Auto merge of #16900 - emilio:pseudos, r=bholley

Bug 1364850: Move PseudoElement to be just another combinator in selectors. r=bholley

On top of https://github.com/servo/servo/pull/16890.

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19 files changed, 675 insertions, 541 deletions

diff --git a/components/script/dom/element.rs b/components/script/dom/element.rs
index 011b87aabf1..6b844dd83a2 100644
--- a/components/script/dom/element.rs
+++ b/components/script/dom/element.rs
@@ -86,7 +86,7 @@ use net_traits::request::CorsSettings;
 use ref_filter_map::ref_filter_map;
 use script_layout_interface::message::ReflowQueryType;
 use script_thread::Runnable;
-use selectors::matching::{ElementSelectorFlags, MatchingContext, matches_selector_list};
+use selectors::matching::{ElementSelectorFlags, MatchingContext, MatchingMode, matches_selector_list};
 use selectors::matching::{HAS_EDGE_CHILD_SELECTOR, HAS_SLOW_SELECTOR, HAS_SLOW_SELECTOR_LATER_SIBLINGS};
 use selectors::parser::{AttrSelector, NamespaceConstraint};
 use servo_atoms::Atom;
@@ -104,7 +104,7 @@ use style::properties::{Importance, PropertyDeclaration, PropertyDeclarationBloc
 use style::properties::longhands::{self, background_image, border_spacing, font_family, font_size, overflow_x};
 use style::restyle_hints::RESTYLE_SELF;
 use style::rule_tree::CascadeLevel;
-use style::selector_parser::{NonTSPseudoClass, RestyleDamage, SelectorImpl, SelectorParser};
+use style::selector_parser::{NonTSPseudoClass, PseudoElement, RestyleDamage, SelectorImpl, SelectorParser};
 use style::shared_lock::{SharedRwLock, Locked};
 use style::sink::Push;
 use style::stylearc::Arc;
@@ -2058,7 +2058,8 @@ impl ElementMethods for Element {
         match SelectorParser::parse_author_origin_no_namespace(&selectors) {
             Err(()) => Err(Error::Syntax),
             Ok(selectors) => {
-                Ok(matches_selector_list(&selectors.0, &Root::from_ref(self), None))
+                let mut ctx = MatchingContext::new(MatchingMode::Normal, None);
+                Ok(matches_selector_list(&selectors.0, &Root::from_ref(self), &mut ctx))
             }
         }
     }
@@ -2076,8 +2077,8 @@ impl ElementMethods for Element {
                 let root = self.upcast::<Node>();
                 for element in root.inclusive_ancestors() {
                     if let Some(element) = Root::downcast::<Element>(element) {
-                        if matches_selector_list(&selectors.0, &element, None)
-                        {
+                        let mut ctx = MatchingContext::new(MatchingMode::Normal, None);
+                        if matches_selector_list(&selectors.0, &element, &mut ctx) {
                             return Ok(Some(element));
                         }
                     }
@@ -2386,6 +2387,15 @@ impl<'a> ::selectors::Element for Root<Element> {
         self.upcast::<Node>().GetParentElement()
     }
 
+    fn match_pseudo_element(&self,
+                            _pseudo: &PseudoElement,
+                            _context: &mut MatchingContext)
+                            -> bool
+    {
+        false
+    }
+
+
     fn first_child_element(&self) -> Option<Root<Element>> {
         self.node.child_elements().next()
     }
diff --git a/components/script/dom/node.rs b/components/script/dom/node.rs
index 8c8831801ef..1ad28974f3d 100644
--- a/components/script/dom/node.rs
+++ b/components/script/dom/node.rs
@@ -70,7 +70,7 @@ use script_layout_interface::{LayoutElementType, LayoutNodeType, TrustedNodeAddr
 use script_layout_interface::message::Msg;
 use script_traits::DocumentActivity;
 use script_traits::UntrustedNodeAddress;
-use selectors::matching::matches_selector_list;
+use selectors::matching::{matches_selector_list, MatchingContext, MatchingMode};
 use selectors::parser::SelectorList;
 use servo_url::ServoUrl;
 use std::borrow::ToOwned;
@@ -346,11 +346,14 @@ impl<'a> Iterator for QuerySelectorIterator {
 
     fn next(&mut self) -> Option<Root<Node>> {
         let selectors = &self.selectors.0;
+
         // TODO(cgaebel): Is it worth it to build a bloom filter here
         // (instead of passing `None`)? Probably.
+        let mut ctx = MatchingContext::new(MatchingMode::Normal, None);
+
         self.iterator.by_ref().filter_map(|node| {
             if let Some(element) = Root::downcast(node) {
-                if matches_selector_list(selectors, &element, None) {
+                if matches_selector_list(selectors, &element, &mut ctx) {
                     return Some(Root::upcast(element));
                 }
             }
@@ -717,8 +720,9 @@ impl Node {
             Err(()) => Err(Error::Syntax),
             // Step 3.
             Ok(selectors) => {
+                let mut ctx = MatchingContext::new(MatchingMode::Normal, None);
                 Ok(self.traverse_preorder().filter_map(Root::downcast).find(|element| {
-                    matches_selector_list(&selectors.0, element, None)
+                    matches_selector_list(&selectors.0, element, &mut ctx)
                 }))
             }
         }
diff --git a/components/script/layout_wrapper.rs b/components/script/layout_wrapper.rs
index 7802d446114..4cf1789beef 100644
--- a/components/script/layout_wrapper.rs
+++ b/components/script/layout_wrapper.rs
@@ -652,6 +652,14 @@ impl<'le> ::selectors::Element for ServoLayoutElement<'le> {
         self.element.namespace()
     }
 
+    fn match_pseudo_element(&self,
+                            _pseudo: &PseudoElement,
+                            _context: &mut MatchingContext)
+                            -> bool
+    {
+        false
+    }
+
     fn match_non_ts_pseudo_class<F>(&self,
                                     pseudo_class: &NonTSPseudoClass,
                                     _: &mut MatchingContext,
@@ -1150,6 +1158,14 @@ impl<'le> ::selectors::Element for ServoThreadSafeLayoutElement<'le> {
         self.element.get_namespace()
     }
 
+    fn match_pseudo_element(&self,
+                            _pseudo: &PseudoElement,
+                            _context: &mut MatchingContext)
+                            -> bool
+    {
+        false
+    }
+
     fn match_non_ts_pseudo_class<F>(&self,
                                     _: &NonTSPseudoClass,
                                     _: &mut MatchingContext,
diff --git a/components/script_layout_interface/wrapper_traits.rs b/components/script_layout_interface/wrapper_traits.rs
index 4f2870aace0..2ba72231269 100644
--- a/components/script_layout_interface/wrapper_traits.rs
+++ b/components/script_layout_interface/wrapper_traits.rs
@@ -20,7 +20,6 @@ use style::context::SharedStyleContext;
 use style::data::ElementData;
 use style::dom::{LayoutIterator, NodeInfo, PresentationalHintsSynthesizer, TNode};
 use style::dom::OpaqueNode;
-use style::element_state::ElementState;
 use style::font_metrics::ServoMetricsProvider;
 use style::properties::{CascadeFlags, ServoComputedValues};
 use style::selector_parser::{PseudoElement, PseudoElementCascadeType, SelectorImpl};
@@ -435,7 +434,6 @@ pub trait ThreadSafeLayoutElement: Clone + Copy + Sized + Debug +
                                            &context.guards,
                                            unsafe { &self.unsafe_get() },
                                            &style_pseudo,
-                                           ElementState::empty(),
                                            data.styles().primary.values(),
                                            &ServoMetricsProvider);
                             data.styles_mut().cached_pseudos
diff --git a/components/selectors/gecko_like_types.rs b/components/selectors/gecko_like_types.rs
index bbb78823c50..9ffffaf2aed 100644
--- a/components/selectors/gecko_like_types.rs
+++ b/components/selectors/gecko_like_types.rs
@@ -19,9 +19,6 @@ pub enum PseudoElement {
     B,
 }
 
-#[derive(Eq, PartialEq, Clone, Debug)]
-pub struct PseudoElementSelector(PseudoElement, u64);
-
 #[derive(Eq, PartialEq, Clone, Debug, Default)]
 pub struct Atom(usize);
 
diff --git a/components/selectors/matching.rs b/components/selectors/matching.rs
index c4e19f47fd3..9c60e6b78d7 100644
--- a/components/selectors/matching.rs
+++ b/components/selectors/matching.rs
@@ -69,28 +69,67 @@ impl ElementSelectorFlags {
     }
 }
 
+/// What kind of selector matching mode we should use.
+///
+/// There are two modes of selector matching. The difference is only noticeable
+/// in presence of pseudo-elements.
+#[derive(Debug, PartialEq)]
+pub enum MatchingMode {
+    /// Don't ignore any pseudo-element selectors.
+    Normal,
+
+    /// Ignores any stateless pseudo-element selectors in the rightmost sequence
+    /// of simple selectors.
+    ///
+    /// This is useful, for example, to match against ::before when you aren't a
+    /// pseudo-element yourself.
+    ///
+    /// For example, in presence of `::before:hover`, it would never match, but
+    /// `::before` would be ignored as in "matching".
+    ///
+    /// It's required for all the selectors you match using this mode to have a
+    /// pseudo-element.
+    ForStatelessPseudoElement,
+}
+
+
 /// Data associated with the matching process for a element.  This context is
 /// used across many selectors for an element, so it's not appropriate for
 /// transient data that applies to only a single selector.
-#[derive(Default)]
-pub struct MatchingContext {
+pub struct MatchingContext<'a> {
     /// Output that records certains relations between elements noticed during
     /// matching (and also extended after matching).
     pub relations: StyleRelations,
+    /// The matching mode we should use when matching selectors.
+    pub matching_mode: MatchingMode,
+    /// The bloom filter used to fast-reject selectors.
+    pub bloom_filter: Option<&'a BloomFilter>,
+}
+
+impl<'a> MatchingContext<'a> {
+    /// Constructs a new `MatchingContext`.
+    pub fn new(matching_mode: MatchingMode,
+               bloom_filter: Option<&'a BloomFilter>)
+               -> Self
+    {
+        Self {
+            relations: StyleRelations::empty(),
+            matching_mode: matching_mode,
+            bloom_filter: bloom_filter,
+        }
+    }
 }
 
 pub fn matches_selector_list<E>(selector_list: &[Selector<E::Impl>],
                                 element: &E,
-                                parent_bf: Option<&BloomFilter>)
+                                context: &mut MatchingContext)
                                 -> bool
     where E: Element
 {
     selector_list.iter().any(|selector| {
-        selector.pseudo_element.is_none() &&
         matches_selector(&selector.inner,
                          element,
-                         parent_bf,
-                         &mut MatchingContext::default(),
+                         context,
                          &mut |_, _| {})
     })
 }
@@ -115,27 +154,6 @@ fn may_match<E>(sel: &SelectorInner<E::Impl>,
     true
 }
 
-/// Determines whether the given element matches the given complex selector.
-pub fn matches_selector<E, F>(selector: &SelectorInner<E::Impl>,
-                              element: &E,
-                              parent_bf: Option<&BloomFilter>,
-                              context: &mut MatchingContext,
-                              flags_setter: &mut F)
-                              -> bool
-    where E: Element,
-          F: FnMut(&E, ElementSelectorFlags),
-{
-    // Use the bloom filter to fast-reject.
-    if let Some(filter) = parent_bf {
-        if !may_match::<E>(selector, filter) {
-            return false;
-        }
-    }
-
-    // Match the selector.
-    matches_complex_selector(&selector.complex, element, context, flags_setter)
-}
-
 /// A result of selector matching, includes 3 failure types,
 ///
 ///   NotMatchedAndRestartFromClosestLaterSibling
@@ -186,16 +204,65 @@ enum SelectorMatchingResult {
     NotMatchedGlobally,
 }
 
