AK: Rename downcast<T> => verify_cast<T>

This makes it much clearer what this cast actually does: it will
VERIFY that the thing we're casting is a T (using is<T>()).

AK/TypeCasts.h

@@ -28,7 +28,7 @@ ALWAYS_INLINE bool is(InputType* input)
 }
 
 template<typename OutputType, typename InputType>
-ALWAYS_INLINE CopyConst<InputType, OutputType>* downcast(InputType* input)
+ALWAYS_INLINE CopyConst<InputType, OutputType>* verify_cast(InputType* input)
 {
     static_assert(IsBaseOf<InputType, OutputType>);
     VERIFY(!input || is<OutputType>(*input));
@@ -36,7 +36,7 @@ ALWAYS_INLINE CopyConst<InputType, OutputType>* downcast(InputType* input)
 }
 
 template<typename OutputType, typename InputType>
-ALWAYS_INLINE CopyConst<InputType, OutputType>& downcast(InputType& input)
+ALWAYS_INLINE CopyConst<InputType, OutputType>& verify_cast(InputType& input)
 {
     static_assert(IsBaseOf<InputType, OutputType>);
     VERIFY(is<OutputType>(input));
@@ -45,5 +45,5 @@ ALWAYS_INLINE CopyConst<InputType, OutputType>& downcast(InputType& input)
 
 }
 
-using AK::downcast;
 using AK::is;
+using AK::verify_cast;

AK/Variant.h

@@ -319,7 +319,7 @@ public:
     }
 
     template<typename... NewTs>
-    Variant<NewTs...> downcast() &&
+    Variant<NewTs...> verify_cast() &&
     {
         Variant<NewTs...> instance { Variant<NewTs...>::invalid_index, Detail::VariantConstructTag {} };
         visit([&](auto& value) {
@@ -331,7 +331,7 @@ public:
     }
 
     template<typename... NewTs>
-    Variant<NewTs...> downcast() &
+    Variant<NewTs...> verify_cast() &
     {
         Variant<NewTs...> instance { Variant<NewTs...>::invalid_index, Detail::VariantConstructTag {} };
         visit([&](const auto& value) {

Tests/AK/TestVariant.cpp

@@ -77,17 +77,17 @@ TEST_CASE(move_moves)
     EXPECT(second_variant.has<NoCopy>());
 }
 
-TEST_CASE(downcast)
+TEST_CASE(verify_cast)
 {
     Variant<i8, i16, i32, i64> one_integer_to_rule_them_all { static_cast<i32>(42) };
-    auto fake_integer = one_integer_to_rule_them_all.downcast<i8, i32>();
+    auto fake_integer = one_integer_to_rule_them_all.verify_cast<i8, i32>();
     EXPECT(fake_integer.has<i32>());
     EXPECT(one_integer_to_rule_them_all.has<i32>());
     EXPECT_EQ(fake_integer.get<i32>(), 42);
     EXPECT_EQ(one_integer_to_rule_them_all.get<i32>(), 42);
 
     fake_integer = static_cast<i8>(60);
-    one_integer_to_rule_them_all = fake_integer.downcast<i8, i16>().downcast<i8, i32, float>().downcast<i8, i16, i32, i64>();
+    one_integer_to_rule_them_all = fake_integer.verify_cast<i8, i16>().verify_cast<i8, i32, float>().verify_cast<i8, i16, i32, i64>();
     EXPECT(fake_integer.has<i8>());
     EXPECT(one_integer_to_rule_them_all.has<i8>());
     EXPECT_EQ(fake_integer.get<i8>(), 60);

Userland/Applications/Browser/BrowserWindow.cpp

@@ -479,7 +479,7 @@ GUI::TabWidget& BrowserWindow::tab_widget()
 
 Tab& BrowserWindow::active_tab()
 {
-    return downcast<Tab>(*tab_widget().active_widget());
+    return verify_cast<Tab>(*tab_widget().active_widget());
 }
 
 void BrowserWindow::set_window_title_for_tab(Tab const& tab)

Userland/Applications/Browser/InspectorWidget.cpp

@@ -22,7 +22,7 @@ void InspectorWidget::set_inspected_node(Web::DOM::Node* node)
 {
     m_document->set_inspected_node(node);
     if (node && node->is_element()) {
-        auto& element = downcast<Web::DOM::Element>(*node);
+        auto& element = verify_cast<Web::DOM::Element>(*node);
         if (element.specified_css_values()) {
             m_style_table_view->set_model(Web::StylePropertiesModel::create(*element.specified_css_values()));
             m_computed_style_table_view->set_model(Web::StylePropertiesModel::create(*element.computed_style()));

