LibWeb: Replace is<T>() with as_if<T>() where possible

Author: https://github.com/tcl3
Commit: cb1a1a5cb5
Pull-request: https://github.com/LadybirdBrowser/ladybird/pull/5985
Reviewed-by: https://github.com/gmta ✅

Libraries/LibWeb/CSS/FontFace.cpp

@@ -477,9 +477,8 @@ GC::Ref<WebIDL::Promise> FontFace::load()
 
         // FIXME: We should probably put the 'font cache' on the WindowOrWorkerGlobalScope instead of tying it to the document's style computer
         auto& global = HTML::relevant_global_object(*font);
-        if (is<HTML::Window>(global)) {
+        if (auto* window = as_if<HTML::Window>(global)) {
-            auto& window = static_cast<HTML::Window&>(global);
+            auto& style_computer = const_cast<StyleComputer&>(window->document()->style_computer());
-            auto& style_computer = const_cast<StyleComputer&>(window.document()->style_computer());
 
             // FIXME: The ParsedFontFace is kind of expensive to create. We should be using a shared sub-object for the data
             ParsedFontFace parsed_font_face {

Libraries/LibWeb/CSS/Interpolation.cpp

@@ -638,8 +638,8 @@ RefPtr<StyleValue const> interpolate_transform(DOM::Element& element, StyleValue
             return {};
         Optional<Painting::PaintableBox const&> paintable_box;
         if (auto layout_node = element.layout_node()) {
-            if (auto paintable = layout_node->first_paintable(); paintable && is<Painting::PaintableBox>(paintable))
+            if (auto* paintable = as_if<Painting::PaintableBox>(layout_node->first_paintable()))
-                paintable_box = *static_cast<Painting::PaintableBox*>(paintable);
+                paintable_box = *paintable;
         }
         if (auto matrix = transformation->to_matrix(paintable_box); !matrix.is_error())
             return matrix.value();

Libraries/LibWeb/CSS/StyleComputer.cpp

@@ -508,7 +508,7 @@ bool StyleComputer::invalidation_property_used_in_has_selector(InvalidationSet::
 Vector<MatchingRule const*> StyleComputer::collect_matching_rules(DOM::Element const& element, CascadeOrigin cascade_origin, Optional<CSS::PseudoElement> pseudo_element, PseudoClassBitmap& attempted_pseudo_class_matches, Optional<FlyString const> qualified_layer_name) const
 {
     auto const& root_node = element.root();
-    auto shadow_root = is<DOM::ShadowRoot>(root_node) ? static_cast<DOM::ShadowRoot const*>(&root_node) : nullptr;
+    auto shadow_root = as_if<DOM::ShadowRoot>(root_node);
     auto element_shadow_root = element.shadow_root();
     auto const& element_namespace_uri = element.namespace_uri();
 

Libraries/LibWeb/ContentSecurityPolicy/Directives/DirectiveOperations.cpp

@@ -897,9 +897,8 @@ MatchResult does_element_match_source_list_for_type_and_source(GC::Ptr<DOM::Elem
                 VERIFY(is<HTML::HTMLElement>(element.ptr()) || is<SVG::SVGElement>(element.ptr()));
 
                 String element_nonce;
-                if (is<HTML::HTMLElement>(element.ptr())) {
+                if (auto* html_element = as_if<HTML::HTMLElement>(element.ptr())) {
-                    auto const& html_element = static_cast<HTML::HTMLElement const&>(*element);
+                    element_nonce = html_element->nonce();
-                    element_nonce = html_element.nonce();
                 } else {
                     auto const& svg_element = as<SVG::SVGElement>(*element);
                     element_nonce = svg_element.nonce();

Libraries/LibWeb/Crypto/CryptoKey.cpp

@@ -117,9 +117,10 @@ static JS::ThrowCompletionOr<CryptoKeyPair*> impl_from(JS::VM& vm)
     else
         this_object = TRY(this_value.to_object(vm));
 
-    if (!is<CryptoKeyPair>(this_object))
+    auto* crypto_key_pair = as_if<CryptoKeyPair>(this_object);
+    if (!crypto_key_pair)
         return vm.throw_completion<JS::TypeError>(JS::ErrorType::NotAnObjectOfType, "CryptoKeyPair");
-    return static_cast<CryptoKeyPair*>(this_object);
+    return crypto_key_pair;
 }
 
