Add some fmt::Debug implementations

components/style/dom.rs

@@ -201,7 +201,7 @@ pub trait PresentationalHintsSynthetizer {
         where V: Push<DeclarationBlock<Vec<PropertyDeclaration>>>;
 }
 
-pub trait TElement : PartialEq + Sized + Copy + Clone + ElementExt + PresentationalHintsSynthetizer {
+pub trait TElement : PartialEq + Debug + Sized + Copy + Clone + ElementExt + PresentationalHintsSynthetizer {
     type ConcreteNode: TNode<ConcreteElement = Self, ConcreteDocument = Self::ConcreteDocument>;
     type ConcreteDocument: TDocument<ConcreteNode = Self::ConcreteNode, ConcreteElement = Self>;
 

components/style/properties/properties.mako.rs

@@ -803,7 +803,7 @@ impl<T: ToCss> ToCss for DeclaredValue<T> {
     }
 }
 
-#[derive(PartialEq, Clone, Debug)]
+#[derive(PartialEq, Clone)]
 #[cfg_attr(feature = "servo", derive(HeapSizeOf))]
 pub enum PropertyDeclaration {
     % for property in data.longhands:
@@ -867,6 +867,24 @@ impl fmt::Display for PropertyDeclarationName {
         }
     }
 }
+
+impl fmt::Debug for PropertyDeclaration {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        try!(write!(f, "{}: ", self.name()));
+        match *self {
+            % for property in data.longhands:
+                % if not property.derived_from:
+                    PropertyDeclaration::${property.camel_case}(ref value) => value.to_css(f),
+                % endif
+            % endfor
+            PropertyDeclaration::Custom(_, ref value) => value.to_css(f),
+            % if any(property.derived_from for property in data.longhands):
+                _ => Err(fmt::Error),
+            % endif
+        }
+    }
+}
+
 impl ToCss for PropertyDeclaration {
     fn to_css<W>(&self, dest: &mut W) -> fmt::Result where W: fmt::Write {
         match *self {

components/style/selector_matching.rs

@@ -21,6 +21,7 @@ use selectors::parser::Selector;
 use sink::Push;
 use smallvec::VecLike;
 use std::collections::HashMap;
+use std::fmt;
 use std::hash::BuildHasherDefault;
 use std::sync::Arc;
 use string_cache::Atom;
@@ -275,6 +276,7 @@ impl Stylist {
                                                   parent: &Arc<ComputedValues>)
                                                   -> Option<Arc<ComputedValues>>
         where E: Element<Impl=TheSelectorImpl> +
+              Debug +
               PresentationalHintsSynthetizer
     {
         debug_assert!(TheSelectorImpl::pseudo_element_cascade_type(pseudo).is_lazy());
@@ -343,6 +345,7 @@ impl Stylist {
                                         pseudo_element: Option<&PseudoElement>,
                                         applicable_declarations: &mut V) -> StyleRelations
         where E: Element<Impl=TheSelectorImpl> +
+                                                 fmt::Debug +
                  PresentationalHintsSynthetizer,
               V: Push<DeclarationBlock> + VecLike<DeclarationBlock>
     {