Userland/Applications/PixelPaint/main.cpp

@@ -68,7 +68,7 @@ int main(int argc, char** argv)
     auto current_image_editor = [&]() -> PixelPaint::ImageEditor* {
         if (!tab_widget.active_widget())
             return nullptr;
-        return downcast<PixelPaint::ImageEditor>(tab_widget.active_widget());
+        return verify_cast<PixelPaint::ImageEditor>(tab_widget.active_widget());
     };
 
     Function<PixelPaint::ImageEditor&(NonnullRefPtr<PixelPaint::Image>)> create_new_editor;
@@ -552,14 +552,14 @@ int main(int argc, char** argv)
     };
 
     tab_widget.on_tab_close_click = [&](auto& widget) {
-        auto& image_editor = downcast<PixelPaint::ImageEditor>(widget);
+        auto& image_editor = verify_cast<PixelPaint::ImageEditor>(widget);
         tab_widget.deferred_invoke([&](auto&) {
             tab_widget.remove_tab(image_editor);
         });
     };
 
     tab_widget.on_change = [&](auto& widget) {
-        auto& image_editor = downcast<PixelPaint::ImageEditor>(widget);
+        auto& image_editor = verify_cast<PixelPaint::ImageEditor>(widget);
         palette_widget.set_image_editor(image_editor);
         layer_list_widget.set_image(&image_editor.image());
         layer_properties_widget.set_layer(nullptr);

Userland/Applications/SystemMonitor/ThreadStackWidget.cpp

@@ -74,7 +74,7 @@ void ThreadStackWidget::refresh()
 
 void ThreadStackWidget::custom_event(Core::CustomEvent& event)
 {
-    auto& completion_event = downcast<CompletionEvent>(event);
+    auto& completion_event = verify_cast<CompletionEvent>(event);
 
     StringBuilder builder;
 

Userland/Libraries/LibGUI/StackWidget.cpp

@@ -54,7 +54,7 @@ void StackWidget::child_event(Core::ChildEvent& event)
 {
     if (!event.child() || !is<Widget>(*event.child()))
         return Widget::child_event(event);
-    auto& child = downcast<Widget>(*event.child());
+    auto& child = verify_cast<Widget>(*event.child());
     if (event.type() == Event::ChildAdded) {
         if (!m_active_widget)
             set_active_widget(&child);

Userland/Libraries/LibGUI/TabWidget.cpp

@@ -134,7 +134,7 @@ void TabWidget::child_event(Core::ChildEvent& event)
 {
     if (!event.child() || !is<Widget>(*event.child()))
         return Widget::child_event(event);
-    auto& child = downcast<Widget>(*event.child());
+    auto& child = verify_cast<Widget>(*event.child());
     if (event.type() == Event::ChildAdded) {
         if (!m_active_widget)
             set_active_widget(&child);

Userland/Libraries/LibGUI/Widget.cpp

@@ -147,22 +147,22 @@ void Widget::child_event(Core::ChildEvent& event)
     if (event.type() == Event::ChildAdded) {
         if (event.child() && is<Widget>(*event.child()) && layout()) {
             if (event.insertion_before_child() && is<Widget>(event.insertion_before_child()))
-                layout()->insert_widget_before(downcast<Widget>(*event.child()), downcast<Widget>(*event.insertion_before_child()));
+                layout()->insert_widget_before(verify_cast<Widget>(*event.child()), verify_cast<Widget>(*event.insertion_before_child()));
             else
-                layout()->add_widget(downcast<Widget>(*event.child()));
+                layout()->add_widget(verify_cast<Widget>(*event.child()));
         }
         if (window() && event.child() && is<Widget>(*event.child()))
-            window()->did_add_widget({}, downcast<Widget>(*event.child()));
+            window()->did_add_widget({}, verify_cast<Widget>(*event.child()));
     }
     if (event.type() == Event::ChildRemoved) {
         if (layout()) {
             if (event.child() && is<Widget>(*event.child()))
-                layout()->remove_widget(downcast<Widget>(*event.child()));
+                layout()->remove_widget(verify_cast<Widget>(*event.child()));
             else
                 invalidate_layout();
         }
         if (window() && event.child() && is<Widget>(*event.child()))
-            window()->did_remove_widget({}, downcast<Widget>(*event.child()));
+            window()->did_remove_widget({}, verify_cast<Widget>(*event.child()));
         update();
     }
     return Core::Object::child_event(event);
@@ -563,7 +563,7 @@ Widget* Widget::child_at(const Gfx::IntPoint& point) const
     for (int i = children().size() - 1; i >= 0; --i) {
         if (!is<Widget>(children()[i]))
             continue;
-        auto& child = downcast<Widget>(children()[i]);
+        auto& child = verify_cast<Widget>(children()[i]);
         if (!child.is_visible())
             continue;
         if (child.content_rect().contains(point))