 JS_DEFINE_NATIVE_FUNCTION(CryptoKeyPair::public_key_getter)

Libraries/LibWeb/DOM/Document.cpp

@@ -904,9 +904,7 @@ HTML::HTMLHtmlElement* Document::html_element()
 {
     // The html element of a document is its document element, if it's an html element, and null otherwise.
     auto* html = document_element();
-    if (is<HTML::HTMLHtmlElement>(html))
+    return as_if<HTML::HTMLHtmlElement>(html);
-        return as<HTML::HTMLHtmlElement>(html);
-    return nullptr;
 }
 
 // https://html.spec.whatwg.org/multipage/dom.html#the-head-element-2

Libraries/LibWeb/DOM/Element.cpp

@@ -1049,14 +1049,15 @@ WebIDL::ExceptionOr<void> Element::set_inner_html(StringView value)
     auto fragment = TRY(as<Element>(*context).parse_fragment(value));
 
     // 4. If context is a template element, then set context to the template element's template contents (a DocumentFragment).
-    if (is<HTML::HTMLTemplateElement>(*context))
+    auto* template_element = as_if<HTML::HTMLTemplateElement>(*context);
-        context = as<HTML::HTMLTemplateElement>(*context).content();
+    if (template_element)
+        context = template_element->content();
 
     // 5. Replace all with fragment within context.
     context->replace_all(fragment);
 
     // NOTE: We don't invalidate style & layout for <template> elements since they don't affect rendering.
-    if (!is<HTML::HTMLTemplateElement>(*context)) {
+    if (!template_element) {
         context->set_needs_style_update(true);
 
         if (context->is_connected()) {

Libraries/LibWeb/DOM/Element.h

@@ -491,10 +491,11 @@ public:
     void for_each_numbered_item_owned_by_list_owner(Callback callback)
     {
         for (auto* node = this->first_child(); node != nullptr; node = node->next_in_pre_order(this)) {
-            if (!is<Element>(*node))
+            auto* element = as_if<Element>(node);
+            if (!element)
                 continue;
 
-            static_cast<Element*>(node)->m_is_contained_in_list_subtree = true;
+            element->m_is_contained_in_list_subtree = true;
 
             if (node->is_html_ol_ul_menu_element()) {
                 // Skip list nodes and their descendents. They have their own, unrelated ordinals.
@@ -507,8 +508,6 @@ public:
             if (!node->layout_node())
                 continue; // Skip nodes that do not participate in the layout.
 
-            auto* element = static_cast<Element*>(node);
-
             if (!element->computed_properties()->display().is_list_item())
                 continue; // Skip nodes that are not list items.
 

Libraries/LibWeb/DOM/EventTarget.cpp

@@ -164,8 +164,7 @@ static bool default_passive_value(FlyString const& type, EventTarget* event_targ
         if (is<HTML::Window>(event_target))
             return true;
 
-        if (is<Node>(event_target)) {
+        if (auto* node = as_if<Node>(event_target)) {
-            auto* node = as<Node>(event_target);
             if (&node->document() == event_target || node->document().document_element() == event_target || node->document().body() == event_target)
                 return true;
         }
@@ -400,8 +399,7 @@ WebIDL::CallbackType* EventTarget::get_current_value_of_event_handler(FlyString
         GC::Ptr<Element> element;
         GC::Ptr<Document> document;
 
-        if (is<Element>(this)) {
+        if (auto* element_event_target = as_if<Element>(this)) {
-            auto* element_event_target = as<Element>(this);
             element = element_event_target;
             document = &element_event_target->document();
         } else {

Libraries/LibWeb/DOM/Node.cpp

@@ -136,11 +136,11 @@ String Node::base_uri() const
 const HTML::HTMLAnchorElement* Node::enclosing_link_element() const
 {
     for (auto* node = this; node; node = node->parent()) {
-        if (!is<HTML::HTMLAnchorElement>(*node))
+        auto const* anchor_element = as_if<HTML::HTMLAnchorElement>(*node);
+        if (!anchor_element)
             continue;
-        auto const& anchor_element = static_cast<HTML::HTMLAnchorElement const&>(*node);
+        if (anchor_element->has_attribute(HTML::AttributeNames::href))
-        if (anchor_element.has_attribute(HTML::AttributeNames::href))
+            return anchor_element;
-            return &anchor_element;
     }
     return nullptr;
 }
@@ -153,8 +153,8 @@ const HTML::HTMLElement* Node::enclosing_html_element() const
 const HTML::HTMLElement* Node::enclosing_html_element_with_attribute(FlyString const& attribute) const
 {
     for (auto* node = this; node; node = node->parent()) {
-        if (is<HTML::HTMLElement>(*node) && as<HTML::HTMLElement>(*node).has_attribute(attribute))
+        if (auto* html_element = as_if<HTML::HTMLElement>(*node); html_element && html_element->has_attribute(attribute))
-            return as<HTML::HTMLElement>(node);
+            return html_element;
     }
     return nullptr;
 }
@@ -354,13 +354,13 @@ Optional<String> Node::node_value() const
     // The nodeValue getter steps are to return the following, switching on the interface this implements:
 
