @@ use dom::htmlelement::HTMLElement;
 use dom::node::{Node, ElementNodeTypeId};
 use servo_util::str::DOMString;
 
-#[deriving(Encodable)]
+#[jstraceable]
 #[must_root]
 pub struct HTMLFrameElement {
     pub htmlelement: HTMLElement

components/script/dom/htmlframesetelement.rs

@@ -13,7 +13,7 @@ use dom::htmlelement::HTMLElement;
 use dom::node::{Node, ElementNodeTypeId};
 use servo_util::str::DOMString;
 
-#[deriving(Encodable)]
+#[jstraceable]
 #[must_root]
 pub struct HTMLFrameSetElement {
     pub htmlelement: HTMLElement

components/script/dom/htmlheadelement.rs

@@ -13,7 +13,7 @@ use dom::htmlelement::HTMLElement;
 use dom::node::{Node, ElementNodeTypeId};
 use servo_util::str::DOMString;
 
-#[deriving(Encodable)]
+#[jstraceable]
 #[must_root]
 pub struct HTMLHeadElement {
     pub htmlelement: HTMLElement

components/script/dom/htmlheadingelement.rs

@@ -13,7 +13,7 @@ use dom::htmlelement::HTMLElement;
 use dom::node::{Node, ElementNodeTypeId};
 use servo_util::str::DOMString;
 
-#[deriving(Encodable)]
+#[jstraceable]
 pub enum HeadingLevel {
     Heading1,
     Heading2,
@@ -23,7 +23,7 @@ pub enum HeadingLevel {
     Heading6,
 }
 
-#[deriving(Encodable)]
+#[jstraceable]
 #[must_root]
 pub struct HTMLHeadingElement {
     pub htmlelement: HTMLElement,

components/script/dom/htmlhrelement.rs

@@ -13,7 +13,7 @@ use dom::htmlelement::HTMLElement;
 use dom::node::{Node, ElementNodeTypeId};
 use servo_util::str::DOMString;
 
-#[deriving(Encodable)]
+#[jstraceable]
 #[must_root]
 pub struct HTMLHRElement {
     pub htmlelement: HTMLElement,

components/script/dom/htmlhtmlelement.rs

@@ -13,7 +13,7 @@ use dom::htmlelement::HTMLElement;
 use dom::node::{Node, ElementNodeTypeId};
 use servo_util::str::DOMString;
 
-#[deriving(Encodable)]
+#[jstraceable]
 #[must_root]
 pub struct HTMLHtmlElement {
     pub htmlelement: HTMLElement

components/script/dom/htmliframeelement.rs

@@ -41,7 +41,7 @@ enum SandboxAllowance {
     AllowPopups = 0x20
 }
 
-#[deriving(Encodable)]
+#[jstraceable]
 #[must_root]
 pub struct HTMLIFrameElement {
     pub htmlelement: HTMLElement,
@@ -55,7 +55,7 @@ impl HTMLIFrameElementDerived for EventTarget {
     }
 }
 
-#[deriving(Encodable)]
+#[jstraceable]
 pub struct IFrameSize {
     pub pipeline_id: PipelineId,
     pub subpage_id: SubpageId,

components/script/dom/htmlimageelement.rs

@@ -25,7 +25,7 @@ use url::{Url, UrlParser};
 
 use std::cell::RefCell;
 
-#[deriving(Encodable)]
+#[jstraceable]
 #[must_root]
 pub struct HTMLImageElement {
     pub htmlelement: HTMLElement,

components/script/dom/htmlinputelement.rs

@@ -18,7 +18,7 @@ use dom::virtualmethods::VirtualMethods;
 use servo_util::atom::Atom;
 use servo_util::str::DOMString;
 
-#[deriving(Encodable)]
+#[jstraceable]
 #[must_root]
 pub struct HTMLInputElement {
     pub htmlelement: HTMLElement,

components/script/dom/htmllabelelement.rs

@@ -13,7 +13,7 @@ use dom::htmlelement::HTMLElement;
 use dom::node::{Node, ElementNodeTypeId};
 use servo_util::str::DOMString;
 
-#[deriving(Encodable)]
+#[jstraceable]
 #[must_root]
 pub struct HTMLLabelElement {
     pub htmlelement: HTMLElement,

components/script/dom/htmllegendelement.rs

@@ -13,7 +13,7 @@ use dom::htmlelement::HTMLElement;
 use dom::node::{Node, ElementNodeTypeId};
 use servo_util::str::DOMString;
 
-#[deriving(Encodable)]
+#[jstraceable]
 #[must_root]
 pub struct HTMLLegendElement {
     pub htmlelement: HTMLElement,

components/script/dom/htmllielement.rs

@@ -13,7 +13,7 @@ use dom::htmlelement::HTMLElement;
 use dom::node::{Node, ElementNodeTypeId};
 use servo_util::str::DOMString;
 