Userland/Libraries/LibGUI/Widget.h

@@ -245,7 +245,7 @@ public:
     {
         for_each_child([&](auto& child) {
             if (is<Widget>(child))
-                return callback(downcast<Widget>(child));
+                return callback(verify_cast<Widget>(child));
             return IterationDecision::Continue;
         });
     }
@@ -370,13 +370,13 @@ private:
 inline Widget* Widget::parent_widget()
 {
     if (parent() && is<Widget>(*parent()))
-        return &downcast<Widget>(*parent());
+        return &verify_cast<Widget>(*parent());
     return nullptr;
 }
 inline const Widget* Widget::parent_widget() const
 {
     if (parent() && is<Widget>(*parent()))
-        return &downcast<const Widget>(*parent());
+        return &verify_cast<const Widget>(*parent());
     return nullptr;
 }
 }

Userland/Libraries/LibJS/Parser.cpp

@@ -1691,7 +1691,7 @@ NonnullRefPtr<VariableDeclaration> Parser::parse_variable_declaration(bool for_l
 
         declarations.append(create_ast_node<VariableDeclarator>(
             { m_state.current_token.filename(), rule_start.position(), position() },
-            move(target).downcast<NonnullRefPtr<Identifier>, NonnullRefPtr<BindingPattern>>(),
+            move(target).verify_cast<NonnullRefPtr<Identifier>, NonnullRefPtr<BindingPattern>>(),
             move(init)));
 
         if (match(TokenType::Comma)) {

Userland/Libraries/LibWasm/AbstractMachine/AbstractMachine.cpp

@@ -397,7 +397,7 @@ Optional<InstantiationError> AbstractMachine::allocate_all_initial_phase(Module
 
             module_instance.exports().append(ExportInstance {
                 entry.name(),
-                move(address).downcast<FunctionAddress, TableAddress, MemoryAddress, GlobalAddress>(),
+                move(address).verify_cast<FunctionAddress, TableAddress, MemoryAddress, GlobalAddress>(),
             });
         }
     });

Userland/Libraries/LibWeb/Bindings/CSSStyleDeclarationWrapperCustom.cpp

@@ -41,7 +41,7 @@ bool CSSStyleDeclarationWrapper::put(const JS::PropertyName& name, JS::Value val
         return false;
 
     ScopeGuard style_invalidation_guard = [&] {
-        auto& declaration = downcast<CSS::ElementInlineCSSStyleDeclaration>(impl());
+        auto& declaration = verify_cast<CSS::ElementInlineCSSStyleDeclaration>(impl());
         if (auto* element = declaration.element())
             element->invalidate_style();
     };