+/// Matches an inner selector.
+pub fn matches_selector<E, F>(selector: &SelectorInner<E::Impl>,
+                              element: &E,
+                              context: &mut MatchingContext,
+                              flags_setter: &mut F)
+                              -> bool
+    where E: Element,
+          F: FnMut(&E, ElementSelectorFlags),
+{
+    // Use the bloom filter to fast-reject.
+    if let Some(filter) = context.bloom_filter {
+        if !may_match::<E>(&selector, filter) {
+            return false;
+        }
+    }
+
+    matches_complex_selector(&selector.complex, element, context, flags_setter)
+}
+
 /// Matches a complex selector.
-pub fn matches_complex_selector<E, F>(selector: &ComplexSelector<E::Impl>,
+///
+/// Use `matches_selector` if you need to skip pseudos.
+pub fn matches_complex_selector<E, F>(complex_selector: &ComplexSelector<E::Impl>,
                                       element: &E,
                                       context: &mut MatchingContext,
                                       flags_setter: &mut F)
                                       -> bool
-     where E: Element,
-           F: FnMut(&E, ElementSelectorFlags),
+    where E: Element,
+          F: FnMut(&E, ElementSelectorFlags),
 {
-    match matches_complex_selector_internal(selector.iter(),
+    let mut iter = complex_selector.iter();
+
+    if cfg!(debug_assertions) {
+        if context.matching_mode == MatchingMode::ForStatelessPseudoElement {
+            assert!(complex_selector.iter().any(|c| {
+                matches!(*c, Component::PseudoElement(..))
+            }));
+        }
+    }
+
+    if context.matching_mode == MatchingMode::ForStatelessPseudoElement {
+        match *iter.next().unwrap() {
+            // Stateful pseudo, just don't match.
+            Component::NonTSPseudoClass(..) => return false,
+            Component::PseudoElement(..) => {
+                // Pseudo, just eat the whole sequence.
+                let next = iter.next();
+                debug_assert!(next.is_none(),
+                              "Someone messed up pseudo-element parsing?");
+
+                if iter.next_sequence().is_none() {
+                    return true;
+                }
+            }
+            _ => panic!("Used MatchingMode::ForStatelessPseudoElement in a non-pseudo selector"),
+        }
+    }
+
+    match matches_complex_selector_internal(iter,
                                             element,
                                             context,
                                             flags_setter) {
@@ -229,12 +296,19 @@ fn matches_complex_selector_internal<E, F>(mut selector_iter: SelectorIter<E::Im
     match combinator {
         None => SelectorMatchingResult::Matched,
         Some(c) => {
-            let (mut next_element, candidate_not_found) = if siblings {
-                (element.prev_sibling_element(),
-                 SelectorMatchingResult::NotMatchedAndRestartFromClosestDescendant)
-            } else {
-                (element.parent_element(),
-                 SelectorMatchingResult::NotMatchedGlobally)
+            let (mut next_element, candidate_not_found) = match c {
+                Combinator::NextSibling | Combinator::LaterSibling => {
+                    (element.prev_sibling_element(),
+                     SelectorMatchingResult::NotMatchedAndRestartFromClosestDescendant)
+                }
+                Combinator::Child | Combinator::Descendant => {
+                    (element.parent_element(),
+                     SelectorMatchingResult::NotMatchedGlobally)
+                }
+                Combinator::PseudoElement => {
+                    (element.pseudo_element_originating_element(),
+                     SelectorMatchingResult::NotMatchedGlobally)
+                }
             };
 
             loop {
@@ -253,6 +327,7 @@ fn matches_complex_selector_internal<E, F>(mut selector_iter: SelectorIter<E::Im
 
                     // Upgrade the failure status to
                     // NotMatchedAndRestartFromClosestDescendant.
+                    (_, Combinator::PseudoElement) |
                     (_, Combinator::Child) => return SelectorMatchingResult::NotMatchedAndRestartFromClosestDescendant,
 
                     // Return the status directly.
@@ -306,6 +381,9 @@ fn matches_simple_selector<E, F>(
 
     match *selector {
         Component::Combinator(_) => unreachable!(),
+        Component::PseudoElement(ref pseudo) => {
+            element.match_pseudo_element(pseudo, context)
+        }
         Component::LocalName(LocalName { ref name, ref lower_name }) => {
             let name = if element.is_html_element_in_html_document() { lower_name } else { name };
             element.get_local_name() == name.borrow()
diff --git a/components/selectors/parser.rs b/components/selectors/parser.rs
index 34ed4418b3d..01f1eafc07c 100644
--- a/components/selectors/parser.rs
+++ b/components/selectors/parser.rs
@@ -16,6 +16,22 @@ use std::slice;
 use tree::SELECTOR_WHITESPACE;
 use visitor::SelectorVisitor;
 
+/// A trait that represents a pseudo-element.
+pub trait PseudoElement : Sized + ToCss {
+    /// The `SelectorImpl` this pseudo-element is used for.
+    type Impl: SelectorImpl;
+
+    /// Whether the pseudo-element supports a given state selector to the right
+    /// of it.
+    fn supports_pseudo_class(
+        &self,
+        _pseudo_class: &<Self::Impl as SelectorImpl>::NonTSPseudoClass)
+        -> bool
+    {
+        false
+    }
+}
+
 macro_rules! with_all_bounds {
     (
         [ $( $InSelector: tt )* ]
@@ -60,7 +76,7 @@ macro_rules! with_all_bounds {
             type NonTSPseudoClass: $($CommonBounds)* + Sized + ToCss + SelectorMethods<Impl = Self>;
 
             /// pseudo-elements
-            type PseudoElementSelector: $($CommonBounds)* + Sized + ToCss;
+            type PseudoElement: $($CommonBounds)* + PseudoElement<Impl = Self>;
         }
     }
 }
@@ -97,8 +113,8 @@ pub trait Parser {
         Err(())
     }
 
-    fn parse_pseudo_element(&self, _name: Cow<str>, _input: &mut CssParser)
-                            -> Result<<Self::Impl as SelectorImpl>::PseudoElementSelector, ()> {
+    fn parse_pseudo_element(&self, _name: Cow<str>)
+                            -> Result<<Self::Impl as SelectorImpl>::PseudoElement, ()> {
         Err(())
     }
 
@@ -178,18 +194,57 @@ impl<Impl: SelectorImpl> SelectorInner<Impl> {
 #[derive(PartialEq, Eq, Clone)]
 pub struct Selector<Impl: SelectorImpl> {
     pub inner: SelectorInner<Impl>,
-    pub pseudo_element: Option<Impl::PseudoElementSelector>,
-    pub specificity: u32,
+    specificity_and_flags: u32,
 }
 
+impl<Impl: SelectorImpl> ::std::borrow::Borrow<SelectorInner<Impl>> for Selector<Impl> {
+    fn borrow(&self) -> &SelectorInner<Impl> {
+        &self.inner
+    }
+}
+
+const HAS_PSEUDO_BIT: u32 = 1 << 30;
+
 impl<Impl: SelectorImpl> Selector<Impl> {
+    pub fn specificity(&self) -> u32 {
+        self.specificity_and_flags & !HAS_PSEUDO_BIT
+    }
+
+    pub fn new_for_unit_testing(inner: SelectorInner<Impl>, specificity: u32) -> Self {
+        Self {
+            inner: inner,
+            specificity_and_flags: specificity,
+        }
+    }
+
+    pub fn pseudo_element(&self) -> Option<&Impl::PseudoElement> {
+        if !self.has_pseudo_element() {
+            return None
+        }
+
+        for component in self.inner.complex.iter() {
+            if let Component::PseudoElement(ref pseudo) = *component {
+                return Some(pseudo)
+            }
+        }
+
+        debug_assert!(false, "has_pseudo_element lied!");
+        None
+    }
+
+    pub fn has_pseudo_element(&self) -> bool {
+        (self.specificity_and_flags & HAS_PSEUDO_BIT) != 0
+    }
+
     /// Whether this selector (pseudo-element part excluded) matches every element.
     ///
     /// Used for "pre-computed" pseudo-elements in components/style/stylist.rs
     pub fn is_universal(&self) -> bool {
         self.inner.complex.iter_raw().all(|c| matches!(*c,
             Component::ExplicitUniversalType |
-            Component::ExplicitAnyNamespace
+            Component::ExplicitAnyNamespace |
+            Component::Combinator(Combinator::PseudoElement) |
+            Component::PseudoElement(..)
         ))
     }
 }
@@ -361,7 +416,8 @@ impl<'a, Impl: 'a + SelectorImpl> SelectorIter<'a, Impl> {
 impl<'a, Impl: SelectorImpl> Iterator for SelectorIter<'a, Impl> {
     type Item = &'a Component<Impl>;
     fn next(&mut self) -> Option<Self::Item> {
-        debug_assert!(self.next_combinator.is_none(), "Should call take_combinator!");
+        debug_assert!(self.next_combinator.is_none(),
+                      "You should call next_sequence!");
         match self.iter.next() {
             None => None,
             Some(&Component::Combinator(c)) => {
@@ -384,12 +440,12 @@ impl<'a, Impl: 'a + SelectorImpl> AncestorIter<'a, Impl> {
         result
     }
 
-    /// Skips a sequence of simple selectors and all subsequent sequences until an
-    /// ancestor combinator is reached.
+    /// Skips a sequence of simple selectors and all subsequent sequences until
+    /// a non-pseudo-element ancestor combinator is reached.
     fn skip_until_ancestor(&mut self) {
         loop {
-            while let Some(_) = self.0.next() {}
-            if self.0.next_sequence().map_or(true, |x| x.is_ancestor()) {
+            while self.0.next().is_some() {}
+            if self.0.next_sequence().map_or(true, |x| matches!(x, Combinator::Child | Combinator::Descendant)) {
                 break;
             }
         }
@@ -407,7 +463,7 @@ impl<'a, Impl: SelectorImpl> Iterator for AncestorIter<'a, Impl> {
 
         // See if there are more sequences. If so, skip any non-ancestor sequences.
         if let Some(combinator) = self.0.next_sequence() {
-            if !combinator.is_ancestor() {
+            if !matches!(combinator, Combinator::Child | Combinator::Descendant) {
                 self.skip_until_ancestor();
             }
         }
@@ -422,12 +478,24 @@ pub enum Combinator {
     Descendant,  // space
     NextSibling,  // +
     LaterSibling,  // ~
+    /// A dummy combinator we use to the left of pseudo-elements.
+    ///
+    /// It serializes as the empty string, and acts effectively as a child
+    /// combinator.
+    PseudoElement,
 }
 
 impl Combinator {
     /// Returns true if this combinator is a child or descendant combinator.
     pub fn is_ancestor(&self) -> bool {
-        matches!(*self, Combinator::Child | Combinator::Descendant)
+        matches!(*self, Combinator::Child |
+                        Combinator::Descendant |
+                        Combinator::PseudoElement)
+    }
+
+    /// Returns true if this combinator is a pseudo-element combinator.
+    pub fn is_pseudo_element(&self) -> bool {
+        matches!(*self, Combinator::PseudoElement)
     }
 
     /// Returns true if this combinator is a next- or later-sibling combinator.
@@ -491,6 +559,7 @@ pub enum Component<Impl: SelectorImpl> {
     LastOfType,
     OnlyOfType,
     NonTSPseudoClass(Impl::NonTSPseudoClass),
+    PseudoElement(Impl::PseudoElement),
     // ...
 }
 
@@ -582,7 +651,7 @@ impl<Impl: SelectorImpl> Debug for Selector<Impl> {
     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
         f.write_str("Selector(")?;
         self.to_css(f)?;
-        write!(f, ", specificity = 0x{:x})", self.specificity)
+        write!(f, ", specificity = 0x{:x})", self.specificity())
     }
 }
 
@@ -621,11 +690,7 @@ impl<Impl: SelectorImpl> ToCss for SelectorList<Impl> {
 
 impl<Impl: SelectorImpl> ToCss for Selector<Impl> {
     fn to_css<W>(&self, dest: &mut W) -> fmt::Result where W: fmt::Write {
-        self.inner.complex.to_css(dest)?;
-        if let Some(ref pseudo) = self.pseudo_element {
-            pseudo.to_css(dest)?;
-        }
-        Ok(())
+        self.inner.complex.to_css(dest)
     }
 }
 
@@ -646,6 +711,7 @@ impl ToCss for Combinator {
             Combinator::Descendant => dest.write_str(" "),
             Combinator::NextSibling => dest.write_str(" + "),
             Combinator::LaterSibling => dest.write_str(" ~ "),
+            Combinator::PseudoElement => Ok(()),
         }
     }
 }
@@ -657,6 +723,9 @@ impl<Impl: SelectorImpl> ToCss for Component<Impl> {
             Combinator(ref c) => {
                 c.to_css(dest)
             }
+            PseudoElement(ref p) => {
+                p.to_css(dest)
+            }
             ID(ref s) => {
                 dest.write_char('#')?;
                 display_to_css_identifier(s, dest)
@@ -841,25 +910,23 @@ impl From<Specificity> for u32 {
     }
 }
 
-fn specificity<Impl>(complex_selector: &ComplexSelector<Impl>,
-                     pseudo_element: Option<&Impl::PseudoElementSelector>)
-                     -> u32
-                     where Impl: SelectorImpl {
-    let mut specificity = complex_selector_specificity(complex_selector);
-    if pseudo_element.is_some() {
-        specificity.element_selectors += 1;
-    }
-    specificity.into()
+fn specificity<Impl>(complex_selector: &ComplexSelector<Impl>) -> u32
+    where Impl: SelectorImpl
+{
+    complex_selector_specificity(complex_selector).into()
 }
 
 fn complex_selector_specificity<Impl>(selector: &ComplexSelector<Impl>)
                                       -> Specificity
-                                      where Impl: SelectorImpl {
+    where Impl: SelectorImpl
+{
     fn simple_selector_specificity<Impl>(simple_selector: &Component<Impl>,
                                          specificity: &mut Specificity)
-                                         where Impl: SelectorImpl {
+        where Impl: SelectorImpl
+    {
         match *simple_selector {
             Component::Combinator(..) => unreachable!(),
+            Component::PseudoElement(..) |
             Component::LocalName(..) => {
                 specificity.element_selectors += 1
             }
@@ -928,12 +995,14 @@ fn complex_selector_specificity<Impl>(selector: &ComplexSelector<Impl>)
 fn parse_selector<P, Impl>(parser: &P, input: &mut CssParser) -> Result<Selector<Impl>, ()>
     where P: Parser<Impl=Impl>, Impl: SelectorImpl
 {
-    let (complex, pseudo_element) =
-        parse_complex_selector_and_pseudo_element(parser, input)?;
+    let (complex, has_pseudo_element) = parse_complex_selector(parser, input)?;
+    let mut specificity = specificity(&complex);
+    if has_pseudo_element {
+        specificity |= HAS_PSEUDO_BIT;
+    }
     Ok(Selector {
-        specificity: specificity(&complex, pseudo_element.as_ref()),
+        specificity_and_flags: specificity,
         inner: SelectorInner::new(complex),
-        pseudo_element: pseudo_element,
     })
 }
 
