Backed out changeset 8c89fd37b79d (bug 1544242) for failures in browser_rules_shadowdom_slot_rules.js CLOSED TREE

layout/base/RestyleManager.cpp

@@ -2516,8 +2516,9 @@ static void UpdateBackdropIfNeeded(nsIFrame* aFrame, ServoStyleSet& aStyleSet,
              PseudoStyleType::backdrop);
 
   RefPtr<ComputedStyle> newStyle = aStyleSet.ResolvePseudoElementStyle(
-      *aFrame->GetContent()->AsElement(), PseudoStyleType::backdrop,
+      aFrame->GetContent()->AsElement(), PseudoStyleType::backdrop,
-      aFrame->Style());
+      aFrame->Style(),
+      /* aPseudoElement = */ nullptr);
 
   // NOTE(emilio): We can't use the changes handled for the owner of the
   // backdrop frame, since it's out of flow, and parented to the viewport or
@@ -2560,7 +2561,8 @@ static void UpdateOneAdditionalComputedStyle(nsIFrame* aFrame, uint32_t aIndex,
 
   RefPtr<ComputedStyle> newStyle =
       aRestyleState.StyleSet().ResolvePseudoElementStyle(
-          *aFrame->GetContent()->AsElement(), pseudoType, aFrame->Style());
+          aFrame->GetContent()->AsElement(), pseudoType, aFrame->Style(),
+          /* aPseudoElement = */ nullptr);
 
   uint32_t equalStructs;  // Not used, actually.
   nsChangeHint childHint =
@@ -2757,8 +2759,8 @@ bool RestyleManager::ProcessPostTraversal(Element* aElement,
         styleFrame->IsBlockFrameOrSubclass() &&
         !nsLayoutUtils::GetMarkerPseudo(aElement)) {
       RefPtr<ComputedStyle> pseudoStyle =
-          aRestyleState.StyleSet().ProbeMarkerPseudoStyle(*aElement,
+          aRestyleState.StyleSet().ProbePseudoElementStyle(
-                                                          *upToDateStyleIfRestyled);
+              *aElement, PseudoStyleType::marker, upToDateStyleIfRestyled);
       if (pseudoStyle) {
         changeHint |= nsChangeHint_ReconstructFrame;
       }

layout/base/nsCSSFrameConstructor.cpp

@@ -1160,8 +1160,9 @@ void nsFrameConstructorState::ConstructBackdropFrameFor(nsIContent* aContent,
 
   RefPtr<ComputedStyle> style =
       mPresShell->StyleSet()->ResolvePseudoElementStyle(
-          *aContent->AsElement(), PseudoStyleType::backdrop,
+          aContent->AsElement(), PseudoStyleType::backdrop,
-          /* aParentStyle */ nullptr);
+          /* aParentComputedStyle */ nullptr,
+          /* aPseudoElement */ nullptr);
   MOZ_ASSERT(style->StyleDisplay()->mTopLayer == NS_STYLE_TOP_LAYER_TOP);
   nsContainerFrame* parentFrame =
       GetGeometricParent(*style->StyleDisplay(), nullptr);
@@ -1702,27 +1703,24 @@ void nsCSSFrameConstructor::CreateGeneratedContentItem(
   ServoStyleSet* styleSet = mPresShell->StyleSet();
 
   // Probe for the existence of the pseudo-element
-  RefPtr<ComputedStyle> pseudoStyle;
+  RefPtr<ComputedStyle> pseudoStyle = styleSet->ProbePseudoElementStyle(
+      aOriginatingElement, aPseudoElement, &aStyle);
+  if (!pseudoStyle) {
+    return;
+  }
+
   nsAtom* elemName = nullptr;
   nsAtom* property = nullptr;
   switch (aPseudoElement) {
     case PseudoStyleType::before:
-      pseudoStyle = styleSet->ProbePseudoElementStyle(aOriginatingElement,
-                                                      aPseudoElement, &aStyle);
       elemName = nsGkAtoms::mozgeneratedcontentbefore;
       property = nsGkAtoms::beforePseudoProperty;
       break;
     case PseudoStyleType::after:
-      pseudoStyle = styleSet->ProbePseudoElementStyle(aOriginatingElement,
-                                                      aPseudoElement, &aStyle);
       elemName = nsGkAtoms::mozgeneratedcontentafter;
       property = nsGkAtoms::afterPseudoProperty;
       break;
     case PseudoStyleType::marker:
-      // We want to get a marker style even if we match no rules, but we still
-      // want to check the result of GeneratedContentPseudoExists.
-      pseudoStyle = styleSet->ProbeMarkerPseudoStyle(aOriginatingElement,
-                                                     aStyle);
       elemName = nsGkAtoms::mozgeneratedcontentmarker;
       property = nsGkAtoms::markerPseudoProperty;
       break;
@@ -1730,10 +1728,6 @@ void nsCSSFrameConstructor::CreateGeneratedContentItem(
       MOZ_ASSERT_UNREACHABLE("unexpected aPseudoElement");
   }
 
