Derive the Default trait for dictionaries containing GC values.

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

@@ -4028,12 +4028,18 @@ impl super::%s {
     }
 }
 
+impl Default for super::%s {
+  fn default() -> super::%s {
+    pairs[0].1
+  }
+}
+
 impl ToJSValConvertible for super::%s {
     unsafe fn to_jsval(&self, cx: *mut JSContext, rval: MutableHandleValue) {
         pairs[*self as usize].0.to_jsval(cx, rval);
     }
 }
-    """ % (ident, pairs, ident, ident)
+    """ % (ident, pairs, ident, ident, ident, ident)
         self.cgRoot = CGList([
             CGGeneric(decl),
             CGNamespace.build([ident + "Values"],
@@ -6038,17 +6044,22 @@ class CGDictionary(CGThing):
                        (self.makeMemberName(m[0].identifier.name), self.getMemberType(m))
                        for m in self.memberInfo]
 
-        mustRoot = "#[must_root]\n" if self.membersNeedTracing() else ""
+        derive = ["JSTraceable"]
+        mustRoot = ""
+        if self.membersNeedTracing():
+            mustRoot = "#[must_root]\n"
+            derive += ["Default"]
 
         return (string.Template(
-                "#[derive(JSTraceable)]\n"
+                "#[derive(${derive})]\n"
                 "${mustRoot}" +
                 "pub struct ${selfName} {\n" +
                 "${inheritance}" +
                 "\n".join(memberDecls) + "\n" +
                 "}").substitute({"selfName": self.makeClassName(d),
                                  "inheritance": inheritance,
-                                 "mustRoot": mustRoot}))
+                                 "mustRoot": mustRoot,
+                                 "derive": ', '.join(derive)}))
 
     def impl(self):
         d = self.dictionary

components/script/dom/bindings/num.rs

@@ -6,6 +6,7 @@
 
 use heapsize::HeapSizeOf;
 use num_traits::Float;
+use std::default::Default;
 use std::ops::Deref;
 
 /// Encapsulates the IDL restricted float type.
@@ -45,3 +46,9 @@ impl<T: Float + HeapSizeOf> HeapSizeOf for Finite<T> {
         (**self).heap_size_of_children()
     }
 }
+
+impl<T: Float + Default> Default for Finite<T> {
+    fn default() -> Finite<T> {
+        Finite::wrap(T::default())
+    }
+}

components/script/dom/bindings/str.rs

@@ -9,6 +9,7 @@ use html5ever::{LocalName, Namespace};
 use servo_atoms::Atom;
 use std::ascii::AsciiExt;
 use std::borrow::{Borrow, Cow, ToOwned};
+use std::default::Default;
 use std::fmt;
 use std::hash::{Hash, Hasher};
 use std::marker::PhantomData;
@@ -18,7 +19,7 @@ use std::str;
 use std::str::{Bytes, FromStr};
 
 /// Encapsulates the IDL `ByteString` type.
-#[derive(Clone, Debug, Eq, HeapSizeOf, JSTraceable, PartialEq)]
+#[derive(Clone, Debug, Default, Eq, HeapSizeOf, JSTraceable, PartialEq)]
 pub struct ByteString(Vec<u8>);
 
 impl ByteString {
@@ -77,7 +78,7 @@ impl ops::Deref for ByteString {
 
 /// A string that is constructed from a UCS-2 buffer by replacing invalid code
 /// points with the replacement character.
-#[derive(Clone, HeapSizeOf)]
+#[derive(Clone, Default, HeapSizeOf)]
 pub struct USVString(pub String);
 
 

components/script/dom/bindings/trace.rs

@@ -769,6 +769,12 @@ impl<T: JSTraceable + 'static> RootedTraceableBox<T> {
     }
 }
 
+impl<T: JSTraceable + Default> Default for RootedTraceableBox<T> {
+    fn default() -> RootedTraceableBox<T> {
+        RootedTraceableBox::new(T::default())
+    }
+}
+
 impl<T: JSTraceable> Deref for RootedTraceableBox<T> {
     type Target = T;
     fn deref(&self) -> &T {

components/script/dom/event.rs

@@ -522,3 +522,12 @@ fn inner_invoke(window: Option<&Window>,
     // Step 3.
     found
 }
+
+impl Default for EventBinding::EventInit {
+    fn default() -> EventBinding::EventInit {
+        EventBinding::EventInit {
+            bubbles: false,
+            cancelable: false,
+        }
+    }
+}

components/script/dom/extendableevent.rs

@@ -2,7 +2,7 @@
  * 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 dom::bindings::codegen::Bindings::EventBinding::EventMethods;
+use dom::bindings::codegen::Bindings::EventBinding::{self, EventMethods};
 use dom::bindings::codegen::Bindings::ExtendableEventBinding;
 use dom::bindings::error::{Error, ErrorResult, Fallible};
 use dom::bindings::inheritance::Castable;
@@ -67,3 +67,11 @@ impl ExtendableEvent {
         self.event.IsTrusted()
     }
 }
+
+impl Default for ExtendableEventBinding::ExtendableEventInit {
+    fn default() -> ExtendableEventBinding::ExtendableEventInit {
+        ExtendableEventBinding::ExtendableEventInit {
+            parent: EventBinding::EventInit::default(),
+        }
+    }
+}