-#[deriving(Encodable)]
+#[jstraceable]
 #[must_root]
 pub struct HTMLLIElement {
     pub htmlelement: HTMLElement,

components/script/dom/htmllinkelement.rs

@@ -22,7 +22,7 @@ use servo_util::namespace::Null;
 use std::ascii::StrAsciiExt;
 use url::UrlParser;
 
-#[deriving(Encodable)]
+#[jstraceable]
 #[must_root]
 pub struct HTMLLinkElement {
     pub htmlelement: HTMLElement,

components/script/dom/htmlmapelement.rs

@@ -13,7 +13,7 @@ use dom::htmlelement::HTMLElement;
 use dom::node::{Node, ElementNodeTypeId};
 use servo_util::str::DOMString;
 
-#[deriving(Encodable)]
+#[jstraceable]
 #[must_root]
 pub struct HTMLMapElement {
     pub htmlelement: HTMLElement

components/script/dom/htmlmediaelement.rs

@@ -12,7 +12,7 @@ use dom::htmlelement::HTMLElement;
 use dom::node::ElementNodeTypeId;
 use servo_util::str::DOMString;
 
-#[deriving(Encodable)]
+#[jstraceable]
 #[must_root]
 pub struct HTMLMediaElement {
     pub htmlelement: HTMLElement,

components/script/dom/htmlmetaelement.rs

@@ -13,7 +13,7 @@ use dom::htmlelement::HTMLElement;
 use dom::node::{Node, ElementNodeTypeId};
 use servo_util::str::DOMString;
 
-#[deriving(Encodable)]
+#[jstraceable]
 #[must_root]
 pub struct HTMLMetaElement {
     pub htmlelement: HTMLElement,

components/script/dom/htmlmeterelement.rs

@@ -13,7 +13,7 @@ use dom::htmlelement::HTMLElement;
 use dom::node::{Node, ElementNodeTypeId};
 use servo_util::str::DOMString;
 
-#[deriving(Encodable)]
+#[jstraceable]
 #[must_root]
 pub struct HTMLMeterElement {
     pub htmlelement: HTMLElement

components/script/dom/htmlmodelement.rs

@@ -13,7 +13,7 @@ use dom::htmlelement::HTMLElement;
 use dom::node::{Node, ElementNodeTypeId};
 use servo_util::str::DOMString;
 
-#[deriving(Encodable)]
+#[jstraceable]
 #[must_root]
 pub struct HTMLModElement {
     pub htmlelement: HTMLElement

components/script/dom/htmlobjectelement.rs

@@ -26,7 +26,7 @@ use servo_util::str::DOMString;
 
 use url::Url;
 
-#[deriving(Encodable)]
+#[jstraceable]
 #[must_root]
 pub struct HTMLObjectElement {
     pub htmlelement: HTMLElement,

components/script/dom/htmlolistelement.rs

@@ -13,7 +13,7 @@ use dom::htmlelement::HTMLElement;
 use dom::node::{Node, ElementNodeTypeId};
 use servo_util::str::DOMString;
 
-#[deriving(Encodable)]
+#[jstraceable]
 #[must_root]
 pub struct HTMLOListElement {
     pub htmlelement: HTMLElement,

components/script/dom/htmloptgroupelement.rs

@@ -18,7 +18,7 @@ use dom::virtualmethods::VirtualMethods;
 use servo_util::atom::Atom;
 use servo_util::str::DOMString;
 
-#[deriving(Encodable)]
+#[jstraceable]
 #[must_root]
 pub struct HTMLOptGroupElement {
     pub htmlelement: HTMLElement

components/script/dom/htmloptionelement.rs

@@ -23,7 +23,7 @@ use servo_util::atom::Atom;
 use servo_util::namespace;
 use servo_util::str::{DOMString, split_html_space_chars};
 
-#[deriving(Encodable)]
+#[jstraceable]
 #[must_root]
 pub struct HTMLOptionElement {
     pub htmlelement: HTMLElement

components/script/dom/htmloutputelement.rs

@@ -15,7 +15,7 @@ use dom::node::{Node, ElementNodeTypeId, window_from_node};
 use dom::validitystate::ValidityState;
 use servo_util::str::DOMString;
 
-#[deriving(Encodable)]
+#[jstraceable]
 #[must_root]
 pub struct HTMLOutputElement {
     pub htmlelement: HTMLElement

components/script/dom/htmlparagraphelement.rs

@@ -13,7 +13,7 @@ use dom::htmlelement::HTMLElement;
 use dom::node::{Node, ElementNodeTypeId};
 use servo_util::str::DOMString;
 