-  if (!pseudoStyle) {
-    return;
-  }
-
   // |ProbePseudoStyleFor| checked the 'display' property and the
   // |ContentCount()| of the 'content' property for us.
   RefPtr<NodeInfo> nodeInfo = mDocument->NodeInfoManager()->GetNodeInfo(
@@ -8718,7 +8712,8 @@ already_AddRefed<ComputedStyle> nsCSSFrameConstructor::GetFirstLetterStyle(
     nsIContent* aContent, ComputedStyle* aComputedStyle) {
   if (aContent) {
     return mPresShell->StyleSet()->ResolvePseudoElementStyle(
-        *aContent->AsElement(), PseudoStyleType::firstLetter, aComputedStyle);
+        aContent->AsElement(), PseudoStyleType::firstLetter, aComputedStyle,
+        nullptr);
   }
   return nullptr;
 }
@@ -8727,7 +8722,8 @@ already_AddRefed<ComputedStyle> nsCSSFrameConstructor::GetFirstLineStyle(
     nsIContent* aContent, ComputedStyle* aComputedStyle) {
   if (aContent) {
     return mPresShell->StyleSet()->ResolvePseudoElementStyle(
-        *aContent->AsElement(), PseudoStyleType::firstLine, aComputedStyle);
+        aContent->AsElement(), PseudoStyleType::firstLine, aComputedStyle,
+        nullptr);
   }
   return nullptr;
 }

layout/forms/nsButtonFrameRenderer.cpp

@@ -500,12 +500,13 @@ ImgDrawResult nsButtonFrameRenderer::PaintBorder(nsDisplayListBuilder* aBuilder,
  */
 void nsButtonFrameRenderer::ReResolveStyles(nsPresContext* aPresContext) {
   // get all the styles
+  ComputedStyle* context = mFrame->Style();
   ServoStyleSet* styleSet = aPresContext->StyleSet();
 
   // get styles assigned to -moz-focus-inner (ie dotted border on Windows)
   mInnerFocusStyle = styleSet->ProbePseudoElementStyle(
       *mFrame->GetContent()->AsElement(), PseudoStyleType::mozFocusInner,
-      mFrame->Style());
+      context);
 }
 
 ComputedStyle* nsButtonFrameRenderer::GetComputedStyle(int32_t aIndex) const {

layout/generic/nsBlockFrame.cpp

@@ -5465,7 +5465,8 @@ void nsBlockFrame::UpdateFirstLetterStyle(ServoRestyleState& aRestyleState) {
   ComputedStyle* parentStyle = styleParent->Style();
   RefPtr<ComputedStyle> firstLetterStyle =
       aRestyleState.StyleSet().ResolvePseudoElementStyle(
-          *mContent->AsElement(), PseudoStyleType::firstLetter, parentStyle);
+          mContent->AsElement(), PseudoStyleType::firstLetter, parentStyle,
+          nullptr);
   // Note that we don't need to worry about changehints for the continuation
   // styles: those will be handled by the styleParent already.
   RefPtr<ComputedStyle> continuationStyle =
@@ -7187,7 +7188,8 @@ void nsBlockFrame::UpdatePseudoElementStyles(ServoRestyleState& aRestyleState) {
     ComputedStyle* parentStyle = styleParent->Style();
     RefPtr<ComputedStyle> firstLineStyle =
         aRestyleState.StyleSet().ResolvePseudoElementStyle(
-            *mContent->AsElement(), PseudoStyleType::firstLine, parentStyle);
+            mContent->AsElement(), PseudoStyleType::firstLine, parentStyle,
+            nullptr);
 
     // FIXME(bz): Can we make first-line continuations be non-inheriting anon
     // boxes?