     // If Attr, return this’s value.
-    if (is<Attr>(this)) {
+    if (auto* attr = as_if<Attr>(this)) {
-        return as<Attr>(this)->value();
+        return attr->value();
     }
 
     // If CharacterData, return this’s data.
-    if (is<CharacterData>(this)) {
+    if (auto* character_data = as_if<CharacterData>(this)) {
-        return as<CharacterData>(this)->data().to_utf8_but_should_be_ported_to_utf16();
+        return character_data->data().to_utf8_but_should_be_ported_to_utf16();
     }
 
     // Otherwise, return null.
@@ -375,11 +375,11 @@ void Node::set_node_value(Optional<String> const& maybe_value)
     auto value = maybe_value.value_or(String {});
 
     // If Attr, set an existing attribute value with this and the given value.
-    if (is<Attr>(this)) {
+    if (auto* attr = as_if<Attr>(this)) {
-        as<Attr>(this)->set_value(move(value));
+        attr->set_value(move(value));
-    } else if (is<CharacterData>(this)) {
+    } else if (auto* character_data = as_if<CharacterData>(this)) {
         // If CharacterData, replace data with node this, offset 0, count this’s length, and data the given value.
-        as<CharacterData>(this)->set_data(Utf16String::from_utf8(value));
+        character_data->set_data(Utf16String::from_utf8(value));
     }
 
     // Otherwise, do nothing.
@@ -545,8 +545,8 @@ Node& Node::shadow_including_root()
     // The shadow-including root of an object is its root’s host’s shadow-including root,
     // if the object’s root is a shadow root; otherwise its root.
     auto& node_root = root();
-    if (is<ShadowRoot>(node_root)) {
+    if (auto* shadow_root = as_if<ShadowRoot>(node_root)) {
-        if (auto* host = static_cast<ShadowRoot&>(node_root).host(); host)
+        if (auto* host = shadow_root->host(); host)
             return host->shadow_including_root();
     }
     return node_root;

Libraries/LibWeb/HTML/EventLoop/EventLoop.cpp

@@ -526,10 +526,8 @@ TaskID queue_global_task(HTML::Task::Source source, JS::Object& global_object, G
 
     // 2. Let document be global's associated Document, if global is a Window object; otherwise null.
     DOM::Document* document { nullptr };
-    if (is<HTML::Window>(global_object)) {
+    if (auto* window_object = as_if<HTML::Window>(global_object))
-        auto& window_object = as<HTML::Window>(global_object);
+        document = &window_object->associated_document();
-        document = &window_object.associated_document();
-    }
 
     // 3. Queue a task given source, event loop, document, and steps.
     return queue_a_task(source, *event_loop, document, steps);

Libraries/LibWeb/HTML/HTMLElement.cpp

@@ -215,11 +215,12 @@ static void merge_with_the_next_text_node(DOM::Text& node)
     auto next = node.next_sibling();
 
     // 2. If next is not a Text node, then return.
-    if (!is<DOM::Text>(next))
+    auto* text = as_if<DOM::Text>(next);
+    if (!text)
         return;
 
     // 3. Replace data with node, node's data's length, 0, and next's data.
-    MUST(node.replace_data(node.length_in_utf16_code_units(), 0, static_cast<DOM::Text const&>(*next).data()));
+    MUST(node.replace_data(node.length_in_utf16_code_units(), 0, text->data()));
 
     // 4. Remove next.
     next->remove();
@@ -253,8 +254,8 @@ WebIDL::ExceptionOr<void> HTMLElement::set_outer_text(Utf16View const& value)
         merge_with_the_next_text_node(static_cast<DOM::Text&>(*next->previous_sibling()));
 