@@ -947,19 +1016,25 @@ fn parse_selector<P, Impl>(parser: &P, input: &mut CssParser) -> Result<Selector
 /// If we parse N > 8 entries, we save two reallocations.
 type ParseVec<Impl> = SmallVec<[Component<Impl>; 8]>;
 
-fn parse_complex_selector_and_pseudo_element<P, Impl>(
+/// Parses a complex selector, including any pseudo-element.
+///
+/// For now, it always forces the pseudo-element to be at the end of the
+/// selector, and the boolean represents whether the last thing parsed was a
+/// pseudo-element.
+fn parse_complex_selector<P, Impl>(
         parser: &P,
         input: &mut CssParser)
-        -> Result<(ComplexSelector<Impl>, Option<Impl::PseudoElementSelector>), ()>
+        -> Result<(ComplexSelector<Impl>, bool), ()>
     where P: Parser<Impl=Impl>, Impl: SelectorImpl
 {
     let mut sequence = ParseVec::new();
-    let mut pseudo_element;
+    let mut parsed_pseudo_element;
     'outer_loop: loop {
         // Parse a sequence of simple selectors.
-        pseudo_element = parse_compound_selector(parser, input, &mut sequence,
-                                                 /* inside_negation = */ false)?;
-        if pseudo_element.is_some() {
+        parsed_pseudo_element =
+            parse_compound_selector(parser, input, &mut sequence,
+                                    /* inside_negation = */ false)?;
+        if parsed_pseudo_element {
             break;
         }
 
@@ -998,17 +1073,17 @@ fn parse_complex_selector_and_pseudo_element<P, Impl>(
     }
 
     let complex = ComplexSelector(ArcSlice::new(sequence.into_vec().into_boxed_slice()));
-    Ok((complex, pseudo_element))
+    Ok((complex, parsed_pseudo_element))
 }
 
 impl<Impl: SelectorImpl> ComplexSelector<Impl> {
-    /// Parse a complex selector.
+    /// Parse a complex selector, without any pseudo-element.
     pub fn parse<P>(parser: &P, input: &mut CssParser) -> Result<Self, ()>
         where P: Parser<Impl=Impl>
     {
-        let (complex, pseudo_element) =
-            parse_complex_selector_and_pseudo_element(parser, input)?;
-        if pseudo_element.is_some() {
+        let (complex, has_pseudo_element) =
+            parse_complex_selector(parser, input)?;
+        if has_pseudo_element {
             return Err(())
         }
         Ok(complex)
@@ -1062,7 +1137,7 @@ fn parse_type_selector<P, Impl>(parser: &P, input: &mut CssParser, sequence: &mu
 #[derive(Debug)]
 enum SimpleSelectorParseResult<Impl: SelectorImpl> {
     SimpleSelector(Component<Impl>),
-    PseudoElement(Impl::PseudoElementSelector),
+    PseudoElement(Impl::PseudoElement),
 }
 
 #[derive(Debug)]
@@ -1295,13 +1370,15 @@ fn single_simple_selector<Impl: SelectorImpl>(v: &[Component<Impl>]) -> bool {
 /// : [ type_selector | universal ] [ HASH | class | attrib | pseudo | negation ]*
 /// | [ HASH | class | attrib | pseudo | negation ]+
 ///
-/// `Err(())` means invalid selector
+/// `Err(())` means invalid selector.
+///
+/// The boolean represent whether a pseudo-element has been parsed.
 fn parse_compound_selector<P, Impl>(
     parser: &P,
     input: &mut CssParser,
     mut sequence: &mut ParseVec<Impl>,
     inside_negation: bool)
-    -> Result<Option<Impl::PseudoElementSelector>, ()>
+    -> Result<bool, ()>
     where P: Parser<Impl=Impl>, Impl: SelectorImpl
 {
     // Consume any leading whitespace.
@@ -1328,7 +1405,7 @@ fn parse_compound_selector<P, Impl>(
         empty = false;
     }
 
-    let mut pseudo_element = None;
+    let mut pseudo = false;
     loop {
         match parse_one_simple_selector(parser, input, inside_negation)? {
             None => break,
@@ -1337,7 +1414,41 @@ fn parse_compound_selector<P, Impl>(
                 empty = false
             }
             Some(SimpleSelectorParseResult::PseudoElement(p)) => {
-                pseudo_element = Some(p);
+                // Try to parse state to its right.
+                let mut state_selectors = ParseVec::new();
+
+                loop {
+                    match input.next_including_whitespace() {
+                        Ok(Token::Colon) => {},
+                        Ok(Token::WhiteSpace(_)) | Err(()) => break,
+                        _ => return Err(()),
+                    }
+
+                    // TODO(emilio): Functional pseudo-classes too?
+                    // We don't need it for now.
+                    let name = match input.next_including_whitespace() {
+                        Ok(Token::Ident(name)) => name,
+                        _ => return Err(()),
+                    };
+
+                    let pseudo_class =
+                        P::parse_non_ts_pseudo_class(parser, name)?;
+                    if !p.supports_pseudo_class(&pseudo_class) {
+                        return Err(());
+                    }
+                    state_selectors.push(Component::NonTSPseudoClass(pseudo_class));
+                }
+
+                if !sequence.is_empty() {
+                    sequence.push(Component::Combinator(Combinator::PseudoElement));
+                }
+
+                sequence.push(Component::PseudoElement(p));
+                for state_selector in state_selectors {
+                    sequence.push(state_selector);
+                }
+
+                pseudo = true;
                 empty = false;
                 break
             }
@@ -1347,7 +1458,7 @@ fn parse_compound_selector<P, Impl>(
         // An empty selector is invalid.
         Err(())
     } else {
-        Ok(pseudo_element)
+        Ok(pseudo)
     }
 }
 
@@ -1423,7 +1534,7 @@ fn parse_one_simple_selector<P, Impl>(parser: &P,
                        name.eq_ignore_ascii_case("after") ||
                        name.eq_ignore_ascii_case("first-line") ||
                        name.eq_ignore_ascii_case("first-letter") {
-                        let pseudo_element = P::parse_pseudo_element(parser, name, input)?;
+                        let pseudo_element = P::parse_pseudo_element(parser, name)?;
                         Ok(Some(SimpleSelectorParseResult::PseudoElement(pseudo_element)))
                     } else {
                         let pseudo_class = parse_simple_pseudo_class(parser, name)?;
@@ -1439,7 +1550,7 @@ fn parse_one_simple_selector<P, Impl>(parser: &P,
                 Ok(Token::Colon) => {
                     match input.next_including_whitespace() {
                         Ok(Token::Ident(name)) => {
-                            let pseudo = P::parse_pseudo_element(parser, name, input)?;
+                            let pseudo = P::parse_pseudo_element(parser, name)?;
                             Ok(Some(SimpleSelectorParseResult::PseudoElement(pseudo)))
                         }
                         _ => Err(())
@@ -1478,6 +1589,7 @@ fn parse_simple_pseudo_class<P, Impl>(parser: &P, name: Cow<str>) -> Result<Comp
 #[cfg(test)]
 pub mod tests {
     use cssparser::{Parser as CssParser, ToCss, serialize_identifier};
+    use parser;
     use std::borrow::Cow;
     use std::collections::HashMap;
     use std::fmt;
@@ -1486,6 +1598,7 @@ pub mod tests {
     #[derive(PartialEq, Clone, Debug, Eq)]
     pub enum PseudoClass {
         Hover,
+        Active,
         Lang(String),
     }
 
@@ -1495,10 +1608,23 @@ pub mod tests {
         After,
     }
 
+    impl parser::PseudoElement for PseudoElement {
+        type Impl = DummySelectorImpl;
+
+        fn supports_pseudo_class(&self, pc: &PseudoClass) -> bool {
+            match *pc {
+                PseudoClass::Hover => true,
+                PseudoClass::Active |
+                PseudoClass::Lang(..) => false,
+            }
+        }
+    }
+
     impl ToCss for PseudoClass {
         fn to_css<W>(&self, dest: &mut W) -> fmt::Result where W: fmt::Write {
             match *self {
                 PseudoClass::Hover => dest.write_str(":hover"),
+                PseudoClass::Active => dest.write_str(":active"),
                 PseudoClass::Lang(ref lang) => {
                     dest.write_str(":lang(")?;
                     serialize_identifier(lang, dest)?;
@@ -1543,7 +1669,7 @@ pub mod tests {
         type BorrowedLocalName = DummyAtom;
         type BorrowedNamespaceUrl = DummyAtom;
         type NonTSPseudoClass = PseudoClass;
-        type PseudoElementSelector = PseudoElement;
+        type PseudoElement = PseudoElement;
     }
 
     #[derive(Default, Debug, Clone, PartialEq, Eq, Hash)]
@@ -1580,6 +1706,7 @@ pub mod tests {
                                      -> Result<PseudoClass, ()> {
             match_ignore_ascii_case! { &name,
                 "hover" => Ok(PseudoClass::Hover),
+                "active" => Ok(PseudoClass::Active),
                 _ => Err(())
             }
         }
@@ -1593,8 +1720,7 @@ pub mod tests {
             }
         }
 
