More dynamicDowncast<Element> adoption in markup and LocalDOMWindow

https://bugs.webkit.org/show_bug.cgi?id=268226

Reviewed by Chris Dumez.

* Source/WebCore/editing/markup.cpp:
(WebCore::StyledMarkupAccumulator::traverseNodesForSerialization):
(WebCore::styleFromMatchedRulesAndInlineDecl):
* Source/WebCore/page/LocalDOMWindow.cpp:
(WebCore::LocalDOMWindow::collectMatchingElementsInFlatTree):
(WebCore::LocalDOMWindow::matchingElementInFlatTree):

Canonical link: https://commits.webkit.org/273623@main

Source/WebCore/editing/markup.cpp

@@ -745,7 +745,8 @@ RefPtr<Node> StyledMarkupAccumulator::traverseNodesForSerialization(Node& startN
                 return false;
         }
 
-        bool isDisplayContents = is<Element>(node) && downcast<Element>(node).hasDisplayContents();
+        RefPtr element = dynamicDowncast<Element>(node);
+        bool isDisplayContents = element && element->hasDisplayContents();
         if (!node.renderer() && !isDisplayContents && !enclosingElementWithTag(firstPositionInOrBeforeNode(&node), selectTag))
             return false;
 
@@ -916,12 +917,12 @@ static bool needInterchangeNewlineAfter(const VisiblePosition& v)
 
 static RefPtr<EditingStyle> styleFromMatchedRulesAndInlineDecl(Node& node)
 {
-    if (!is<HTMLElement>(node))
+    RefPtr element = dynamicDowncast<HTMLElement>(node);
+    if (!element)
         return nullptr;
 
-    Ref element = downcast<HTMLElement>(node);
-    auto style = EditingStyle::create(element->inlineStyle());
-    style->mergeStyleFromRules(element);
+    Ref style = EditingStyle::create(element->inlineStyle());
+    style->mergeStyleFromRules(*element);
     return style;
 }
 

Source/WebCore/page/LocalDOMWindow.cpp

@@ -632,15 +632,16 @@ ExceptionOr<Ref<NodeList>> LocalDOMWindow::collectMatchingElementsInFlatTree(Nod
     if (queryOrException.hasException())
         return queryOrException.releaseException();
 
-    if (!is<ContainerNode>(scope))
+    RefPtr scopeContainer = dynamicDowncast<ContainerNode>(scope);
+    if (!scopeContainer)
         return Ref<NodeList> { StaticElementList::create() };
 
     SelectorQuery& query = queryOrException.releaseReturnValue();
 
     Vector<Ref<Element>> result;
-    for (auto& node : composedTreeDescendants(downcast<ContainerNode>(scope))) {
-        if (is<Element>(node) && query.matches(downcast<Element>(node)) && !node.isInUserAgentShadowTree())
-            result.append(downcast<Element>(node));
+    for (auto& node : composedTreeDescendants(*scopeContainer)) {
+        if (RefPtr element = dynamicDowncast<Element>(node); element && query.matches(*element) && !node.isInUserAgentShadowTree())
+            result.append(element.releaseNonNull());
     }
 
     return Ref<NodeList> { StaticElementList::create(WTFMove(result)) };
@@ -652,14 +653,15 @@ ExceptionOr<RefPtr<Element>> LocalDOMWindow::matchingElementInFlatTree(Node& sco
     if (queryOrException.hasException())
         return queryOrException.releaseException();
 
-    if (!is<ContainerNode>(scope))
+    RefPtr scopeContainer = dynamicDowncast<ContainerNode>(scope);
+    if (!scopeContainer)
         return RefPtr<Element> { nullptr };
 
     SelectorQuery& query = queryOrException.releaseReturnValue();
 
-    for (auto& node : composedTreeDescendants(downcast<ContainerNode>(scope))) {
-        if (is<Element>(node) && query.matches(downcast<Element>(node)) && !node.isInUserAgentShadowTree())
-            return &downcast<Element>(node);
+    for (auto& node : composedTreeDescendants(*scopeContainer)) {
+        if (RefPtr element = dynamicDowncast<Element>(node); element && query.matches(*element) && !node.isInUserAgentShadowTree())
+            return element;
     }
 
     return RefPtr<Element> { nullptr };