     // 8. If previous is a Text node, then merge with the next text node given previous.
-    if (is<DOM::Text>(previous))
+    if (auto* previous_text = as_if<DOM::Text>(previous))
-        merge_with_the_next_text_node(static_cast<DOM::Text&>(*previous));
+        merge_with_the_next_text_node(*previous_text);
 
     set_needs_style_update(true);
     return {};
@@ -842,7 +843,8 @@ GC::Ptr<DOM::NodeList> HTMLElement::labels()
 
     if (!m_labels) {
         m_labels = DOM::LiveNodeList::create(realm(), root(), DOM::LiveNodeList::Scope::Descendants, [&](auto& node) {
-            return is<HTMLLabelElement>(node) && as<HTMLLabelElement>(node).control() == this;
+            auto* label_element = as_if<HTMLLabelElement>(node);
+            return label_element && label_element->control() == this;
         });
     }
 

Libraries/LibWeb/HTML/HTMLImageElement.cpp

@@ -1087,8 +1087,8 @@ static void update_the_source_set(DOM::Element& element)
     VERIFY(is<HTMLImageElement>(element) || is<HTMLLinkElement>(element));
 
     // 1. Set el's source set to an empty source set.
-    if (is<HTMLImageElement>(element))
+    if (auto* image_element = as_if<HTMLImageElement>(element))
-        static_cast<HTMLImageElement&>(element).set_source_set(SourceSet {});
+        image_element->set_source_set(SourceSet {});
     else if (is<HTMLLinkElement>(element))
         TODO();
 

Libraries/LibWeb/HTML/HTMLInputElement.cpp

@@ -494,11 +494,9 @@ WebIDL::ExceptionOr<void> HTMLInputElement::run_input_activation_behavior(DOM::E
 
         // 3. If the user activated the control while explicitly selecting a coordinate, then set the element's selected
         //    coordinate to that coordinate.
-        if (event.is_trusted() && is<UIEvents::MouseEvent>(event)) {
+        if (auto* mouse_event = as_if<UIEvents::MouseEvent>(event); mouse_event && event.is_trusted()) {
-            auto const& mouse_event = static_cast<UIEvents::MouseEvent const&>(event);
+            CSSPixels x { mouse_event->offset_x() };
-
+            CSSPixels y { mouse_event->offset_y() };
-            CSSPixels x { mouse_event.offset_x() };
-            CSSPixels y { mouse_event.offset_y() };
 
             m_selected_coordinate = { x.to_int(), y.to_int() };
         }

Libraries/LibWeb/HTML/HTMLMediaElement.cpp

@@ -715,8 +715,8 @@ private:
         }
 
         // 14. ⌛ If the node after pointer is a source element, let candidate be that element.
-        if (is<HTMLSourceElement>(next_sibling))
+        if (auto* source_element = as_if<HTMLSourceElement>(next_sibling))
-            candidate = static_cast<HTMLSourceElement*>(next_sibling);
+            candidate = source_element;
 
         // 15. ⌛ Advance pointer so that the node before pointer is now the node that was after pointer, and the node
         //     after pointer is the node after the node that used to be after pointer, if any.