-        fn parse_pseudo_element(&self, name: Cow<str>, _input: &mut CssParser)
-                                -> Result<PseudoElement, ()> {
+        fn parse_pseudo_element(&self, name: Cow<str>) -> Result<PseudoElement, ()> {
             match_ignore_ascii_case! { &name,
                 "before" => Ok(PseudoElement::Before),
                 "after" => Ok(PseudoElement::After),
@@ -1647,11 +1773,9 @@ pub mod tests {
             inner: SelectorInner::from_vec(vec!(
                 Component::LocalName(LocalName {
                     name: DummyAtom::from("EeÉ"),
-                    lower_name: DummyAtom::from("eeÉ")
-                }),
-            )),
-            pseudo_element: None,
-            specificity: specificity(0, 0, 1),
+                    lower_name: DummyAtom::from("eeÉ") })),
+            ),
+            specificity_and_flags: specificity(0, 0, 1),
         }))));
         assert_eq!(parse("|e"), Ok(SelectorList(vec!(Selector {
             inner: SelectorInner::from_vec(vec!(
@@ -1661,8 +1785,7 @@ pub mod tests {
                     lower_name: DummyAtom::from("e")
                 }),
             )),
-            pseudo_element: None,
-            specificity: specificity(0, 0, 1),
+            specificity_and_flags: specificity(0, 0, 1),
         }))));
         // https://github.com/servo/servo/issues/16020
         assert_eq!(parse("*|e"), Ok(SelectorList(vec!(Selector {
@@ -1673,44 +1796,38 @@ pub mod tests {
                     lower_name: DummyAtom::from("e")
                 }),
             )),
-            pseudo_element: None,
-            specificity: specificity(0, 0, 1),
+            specificity_and_flags: specificity(0, 0, 1),
         }))));
         assert_eq!(parse("*"), Ok(SelectorList(vec!(Selector {
             inner: SelectorInner::from_vec(vec!(
                 Component::ExplicitUniversalType,
             )),
-            pseudo_element: None,
-            specificity: specificity(0, 0, 0),
+            specificity_and_flags: specificity(0, 0, 0),
         }))));
         assert_eq!(parse("|*"), Ok(SelectorList(vec!(Selector {
             inner: SelectorInner::from_vec(vec!(
                 Component::ExplicitNoNamespace,
                 Component::ExplicitUniversalType,
             )),
-            pseudo_element: None,
-            specificity: specificity(0, 0, 0),
+            specificity_and_flags: specificity(0, 0, 0),
         }))));
         assert_eq!(parse("*|*"), Ok(SelectorList(vec!(Selector {
             inner: SelectorInner::from_vec(vec!(
                 Component::ExplicitAnyNamespace,
                 Component::ExplicitUniversalType,
             )),
-            pseudo_element: None,
-            specificity: specificity(0, 0, 0),
+            specificity_and_flags: specificity(0, 0, 0),
         }))));
         assert_eq!(parse(".foo:lang(en-US)"), Ok(SelectorList(vec!(Selector {
             inner: SelectorInner::from_vec(vec![
                     Component::Class(DummyAtom::from("foo")),
                     Component::NonTSPseudoClass(PseudoClass::Lang("en-US".to_owned()))
             ]),
-            pseudo_element: None,
-            specificity: specificity(0, 2, 0),
+            specificity_and_flags: specificity(0, 2, 0),
         }))));
         assert_eq!(parse("#bar"), Ok(SelectorList(vec!(Selector {
             inner: SelectorInner::from_vec(vec!(Component::ID(DummyAtom::from("bar")))),
-            pseudo_element: None,
-            specificity: specificity(1, 0, 0),
+            specificity_and_flags: specificity(1, 0, 0),
         }))));
         assert_eq!(parse("e.foo#bar"), Ok(SelectorList(vec!(Selector {
             inner: SelectorInner::from_vec(vec!(Component::LocalName(LocalName {
@@ -1718,8 +1835,7 @@ pub mod tests {
                                             lower_name: DummyAtom::from("e") }),
                                        Component::Class(DummyAtom::from("foo")),
                                        Component::ID(DummyAtom::from("bar")))),
-            pseudo_element: None,
-            specificity: specificity(1, 1, 1),
+            specificity_and_flags: specificity(1, 1, 1),
         }))));
         assert_eq!(parse("e.foo #bar"), Ok(SelectorList(vec!(Selector {
             inner: SelectorInner::from_vec(vec!(
@@ -1731,8 +1847,7 @@ pub mod tests {
                            Component::Combinator(Combinator::Descendant),
                            Component::ID(DummyAtom::from("bar")),
                        )),
-            pseudo_element: None,
-            specificity: specificity(1, 1, 1),
+            specificity_and_flags: specificity(1, 1, 1),
         }))));
         // Default namespace does not apply to attribute selectors
         // https://github.com/mozilla/servo/pull/1652
@@ -1746,8 +1861,7 @@ pub mod tests {
                         prefix: None,
                         url: "".into(),
                     }) }))),
-            pseudo_element: None,
-            specificity: specificity(0, 1, 0),
+            specificity_and_flags: specificity(0, 1, 0),
         }))));
         assert_eq!(parse_ns("svg|circle", &parser), Err(()));
         parser.ns_prefixes.insert(DummyAtom("svg".into()), DummyAtom(SVG.into()));
@@ -1760,8 +1874,7 @@ pub mod tests {
                         lower_name: DummyAtom::from("circle"),
                     })
                 ]),
-            pseudo_element: None,
-            specificity: specificity(0, 0, 1),
+            specificity_and_flags: specificity(0, 0, 1),
         }])));
         assert_eq!(parse_ns("svg|*", &parser), Ok(SelectorList(vec![Selector {
             inner: SelectorInner::from_vec(
@@ -1769,8 +1882,7 @@ pub mod tests {
                     Component::Namespace(DummyAtom("svg".into()), SVG.into()),
                     Component::ExplicitUniversalType,
                 ]),
-            pseudo_element: None,
-            specificity: specificity(0, 0, 0),
+            specificity_and_flags: specificity(0, 0, 0),
         }])));
         // Default namespace does not apply to attribute selectors
         // https://github.com/mozilla/servo/pull/1652
@@ -1790,8 +1902,7 @@ pub mod tests {
                         }),
                     }),
                 ]),
-            pseudo_element: None,
-            specificity: specificity(0, 1, 0),
+            specificity_and_flags: specificity(0, 1, 0),
         }))));
         // Default namespace does apply to type selectors
         assert_eq!(parse_ns("e", &parser), Ok(SelectorList(vec!(Selector {
@@ -1802,8 +1913,7 @@ pub mod tests {
                         name: DummyAtom::from("e"),
                         lower_name: DummyAtom::from("e") }),
                 )),
-            pseudo_element: None,
-            specificity: specificity(0, 0, 1),
+            specificity_and_flags: specificity(0, 0, 1),
         }))));
         assert_eq!(parse_ns("*", &parser), Ok(SelectorList(vec!(Selector {
             inner: SelectorInner::from_vec(
@@ -1811,8 +1921,7 @@ pub mod tests {
                     Component::DefaultNamespace(MATHML.into()),
                     Component::ExplicitUniversalType,
                 )),
-            pseudo_element: None,
-            specificity: specificity(0, 0, 0),
+            specificity_and_flags: specificity(0, 0, 0),
         }))));
         assert_eq!(parse_ns("*|*", &parser), Ok(SelectorList(vec!(Selector {
             inner: SelectorInner::from_vec(
@@ -1820,8 +1929,7 @@ pub mod tests {
                     Component::ExplicitAnyNamespace,
                     Component::ExplicitUniversalType,
                 )),
-            pseudo_element: None,
-            specificity: specificity(0, 0, 0),
+            specificity_and_flags: specificity(0, 0, 0),
         }))));
         // Default namespace applies to universal and type selectors inside :not and :matches,
         // but not otherwise.
@@ -1832,8 +1940,7 @@ pub mod tests {
                     Component::Class(DummyAtom::from("cl"))
                 ].into_boxed_slice()),
             )),
-            pseudo_element: None,
-            specificity: specificity(0, 1, 0),
+            specificity_and_flags: specificity(0, 1, 0),
         }))));
         assert_eq!(parse_ns(":not(*)", &parser), Ok(SelectorList(vec!(Selector {
             inner: SelectorInner::from_vec(vec!(
@@ -1843,8 +1950,7 @@ pub mod tests {
                     Component::ExplicitUniversalType,
                 ].into_boxed_slice()),
             )),
-            pseudo_element: None,
-            specificity: specificity(0, 0, 0),
+            specificity_and_flags: specificity(0, 0, 0),
         }))));
         assert_eq!(parse_ns(":not(e)", &parser), Ok(SelectorList(vec!(Selector {
             inner: SelectorInner::from_vec(vec!(
@@ -1857,8 +1963,7 @@ pub mod tests {
                     }),
                 ].into_boxed_slice())
             )),
-            pseudo_element: None,
-            specificity: specificity(0, 0, 1),
+            specificity_and_flags: specificity(0, 0, 1),
         }))));
         assert_eq!(parse("[attr |= \"foo\"]"), Ok(SelectorList(vec![Selector {
             inner: SelectorInner::from_vec(
@@ -1872,15 +1977,42 @@ pub mod tests {
                         }),
                     }, DummyAtom::from("foo"))
                 ]),
-            pseudo_element: None,
-            specificity: specificity(0, 1, 0),
+            specificity_and_flags: specificity(0, 1, 0),
         }])));
         // https://github.com/mozilla/servo/issues/1723
         assert_eq!(parse("::before"), Ok(SelectorList(vec!(Selector {
-            inner: SelectorInner::from_vec(vec![]),
-            pseudo_element: Some(PseudoElement::Before),
-            specificity: specificity(0, 0, 1),
+            inner: SelectorInner::from_vec(
+                vec![
+                    Component::PseudoElement(PseudoElement::Before),
+                ]
+            ),
+            specificity_and_flags: specificity(0, 0, 1) | HAS_PSEUDO_BIT,
         }))));
+        assert_eq!(parse("::before:hover"), Ok(SelectorList(vec!(Selector {
+            inner: SelectorInner::from_vec(
+                vec![
+                    Component::PseudoElement(PseudoElement::Before),
+                    Component::NonTSPseudoClass(PseudoClass::Hover),
+                ]
+            ),
+            specificity_and_flags: specificity(0, 1, 1) | HAS_PSEUDO_BIT,
+        }))));
+        assert_eq!(parse("::before:hover:hover"), Ok(SelectorList(vec!(Selector {
+            inner: SelectorInner::from_vec(
+                vec![
+                    Component::PseudoElement(PseudoElement::Before),
+                    Component::NonTSPseudoClass(PseudoClass::Hover),
+                    Component::NonTSPseudoClass(PseudoClass::Hover),
+                ]
+            ),
+            specificity_and_flags: specificity(0, 2, 1) | HAS_PSEUDO_BIT,
+        }))));
+        assert_eq!(parse("::before:hover:active"), Err(()));
+        assert_eq!(parse("::before:hover .foo"), Err(()));
+        assert_eq!(parse("::before .foo"), Err(()));
+        assert_eq!(parse("::before ~ bar"), Err(()));
+        assert_eq!(parse("::before:active"), Err(()));
+
         // https://github.com/servo/servo/issues/15335
         assert_eq!(parse(":: before"), Err(()));
         assert_eq!(parse("div ::after"), Ok(SelectorList(vec!(Selector {
@@ -1890,9 +2022,10 @@ pub mod tests {
                         name: DummyAtom::from("div"),
                         lower_name: DummyAtom::from("div") }),
                     Component::Combinator(Combinator::Descendant),
+                    Component::Combinator(Combinator::PseudoElement),
+                    Component::PseudoElement(PseudoElement::After),
                 ]),
-            pseudo_element: Some(PseudoElement::After),
-            specificity: specificity(0, 0, 2),
+            specificity_and_flags: specificity(0, 0, 2) | HAS_PSEUDO_BIT,
         }))));
         assert_eq!(parse("#d1 > .ok"), Ok(SelectorList(vec![Selector {
             inner: SelectorInner::from_vec(
@@ -1901,8 +2034,7 @@ pub mod tests {
                     Component::Combinator(Combinator::Child),
                     Component::Class(DummyAtom::from("ok")),
                 ]),
-            pseudo_element: None,
-            specificity: (1 << 20) + (1 << 10) + (0 << 0),
+            specificity_and_flags: (1 << 20) + (1 << 10) + (0 << 0),
         }])));
         parser.default_ns = None;
         assert_eq!(parse(":not(#provel.old)"), Err(()));
@@ -1914,8 +2046,7 @@ pub mod tests {
                     Component::ID(DummyAtom::from("provel")),
                 ].into_boxed_slice()
             ))),
-            pseudo_element: None,
-            specificity: specificity(1, 0, 0),
+            specificity_and_flags: specificity(1, 0, 0),
         }))));
         assert_eq!(parse_ns(":not(svg|circle)", &parser), Ok(SelectorList(vec!(Selector {
             inner: SelectorInner::from_vec(vec!(Component::Negation(
@@ -1927,8 +2058,7 @@ pub mod tests {
                     }),
                 ].into_boxed_slice()
             ))),
-            pseudo_element: None,
-            specificity: specificity(0, 0, 1),
+            specificity_and_flags: specificity(0, 0, 1),
         }))));
         // https://github.com/servo/servo/issues/16017
         assert_eq!(parse_ns(":not(*)", &parser), Ok(SelectorList(vec!(Selector {
@@ -1937,8 +2067,7 @@ pub mod tests {
                     Component::ExplicitUniversalType,
                 ].into_boxed_slice()
             ))),
-            pseudo_element: None,
-            specificity: specificity(0, 0, 0),
+            specificity_and_flags: specificity(0, 0, 0),
         }))));
         assert_eq!(parse_ns(":not(|*)", &parser), Ok(SelectorList(vec!(Selector {
             inner: SelectorInner::from_vec(vec!(Component::Negation(
@@ -1947,8 +2076,7 @@ pub mod tests {
                     Component::ExplicitUniversalType,
                 ].into_boxed_slice()
             ))),
-            pseudo_element: None,
-            specificity: specificity(0, 0, 0),
+            specificity_and_flags: specificity(0, 0, 0),
         }))));
         assert_eq!(parse_ns(":not(*|*)", &parser), Ok(SelectorList(vec!(Selector {
             inner: SelectorInner::from_vec(vec!(Component::Negation(
@@ -1957,8 +2085,7 @@ pub mod tests {
                     Component::ExplicitUniversalType,
                 ].into_boxed_slice()
             ))),
-            pseudo_element: None,
-            specificity: specificity(0, 0, 0),
+            specificity_and_flags: specificity(0, 0, 0),
         }))));
         assert_eq!(parse_ns(":not(svg|*)", &parser), Ok(SelectorList(vec!(Selector {
             inner: SelectorInner::from_vec(vec!(Component::Negation(
@@ -1967,11 +2094,40 @@ pub mod tests {
                     Component::ExplicitUniversalType,
                 ].into_boxed_slice()
             ))),
-            pseudo_element: None,
-            specificity: specificity(0, 0, 0),
+            specificity_and_flags: specificity(0, 0, 0),
         }))));
     }
 
+    #[test]
+    fn test_pseudo_iter() {
+        let selector = &parse("q::before").unwrap().0[0];
+        assert!(!selector.is_universal());
+        let mut iter = selector.inner.complex.iter();
+        assert_eq!(iter.next(), Some(&Component::PseudoElement(PseudoElement::Before)));
+        assert_eq!(iter.next(), None);
+        let combinator = iter.next_sequence();
+        assert_eq!(combinator, Some(Combinator::PseudoElement));
+        assert!(matches!(iter.next(), Some(&Component::LocalName(..))));
+        assert_eq!(iter.next(), None);
+        assert_eq!(iter.next_sequence(), None);
+    }
+
+    #[test]
+    fn test_universal() {
+        let selector = &parse("*|*::before").unwrap().0[0];
+        assert!(selector.is_universal());
+    }
+
+    #[test]
+    fn test_empty_pseudo_iter() {
+        let selector = &parse("::before").unwrap().0[0];
+        assert!(selector.is_universal());
+        let mut iter = selector.inner.complex.iter();
+        assert_eq!(iter.next(), Some(&Component::PseudoElement(PseudoElement::Before)));
+        assert_eq!(iter.next(), None);
+        assert_eq!(iter.next_sequence(), None);
+    }
+
     struct TestVisitor {
         seen: Vec<String>,
     }
@@ -1992,5 +2148,9 @@ pub mod tests {
         let mut test_visitor = TestVisitor { seen: vec![], };
         parse(":not(:hover) ~ label").unwrap().0[0].visit(&mut test_visitor);
         assert!(test_visitor.seen.contains(&":hover".into()));
+
+        let mut test_visitor = TestVisitor { seen: vec![], };
+        parse("::before:hover").unwrap().0[0].visit(&mut test_visitor);
+        assert!(test_visitor.seen.contains(&":hover".into()));
     }
 }
diff --git a/components/selectors/size_of_tests.rs b/components/selectors/size_of_tests.rs
index 1d06278abd5..c03a0c80db5 100644
--- a/components/selectors/size_of_tests.rs
+++ b/components/selectors/size_of_tests.rs
@@ -3,14 +3,16 @@
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
 use cssparser::ToCss;
+use gecko_like_types;
 use gecko_like_types::*;
+use parser;
 use parser::*;
 use precomputed_hash::PrecomputedHash;
 use std::fmt;
 use visitor::SelectorVisitor;
 
-size_of_test!(size_of_selector, Selector<Impl>, 72);
-size_of_test!(size_of_pseudo_element, PseudoElementSelector, 16);
+size_of_test!(size_of_selector, Selector<Impl>, 48);
+size_of_test!(size_of_pseudo_element, gecko_like_types::PseudoElement, 1);
 size_of_test!(size_of_selector_inner, SelectorInner<Impl>, 40);
 size_of_test!(size_of_complex_selector, ComplexSelector<Impl>, 24);
 