Userland/Libraries/LibWeb/Bindings/NodeWrapperFactory.cpp

@@ -164,163 +164,163 @@ namespace Web::Bindings {
 NodeWrapper* wrap(JS::GlobalObject& global_object, DOM::Node& node)
 {
     if (is<DOM::Document>(node))
-        return static_cast<NodeWrapper*>(wrap_impl(global_object, downcast<DOM::Document>(node)));
+        return static_cast<NodeWrapper*>(wrap_impl(global_object, verify_cast<DOM::Document>(node)));
     if (is<DOM::DocumentType>(node))
-        return static_cast<NodeWrapper*>(wrap_impl(global_object, downcast<DOM::DocumentType>(node)));
+        return static_cast<NodeWrapper*>(wrap_impl(global_object, verify_cast<DOM::DocumentType>(node)));
     if (is<HTML::HTMLAnchorElement>(node))
-        return static_cast<NodeWrapper*>(wrap_impl(global_object, downcast<HTML::HTMLAnchorElement>(node)));
+        return static_cast<NodeWrapper*>(wrap_impl(global_object, verify_cast<HTML::HTMLAnchorElement>(node)));
     if (is<HTML::HTMLAreaElement>(node))
-        return static_cast<NodeWrapper*>(wrap_impl(global_object, downcast<HTML::HTMLAreaElement>(node)));
+        return static_cast<NodeWrapper*>(wrap_impl(global_object, verify_cast<HTML::HTMLAreaElement>(node)));
     if (is<HTML::HTMLAudioElement>(node))
-        return static_cast<NodeWrapper*>(wrap_impl(global_object, downcast<HTML::HTMLAudioElement>(node)));
+        return static_cast<NodeWrapper*>(wrap_impl(global_object, verify_cast<HTML::HTMLAudioElement>(node)));
     if (is<HTML::HTMLBaseElement>(node))
-        return static_cast<NodeWrapper*>(wrap_impl(global_object, downcast<HTML::HTMLBaseElement>(node)));
+        return static_cast<NodeWrapper*>(wrap_impl(global_object, verify_cast<HTML::HTMLBaseElement>(node)));
     if (is<HTML::HTMLBodyElement>(node))
-        return static_cast<NodeWrapper*>(wrap_impl(global_object, downcast<HTML::HTMLBodyElement>(node)));
+        return static_cast<NodeWrapper*>(wrap_impl(global_object, verify_cast<HTML::HTMLBodyElement>(node)));
     if (is<HTML::HTMLBRElement>(node))
-        return static_cast<NodeWrapper*>(wrap_impl(global_object, downcast<HTML::HTMLBRElement>(node)));
+        return static_cast<NodeWrapper*>(wrap_impl(global_object, verify_cast<HTML::HTMLBRElement>(node)));
     if (is<HTML::HTMLButtonElement>(node))
-        return static_cast<NodeWrapper*>(wrap_impl(global_object, downcast<HTML::HTMLButtonElement>(node)));
+        return static_cast<NodeWrapper*>(wrap_impl(global_object, verify_cast<HTML::HTMLButtonElement>(node)));
     if (is<HTML::HTMLCanvasElement>(node))
-        return static_cast<NodeWrapper*>(wrap_impl(global_object, downcast<HTML::HTMLCanvasElement>(node)));
+        return static_cast<NodeWrapper*>(wrap_impl(global_object, verify_cast<HTML::HTMLCanvasElement>(node)));
     if (is<HTML::HTMLDataElement>(node))
-        return static_cast<NodeWrapper*>(wrap_impl(global_object, downcast<HTML::HTMLDataElement>(node)));
+        return static_cast<NodeWrapper*>(wrap_impl(global_object, verify_cast<HTML::HTMLDataElement>(node)));
     if (is<HTML::HTMLDataListElement>(node))
-        return static_cast<NodeWrapper*>(wrap_impl(global_object, downcast<HTML::HTMLDataListElement>(node)));
+        return static_cast<NodeWrapper*>(wrap_impl(global_object, verify_cast<HTML::HTMLDataListElement>(node)));
     if (is<HTML::HTMLDetailsElement>(node))
-        return static_cast<NodeWrapper*>(wrap_impl(global_object, downcast<HTML::HTMLDetailsElement>(node)));
+        return static_cast<NodeWrapper*>(wrap_impl(global_object, verify_cast<HTML::HTMLDetailsElement>(node)));
     if (is<HTML::HTMLDialogElement>(node))
-        return static_cast<NodeWrapper*>(wrap_impl(global_object, downcast<HTML::HTMLDialogElement>(node)));
+        return static_cast<NodeWrapper*>(wrap_impl(global_object, verify_cast<HTML::HTMLDialogElement>(node)));
     if (is<HTML::HTMLDirectoryElement>(node))
-        return static_cast<NodeWrapper*>(wrap_impl(global_object, downcast<HTML::HTMLDirectoryElement>(node)));
+        return static_cast<NodeWrapper*>(wrap_impl(global_object, verify_cast<HTML::HTMLDirectoryElement>(node)));
     if (is<HTML::HTMLDivElement>(node))
