Implement FromJSValConvertible for JS<T>.

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

@@ -1920,6 +1920,32 @@ class CGWrapMethod(CGAbstractMethod):
   raw.mut_reflector().set_jsobject(obj);
   return raw;""" % CreateBindingJSObject(self.descriptor)
 
+
+class CGIDLInterface(CGThing):
+    """
+    Class for codegen of an implementation of the IDLInterface trait.
+    """
+    def __init__(self, descriptor):
+        CGThing.__init__(self)
+        self.descriptor = descriptor
+
+    def define(self):
+        replacer = {
+            'type': self.descriptor.name,
+            'depth': self.descriptor.interface.inheritanceDepth(),
+        }
+        return string.Template("""
+impl IDLInterface for ${type} {
+    fn get_prototype_id(_: Option<${type}>) -> PrototypeList::id::ID {
+        PrototypeList::id::${type}
+    }
+    fn get_prototype_depth(_: Option<${type}>) -> uint {
+        ${depth}
+    }
+}
+""").substitute(replacer)
+
+
 class CGAbstractExternMethod(CGAbstractMethod):
     """
     Abstract base class for codegen of implementation-only (no
@@ -4080,6 +4106,8 @@ class CGDescriptor(CGThing):
 
             cgThings.append(CGWrapMethod(descriptor))
 
+        cgThings.append(CGIDLInterface(descriptor))
+
         cgThings = CGList(cgThings, "\n")
         cgThings = CGWrapper(cgThings, pre='\n', post='\n')
         #self.cgRoot = CGWrapper(CGNamespace(toBindingNamespace(descriptor.name),
@@ -4496,6 +4524,7 @@ class CGBindingRoot(CGThing):
             'dom::bindings::callback::{CallSetup,ExceptionHandling}',
             'dom::bindings::callback::{WrapCallThisObject}',
             'dom::bindings::conversions::{FromJSValConvertible, ToJSValConvertible}',
+            'dom::bindings::conversions::IDLInterface',
             'dom::bindings::conversions::{Default, Empty}',
             'dom::bindings::codegen::*',
             'dom::bindings::codegen::UnionTypes::*',

src/components/script/dom/bindings/conversions.rs

@@ -5,6 +5,7 @@
 use dom::bindings::js::JS;
 use dom::bindings::utils::Reflectable;
 use dom::bindings::utils::jsstring_to_str;
+use dom::bindings::utils::unwrap_jsmanaged;
 use servo_util::str::DOMString;
 
 use js::jsapi::{JSBool, JSContext};
@@ -20,6 +21,15 @@ use js::glue::RUST_JS_NumberValue;
 use std::default::Default;
 use std::libc;
 
+use dom::bindings::codegen::PrototypeList;
+
+// FIXME (https://github.com/rust-lang/rfcs/pull/4)
+//       remove Option<Self> arguments.
+pub trait IDLInterface {
+    fn get_prototype_id(_: Option<Self>) -> PrototypeList::id::ID;
+    fn get_prototype_depth(_: Option<Self>) -> uint;
+}
+
 pub trait ToJSValConvertible {
     fn to_jsval(&self, cx: *JSContext) -> JSVal;
 }
@@ -255,6 +265,17 @@ impl<T: Reflectable> ToJSValConvertible for JS<T> {
     }
 }
 
+impl<T: Reflectable+IDLInterface> FromJSValConvertible<()> for JS<T> {
+    fn from_jsval(_cx: *JSContext, value: JSVal, _option: ()) -> Result<JS<T>, ()> {
+        if !value.is_object() {
+            return Err(());
+        }
+        unwrap_jsmanaged(value.to_object(),
+                         IDLInterface::get_prototype_id(None::<T>),
+                         IDLInterface::get_prototype_depth(None::<T>))
+    }
+}
+
 impl<T: ToJSValConvertible> ToJSValConvertible for Option<T> {
     fn to_jsval(&self, cx: *JSContext) -> JSVal {
         match self {

src/components/script/dom/bindings/utils.rs

@@ -4,6 +4,7 @@
 
 use dom::bindings::codegen::PrototypeList;
 use dom::bindings::codegen::PrototypeList::MAX_PROTO_CHAIN_LENGTH;
+use dom::bindings::conversions::FromJSValConvertible;
 use dom::bindings::js::JS;
 use dom::window;
 use servo_util::str::DOMString;
@@ -34,8 +35,8 @@ use js::jsapi::{JSString};
 use js::jsapi::{JS_AllowGC, JS_InhibitGC};
 use js::jsfriendapi::bindgen::JS_NewObjectWithUniqueType;
 use js::jsval::JSVal;
-use js::jsval::{PrivateValue, ObjectValue, NullValue, Int32Value};
-use js::jsval::{UInt32Value, DoubleValue, BooleanValue, UndefinedValue};
+use js::jsval::{PrivateValue, ObjectValue, NullValue, ObjectOrNullValue};
+use js::jsval::{Int32Value, UInt32Value, DoubleValue, BooleanValue, UndefinedValue};
 use js::{JSPROP_ENUMERATE, JSCLASS_IS_GLOBAL, JSCLASS_IS_DOMJSCLASS};
 use js::JSPROP_PERMANENT;
 use js::{JSFUN_CONSTRUCTOR, JSPROP_READONLY};
@@ -532,11 +533,8 @@ pub fn global_object_for_js_object(obj: *JSObject) -> JS<window::Window> {
         let global = GetGlobalForObjectCrossCompartment(obj);
         let clasp = JS_GetClass(global);
         assert!(((*clasp).flags & (JSCLASS_IS_DOMJSCLASS | JSCLASS_IS_GLOBAL)) != 0);
-        // FIXME(jdm): Either don't hardcode or sanity assert prototype stuff.
-        match unwrap_object(global, PrototypeList::id::Window, 1) {
-            Ok(win) => JS::from_raw(win),
-            Err(_) => fail!("found DOM global that doesn't unwrap to Window"),
-        }
+        FromJSValConvertible::from_jsval(ptr::null(), ObjectOrNullValue(global), ())
+            .ok().expect("found DOM global that doesn't unwrap to Window")
     }
 }