-#[deriving(Encodable)]
+#[jstraceable]
 #[must_root]
 pub struct HTMLParagraphElement {
     pub htmlelement: HTMLElement

components/script/dom/htmlparamelement.rs

@@ -13,7 +13,7 @@ use dom::htmlelement::HTMLElement;
 use dom::node::{Node, ElementNodeTypeId};
 use servo_util::str::DOMString;
 
-#[deriving(Encodable)]
+#[jstraceable]
 #[must_root]
 pub struct HTMLParamElement {
     pub htmlelement: HTMLElement

components/script/dom/htmlpreelement.rs

@@ -13,7 +13,7 @@ use dom::htmlelement::HTMLElement;
 use dom::node::{Node, ElementNodeTypeId};
 use servo_util::str::DOMString;
 
-#[deriving(Encodable)]
+#[jstraceable]
 #[must_root]
 pub struct HTMLPreElement {
     pub htmlelement: HTMLElement,

components/script/dom/htmlprogresselement.rs

@@ -13,7 +13,7 @@ use dom::htmlelement::HTMLElement;
 use dom::node::{Node, ElementNodeTypeId};
 use servo_util::str::DOMString;
 
-#[deriving(Encodable)]
+#[jstraceable]
 #[must_root]
 pub struct HTMLProgressElement {
     pub htmlelement: HTMLElement,

components/script/dom/htmlquoteelement.rs

@@ -13,7 +13,7 @@ use dom::htmlelement::HTMLElement;
 use dom::node::{Node, ElementNodeTypeId};
 use servo_util::str::DOMString;
 
-#[deriving(Encodable)]
+#[jstraceable]
 #[must_root]
 pub struct HTMLQuoteElement {
     pub htmlelement: HTMLElement,

components/script/dom/htmlscriptelement.rs

@@ -19,7 +19,7 @@ use dom::node::{Node, NodeHelpers, ElementNodeTypeId};
 use servo_util::namespace::Null;
 use servo_util::str::{DOMString, HTML_SPACE_CHARACTERS, StaticStringVec};
 
-#[deriving(Encodable)]
+#[jstraceable]
 #[must_root]
 pub struct HTMLScriptElement {
     pub htmlelement: HTMLElement,

components/script/dom/htmlselectelement.rs

@@ -21,7 +21,7 @@ use dom::virtualmethods::VirtualMethods;
 use servo_util::atom::Atom;
 use servo_util::str::DOMString;
 
-#[deriving(Encodable)]
+#[jstraceable]
 #[must_root]
 pub struct HTMLSelectElement {
     pub htmlelement: HTMLElement

components/script/dom/htmlsourceelement.rs

@@ -13,7 +13,7 @@ use dom::htmlelement::HTMLElement;
 use dom::node::{Node, ElementNodeTypeId};
 use servo_util::str::DOMString;
 
-#[deriving(Encodable)]
+#[jstraceable]
 #[must_root]
 pub struct HTMLSourceElement {
     pub htmlelement: HTMLElement

components/script/dom/htmlspanelement.rs

@@ -13,7 +13,7 @@ use dom::htmlelement::HTMLElement;
 use dom::node::{Node, ElementNodeTypeId};
 use servo_util::str::DOMString;
 
-#[deriving(Encodable)]
+#[jstraceable]
 #[must_root]
 pub struct HTMLSpanElement {
     pub htmlelement: HTMLElement

components/script/dom/htmlstyleelement.rs

@@ -17,7 +17,7 @@ use layout_interface::{AddStylesheetMsg, LayoutChan};
 use servo_util::str::DOMString;
 use style::Stylesheet;
 
-#[deriving(Encodable)]
+#[jstraceable]
 #[must_root]
 pub struct HTMLStyleElement {
     pub htmlelement: HTMLElement,

components/script/dom/htmltablecaptionelement.rs

@@ -13,7 +13,7 @@ use dom::htmlelement::HTMLElement;
 use dom::node::{Node, ElementNodeTypeId};
 use servo_util::str::DOMString;
 
-#[deriving(Encodable)]
+#[jstraceable]
 #[must_root]
 pub struct HTMLTableCaptionElement {
     pub htmlelement: HTMLElement

components/script/dom/htmltablecellelement.rs

@@ -12,7 +12,7 @@ use dom::htmlelement::HTMLElement;
 use dom::node::ElementNodeTypeId;
 use servo_util::str::DOMString;
 
-#[deriving(Encodable)]
+#[jstraceable]
 #[must_root]
 pub struct HTMLTableCellElement {
     pub htmlelement: HTMLElement,

components/script/dom/htmltablecolelement.rs

@@ -13,7 +13,7 @@ use dom::htmlelement::HTMLElement;
 use dom::node::{Node, ElementNodeTypeId};
 use servo_util::str::DOMString;
 