@@ -18,6 +20,9 @@ size_of_test!(size_of_component, Component<Impl>, 64);
 size_of_test!(size_of_attr_selector, AttrSelector<Impl>, 48);
 size_of_test!(size_of_pseudo_class, PseudoClass, 24);
 
+impl parser::PseudoElement for gecko_like_types::PseudoElement {
+    type Impl = Impl;
+}
 
 // Boilerplate
 
@@ -31,7 +36,7 @@ impl SelectorImpl for Impl {
     type BorrowedLocalName = Atom;
     type BorrowedNamespaceUrl = Atom;
     type NonTSPseudoClass = PseudoClass;
-    type PseudoElementSelector = PseudoElementSelector;
+    type PseudoElement = gecko_like_types::PseudoElement;
 }
 
 impl SelectorMethods for PseudoClass {
@@ -45,7 +50,7 @@ impl ToCss for PseudoClass {
     fn to_css<W>(&self, _: &mut W) -> fmt::Result where W: fmt::Write { unimplemented!() }
 }
 
-impl ToCss for PseudoElementSelector {
+impl ToCss for gecko_like_types::PseudoElement {
     fn to_css<W>(&self, _: &mut W) -> fmt::Result where W: fmt::Write { unimplemented!() }
 }
 
diff --git a/components/selectors/tree.rs b/components/selectors/tree.rs
index 6514a786673..e5a4539e3cc 100644
--- a/components/selectors/tree.rs
+++ b/components/selectors/tree.rs
@@ -123,6 +123,14 @@ impl<T> MatchAttr for T where T: MatchAttrGeneric, T::Impl: SelectorImpl<AttrVal
 pub trait Element: MatchAttr + Sized {
     fn parent_element(&self) -> Option<Self>;
 
+    /// The parent of a given pseudo-element, after matching a pseudo-element
+    /// selector.
+    ///
+    /// This is guaranteed to be called in a pseudo-element.
+    fn pseudo_element_originating_element(&self) -> Option<Self> {
+        self.parent_element()
+    }
+
     // Skips non-element nodes
     fn first_child_element(&self) -> Option<Self>;
 
@@ -145,6 +153,11 @@ pub trait Element: MatchAttr + Sized {
                                     flags_setter: &mut F) -> bool
         where F: FnMut(&Self, ElementSelectorFlags);
 
+    fn match_pseudo_element(&self,
+                            pe: &<Self::Impl as SelectorImpl>::PseudoElement,
+                            context: &mut MatchingContext)
+                            -> bool;
+
     fn get_id(&self) -> Option<<Self::Impl as SelectorImpl>::Identifier>;
     fn has_class(&self, name: &<Self::Impl as SelectorImpl>::ClassName) -> bool;
 
diff --git a/components/style/gecko/pseudo_element.rs b/components/style/gecko/pseudo_element.rs
index f01c182802e..b15e17e6f38 100644
--- a/components/style/gecko/pseudo_element.rs
+++ b/components/style/gecko/pseudo_element.rs
@@ -10,12 +10,24 @@
 
 use cssparser::ToCss;
 use gecko_bindings::structs::{self, CSSPseudoElementType};
-use selector_parser::PseudoElementCascadeType;
+use selector_parser::{NonTSPseudoClass, PseudoElementCascadeType, SelectorImpl};
 use std::fmt;
 use string_cache::Atom;
 
 include!(concat!(env!("OUT_DIR"), "/gecko/pseudo_element_definition.rs"));
 
+impl ::selectors::parser::PseudoElement for PseudoElement {
+    type Impl = SelectorImpl;
+
+    fn supports_pseudo_class(&self, pseudo_class: &NonTSPseudoClass) -> bool {
+        if !self.supports_user_action_state() {
+            return false;
+        }
+
+        return pseudo_class.is_safe_user_action_state();
+    }
+}
+
 impl PseudoElement {
     /// Returns the kind of cascade type that a given pseudo is going to use.
     ///
diff --git a/components/style/gecko/selector_parser.rs b/components/style/gecko/selector_parser.rs
index 22abaf63b67..787ecd5b2cb 100644
--- a/components/style/gecko/selector_parser.rs
+++ b/components/style/gecko/selector_parser.rs
@@ -5,7 +5,6 @@
 //! Gecko-specific bits for selector-parsing.
 
 use cssparser::{Parser, ToCss};
-use element_state::{IN_ACTIVE_STATE, IN_FOCUS_STATE, IN_HOVER_STATE};
 use element_state::ElementState;
 use gecko_bindings::structs::CSSPseudoClassType;
 use selector_parser::{SelectorParser, PseudoElementCascadeType};
@@ -132,7 +131,7 @@ impl NonTSPseudoClass {
     /// https://drafts.csswg.org/selectors-4/#useraction-pseudos
     ///
     /// We intentionally skip the link-related ones.
-    fn is_safe_user_action_state(&self) -> bool {
+    pub fn is_safe_user_action_state(&self) -> bool {
         matches!(*self, NonTSPseudoClass::Hover |
                         NonTSPseudoClass::Active |
                         NonTSPseudoClass::Focus)
@@ -195,58 +194,6 @@ impl NonTSPseudoClass {
 #[derive(Clone, Debug, PartialEq, Eq)]
 pub struct SelectorImpl;
 
-/// Some subset of pseudo-elements in Gecko are sensitive to some state
-/// selectors.
-///
-/// We store the sensitive states in this struct in order to properly handle
-/// these.
-#[derive(Clone, Debug, PartialEq, Eq, Hash)]
-pub struct PseudoElementSelector {
-    pseudo: PseudoElement,
-    state: ElementState,
-}
-
-impl PseudoElementSelector {
-    /// Returns the pseudo-element this selector represents.
-    pub fn pseudo_element(&self) -> &PseudoElement {
-        &self.pseudo
-    }
-
-    /// Returns the pseudo-element selector state.
-    pub fn state(&self) -> ElementState {
-        self.state
-    }
-}
-
-impl ToCss for PseudoElementSelector {
-    fn to_css<W>(&self, dest: &mut W) -> fmt::Result
-        where W: fmt::Write,
-    {
-        if cfg!(debug_assertions) {
-            let mut state = self.state;
-            state.remove(IN_HOVER_STATE | IN_ACTIVE_STATE | IN_FOCUS_STATE);
-            assert_eq!(state, ElementState::empty(),
-                       "Unhandled pseudo-element state selector?");
-        }
-
-        self.pseudo.to_css(dest)?;
-
-        if self.state.contains(IN_HOVER_STATE) {
-            dest.write_str(":hover")?
-        }
-
-        if self.state.contains(IN_ACTIVE_STATE) {
-            dest.write_str(":active")?
-        }
-
-        if self.state.contains(IN_FOCUS_STATE) {
-            dest.write_str(":focus")?
-        }
-
-        Ok(())
-    }
-}
-
 impl ::selectors::SelectorImpl for SelectorImpl {
     type AttrValue = Atom;
     type Identifier = Atom;
@@ -257,7 +204,7 @@ impl ::selectors::SelectorImpl for SelectorImpl {
     type BorrowedNamespaceUrl = WeakNamespace;
     type BorrowedLocalName = WeakAtom;
 
-    type PseudoElementSelector = PseudoElementSelector;
+    type PseudoElement = PseudoElement;
     type NonTSPseudoClass = NonTSPseudoClass;
 }
 
@@ -319,38 +266,9 @@ impl<'a> ::selectors::Parser for SelectorParser<'a> {
         }
     }
 
-    fn parse_pseudo_element(&self, name: Cow<str>, input: &mut Parser) -> Result<PseudoElementSelector, ()> {
-        let pseudo =
-            match PseudoElement::from_slice(&name, self.in_user_agent_stylesheet()) {
-                Some(pseudo) => pseudo,
-                None => return Err(()),
-            };
-
-        let state = if pseudo.supports_user_action_state() {
-            input.try(|input| {
-                let mut state = ElementState::empty();
-
-                while !input.is_exhausted() {
-                    input.expect_colon()?;
-                    let ident = input.expect_ident()?;
-                    let pseudo_class = self.parse_non_ts_pseudo_class(ident)?;
-
-                    if !pseudo_class.is_safe_user_action_state() {
-                        return Err(())
-                    }
-                    state.insert(pseudo_class.state_flag());
-                }
-
-                Ok(state)
-            }).ok()
-        } else {
-            None
-        };
-
-        Ok(PseudoElementSelector {
-            pseudo: pseudo,
-            state: state.unwrap_or(ElementState::empty()),
-        })
+    fn parse_pseudo_element(&self, name: Cow<str>) -> Result<PseudoElement, ()> {
+        PseudoElement::from_slice(&name, self.in_user_agent_stylesheet())
+            .ok_or(())
     }
 
     fn default_namespace(&self) -> Option<Namespace> {
diff --git a/components/style/gecko/wrapper.rs b/components/style/gecko/wrapper.rs
index c171404d3eb..cef8962df3c 100644
--- a/components/style/gecko/wrapper.rs
+++ b/components/style/gecko/wrapper.rs
@@ -64,7 +64,7 @@ use properties::style_structs::Font;
 use rule_tree::CascadeLevel as ServoCascadeLevel;
 use selector_parser::ElementExt;
 use selectors::Element;
-use selectors::matching::{ElementSelectorFlags, MatchingContext};
+use selectors::matching::{ElementSelectorFlags, MatchingContext, MatchingMode};
 use selectors::parser::{AttrSelector, NamespaceConstraint};
 use shared_lock::Locked;
 use sink::Push;
@@ -1055,6 +1055,11 @@ impl<'le> ::selectors::Element for GeckoElement<'le> {
         parent_node.and_then(|n| n.as_element())
     }
 
+    fn pseudo_element_originating_element(&self) -> Option<Self> {
+        debug_assert!(self.implemented_pseudo_element().is_some());
+        self.closest_non_native_anonymous_ancestor()
+    }
+
     fn first_child_element(&self) -> Option<Self> {
         let mut child = self.as_node().first_child();
         while let Some(child_node) = child {
@@ -1244,6 +1249,20 @@ impl<'le> ::selectors::Element for GeckoElement<'le> {
         }
     }
 
+    fn match_pseudo_element(&self,
+                            pseudo_element: &PseudoElement,
+                            _context: &mut MatchingContext)
+                            -> bool
+    {
+        // TODO(emilio): I believe we could assert we are a pseudo-element and
+        // match the proper pseudo-element, given how we rulehash the stuff
+        // based on the pseudo.
+        match self.implemented_pseudo_element() {
+            Some(ref pseudo) => pseudo == pseudo_element,
+            None => false,
+        }
+    }
+
     fn get_id(&self) -> Option<Atom> {
         let ptr = unsafe {
             bindings::Gecko_AtomAttrValue(self.0,
@@ -1378,8 +1397,9 @@ impl<'le> ::selectors::MatchAttr for GeckoElement<'le> {
 impl<'le> ElementExt for GeckoElement<'le> {
     #[inline]
     fn is_link(&self) -> bool {
+        let mut context = MatchingContext::new(MatchingMode::Normal, None);
         self.match_non_ts_pseudo_class(&NonTSPseudoClass::AnyLink,
-                                       &mut MatchingContext::default(),
+                                       &mut context,
                                        &mut |_, _| {})
     }
 
diff --git a/components/style/matching.rs b/components/style/matching.rs
index 24cb5c2abe7..4765e89004c 100644
--- a/components/style/matching.rs
+++ b/components/style/matching.rs
@@ -15,7 +15,6 @@ use cascade_info::CascadeInfo;
 use context::{CurrentElementInfo, SelectorFlagsMap, SharedStyleContext, StyleContext};
 use data::{ComputedStyle, ElementData, ElementStyles, RestyleData};
 use dom::{AnimationRules, SendElement, TElement, TNode};
-use element_state::ElementState;
 use font_metrics::FontMetricsProvider;
 use properties::{CascadeFlags, ComputedValues, SKIP_ROOT_AND_ITEM_BASED_DISPLAY_FIXUP, cascade};
 use properties::longhands::display::computed_value as display;
@@ -24,7 +23,7 @@ use restyle_hints::{RESTYLE_STYLE_ATTRIBUTE, RESTYLE_SMIL};
 use rule_tree::{CascadeLevel, RuleTree, StrongRuleNode};
 use selector_parser::{PseudoElement, RestyleDamage, SelectorImpl};
 use selectors::bloom::BloomFilter;
-use selectors::matching::{ElementSelectorFlags, MatchingContext, StyleRelations};
+use selectors::matching::{ElementSelectorFlags, MatchingContext, MatchingMode, StyleRelations};
 use selectors::matching::AFFECTED_BY_PSEUDO_ELEMENTS;
 use shared_lock::StylesheetGuards;
 use sink::ForgetfulSink;
@@ -895,10 +894,10 @@ pub trait MatchMethods : TElement {
                          sharing: StyleSharingBehavior)
     {
         // Perform selector matching for the primary style.
-        let mut primary_matching_context = MatchingContext::default();
+        let mut relations = StyleRelations::empty();
         let _rule_node_changed = self.match_primary(context,
                                                     data,
-                                                    &mut primary_matching_context);
+                                                    &mut relations);
 
         // Cascade properties and compute primary values.
         self.cascade_primary(context, data);
@@ -912,7 +911,7 @@ pub trait MatchMethods : TElement {
 