layout/mathml/nsMathMLFrame.cpp

@@ -98,7 +98,7 @@ void nsMathMLFrame::ResolveMathMLCharStyle(nsPresContext* aPresContext,
   PseudoStyleType pseudoType = PseudoStyleType::mozMathAnonymous;  // savings
   RefPtr<ComputedStyle> newComputedStyle;
   newComputedStyle = aPresContext->StyleSet()->ResolvePseudoElementStyle(
-      *aContent->AsElement(), pseudoType, aParentComputedStyle);
+      aContent->AsElement(), pseudoType, aParentComputedStyle, nullptr);
 
   aMathMLChar->SetComputedStyle(newComputedStyle);
 }

layout/style/ComputedStyle.cpp

@@ -374,6 +374,8 @@ Maybe<StyleStructID> ComputedStyle::LookupStruct(const nsACString& aName) {
 ComputedStyle* ComputedStyle::GetCachedLazyPseudoStyle(
     PseudoStyleType aPseudo) const {
   MOZ_ASSERT(PseudoStyle::IsPseudoElement(aPseudo));
+  MOZ_ASSERT(!IsLazilyCascadedPseudoElement(),
+             "Lazy pseudos can't inherit lazy pseudos");
 
   if (nsCSSPseudoElements::PseudoElementSupportsUserActionState(aPseudo)) {
     return nullptr;

layout/style/ComputedStyle.h

@@ -194,6 +194,8 @@ class ComputedStyle {
   void SetCachedLazyPseudoStyle(ComputedStyle* aStyle) {
     MOZ_ASSERT(aStyle->IsPseudoElement());
     MOZ_ASSERT(!GetCachedLazyPseudoStyle(aStyle->GetPseudoType()));
+    MOZ_ASSERT(!IsLazilyCascadedPseudoElement(),
+               "lazy pseudos can't inherit lazy pseudos");
     MOZ_ASSERT(aStyle->IsLazilyCascadedPseudoElement());
 
     // Since we're caching lazy pseudo styles on the ComputedValues of the

layout/style/ServoStyleSet.cpp

@@ -440,55 +440,38 @@ static inline bool LazyPseudoIsCacheable(PseudoStyleType aType,
 }
 
 already_AddRefed<ComputedStyle> ServoStyleSet::ResolvePseudoElementStyle(
-    const Element& aOriginatingElement, PseudoStyleType aType,
+    Element* aOriginatingElement, PseudoStyleType aType,
-    ComputedStyle* aParentStyle, IsProbe aIsProbe) {
+    ComputedStyle* aParentStyle, Element* aPseudoElement) {
   // Runs from frame construction, this should have clean styles already, except
   // with non-lazy FC...
   UpdateStylistIfNeeded();
   MOZ_ASSERT(PseudoStyle::IsPseudoElement(aType));
 
-  const bool cacheable =
+  RefPtr<ComputedStyle> computedValues;
-      LazyPseudoIsCacheable(aType, aOriginatingElement, aParentStyle);
-  RefPtr<ComputedStyle> style =
-      cacheable ? aParentStyle->GetCachedLazyPseudoStyle(aType) : nullptr;
 
-  const bool isProbe = aIsProbe == IsProbe::Yes;
+  if (aPseudoElement) {
+    MOZ_ASSERT(aType == aPseudoElement->GetPseudoElementType());
+    computedValues =
+        Servo_ResolveStyle(aPseudoElement, mRawSet.get()).Consume();
+  } else {
+    bool cacheable =
+        LazyPseudoIsCacheable(aType, *aOriginatingElement, aParentStyle);
+    computedValues =
+        cacheable ? aParentStyle->GetCachedLazyPseudoStyle(aType) : nullptr;
 
-  if (!style) {
+    if (!computedValues) {
-    // FIXME(emilio): Why passing null for probing as the parent style?
+      computedValues = Servo_ResolvePseudoStyle(aOriginatingElement, aType,
-    //
+                                                /* is_probe = */ false,
-    // There are callers which do pass the wrong parent style and it would
+                                                aParentStyle, mRawSet.get())
-    // assert (like ComputeSelectionStyle()). That's messy!
+                           .Consume();
-    style = Servo_ResolvePseudoStyle(&aOriginatingElement, aType, isProbe,
+      if (cacheable) {
-                                     isProbe ? nullptr : aParentStyle,
+        aParentStyle->SetCachedLazyPseudoStyle(computedValues);
-                                     mRawSet.get())
+      }
-                .Consume();
-    if (!style) {
-      MOZ_ASSERT(isProbe);
-      return nullptr;
-    }
-    if (cacheable) {
-      aParentStyle->SetCachedLazyPseudoStyle(style);
     }
   }
 