-#[deriving(Encodable)]
+#[jstraceable]
 #[must_root]
 pub struct HTMLTableColElement {
     pub htmlelement: HTMLElement,

components/script/dom/htmltabledatacellelement.rs

@@ -13,7 +13,7 @@ use dom::htmltablecellelement::HTMLTableCellElement;
 use dom::node::{Node, ElementNodeTypeId};
 use servo_util::str::DOMString;
 
-#[deriving(Encodable)]
+#[jstraceable]
 #[must_root]
 pub struct HTMLTableDataCellElement {
     pub htmltablecellelement: HTMLTableCellElement,

components/script/dom/htmltableelement.rs

@@ -17,7 +17,7 @@ use dom::htmltablecaptionelement::HTMLTableCaptionElement;
 use dom::node::{Node, NodeHelpers, ElementNodeTypeId};
 use servo_util::str::DOMString;
 
-#[deriving(Encodable)]
+#[jstraceable]
 #[must_root]
 pub struct HTMLTableElement {
     pub htmlelement: HTMLElement,

components/script/dom/htmltableheadercellelement.rs

@@ -13,7 +13,7 @@ use dom::htmltablecellelement::HTMLTableCellElement;
 use dom::node::{Node, ElementNodeTypeId};
 use servo_util::str::DOMString;
 
-#[deriving(Encodable)]
+#[jstraceable]
 #[must_root]
 pub struct HTMLTableHeaderCellElement {
     pub htmltablecellelement: HTMLTableCellElement,

components/script/dom/htmltablerowelement.rs

@@ -13,7 +13,7 @@ use dom::htmlelement::HTMLElement;
 use dom::node::{Node, ElementNodeTypeId};
 use servo_util::str::DOMString;
 
-#[deriving(Encodable)]
+#[jstraceable]
 #[must_root]
 pub struct HTMLTableRowElement {
     pub htmlelement: HTMLElement,

components/script/dom/htmltablesectionelement.rs

@@ -13,7 +13,7 @@ use dom::htmlelement::HTMLElement;
 use dom::node::{Node, ElementNodeTypeId};
 use servo_util::str::DOMString;
 
-#[deriving(Encodable)]
+#[jstraceable]
 #[must_root]
 pub struct HTMLTableSectionElement {
     pub htmlelement: HTMLElement,

components/script/dom/htmltemplateelement.rs

@@ -13,7 +13,7 @@ use dom::htmlelement::HTMLElement;
 use dom::node::{Node, ElementNodeTypeId};
 use servo_util::str::DOMString;
 
-#[deriving(Encodable)]
+#[jstraceable]
 #[must_root]
 pub struct HTMLTemplateElement {
     pub htmlelement: HTMLElement,

components/script/dom/htmltextareaelement.rs

@@ -18,7 +18,7 @@ use dom::virtualmethods::VirtualMethods;
 use servo_util::atom::Atom;
 use servo_util::str::DOMString;
 
-#[deriving(Encodable)]
+#[jstraceable]
 #[must_root]
 pub struct HTMLTextAreaElement {
     pub htmlelement: HTMLElement,

components/script/dom/htmltimeelement.rs

@@ -13,7 +13,7 @@ use dom::htmlelement::HTMLElement;
 use dom::node::{Node, ElementNodeTypeId};
 use servo_util::str::DOMString;
 
-#[deriving(Encodable)]
+#[jstraceable]
 #[must_root]
 pub struct HTMLTimeElement {
     pub htmlelement: HTMLElement

components/script/dom/htmltitleelement.rs

@@ -16,7 +16,7 @@ use dom::node::{Node, NodeHelpers, ElementNodeTypeId};
 use dom::text::Text;
 use servo_util::str::DOMString;
 
-#[deriving(Encodable)]
+#[jstraceable]
 #[must_root]
 pub struct HTMLTitleElement {
     pub htmlelement: HTMLElement,

components/script/dom/htmltrackelement.rs

@@ -13,7 +13,7 @@ use dom::htmlelement::HTMLElement;
 use dom::node::{Node, ElementNodeTypeId};
 use servo_util::str::DOMString;
 
-#[deriving(Encodable)]
+#[jstraceable]
 #[must_root]
 pub struct HTMLTrackElement {
     pub htmlelement: HTMLElement,

components/script/dom/htmlulistelement.rs

@@ -13,7 +13,7 @@ use dom::htmlelement::HTMLElement;
 use dom::node::{Node, ElementNodeTypeId};
 use servo_util::str::DOMString;
 
-#[deriving(Encodable)]
+#[jstraceable]
 #[must_root]
 pub struct HTMLUListElement {
     pub htmlelement: HTMLElement