         // If we have any pseudo elements, indicate so in the primary StyleRelations.
         if !data.styles().pseudos.is_empty() {
-            primary_matching_context.relations |= AFFECTED_BY_PSEUDO_ELEMENTS;
+            relations |= AFFECTED_BY_PSEUDO_ELEMENTS;
         }
 
         // If the style is shareable, add it to the LRU cache.
@@ -932,7 +931,7 @@ pub trait MatchMethods : TElement {
                    .style_sharing_candidate_cache
                    .insert_if_possible(self,
                                        data.styles().primary.values(),
-                                       primary_matching_context.relations,
+                                       relations,
                                        revalidation_match_results);
         }
     }
@@ -952,7 +951,7 @@ pub trait MatchMethods : TElement {
     fn match_primary(&self,
                      context: &mut StyleContext<Self>,
                      data: &mut ElementData,
-                     matching_context: &mut MatchingContext)
+                     relations: &mut StyleRelations)
                      -> bool
     {
         let implemented_pseudo = self.implemented_pseudo_element();
@@ -1004,35 +1003,27 @@ pub trait MatchMethods : TElement {
         let animation_rules = self.get_animation_rules();
         let bloom = context.thread_local.bloom_filter.filter();
 
+
         let map = &mut context.thread_local.selector_flags;
         let mut set_selector_flags = |element: &Self, flags: ElementSelectorFlags| {
             self.apply_selector_flags(map, element, flags);
         };
 
-        let selector_matching_target = match implemented_pseudo {
-            Some(..) => {
-                self.closest_non_native_anonymous_ancestor()
-                    .expect("Pseudo-element without non-NAC parent?")
-            },
-            None => *self,
-        };
-
-        let pseudo_and_state = match implemented_pseudo {
-            Some(ref pseudo) => Some((pseudo, self.get_state())),
-            None => None,
-        };
+        let mut matching_context =
+            MatchingContext::new(MatchingMode::Normal, Some(bloom));
 
         // Compute the primary rule node.
-        stylist.push_applicable_declarations(&selector_matching_target,
-                                             Some(bloom),
+        stylist.push_applicable_declarations(self,
+                                             implemented_pseudo.as_ref(),
                                              style_attribute,
                                              smil_override,
                                              animation_rules,
-                                             pseudo_and_state,
                                              &mut applicable_declarations,
-                                             matching_context,
+                                             &mut matching_context,
                                              &mut set_selector_flags);
 
+        *relations = matching_context.relations;
+
         let primary_rule_node =
             compute_rule_node::<Self>(&stylist.rule_tree,
                                       &mut applicable_declarations,
@@ -1041,8 +1032,8 @@ pub trait MatchMethods : TElement {
         return data.set_primary_rules(primary_rule_node);
     }
 
-    /// Runs selector matching to (re)compute eager pseudo-element rule nodes for this
-    /// element.
+    /// Runs selector matching to (re)compute eager pseudo-element rule nodes
+    /// for this element.
     ///
     /// Returns whether any of the pseudo rule nodes changed (including, but not
     /// limited to, cases where we match different pseudos altogether).
@@ -1070,6 +1061,10 @@ pub trait MatchMethods : TElement {
         let rule_tree = &stylist.rule_tree;
         let bloom_filter = context.thread_local.bloom_filter.filter();
 
+        let mut matching_context =
+            MatchingContext::new(MatchingMode::ForStatelessPseudoElement,
+                                 Some(bloom_filter));
+
         // Compute rule nodes for eagerly-cascaded pseudo-elements.
         let mut matches_different_pseudos = false;
         let mut rule_nodes_changed = false;
@@ -1079,13 +1074,12 @@ pub trait MatchMethods : TElement {
             // NB: We handle animation rules for ::before and ::after when
             // traversing them.
             stylist.push_applicable_declarations(self,
-                                                 Some(bloom_filter),
+                                                 Some(&pseudo),
                                                  None,
                                                  None,
                                                  AnimationRules(None, None),
-                                                 Some((&pseudo, ElementState::empty())),
                                                  &mut applicable_declarations,
-                                                 &mut MatchingContext::default(),
+                                                 &mut matching_context,
                                                  &mut set_selector_flags);
 
             if !applicable_declarations.is_empty() {
diff --git a/components/style/restyle_hints.rs b/components/style/restyle_hints.rs
index d0b9cd665f8..23a3cc9f2c3 100644
--- a/components/style/restyle_hints.rs
+++ b/components/style/restyle_hints.rs
@@ -9,14 +9,13 @@
 use Atom;
 use dom::TElement;
 use element_state::*;
-use fnv::FnvHashMap;
 #[cfg(feature = "gecko")]
 use gecko_bindings::structs::nsRestyleHint;
 #[cfg(feature = "servo")]
 use heapsize::HeapSizeOf;
 use selector_parser::{AttrValue, NonTSPseudoClass, PseudoElement, SelectorImpl, Snapshot, SnapshotMap};
 use selectors::{Element, MatchAttr};
-use selectors::matching::{ElementSelectorFlags, MatchingContext};
+use selectors::matching::{ElementSelectorFlags, MatchingContext, MatchingMode};
 use selectors::matching::matches_selector;
 use selectors::parser::{AttrSelector, Combinator, Component, Selector};
 use selectors::parser::{SelectorInner, SelectorMethods};
@@ -406,6 +405,14 @@ impl<'a, E> Element for ElementWrapper<'a, E>
         }
     }
 
+    fn match_pseudo_element(&self,
+                            pseudo_element: &PseudoElement,
+                            context: &mut MatchingContext)
+                            -> bool
+    {
+        self.element.match_pseudo_element(pseudo_element, context)
+    }
+
     fn parent_element(&self) -> Option<Self> {
         self.element.parent_element()
             .map(|e| ElementWrapper::new(e, self.snapshot_map))
@@ -475,6 +482,11 @@ impl<'a, E> Element for ElementWrapper<'a, E>
             _   => self.element.each_class(callback)
         }
     }
+
+    fn pseudo_element_originating_element(&self) -> Option<Self> {
+        self.element.closest_non_native_anonymous_ancestor()
+            .map(|e| ElementWrapper::new(e, self.snapshot_map))
+    }
 }
 
 fn selector_to_state(sel: &Component<SelectorImpl>) -> ElementState {
@@ -507,6 +519,9 @@ fn combinator_to_restyle_hint(combinator: Option<Combinator>) -> RestyleHint {
     match combinator {
         None => RESTYLE_SELF,
         Some(c) => match c {
+            // NB: RESTYLE_SELF is needed to handle properly eager pseudos,
+            // otherwise we may leave a stale style on the parent.
+            Combinator::PseudoElement => RESTYLE_SELF | RESTYLE_DESCENDANTS,
             Combinator::Child => RESTYLE_DESCENDANTS,
             Combinator::Descendant => RESTYLE_DESCENDANTS,
             Combinator::NextSibling => RESTYLE_LATER_SIBLINGS,
@@ -634,13 +649,6 @@ impl SelectorVisitor for SensitivitiesVisitor {
 #[derive(Debug)]
 #[cfg_attr(feature = "servo", derive(HeapSizeOf))]
 pub struct DependencySet {
-    /// A map used for pseudo-element's dependencies.
-    ///
-    /// Note that pseudo-elements are somewhat special, because some of them in
-    /// Gecko track state, and also because they don't do selector-matching as
-    /// normal, but against their parent element.
-    pseudo_dependencies: FnvHashMap<PseudoElement, SelectorMap<PseudoElementDependency>>,
-
     /// This is for all other normal element's selectors/selector parts.
     dependencies: SelectorMap<Dependency>,
 }
@@ -668,34 +676,9 @@ impl DependencySet {
                 index += 1; // Account for the simple selector.
             }
 
-
-            let pseudo_selector_is_state_dependent =
-                sequence_start == 0 &&
-                selector.pseudo_element.as_ref().map_or(false, |pseudo_selector| {
-                    !pseudo_selector.state().is_empty()
-                });
-
-            if pseudo_selector_is_state_dependent {
-                let pseudo_selector = selector.pseudo_element.as_ref().unwrap();
-                self.pseudo_dependencies
-                    .entry(pseudo_selector.pseudo_element().clone())
-                    .or_insert_with(SelectorMap::new)
-                    .insert(PseudoElementDependency {
-                        selector: selector.clone(),
-                    });
-            }
-
             // If we found a sensitivity, add an entry in the dependency set.
             if !visitor.sensitivities.is_empty() {
-                let mut hint = combinator_to_restyle_hint(combinator);
-
-                if sequence_start == 0 && selector.pseudo_element.is_some() {
-                    // FIXME(emilio): Be more granular about this. See the
-                    // comment in `PseudoElementDependency` about how could this
-                    // be modified in order to be more efficient and restyle
-                    // less.
-                    hint |= RESTYLE_DESCENDANTS;
-                }
+                let hint = combinator_to_restyle_hint(combinator);
 
                 let dep_selector = if sequence_start == 0 {
                     // Reuse the bloom hashes if this is the base selector.
@@ -724,82 +707,22 @@ impl DependencySet {
     pub fn new() -> Self {
         DependencySet {
             dependencies: SelectorMap::new(),
-            pseudo_dependencies: FnvHashMap::default(),
         }
     }
 
     /// Return the total number of dependencies that this set contains.
     pub fn len(&self) -> usize {
-        self.dependencies.len() +
-            self.pseudo_dependencies.values().fold(0, |acc, val| acc + val.len())
+        self.dependencies.len()
     }
 
     /// Clear this dependency set.
     pub fn clear(&mut self) {
         self.dependencies = SelectorMap::new();
-        self.pseudo_dependencies.clear()
     }
 
-    fn compute_pseudo_hint<E>(
-        &self,
-        pseudo: &E,
-        pseudo_element: PseudoElement,
-        snapshots: &SnapshotMap)
-        -> RestyleHint
-        where E: TElement,
-    {
-        debug!("compute_pseudo_hint: {:?}, {:?}", pseudo, pseudo_element);
-        debug_assert!(pseudo.has_snapshot());
-
-        let map = match self.pseudo_dependencies.get(&pseudo_element) {
-            Some(map) => map,
-            None => return RestyleHint::empty(),
-        };
-
-        // Only pseudo-element's state is relevant.
-        let pseudo_state_changes =
-            ElementWrapper::new(*pseudo, snapshots).state_changes();
-
-        debug!("pseudo_state_changes: {:?}", pseudo_state_changes);
-        if pseudo_state_changes.is_empty() {
-            return RestyleHint::empty();
-        }
-
-        let selector_matching_target =
-            pseudo.closest_non_native_anonymous_ancestor().unwrap();
-
-        // Note that we rely on that, if the originating element changes, it'll
-        // post a restyle hint that would make us redo selector matching, so we
-        // don't need to care about that.
-        //
-        // If that ever changes, we'd need to share more code with
-        // `compute_element_hint`.
-        let mut hint = RestyleHint::empty();
-        map.lookup(selector_matching_target, &mut |dep| {
-            // If the selector didn't match before, it either doesn't match now
-            // either (or it doesn't matter because our parent posted a restyle
-            // for us above).
-            if !matches_selector(&dep.selector.inner, &selector_matching_target,
-                                 None, &mut MatchingContext::default(),
-                                 &mut |_, _| {}) {
-                return true;
-            }
-
-            let pseudo_selector = dep.selector.pseudo_element.as_ref().unwrap();
-            debug_assert!(!pseudo_selector.state().is_empty());
-
-            if pseudo_selector.state().intersects(pseudo_state_changes) {
-                hint = RESTYLE_SELF;
-                return false;
-            }
-
-            true
-        });
-
-        hint
-    }
-
-    fn compute_element_hint<E>(
+    /// Compute a restyle hint given an element and a snapshot, per the rules
+    /// explained in the rest of the documentation.
+    pub fn compute_hint<E>(
         &self,
         el: &E,
         snapshots: &SnapshotMap)
@@ -838,8 +761,18 @@ impl DependencySet {
             });
         }
 
+        // FIXME(emilio): A bloom filter here would be neat.
+        let mut matching_context =
+            MatchingContext::new(MatchingMode::Normal, None);
+
+        let lookup_element = if el.implemented_pseudo_element().is_some() {
+            el.closest_non_native_anonymous_ancestor().unwrap()
+        } else {
+            *el
+        };
+
         self.dependencies
-            .lookup_with_additional(*el, additional_id, &additional_classes, &mut |dep| {
+            .lookup_with_additional(lookup_element, additional_id, &additional_classes, &mut |dep| {
             trace!("scanning dependency: {:?}", dep);
             if !dep.sensitivities.sensitive_to(attrs_changed,
                                                state_changes) {
@@ -856,12 +789,12 @@ impl DependencySet {
             // been set during original matching for any element that might
             // change its matching behavior here.
             let matched_then =
-                matches_selector(&dep.selector, &snapshot_el, None,
-                                 &mut MatchingContext::default(),
+                matches_selector(&dep.selector, &snapshot_el,
+                                 &mut matching_context,
                                  &mut |_, _| {});
             let matches_now =
-                matches_selector(&dep.selector, el, None,
-                                 &mut MatchingContext::default(),
+                matches_selector(&dep.selector, el,
+                                 &mut matching_context,
                                  &mut |_, _| {});
             if matched_then != matches_now {
                 hint.insert(dep.hint);
@@ -875,21 +808,4 @@ impl DependencySet {
 
         hint
     }
-
-
-    /// Compute a restyle hint given an element and a snapshot, per the rules
-    /// explained in the rest of the documentation.
-    pub fn compute_hint<E>(&self,
-                           el: &E,
-                           snapshots: &SnapshotMap)
-                           -> RestyleHint
-        where E: TElement + Clone,
-    {
-        debug!("DependencySet::compute_hint({:?})", el);
-        if let Some(pseudo) = el.implemented_pseudo_element() {
-            return self.compute_pseudo_hint(el, pseudo, snapshots);
-        }
-
-        self.compute_element_hint(el, snapshots)
-    }
 }
diff --git a/components/style/servo/selector_parser.rs b/components/style/servo/selector_parser.rs
index 6f9ce19f40e..6fd498ee9aa 100644
--- a/components/style/servo/selector_parser.rs
+++ b/components/style/servo/selector_parser.rs
@@ -15,7 +15,7 @@ use fnv::FnvHashMap;
 use restyle_hints::ElementSnapshot;
 use selector_parser::{ElementExt, PseudoElementCascadeType, SelectorParser};
 use selectors::{Element, MatchAttrGeneric};
-use selectors::matching::MatchingContext;
+use selectors::matching::{MatchingContext, MatchingMode};
 use selectors::parser::{AttrSelector, SelectorMethods};
 use selectors::visitor::SelectorVisitor;
 use std::borrow::Cow;
@@ -51,6 +51,14 @@ pub enum PseudoElement {
     ServoInlineAbsolute,
 }
 