-  MOZ_ASSERT(style);
+  MOZ_ASSERT(computedValues);
-
+  return computedValues.forget();
-  if (isProbe && !GeneratedContentPseudoExists(*aParentStyle, *style)) {
-    return nullptr;
-  }
-
-  return style.forget();
-}
-
-already_AddRefed<ComputedStyle> ServoStyleSet::ProbeMarkerPseudoStyle(
-    const dom::Element& aOriginatingElement, ComputedStyle& aParentStyle) {
-  RefPtr<ComputedStyle> markerStyle = ResolvePseudoElementStyle(
-      aOriginatingElement, PseudoStyleType::marker, &aParentStyle);
-  if (!GeneratedContentPseudoExists(aParentStyle, *markerStyle)) {
-    return nullptr;
-  }
-  return markerStyle.forget();
 }
 
 already_AddRefed<ComputedStyle>
@@ -674,35 +657,66 @@ void ServoStyleSet::AddDocStyleSheet(StyleSheet* aSheet) {
   }
 }
 
-bool ServoStyleSet::GeneratedContentPseudoExists(
+already_AddRefed<ComputedStyle> ServoStyleSet::ProbePseudoElementStyle(
-    const ComputedStyle& aParentStyle, const ComputedStyle& aPseudoStyle) {
+    const Element& aOriginatingElement, PseudoStyleType aType,
-  auto type = aPseudoStyle.GetPseudoType();
+    ComputedStyle* aParentStyle) {
-  MOZ_ASSERT(type != PseudoStyleType::NotPseudo);
+  // Runs from frame construction, this should have clean styles already, except
+  // with non-lazy FC...
+  UpdateStylistIfNeeded();
 
-  if (type == PseudoStyleType::marker) {
+  // NB: We ignore aParentStyle, because in some cases
+  // (first-line/first-letter on anonymous box blocks) Gecko passes something
+  // nonsensical there.  In all other cases we want to inherit directly from
+  // aOriginatingElement's styles anyway.
+  MOZ_ASSERT(PseudoStyle::IsPseudoElement(aType));
+
+  bool cacheable =
+      LazyPseudoIsCacheable(aType, aOriginatingElement, aParentStyle);
+
+  RefPtr<ComputedStyle> computedValues =
+      cacheable ? aParentStyle->GetCachedLazyPseudoStyle(aType) : nullptr;
+  if (!computedValues) {
+    computedValues =
+        Servo_ResolvePseudoStyle(&aOriginatingElement, aType,
+                                 /* is_probe = */ true, nullptr, mRawSet.get())
+            .Consume();
+    if (!computedValues) {
+      return nullptr;
+    }
+
+    if (cacheable) {
+      // NB: We don't need to worry about the before/after handling below
+      // because those are eager and thus not |cacheable| anyway.
+      aParentStyle->SetCachedLazyPseudoStyle(computedValues);
+    }
+  }
+
+  if (aType == PseudoStyleType::marker) {
     // ::marker only exist for list items (for now).
-    if (aParentStyle.StyleDisplay()->mDisplay != StyleDisplay::ListItem) {
+    if (aParentStyle->StyleDisplay()->mDisplay != StyleDisplay::ListItem) {
-      return false;
+      return nullptr;
     }
     // display:none is equivalent to not having the pseudo-element at all.
-    if (aPseudoStyle.StyleDisplay()->mDisplay == StyleDisplay::None) {
+    if (computedValues->StyleDisplay()->mDisplay == StyleDisplay::None) {
-      return false;
+      return nullptr;
     }
   }
 
   // For :before and :after pseudo-elements, having display: none or no
   // 'content' property is equivalent to not having the pseudo-element
   // at all.
-  if (type == PseudoStyleType::before || type == PseudoStyleType::after) {
+  bool isBeforeOrAfter =
-    if (aPseudoStyle.StyleDisplay()->mDisplay == StyleDisplay::None) {
+      aType == PseudoStyleType::before || aType == PseudoStyleType::after;
-      return false;
+  if (isBeforeOrAfter) {
-    }
+    const nsStyleDisplay* display = computedValues->StyleDisplay();
-    if (!aPseudoStyle.StyleContent()->ContentCount()) {
+    const nsStyleContent* content = computedValues->StyleContent();
-      return false;
+    if (display->mDisplay == StyleDisplay::None ||
+        content->ContentCount() == 0) {
+      return nullptr;
     }
   }
 
