auto merge of #2101 : jdm/servo/newroot_rebase, r=Ms2ger

As described in #1764, this strategy uses the following properties:
* DOM members are `JS<T>` types. These cannot be used with being explicitly rooted, but they are required for compiler-derived trace hooks.
* Methods that take DOM type arguments receive `&[mut] JSRef<T>`. These are rooted value references that are cloneable but cannot escape.
* Methods that return DOM values use `Unrooted<T>`. These are values that may or may not be rooted elsewhere, but callers must root them in order to interact with them in any way. One unsoundness hole exists - `Unrooted` values must be rooted ASAP, or there exists the danger that JSAPI calls could be made that could cause the underlying JS value to be GCed.
* All methods are implemented on `JSRef<T>`, enforcing the requirement that all DOM values are rooted for the duration of a method call (with a few exceptions for layout-related code, which cannot root values and therefore interacts with `JS<T>` and `&T` values - this is safe under the assumption that layout code interacts with DOM nodes that are in the tree, therefore rooted, and does not run concurrently with content code)

1 files changed, 12 insertions, 6 deletions

diff --git a/src/components/script/dom/domexception.rs b/src/components/script/dom/domexception.rs
index 6bb946e4bed..d3ef0664383 100644
--- a/src/components/script/dom/domexception.rs
+++ b/src/components/script/dom/domexception.rs
@@ -4,7 +4,7 @@
 
 use dom::bindings::codegen::BindingDeclarations::DOMExceptionBinding;
 use dom::bindings::codegen::BindingDeclarations::DOMExceptionBinding::DOMExceptionConstants;
-use dom::bindings::js::JS;
+use dom::bindings::js::{JSRef, Temporary};
 use dom::bindings::utils::{Reflectable, Reflector, reflect_dom_object};
 use dom::window::Window;
 use servo_util::str::DOMString;
@@ -49,7 +49,7 @@ impl DOMException {
         }
     }
 
-    pub fn new(window: &JS<Window>, code: DOMErrorName) -> JS<DOMException> {
+    pub fn new(window: &JSRef<Window>, code: DOMErrorName) -> Temporary<DOMException> {
         reflect_dom_object(~DOMException::new_inherited(code), window, DOMExceptionBinding::Wrap)
     }
 }
@@ -64,9 +64,15 @@ impl Reflectable for DOMException {
     }
 }
 
-impl DOMException {
+pub trait DOMExceptionMethods {
+    fn Code(&self) -> u16;
+    fn Name(&self) -> DOMString;
+    fn Message(&self) -> DOMString;
+}
+
+impl<'a> DOMExceptionMethods for JSRef<'a, DOMException> {
     // http://dom.spec.whatwg.org/#dom-domexception-code
-    pub fn Code(&self) -> u16 {
+    fn Code(&self) -> u16 {
         match self.code {
             // http://dom.spec.whatwg.org/#concept-throw
             EncodingError => 0,
@@ -75,12 +81,12 @@ impl DOMException {
     }
 
     // http://dom.spec.whatwg.org/#error-names-0
-    pub fn Name(&self) -> DOMString {
+    fn Name(&self) -> DOMString {
         self.code.to_str()
     }
 
     // http://dom.spec.whatwg.org/#error-names-0
-    pub fn Message(&self) -> DOMString {
+    fn Message(&self) -> DOMString {
         match self.code {
             IndexSizeError => ~"The index is not in the allowed range.",
             HierarchyRequestError => ~"The operation would yield an incorrect node tree.",