+impl ::selectors::parser::PseudoElement for PseudoElement {
+    type Impl = SelectorImpl;
+
+    fn supports_pseudo_class(&self, _: &NonTSPseudoClass) -> bool {
+        false
+    }
+}
+
 impl ToCss for PseudoElement {
     fn to_css<W>(&self, dest: &mut W) -> fmt::Result where W: fmt::Write {
         use self::PseudoElement::*;
@@ -78,18 +86,6 @@ impl ToCss for PseudoElement {
 pub const EAGER_PSEUDO_COUNT: usize = 3;
 
 impl PseudoElement {
-    /// The pseudo-element, used for compatibility with Gecko's
-    /// `PseudoElementSelector`.
-    pub fn pseudo_element(&self) -> &Self {
-        self
-    }
-
-    /// The pseudo-element selector's state, used for compatibility with Gecko's
-    /// `PseudoElementSelector`.
-    pub fn state(&self) -> ElementState {
-        ElementState::empty()
-    }
-
     /// Gets the canonical index of this eagerly-cascaded pseudo-element.
     #[inline]
     pub fn eager_index(&self) -> usize {
@@ -264,7 +260,7 @@ impl NonTSPseudoClass {
 pub struct SelectorImpl;
 
 impl ::selectors::SelectorImpl for SelectorImpl {
-    type PseudoElementSelector = PseudoElement;
+    type PseudoElement = PseudoElement;
     type NonTSPseudoClass = NonTSPseudoClass;
 
     type AttrValue = String;
@@ -323,9 +319,7 @@ impl<'a> ::selectors::Parser for SelectorParser<'a> {
         Ok(pseudo_class)
     }
 
-    fn parse_pseudo_element(&self,
-                            name: Cow<str>,
-                            _input: &mut CssParser)
+    fn parse_pseudo_element(&self, name: Cow<str>)
                             -> Result<PseudoElement, ()> {
         use self::PseudoElement::*;
         let pseudo_element = match_ignore_ascii_case! { &name,
@@ -579,8 +573,9 @@ impl MatchAttrGeneric for ServoElementSnapshot {
 
 impl<E: Element<Impl=SelectorImpl> + Debug> ElementExt for E {
     fn is_link(&self) -> bool {
+        let mut context = MatchingContext::new(MatchingMode::Normal, None);
         self.match_non_ts_pseudo_class(&NonTSPseudoClass::AnyLink,
-                                       &mut MatchingContext::default(),
+                                       &mut context,
                                        &mut |_, _| {})
     }
 
diff --git a/components/style/stylist.rs b/components/style/stylist.rs
index acef07d054e..644552050b2 100644
--- a/components/style/stylist.rs
+++ b/components/style/stylist.rs
@@ -26,10 +26,9 @@ use properties::PropertyDeclarationBlock;
 use restyle_hints::{RestyleHint, DependencySet};
 use rule_tree::{CascadeLevel, RuleTree, StrongRuleNode, StyleSource};
 use selector_parser::{SelectorImpl, PseudoElement, SnapshotMap};
-use selectors::Element;
 use selectors::bloom::BloomFilter;
 use selectors::matching::{AFFECTED_BY_STYLE_ATTRIBUTE, AFFECTED_BY_PRESENTATIONAL_HINTS};
-use selectors::matching::{ElementSelectorFlags, matches_selector, MatchingContext};
+use selectors::matching::{ElementSelectorFlags, matches_selector, MatchingContext, MatchingMode};
 use selectors::parser::{AttrSelector, Combinator, Component, Selector, SelectorInner, SelectorIter};
 use selectors::parser::{SelectorMethods, LocalName as LocalNameSelector};
 use selectors::visitor::SelectorVisitor;
@@ -479,9 +478,9 @@ impl Stylist {
                        rule: &Arc<Locked<StyleRule>>,
                        stylesheet: &Stylesheet)
     {
-        let map = if let Some(ref pseudo_selector) = selector.pseudo_element {
+        let map = if let Some(pseudo) = selector.pseudo_element() {
             self.pseudos_map
-                .entry(pseudo_selector.pseudo_element().clone())
+                .entry(pseudo.clone())
                 .or_insert_with(PerPseudoElementSelectorMap::new)
                 .borrow_for_origin(&stylesheet.origin)
         } else {
@@ -525,9 +524,6 @@ impl Stylist {
 
     #[inline]
     fn note_attribute_and_state_dependencies(&mut self, selector: &Selector<SelectorImpl>) {
-        if let Some(ref pseudo_selector) = selector.pseudo_element {
-            self.state_dependencies.insert(pseudo_selector.state());
-        }
         selector.visit(&mut AttributeAndStateDependencyVisitor(self));
     }
 
@@ -635,14 +631,13 @@ impl Stylist {
                                                   guards: &StylesheetGuards,
                                                   element: &E,
                                                   pseudo: &PseudoElement,
-                                                  pseudo_state: ElementState,
                                                   parent: &Arc<ComputedValues>,
                                                   font_metrics: &FontMetricsProvider)
                                                   -> Option<ComputedStyle>
         where E: TElement,
     {
         let rule_node =
-            match self.lazy_pseudo_rules(guards, element, pseudo, pseudo_state) {
+            match self.lazy_pseudo_rules(guards, element, pseudo) {
                 Some(rule_node) => rule_node,
                 None => return None
             };
@@ -673,8 +668,7 @@ impl Stylist {
     pub fn lazy_pseudo_rules<E>(&self,
                                 guards: &StylesheetGuards,
                                 element: &E,
-                                pseudo: &PseudoElement,
-                                pseudo_state: ElementState)
+                                pseudo: &PseudoElement)
                                 -> Option<StrongRuleNode>
         where E: TElement
     {
@@ -708,14 +702,15 @@ impl Stylist {
         };
 
         let mut declarations = ApplicableDeclarationList::new();
+        let mut matching_context =
+            MatchingContext::new(MatchingMode::ForStatelessPseudoElement, None);
         self.push_applicable_declarations(element,
-                                          None,
+                                          Some(pseudo),
                                           None,
                                           None,
                                           AnimationRules(None, None),
-                                          Some((pseudo, pseudo_state)),
                                           &mut declarations,
-                                          &mut MatchingContext::default(),
+                                          &mut matching_context,
                                           &mut set_selector_flags);
         if declarations.is_empty() {
             return None
@@ -839,16 +834,15 @@ impl Stylist {
     pub fn push_applicable_declarations<E, V, F>(
                                         &self,
                                         element: &E,
-                                        parent_bf: Option<&BloomFilter>,
+                                        pseudo_element: Option<&PseudoElement>,
                                         style_attribute: Option<&Arc<Locked<PropertyDeclarationBlock>>>,
                                         smil_override: Option<&Arc<Locked<PropertyDeclarationBlock>>>,
                                         animation_rules: AnimationRules,
-                                        pseudo_element: Option<(&PseudoElement, ElementState)>,
                                         applicable_declarations: &mut V,
                                         context: &mut MatchingContext,
                                         flags_setter: &mut F)
         where E: TElement,
-              V: Push<ApplicableDeclarationBlock> + VecLike<ApplicableDeclarationBlock>,
+              V: Push<ApplicableDeclarationBlock> + VecLike<ApplicableDeclarationBlock> + ::std::fmt::Debug,
               F: FnMut(&E, ElementSelectorFlags),
     {
         debug_assert!(!self.is_device_dirty);
@@ -857,20 +851,31 @@ impl Stylist {
         debug_assert!(cfg!(feature = "gecko") ||
                       style_attribute.is_none() || pseudo_element.is_none(),
                       "Style attributes do not apply to pseudo-elements");
-        debug_assert!(pseudo_element.as_ref().map_or(true, |p| !p.0.is_precomputed()));
+        debug_assert!(pseudo_element.map_or(true, |p| !p.is_precomputed()));
 
         let map = match pseudo_element {
-            Some((ref pseudo, _)) => self.pseudos_map.get(pseudo).unwrap(),
+            Some(pseudo) => self.pseudos_map.get(pseudo).unwrap(),
             None => &self.element_map,
         };
 
+        let is_implemented_pseudo =
+            element.implemented_pseudo_element().is_some();
+
+        // NB: This causes use to rule has pseudo selectors based on the
+        // properties of the originating element (which is fine, given the
+        // find_first_from_right usage).
+        let rule_hash_target = if is_implemented_pseudo {
+            element.closest_non_native_anonymous_ancestor().unwrap()
+        } else {
+            *element
+        };
+
         debug!("Determining if style is shareable: pseudo: {}",
                pseudo_element.is_some());
 
         // Step 1: Normal user-agent rules.
         map.user_agent.get_all_matching_rules(element,
-                                              pseudo_element,
-                                              parent_bf,
+                                              &rule_hash_target,
                                               applicable_declarations,
                                               context,
                                               flags_setter,
@@ -893,19 +898,25 @@ impl Stylist {
             debug!("preshints: {:?}", context.relations);
         }
 
-        if element.matches_user_and_author_rules() {
+        // NB: the following condition, although it may look somewhat
+        // inaccurate, would be equivalent to something like:
+        //
+        //     element.matches_user_and_author_rules() ||
+        //     (is_implemented_pseudo &&
+        //      rule_hash_target.matches_user_and_author_rules())
+        //
+        // Which may be more what you would probably expect.
+        if rule_hash_target.matches_user_and_author_rules() {
             // Step 3: User and author normal rules.
             map.user.get_all_matching_rules(element,
-                                            pseudo_element,
-                                            parent_bf,
+                                            &rule_hash_target,
                                             applicable_declarations,
                                             context,
                                             flags_setter,
                                             CascadeLevel::UserNormal);
             debug!("user normal: {:?}", context.relations);
             map.author.get_all_matching_rules(element,
-                                              pseudo_element,
-                                              parent_bf,
+                                              &rule_hash_target,
                                               applicable_declarations,
                                               context,
                                               flags_setter,
@@ -960,7 +971,6 @@ impl Stylist {
                 ApplicableDeclarationBlock::from_declarations(anim, CascadeLevel::Transitions));
         }
         debug!("transition: {:?}", context.relations);
-
         debug!("push_applicable_declarations: shareable: {:?}", context.relations);
     }
 
@@ -993,6 +1003,11 @@ impl Stylist {
         where E: TElement,
               F: FnMut(&E, ElementSelectorFlags),
     {
+        // NB: `MatchingMode` doesn't really matter, given we don't share style
+        // between pseudos.
+        let mut matching_context =
+            MatchingContext::new(MatchingMode::Normal, Some(bloom));
+
         // Note that, by the time we're revalidating, we're guaranteed that the
         // candidate and the entry have the same id, classes, and local name.
         // This means we're guaranteed to get the same rulehash buckets for all
@@ -1002,8 +1017,7 @@ impl Stylist {
         self.selectors_for_cache_revalidation.lookup(*element, &mut |selector| {
             results.push(matches_selector(selector,
                                           element,
-                                          Some(bloom),
-                                          &mut MatchingContext::default(),
+                                          &mut matching_context,
                                           flags_setter));
             true
         });
@@ -1182,6 +1196,7 @@ pub fn needs_revalidation(selector: &Selector<SelectorImpl>) -> bool {
 /// Map that contains the CSS rules for a specific PseudoElement
 /// (or lack of PseudoElement).
 #[cfg_attr(feature = "servo", derive(HeapSizeOf))]
+#[derive(Debug)]
 struct PerPseudoElementSelectorMap {
     /// Rules from user agent stylesheets
     user_agent: SelectorMap<Rule>,
@@ -1283,13 +1298,12 @@ impl SelectorMap<Rule> {
     /// Sort the Rules at the end to maintain cascading order.
     pub fn get_all_matching_rules<E, V, F>(&self,
                                            element: &E,
-                                           pseudo_element: Option<(&PseudoElement, ElementState)>,
-                                           parent_bf: Option<&BloomFilter>,
+                                           rule_hash_target: &E,
                                            matching_rules_list: &mut V,
                                            context: &mut MatchingContext,
                                            flags_setter: &mut F,
                                            cascade_level: CascadeLevel)
-        where E: Element<Impl=SelectorImpl>,
+        where E: TElement,
               V: VecLike<ApplicableDeclarationBlock>,
               F: FnMut(&E, ElementSelectorFlags),
     {
@@ -1299,10 +1313,8 @@ impl SelectorMap<Rule> {
 