-  return true;
+  return computedValues.forget();
 }
 
 bool ServoStyleSet::StyleDocument(ServoTraversalFlags aFlags) {

layout/style/ServoStyleSet.h

@@ -168,36 +168,14 @@ class ServoStyleSet {
   // matching for them is a first step.)
   already_AddRefed<ComputedStyle> ResolveStyleForPlaceholder();
 
-  // Returns whether a given pseudo-element should exist or not.
+  // Get a ComputedStyle for a pseudo-element.  aParentElement must be
-  static bool GeneratedContentPseudoExists(const ComputedStyle& aParentStyle,
+  // non-null.  aPseudoID is the PseudoStyleType for the
-                                           const ComputedStyle& aPseudoStyle);
+  // pseudo-element.  aPseudoElement must be non-null if the pseudo-element
-
+  // type is one that allows user action pseudo-classes after it or allows
-  enum class IsProbe {
+  // style attributes; otherwise, it is ignored.
-    No,
-    Yes,
-  };
-
-  // Get a style for a pseudo-element.
-  //
-  // If IsProbe is Yes, then no style is returned if there are no rules matching
-  // for the pseudo-element, or GeneratedContentPseudoExists returns false.
-  //
-  // If IsProbe is No, then the style is guaranteed to be non-null.
   already_AddRefed<ComputedStyle> ResolvePseudoElementStyle(
-      const dom::Element& aOriginatingElement, PseudoStyleType,
+      dom::Element* aOriginatingElement, PseudoStyleType aType,
-      ComputedStyle* aParentStyle, IsProbe = IsProbe::No);
+      ComputedStyle* aParentStyle, dom::Element* aPseudoElement);
-
-  already_AddRefed<ComputedStyle> ProbePseudoElementStyle(
-      const dom::Element& aOriginatingElement, PseudoStyleType aType,
-      ComputedStyle* aParentStyle) {
-    return ResolvePseudoElementStyle(aOriginatingElement, aType, aParentStyle,
-                                     IsProbe::Yes);
-  }
-
-  // A special one for ::marker since we don want to get a style if no rules
-  // match, but we want to also check GeneratedContentPseudoExists.
-  already_AddRefed<ComputedStyle> ProbeMarkerPseudoStyle(
-      const dom::Element& aOriginatingElement, ComputedStyle& aParentStyle);
 
   // Resolves style for a (possibly-pseudo) Element without assuming that the
   // style has been resolved. If the element was unstyled and a new style
@@ -241,6 +219,11 @@ class ServoStyleSet {
 
   void AddDocStyleSheet(StyleSheet* aSheet);
 
+  // check whether there is ::before/::after style for an element
+  already_AddRefed<ComputedStyle> ProbePseudoElementStyle(
+      const dom::Element& aOriginatingElement, PseudoStyleType aType,
+      ComputedStyle* aParentStyle);
+
   /**
    * Performs a Servo traversal to compute style for all dirty nodes in the
    * document.

servo/components/selectors/builder.rs

@@ -84,6 +84,12 @@ impl<Impl: SelectorImpl> SelectorBuilder<Impl> {
         self.current_len = 0;
     }
 
+    /// Returns true if no simple selectors have ever been pushed to this builder.
+    #[inline(always)]
+    pub fn is_empty(&self) -> bool {
+        self.simple_selectors.is_empty()
+    }
+
     /// Returns true if combinators have ever been pushed to this builder.
     #[inline(always)]
     pub fn has_combinators(&self) -> bool {

servo/components/selectors/matching.rs

@@ -331,11 +331,10 @@ where
             return false;
         }
 
-        // Advance to the non-pseudo-element part of the selector.
+        // Advance to the non-pseudo-element part of the selector, but let the
-        let next_sequence = iter.next_sequence().unwrap();
+        // context note that .
-        debug_assert_eq!(next_sequence, Combinator::PseudoElement);
+        if iter.next_sequence().is_none() {
-        if element.is_pseudo_element() {
+            return true;
-            return false;
         }
     }
 