Libraries/LibWeb/HTML/HTMLTableElement.cpp

@@ -213,8 +213,7 @@ GC::Ptr<HTMLTableSectionElement> HTMLTableElement::t_head()
     // The tHead IDL attribute must return, on getting, the first thead element child of the table element,
     // if any, or null otherwise.
     for (auto* child = first_child(); child; child = child->next_sibling()) {
-        if (is<HTMLTableSectionElement>(*child)) {
+        if (auto* table_section_element = as_if<HTMLTableSectionElement>(*child)) {
-            auto table_section_element = &as<HTMLTableSectionElement>(*child);
             if (table_section_element->local_name() == TagNames::thead)
                 return table_section_element;
         }
@@ -248,8 +247,7 @@ WebIDL::ExceptionOr<void> HTMLTableElement::set_t_head(HTMLTableSectionElement*
             continue;
         if (is<HTMLTableCaptionElement>(*child))
             continue;
-        if (is<HTMLTableColElement>(*child)) {
+        if (auto* table_col_element = as_if<HTMLTableColElement>(*child)) {
-            auto table_col_element = &as<HTMLTableColElement>(*child);
             if (table_col_element->local_name() == TagNames::colgroup)
                 continue;
         }
@@ -280,8 +278,7 @@ GC::Ref<HTMLTableSectionElement> HTMLTableElement::create_t_head()
             continue;
         if (is<HTMLTableCaptionElement>(*child))
             continue;
-        if (is<HTMLTableColElement>(*child)) {
+        if (auto* table_col_element = as_if<HTMLTableColElement>(*child)) {
-            auto table_col_element = &as<HTMLTableColElement>(*child);
             if (table_col_element->local_name() == TagNames::colgroup)
                 continue;
         }
@@ -311,8 +308,7 @@ GC::Ptr<HTMLTableSectionElement> HTMLTableElement::t_foot()
     // The tFoot IDL attribute must return, on getting, the first tfoot element child of the table element,
     // if any, or null otherwise.
     for (auto* child = first_child(); child; child = child->next_sibling()) {
-        if (is<HTMLTableSectionElement>(*child)) {
+        if (auto* table_section_element = as_if<HTMLTableSectionElement>(*child)) {
-            auto table_section_element = &as<HTMLTableSectionElement>(*child);
             if (table_section_element->local_name() == TagNames::tfoot)
                 return table_section_element;
         }
@@ -384,8 +380,7 @@ GC::Ref<HTMLTableSectionElement> HTMLTableElement::create_t_body()
     for (auto* child = last_child(); child; child = child->previous_sibling()) {
         if (!is<HTMLElement>(*child))
             continue;
-        if (is<HTMLTableSectionElement>(*child)) {
+        if (auto* table_section_element = as_if<HTMLTableSectionElement>(*child)) {
-            auto table_section_element = &as<HTMLTableSectionElement>(*child);
             if (table_section_element->local_name() == TagNames::tbody) {
                 // We have found an element which is a <tbody> we'll insert after this
                 child_to_insert_before = child->next_sibling();

Libraries/LibWeb/HTML/Navigable.cpp

@@ -1228,8 +1228,10 @@ static WebIDL::ExceptionOr<Navigable::NavigationParamsVariant> create_navigation
 
     // 26. If navigable's container is an iframe, and response's timing allow passed flag is set,
     //     then set navigable's container's pending resource-timing start time to null.
-    if (navigable->container() && is<HTML::HTMLIFrameElement>(*navigable->container()) && response_holder->response()->timing_allow_passed())
+    if (navigable->container() && response_holder->response()->timing_allow_passed()) {
-        static_cast<HTML::HTMLIFrameElement&>(*navigable->container()).set_pending_resource_start_time({});
+        if (auto* iframe_element = as_if<HTML::HTMLIFrameElement>(*navigable->container()))
+            iframe_element->set_pending_resource_start_time({});
+    }
 
     // 27. Return a new navigation params, with
     //     id: navigationId

Libraries/LibWeb/HTML/Parser/HTMLParser.cpp

@@ -766,8 +766,8 @@ HTMLParser::AdjustedInsertionLocation HTMLParser::find_appropriate_place_for_ins
 
     // 3. If the adjusted insertion location is inside a template element,
     //    let it instead be inside the template element's template contents, after its last child (if any).
-    if (is<HTMLTemplateElement>(*adjusted_insertion_location.parent))
+    if (auto* template_element = as_if<HTMLTemplateElement>(*adjusted_insertion_location.parent))
-        adjusted_insertion_location = { static_cast<HTMLTemplateElement const&>(*adjusted_insertion_location.parent).content().ptr(), nullptr };
+        adjusted_insertion_location = { template_element->content().ptr(), nullptr };
 
     // 4. Return the adjusted insertion location.
     return adjusted_insertion_location;

Libraries/LibWeb/HTML/Window.cpp

@@ -1238,8 +1238,8 @@ WebIDL::ExceptionOr<void> Window::window_post_message_steps(JS::Value message, W
         // FIXME: Use a FrozenArray
         Vector<GC::Root<MessagePort>> new_ports;
         for (auto const& object : deserialize_record.transferred_values) {
-            if (is<HTML::MessagePort>(*object)) {
+            if (auto* message_port = as_if<HTML::MessagePort>(*object)) {
-                new_ports.append(as<MessagePort>(*object));
+                new_ports.append(*message_port);
             }
         }
 

Libraries/LibWeb/Layout/BlockFormattingContext.cpp

@@ -81,9 +81,8 @@ void BlockFormattingContext::run(AvailableSpace const& available_space)
     else
         layout_block_level_children(root(), available_space);
 