         // At the end, we're going to sort the rules that we added, so remember where we began.
         let init_len = matching_rules_list.len();
-        if let Some(id) = element.get_id() {
+        if let Some(id) = rule_hash_target.get_id() {
             SelectorMap::get_matching_rules_from_hash(element,
-                                                      pseudo_element,
-                                                      parent_bf,
                                                       &self.id_hash,
                                                       &id,
                                                       matching_rules_list,
@@ -1311,10 +1323,8 @@ impl SelectorMap<Rule> {
                                                       cascade_level)
         }
 
-        element.each_class(|class| {
+        rule_hash_target.each_class(|class| {
             SelectorMap::get_matching_rules_from_hash(element,
-                                                      pseudo_element,
-                                                      parent_bf,
                                                       &self.class_hash,
                                                       class,
                                                       matching_rules_list,
@@ -1324,18 +1334,14 @@ impl SelectorMap<Rule> {
         });
 
         SelectorMap::get_matching_rules_from_hash(element,
-                                                  pseudo_element,
-                                                  parent_bf,
                                                   &self.local_name_hash,
-                                                  element.get_local_name(),
+                                                  rule_hash_target.get_local_name(),
                                                   matching_rules_list,
                                                   context,
                                                   flags_setter,
                                                   cascade_level);
 
         SelectorMap::get_matching_rules(element,
-                                        pseudo_element,
-                                        parent_bf,
                                         &self.other,
                                         matching_rules_list,
                                         context,
@@ -1372,15 +1378,13 @@ impl SelectorMap<Rule> {
 
     fn get_matching_rules_from_hash<E, Str, BorrowedStr: ?Sized, Vector, F>(
         element: &E,
-        pseudo_element: Option<(&PseudoElement, ElementState)>,
-        parent_bf: Option<&BloomFilter>,
         hash: &FnvHashMap<Str, Vec<Rule>>,
         key: &BorrowedStr,
         matching_rules: &mut Vector,
         context: &mut MatchingContext,
         flags_setter: &mut F,
         cascade_level: CascadeLevel)
-        where E: Element<Impl=SelectorImpl>,
+        where E: TElement,
               Str: Borrow<BorrowedStr> + Eq + Hash,
               BorrowedStr: Eq + Hash,
               Vector: VecLike<ApplicableDeclarationBlock>,
@@ -1388,8 +1392,6 @@ impl SelectorMap<Rule> {
     {
         if let Some(rules) = hash.get(key) {
             SelectorMap::get_matching_rules(element,
-                                            pseudo_element,
-                                            parent_bf,
                                             rules,
                                             matching_rules,
                                             context,
@@ -1400,42 +1402,18 @@ impl SelectorMap<Rule> {
 
     /// Adds rules in `rules` that match `element` to the `matching_rules` list.
     fn get_matching_rules<E, V, F>(element: &E,
-                                   pseudo_element: Option<(&PseudoElement, ElementState)>,
-                                   parent_bf: Option<&BloomFilter>,
                                    rules: &[Rule],
                                    matching_rules: &mut V,
                                    context: &mut MatchingContext,
                                    flags_setter: &mut F,
                                    cascade_level: CascadeLevel)
-        where E: Element<Impl=SelectorImpl>,
+        where E: TElement,
               V: VecLike<ApplicableDeclarationBlock>,
               F: FnMut(&E, ElementSelectorFlags),
     {
-        for rule in rules.iter() {
-            debug_assert_eq!(rule.selector.pseudo_element.is_some(),
-                             pseudo_element.is_some(),
-                             "Testing pseudo-elements against the wrong map");
-
-            if let Some((pseudo, pseudo_state)) = pseudo_element {
-                let pseudo_selector =
-                    rule.selector.pseudo_element.as_ref().unwrap();
-
-                debug_assert_eq!(pseudo_selector.pseudo_element(), pseudo,
-                                 "Testing pseudo-element against the wrong entry");
-
-                let state = pseudo_selector.state();
-
-                // NB: We only allow a subset of the flags here, so using
-                // contains for them is fine, (and it's necessary, to handle
-                // multiple state flags properly).
-                if !state.is_empty() && !pseudo_state.contains(state) {
-                    continue;
-                }
-            }
-
+        for rule in rules {
             if matches_selector(&rule.selector.inner,
                                 element,
-                                parent_bf,
                                 context,
                                 flags_setter) {
                 matching_rules.push(
@@ -1593,45 +1571,70 @@ impl<T> SelectorMap<T> where T: Clone + Borrow<SelectorInner<SelectorImpl>> {
     }
 }
 
+/// Searches the selector from right to left, beginning to the left of the
+/// ::pseudo-element (if any), and ending at the first combinator.
+///
+/// The first non-None value returned from |f| is returned.
+///
+/// Effectively, pseudo-elements are ignored, given only state pseudo-classes
+/// may appear before them.
+fn find_from_right<F, R>(selector: &SelectorInner<SelectorImpl>, mut f: F) -> Option<R>
+    where F: FnMut(&Component<SelectorImpl>) -> Option<R>,
+{
+    let mut iter = selector.complex.iter();
+    for ss in &mut iter {
+        if let Some(r) = f(ss) {
+            return Some(r)
+        }
+    }
+
+    if iter.next_sequence() == Some(Combinator::PseudoElement) {
+        for ss in &mut iter {
+            if let Some(r) = f(ss) {
+                return Some(r)
+            }
+        }
+    }
+
+    None
+}
+
 /// Retrieve the first ID name in the selector, or None otherwise.
 pub fn get_id_name(selector: &SelectorInner<SelectorImpl>) -> Option<Atom> {
-    for ss in selector.complex.iter() {
+    find_from_right(selector, |ss| {
         // TODO(pradeep): Implement case-sensitivity based on the
         // document type and quirks mode.
         if let Component::ID(ref id) = *ss {
             return Some(id.clone());
         }
-    }
-
-    None
+        None
+    })
 }
 
 /// Retrieve the FIRST class name in the selector, or None otherwise.
 pub fn get_class_name(selector: &SelectorInner<SelectorImpl>) -> Option<Atom> {
-    for ss in selector.complex.iter() {
+    find_from_right(selector, |ss| {
         // TODO(pradeep): Implement case-sensitivity based on the
         // document type and quirks mode.
         if let Component::Class(ref class) = *ss {
             return Some(class.clone());
         }
-    }
-
-    None
+        None
+    })
 }
 
 /// Retrieve the name if it is a type selector, or None otherwise.
 pub fn get_local_name(selector: &SelectorInner<SelectorImpl>)
                       -> Option<LocalNameSelector<SelectorImpl>> {
-    for ss in selector.complex.iter() {
+    find_from_right(selector, |ss| {
         if let Component::LocalName(ref n) = *ss {
             return Some(LocalNameSelector {
                 name: n.name.clone(),
                 lower_name: n.lower_name.clone(),
             })
         }
-    }
-
-    None
+        None
+    })
 }
 
 /// A rule, that wraps a style rule, but represents a single selector of the
@@ -1661,7 +1664,7 @@ impl Borrow<SelectorInner<SelectorImpl>> for Rule {
 impl Rule {
     /// Returns the specificity of the rule.
     pub fn specificity(&self) -> u32 {
-        self.selector.specificity
+        self.selector.specificity()
     }
 
     fn to_applicable_declaration_block(&self, level: CascadeLevel) -> ApplicableDeclarationBlock {
diff --git a/ports/geckolib/glue.rs b/ports/geckolib/glue.rs
index f7aca89a524..dfd563a3fb1 100644
--- a/ports/geckolib/glue.rs
+++ b/ports/geckolib/glue.rs
@@ -1068,7 +1068,6 @@ fn get_pseudo_style(guard: &SharedRwLockReadGuard,
             d.stylist.lazily_compute_pseudo_element_style(&guards,
                                                           &element,
                                                           &pseudo,
-                                                          ElementState::empty(),
                                                           base,
                                                           &metrics)
                      .map(|s| s.values().clone())
diff --git a/tests/unit/style/stylesheets.rs b/tests/unit/style/stylesheets.rs
index 81d8a6fffd4..6d2a2d72bee 100644
--- a/tests/unit/style/stylesheets.rs
+++ b/tests/unit/style/stylesheets.rs
@@ -90,8 +90,8 @@ fn test_parse_stylesheet() {
             }))),
             CssRule::Style(Arc::new(stylesheet.shared_lock.wrap(StyleRule {
                 selectors: SelectorList(vec![
-                    Selector {
-                        inner: SelectorInner::from_vec(vec![
+                    Selector::new_for_unit_testing(
+                        SelectorInner::from_vec(vec![
                             Component::DefaultNamespace(NsAtom::from("http://www.w3.org/1999/xhtml")),
                             Component::LocalName(LocalName {
                                 name: local_name!("input"),
@@ -106,9 +106,8 @@ fn test_parse_stylesheet() {
                                 }),
                             }, "hidden".to_owned(), CaseSensitivity::CaseInsensitive)
                         ]),
-                        pseudo_element: None,
-                        specificity: (0 << 20) + (1 << 10) + (1 << 0),
-                    },
+                        (0 << 20) + (1 << 10) + (1 << 0)
+                    ),
                 ]),
                 block: Arc::new(stylesheet.shared_lock.wrap(block_from(vec![
                     (PropertyDeclaration::Display(longhands::display::SpecifiedValue::none),
@@ -124,28 +123,26 @@ fn test_parse_stylesheet() {
             }))),
             CssRule::Style(Arc::new(stylesheet.shared_lock.wrap(StyleRule {
                 selectors: SelectorList(vec![
-                    Selector {
-                        inner: SelectorInner::from_vec(vec![
+                    Selector::new_for_unit_testing(
+                        SelectorInner::from_vec(vec![
                             Component::DefaultNamespace(NsAtom::from("http://www.w3.org/1999/xhtml")),
                             Component::LocalName(LocalName {
                                 name: local_name!("html"),
                                 lower_name: local_name!("html"),
                             }),
                         ]),
-                        pseudo_element: None,
-                        specificity: (0 << 20) + (0 << 10) + (1 << 0),
-                    },
-                    Selector {
-                        inner: SelectorInner::from_vec(vec![
+                        (0 << 20) + (0 << 10) + (1 << 0)
+                    ),
+                    Selector::new_for_unit_testing(
+                        SelectorInner::from_vec(vec![
                             Component::DefaultNamespace(NsAtom::from("http://www.w3.org/1999/xhtml")),
                             Component::LocalName(LocalName {
                                 name: local_name!("body"),
                                 lower_name: local_name!("body"),
                             }),
                         ]),
-                        pseudo_element: None,
-                        specificity: (0 << 20) + (0 << 10) + (1 << 0),
-                    },
+                        (0 << 20) + (0 << 10) + (1 << 0)
+                    ),
                 ]),
                 block: Arc::new(stylesheet.shared_lock.wrap(block_from(vec![
                     (PropertyDeclaration::Display(longhands::display::SpecifiedValue::block),
@@ -158,17 +155,16 @@ fn test_parse_stylesheet() {
             }))),
             CssRule::Style(Arc::new(stylesheet.shared_lock.wrap(StyleRule {
                 selectors: SelectorList(vec![
-                    Selector {
-                        inner: SelectorInner::from_vec(vec![
+                    Selector::new_for_unit_testing(
+                        SelectorInner::from_vec(vec![
                             Component::DefaultNamespace(NsAtom::from("http://www.w3.org/1999/xhtml")),
                             Component::ID(Atom::from("d1")),
                             Component::Combinator(Combinator::Child),
                             Component::DefaultNamespace(NsAtom::from("http://www.w3.org/1999/xhtml")),
                             Component::Class(Atom::from("ok")),
                         ]),
-                        pseudo_element: None,
-                        specificity: (1 << 20) + (1 << 10) + (0 << 0),
-                    },
+                        (1 << 20) + (1 << 10) + (0 << 0)
+                    ),
                 ]),
                 block: Arc::new(stylesheet.shared_lock.wrap(block_from(vec![
                     (PropertyDeclaration::BackgroundColor(
diff --git a/tests/unit/stylo/size_of.rs b/tests/unit/stylo/size_of.rs
index 4ae541c8de0..f8770a8842e 100644
--- a/tests/unit/stylo/size_of.rs
+++ b/tests/unit/stylo/size_of.rs
@@ -12,8 +12,8 @@ fn size_of_selectors_dummy_types() {
     assert_eq!(size_of::<dummies::PseudoClass>(), size_of::<real::NonTSPseudoClass>());
     assert_eq!(align_of::<dummies::PseudoClass>(), align_of::<real::NonTSPseudoClass>());
 
-    assert_eq!(size_of::<dummies::PseudoElementSelector>(), size_of::<real::PseudoElementSelector>());
-    assert_eq!(align_of::<dummies::PseudoElementSelector>(), align_of::<real::PseudoElementSelector>());
+    assert_eq!(size_of::<dummies::PseudoElement>(), size_of::<real::PseudoElement>());
+    assert_eq!(align_of::<dummies::PseudoElement>(), align_of::<real::PseudoElement>());
 
     assert_eq!(size_of::<dummies::Atom>(), size_of::<style::Atom>());
     assert_eq!(align_of::<dummies::Atom>(), align_of::<style::Atom>());