@@ -467,13 +466,7 @@ where
             }
             Some(current_slot)
         },
-        Combinator::PseudoElement => {
+        Combinator::PseudoElement => element.pseudo_element_originating_element(),
-            let next_element = element.pseudo_element_originating_element()?;
-            if next_element.is_pseudo_element() {
-                return None;
-            }
-            Some(next_element)
-        }
     }
 }
 
@@ -684,6 +677,7 @@ where
         Component::Slotted(ref selector) => {
             // <slots> are never flattened tree slottables.
             !element.is_html_slot_element() &&
+                element.assigned_slot().is_some() &&
                 context.shared.nest(|context| {
                     matches_complex_selector(selector.iter(), element, context, flags_setter)
                 })

servo/components/selectors/parser.rs

@@ -1998,7 +1998,9 @@ where
             },
             SimpleSelectorParseResult::SlottedPseudo(selector) => {
                 state.insert(SelectorParsingState::AFTER_SLOTTED);
-                builder.push_combinator(Combinator::SlotAssignment);
+                if !builder.is_empty() {
+                    builder.push_combinator(Combinator::SlotAssignment);
+                }
                 builder.push_simple_selector(Component::Slotted(selector));
             },
             SimpleSelectorParseResult::PseudoElement(p) => {
@@ -2006,7 +2008,9 @@ where
                 if !p.accepts_state_pseudo_classes() {
                     state.insert(SelectorParsingState::AFTER_NON_STATEFUL_PSEUDO_ELEMENT);
                 }
-                builder.push_combinator(Combinator::PseudoElement);
+                if !builder.is_empty() {
+                    builder.push_combinator(Combinator::PseudoElement);
+                }
                 builder.push_simple_selector(Component::PseudoElement(p));
             },
         }
@@ -2811,10 +2815,7 @@ pub mod tests {
         assert_eq!(
             parse("::before"),
             Ok(SelectorList::from_vec(vec![Selector::from_vec(
-                vec![
+                vec![Component::PseudoElement(PseudoElement::Before)],
-                    Component::Combinator(Combinator::PseudoElement),
-                    Component::PseudoElement(PseudoElement::Before),
-                ],
                 specificity(0, 0, 1) | HAS_PSEUDO_BIT,
             )]))
         );
@@ -2822,7 +2823,6 @@ pub mod tests {
             parse("::before:hover"),
             Ok(SelectorList::from_vec(vec![Selector::from_vec(
                 vec![
-                    Component::Combinator(Combinator::PseudoElement),
                     Component::PseudoElement(PseudoElement::Before),
                     Component::NonTSPseudoClass(PseudoClass::Hover),
                 ],
@@ -2833,7 +2833,6 @@ pub mod tests {
             parse("::before:hover:hover"),
             Ok(SelectorList::from_vec(vec![Selector::from_vec(
                 vec![
-                    Component::Combinator(Combinator::PseudoElement),
                     Component::PseudoElement(PseudoElement::Before),
                     Component::NonTSPseudoClass(PseudoClass::Hover),
                     Component::NonTSPseudoClass(PseudoClass::Hover),
@@ -2946,7 +2945,6 @@ pub mod tests {
                 specificity(0, 0, 0),
             )]))
         );
-
         assert_eq!(
             parse_ns(":not(svg|*)", &parser),
             Ok(SelectorList::from_vec(vec![Selector::from_vec(
@@ -3021,8 +3019,6 @@ pub mod tests {
             Some(&Component::PseudoElement(PseudoElement::Before))
         );
         assert_eq!(iter.next(), None);
-        assert_eq!(iter.next_sequence(), Some(Combinator::PseudoElement));
-        assert_eq!(iter.next(), None);
         assert_eq!(iter.next_sequence(), None);
     }
 

servo/components/selectors/tree.rs

@@ -47,13 +47,9 @@ pub trait Element: Sized + Clone + Debug {
     ///
     /// This is guaranteed to be called in a pseudo-element.
     fn pseudo_element_originating_element(&self) -> Option<Self> {
-        debug_assert!(self.is_pseudo_element());
         self.parent_element()
     }
 