-    if (is<FieldSetBox>(root())) {
+    if (auto* fieldset_box = as_if<FieldSetBox>(root())) {
-        auto const& fieldset_box = as<FieldSetBox>(root());
+        if (!fieldset_box->has_rendered_legend()) {
-        if (!(fieldset_box.has_rendered_legend())) {
             return;
         }
 
@@ -188,10 +187,9 @@ void BlockFormattingContext::compute_width(Box const& box, AvailableSpace const&
 
     if (box_is_sized_as_replaced_element(box, available_space)) {
         // FIXME: This should not be done *by* ReplacedBox
-        if (is<ReplacedBox>(box)) {
+        if (auto* replaced = as_if<ReplacedBox>(box)) {
-            auto& replaced = as<ReplacedBox>(box);
             // FIXME: This const_cast is gross.
-            const_cast<ReplacedBox&>(replaced).prepare_for_replaced_layout();
+            const_cast<ReplacedBox&>(*replaced).prepare_for_replaced_layout();
         }
         compute_width_for_block_level_replaced_element_in_normal_flow(box, available_space);
         if (box.is_floating()) {
@@ -822,17 +820,15 @@ void BlockFormattingContext::layout_block_level_box(Box const& box, BlockContain
     // If we do not do this then left-floating elements inside the list item will push the marker to the right,
     // in some cases even causing it to overlap with the non-floating content of the list.
     CSSPixels left_space_before_children_formatted;
-    if (is<ListItemBox>(box)) {
+    if (auto const* li_box = as_if<ListItemBox>(box)) {
-        auto const& li_box = static_cast<ListItemBox const&>(box);
-
         // We need to ensure that our height and width are final before we calculate our left offset.
         // Otherwise, the y at which we calculate the intrusion by floats might be incorrect.
-        ensure_sizes_correct_for_left_offset_calculation(li_box);
+        ensure_sizes_correct_for_left_offset_calculation(*li_box);
 
-        auto const& list_item_state = m_state.get(li_box);
+        auto const& list_item_state = m_state.get(*li_box);
-        auto const& marker_state = m_state.get(*li_box.marker());
+        auto const& marker_state = m_state.get(*li_box->marker());
 
-        auto offset_y = max(CSSPixels(0), (li_box.marker()->computed_values().line_height() - marker_state.content_height()) / 2);
+        auto offset_y = max(CSSPixels(0), (li_box->marker()->computed_values().line_height() - marker_state.content_height()) / 2);
         auto space_used_before_children_formatted = intrusion_by_floats_into_box(list_item_state, offset_y);
 
         left_space_before_children_formatted = space_used_before_children_formatted.left;
@@ -884,8 +880,8 @@ void BlockFormattingContext::layout_block_level_box(Box const& box, BlockContain
     compute_inset(box, content_box_rect(block_container_state).size());
 
     // Now that our children are formatted we place the ListItemBox with the left space we remembered.
-    if (is<ListItemBox>(box))
+    if (auto const* li_box = as_if<ListItemBox>(box))
-        layout_list_item_marker(static_cast<ListItemBox const&>(box), left_space_before_children_formatted);
+        layout_list_item_marker(*li_box, left_space_before_children_formatted);
 
     bottom_of_lowest_margin_box = max(bottom_of_lowest_margin_box, box_state.offset.y() + box_state.content_height() + box_state.margin_box_bottom());
 

Libraries/LibWeb/Layout/FormattingContext.cpp

@@ -871,9 +871,9 @@ void FormattingContext::compute_width_for_absolutely_positioned_replaced_element
     // but the rest of section 10.3.7 is replaced by the following rules:
 
     // 1. The used value of 'width' is determined as for inline replaced elements.
-    if (is<ReplacedBox>(box)) {
+    if (auto const* replaced = as_if<ReplacedBox>(box)) {
         // FIXME: This const_cast is gross.
-        static_cast<ReplacedBox&>(const_cast<Box&>(box)).prepare_for_replaced_layout();
+        const_cast<ReplacedBox&>(*replaced).prepare_for_replaced_layout();
     }
 
     auto width = compute_width_for_replaced_element(box, available_space);