-    /// Whether we're matching on a pseudo-element.
-    fn is_pseudo_element(&self) -> bool;
-
     /// Skips non-element nodes
     fn prev_sibling_element(&self) -> Option<Self>;
 

servo/components/style/dom.rs

@@ -779,7 +779,7 @@ pub trait TElement:
     /// element-backed pseudo-element, in which case we return the originating
     /// element.
     fn rule_hash_target(&self) -> Self {
-        if self.is_pseudo_element() {
+        if self.implemented_pseudo_element().is_some() {
             self.pseudo_element_originating_element()
                 .expect("Trying to collect rules for a detached pseudo-element")
         } else {

servo/components/style/gecko/wrapper.rs

@@ -1098,7 +1098,7 @@ impl<'le> TElement for GeckoElement<'le> {
     type TraversalChildrenIterator = GeckoChildrenIterator<'le>;
 
     fn inheritance_parent(&self) -> Option<Self> {
-        if self.is_pseudo_element() {
+        if self.implemented_pseudo_element().is_some() {
             return self.pseudo_element_originating_element();
         }
 
@@ -1471,7 +1471,7 @@ impl<'le> TElement for GeckoElement<'le> {
     #[inline]
     fn skip_item_display_fixup(&self) -> bool {
         debug_assert!(
-            !self.is_pseudo_element(),
+            self.implemented_pseudo_element().is_none(),
             "Just don't call me if I'm a pseudo, you should know the answer already"
         );
         self.is_root_of_native_anonymous_subtree()
@@ -1918,14 +1918,9 @@ impl<'le> ::selectors::Element for GeckoElement<'le> {
         Some(shadow.host())
     }
 
-    #[inline]
-    fn is_pseudo_element(&self) -> bool {
-        self.implemented_pseudo_element().is_some()
-    }
-
     #[inline]
     fn pseudo_element_originating_element(&self) -> Option<Self> {
-        debug_assert!(self.is_pseudo_element());
+        debug_assert!(self.implemented_pseudo_element().is_some());
         let parent = self.closest_anon_subtree_root_parent()?;
 
         // FIXME(emilio): Special-case for <input type="number">s

servo/components/style/invalidation/element/element_wrapper.rs

@@ -366,10 +366,6 @@ where
         self.element.is_root()
     }
 
-    fn is_pseudo_element(&self) -> bool {
-        self.element.is_pseudo_element()
-    }
-
     fn pseudo_element_originating_element(&self) -> Option<Self> {
         self.element
             .pseudo_element_originating_element()

servo/components/style/style_adjuster.rs

@@ -734,7 +734,10 @@ impl<'a, 'b: 'a> StyleAdjuster<'a, 'b> {
         E: TElement,
     {
         if cfg!(debug_assertions) {
-            if element.map_or(false, |e| e.is_pseudo_element()) {
+            if element
+                .and_then(|e| e.implemented_pseudo_element())
+                .is_some()
+            {
                 // It'd be nice to assert `self.style.pseudo == Some(&pseudo)`,
                 // but we do resolve ::-moz-list pseudos on ::before / ::after
                 // content, sigh.

servo/components/style/style_resolver.rs

@@ -233,7 +233,7 @@ where
 
         let mut pseudo_styles = EagerPseudoStyles::default();
 
-        if !self.element.is_pseudo_element() {
+        if self.element.implemented_pseudo_element().is_none() {
             let layout_parent_style_for_pseudo = if primary_style.style().is_display_contents() {
                 layout_parent_style
             } else {
@@ -293,6 +293,10 @@ where
         layout_parent_style: Option<&ComputedValues>,
         pseudo: Option<&PseudoElement>,
     ) -> ResolvedStyle {
+        debug_assert!(
+            self.element.implemented_pseudo_element().is_none() || pseudo.is_none(),
+            "Pseudo-elements can't have other pseudos!"
+        );
         debug_assert!(pseudo.map_or(true, |p| p.is_eager()));
 
         let implemented_pseudo = self.element.implemented_pseudo_element();
@@ -473,8 +477,8 @@ where
         );
         debug_assert!(pseudo_element.is_eager());
         debug_assert!(
-            !self.element.is_pseudo_element(),
+            self.element.implemented_pseudo_element().is_none(),
-            "Element pseudos can't have any other eager pseudo."
+            "Element pseudos can't have any other pseudo."
         );
 
         let mut applicable_declarations = ApplicableDeclarationList::new();

testing/web-platform/tests/css/css-lists/nested-marker-content-ref.html

@@ -1,23 +0,0 @@
-<!doctype html>
-<title>CSS Test Reference</title>
-<link rel="help" href="https://drafts.csswg.org/css-lists/#list-item">
-<link rel="author" href="mailto:emilio@crisal.io" title="Emilio Cobos Álvarez">
-<link rel="author" href="https://mozilla.org" title="Mozilla">
-<style>
-  div {
-    display: inline-block;
-  }
-  div div {
-    list-style-type: initial;
-    display: list-item;
-  }
-  li {
-    list-style-type: none;
-  }
-</style>
-<ul>
-  <li><div><div>Foo</div></div>Bar
-<script>
-  // 100px from the ref.
-  document.querySelector("ul").style.marginLeft = 100 - document.querySelector("div div").offsetWidth + "px";
-</script>

testing/web-platform/tests/css/css-lists/nested-marker-content.html

@@ -1,17 +0,0 @@
-<!doctype html>
-<title>CSS Test: Nested ::marker with `content` property generates another ::marker</title>
-<link rel="help" href="https://drafts.csswg.org/css-lists/#list-item">
-<link rel="help" href="https://bugzilla.mozilla.org/show_bug.cgi?id=1539171">
-<link rel="help" href="https://bugzilla.mozilla.org/show_bug.cgi?id=1543758">
-<link rel="author" href="mailto:emilio@crisal.io" title="Emilio Cobos Álvarez">
-<link rel="author" href="https://mozilla.org" title="Mozilla">
-<link rel="match" href="nested-marker-content-ref.html">
-<style>
-  ul { margin-left: 100px }
-  ::marker {
-    display: list-item;
-    content: "Foo";
-  }
-</style>
-<ul>
-  <li>Bar

testing/web-platform/tests/css/css-lists/nested-marker-dynamic.html

@@ -1,36 +0,0 @@
-<!doctype html>
-<title>::marker pseudo-elements generated by ::before and ::after are not addressable by selectors</title>
-<link rel="help" href="https://drafts.csswg.org/css-lists/#list-item">
-<link rel="help" href="https://bugzilla.mozilla.org/show_bug.cgi?id=1539171">
-<link rel="help" href="https://bugzilla.mozilla.org/show_bug.cgi?id=1543758">
-<link rel="author" href="mailto:emilio@crisal.io" title="Emilio Cobos Álvarez">
-<link rel="author" href="https://mozilla.org" title="Mozilla">
-<link rel="match" href="nested-marker-ref.html">
-<style>
-  li, ::marker {
-    color: red;
-  }
-  li::before, li::after {
-    display: list-item;
-    content: "Before";
-  }
-  li::after {
-    content: "After";
-  }
-  .tweak::marker {
-    color: blue;
-  }
-  .tweak, .tweak::before, .tweak::after {
-    color: initial;
-  }
-</style>
-<ol>
-  <li>Foo
-  <li>Bar
-<script>
-  window.onload = function() {
-    document.body.offsetTop;
-    for (let li of document.querySelectorAll("li"))
-      li.classList.add("tweak");
-  }
-</script>

testing/web-platform/tests/css/css-lists/nested-marker-ref.html

@@ -1,15 +0,0 @@
-<!doctype html>
-<title>CSS test reference</title>
-<link rel="author" href="mailto:emilio@crisal.io" title="Emilio Cobos Álvarez">
-<link rel="author" href="https://mozilla.org" title="Mozilla">
-<style>
-  li::marker {
-    color: blue;
-  }
-  div {
-    display: list-item;
-  }
-</style>
-<ol>
-  <li><div>Before</div>Foo<div>After</div>
-  <li><div>Before</div>Bar<div>After</div>

testing/web-platform/tests/css/css-lists/nested-marker.html

@@ -1,26 +0,0 @@
-<!doctype html>
-<title>::marker pseudo-elements generated by ::before and ::after are not addressable by global selectors</title>
-<link rel="help" href="https://drafts.csswg.org/css-lists/#list-item">
-<link rel="help" href="https://bugzilla.mozilla.org/show_bug.cgi?id=1539171">
-<link rel="help" href="https://bugzilla.mozilla.org/show_bug.cgi?id=1543758">
-<link rel="author" href="mailto:emilio@crisal.io" title="Emilio Cobos Álvarez">
-<link rel="author" href="https://mozilla.org" title="Mozilla">
-<link rel="match" href="nested-marker-ref.html">
-<style>
-  ::marker {
-    color: red;
-  }
-  li::marker {
-    color: blue;
-  }
-  li::before, li::after {
-    display: list-item;
-    content: "Before";
-  }
-  li::after {
-    content: "After";
-  }
-</style>
-<ol>
-  <li>Foo
-  <li>Bar