Libraries/LibWeb/Layout/InlineFormattingContext.cpp

@@ -308,19 +308,18 @@ void InlineFormattingContext::generate_line_boxes()
             break;
         }
         case InlineLevelIterator::Item::Type::AbsolutelyPositionedElement:
-            if (is<Box>(*item.node)) {
+            if (auto const* box = as_if<Box>(*item.node)) {
-                auto const& box = static_cast<Layout::Box const&>(*item.node);
                 // Calculation of static position for absolute boxes is delayed until trailing whitespaces are removed.
-                absolute_boxes.append(&box);
+                absolute_boxes.append(box);
             }
             break;
 
         case InlineLevelIterator::Item::Type::FloatingElement:
-            if (is<Box>(*item.node)) {
+            if (auto* box = as_if<Box>(*item.node)) {
                 (void)parent().clear_floating_boxes(*item.node, *this);
                 // Even if this introduces clearance, we do NOT reset the margin state, because that is clearance
                 // between floats and does not contribute to the height of the Inline Formatting Context.
-                parent().layout_floating_box(static_cast<Layout::Box const&>(*item.node), containing_block(), *m_available_space, 0, &line_builder);
+                parent().layout_floating_box(*box, containing_block(), *m_available_space, 0, &line_builder);
             }
             break;
 

Libraries/LibWeb/Layout/LineBoxFragment.cpp

@@ -61,9 +61,9 @@ bool LineBoxFragment::is_justifiable_whitespace() const
 
 Utf16View LineBoxFragment::text() const
 {
-    if (!is<TextNode>(layout_node()))
+    if (auto* text_node = as_if<TextNode>(layout_node()))
+        return text_node->text_for_rendering().substring_view(m_start, m_length);
     return {};
-    return as<TextNode>(layout_node()).text_for_rendering().substring_view(m_start, m_length);
 }
 
 bool LineBoxFragment::is_atomic_inline() const

Libraries/LibWeb/Layout/Node.cpp

@@ -1056,10 +1056,9 @@ void NodeWithStyle::propagate_style_to_anonymous_wrappers()
 
     // If this is a `display:table` box with an anonymous wrapper parent,
     // the parent inherits style from *this* node, not the other way around.
-    if (display().is_table_inside() && is<TableWrapper>(parent())) {
+    if (auto* table_wrapper = as_if<TableWrapper>(parent()); table_wrapper && display().is_table_inside()) {
-        auto& table_wrapper = *static_cast<TableWrapper*>(parent());
+        static_cast<CSS::MutableComputedValues&>(static_cast<CSS::ComputedValues&>(const_cast<CSS::ImmutableComputedValues&>(table_wrapper->computed_values()))).inherit_from(computed_values());
-        static_cast<CSS::MutableComputedValues&>(static_cast<CSS::ComputedValues&>(const_cast<CSS::ImmutableComputedValues&>(table_wrapper.computed_values()))).inherit_from(computed_values());
+        transfer_table_box_computed_values_to_wrapper_computed_values(table_wrapper->mutable_computed_values());
-        transfer_table_box_computed_values_to_wrapper_computed_values(table_wrapper.mutable_computed_values());
     }
 
     // Propagate style to all anonymous children (except table wrappers!)

Libraries/LibWeb/Painting/BackgroundPainting.cpp

@@ -41,9 +41,8 @@ static RefPtr<DisplayList> compute_text_clip_paths(DisplayListRecordingContext&
     };
 
     paintable.for_each_in_inclusive_subtree([&](auto& paintable) {
-        if (is<PaintableWithLines>(paintable)) {
+        if (auto* paintable_lines = as_if<PaintableWithLines>(paintable)) {
-            auto const& paintable_lines = static_cast<PaintableWithLines const&>(paintable);
+            for (auto const& fragment : paintable_lines->fragments()) {
-            for (auto const& fragment : paintable_lines.fragments()) {
                 if (is<Layout::TextNode>(fragment.layout_node()))
                     add_text_clip_path(fragment);
             }

Libraries/LibWeb/Painting/PaintableBox.cpp

@@ -132,8 +132,8 @@ void PaintableBox::set_scroll_offset(CSSPixelPoint offset)
     auto& node = layout_node();
     if (auto pseudo_element = node.generated_for_pseudo_element(); pseudo_element.has_value()) {
         node.pseudo_element_generator()->set_scroll_offset(*pseudo_element, offset);
-    } else if (is<DOM::Element>(*dom_node())) {
+    } else if (auto* element = as_if<DOM::Element>(dom_node())) {
-        static_cast<DOM::Element*>(dom_node())->set_scroll_offset({}, offset);
+        element->set_scroll_offset({}, offset);
     } else {
         return;
     }