-        return static_cast<NodeWrapper*>(wrap_impl(global_object, downcast<HTML::HTMLDivElement>(node)));
+        return static_cast<NodeWrapper*>(wrap_impl(global_object, verify_cast<HTML::HTMLDivElement>(node)));
     if (is<HTML::HTMLDListElement>(node))
-        return static_cast<NodeWrapper*>(wrap_impl(global_object, downcast<HTML::HTMLDListElement>(node)));
+        return static_cast<NodeWrapper*>(wrap_impl(global_object, verify_cast<HTML::HTMLDListElement>(node)));
     if (is<HTML::HTMLEmbedElement>(node))
-        return static_cast<NodeWrapper*>(wrap_impl(global_object, downcast<HTML::HTMLEmbedElement>(node)));
+        return static_cast<NodeWrapper*>(wrap_impl(global_object, verify_cast<HTML::HTMLEmbedElement>(node)));
     if (is<HTML::HTMLFieldSetElement>(node))
-        return static_cast<NodeWrapper*>(wrap_impl(global_object, downcast<HTML::HTMLFieldSetElement>(node)));
+        return static_cast<NodeWrapper*>(wrap_impl(global_object, verify_cast<HTML::HTMLFieldSetElement>(node)));
     if (is<HTML::HTMLFontElement>(node))
-        return static_cast<NodeWrapper*>(wrap_impl(global_object, downcast<HTML::HTMLFontElement>(node)));
+        return static_cast<NodeWrapper*>(wrap_impl(global_object, verify_cast<HTML::HTMLFontElement>(node)));
     if (is<HTML::HTMLFormElement>(node))
-        return static_cast<NodeWrapper*>(wrap_impl(global_object, downcast<HTML::HTMLFormElement>(node)));
+        return static_cast<NodeWrapper*>(wrap_impl(global_object, verify_cast<HTML::HTMLFormElement>(node)));
     if (is<HTML::HTMLFrameElement>(node))
-        return static_cast<NodeWrapper*>(wrap_impl(global_object, downcast<HTML::HTMLFrameElement>(node)));
+        return static_cast<NodeWrapper*>(wrap_impl(global_object, verify_cast<HTML::HTMLFrameElement>(node)));
     if (is<HTML::HTMLFrameSetElement>(node))
-        return static_cast<NodeWrapper*>(wrap_impl(global_object, downcast<HTML::HTMLFrameSetElement>(node)));
+        return static_cast<NodeWrapper*>(wrap_impl(global_object, verify_cast<HTML::HTMLFrameSetElement>(node)));
     if (is<HTML::HTMLHeadElement>(node))
-        return static_cast<NodeWrapper*>(wrap_impl(global_object, downcast<HTML::HTMLHeadElement>(node)));
+        return static_cast<NodeWrapper*>(wrap_impl(global_object, verify_cast<HTML::HTMLHeadElement>(node)));
     if (is<HTML::HTMLHeadingElement>(node))
-        return static_cast<NodeWrapper*>(wrap_impl(global_object, downcast<HTML::HTMLHeadingElement>(node)));
+        return static_cast<NodeWrapper*>(wrap_impl(global_object, verify_cast<HTML::HTMLHeadingElement>(node)));
     if (is<HTML::HTMLHRElement>(node))
-        return static_cast<NodeWrapper*>(wrap_impl(global_object, downcast<HTML::HTMLHRElement>(node)));
+        return static_cast<NodeWrapper*>(wrap_impl(global_object, verify_cast<HTML::HTMLHRElement>(node)));
     if (is<HTML::HTMLHtmlElement>(node))
-        return static_cast<NodeWrapper*>(wrap_impl(global_object, downcast<HTML::HTMLHtmlElement>(node)));
+        return static_cast<NodeWrapper*>(wrap_impl(global_object, verify_cast<HTML::HTMLHtmlElement>(node)));
     if (is<HTML::HTMLIFrameElement>(node))
-        return static_cast<NodeWrapper*>(wrap_impl(global_object, downcast<HTML::HTMLIFrameElement>(node)));
+        return static_cast<NodeWrapper*>(wrap_impl(global_object, verify_cast<HTML::HTMLIFrameElement>(node)));
     if (is<HTML::HTMLImageElement>(node))
-        return static_cast<NodeWrapper*>(wrap_impl(global_object, downcast<HTML::HTMLImageElement>(node)));
+        return static_cast<NodeWrapper*>(wrap_impl(global_object, verify_cast<HTML::HTMLImageElement>(node)));
     if (is<HTML::HTMLInputElement>(node))
-        return static_cast<NodeWrapper*>(wrap_impl(global_object, downcast<HTML::HTMLInputElement>(node)));
+        return static_cast<NodeWrapper*>(wrap_impl(global_object, verify_cast<HTML::HTMLInputElement>(node)));
     if (is<HTML::HTMLLabelElement>(node))
-        return static_cast<NodeWrapper*>(wrap_impl(global_object, downcast<HTML::HTMLLabelElement>(node)));
+        return static_cast<NodeWrapper*>(wrap_impl(global_object, verify_cast<HTML::HTMLLabelElement>(node)));
     if (is<HTML::HTMLLegendElement>(node))
-        return static_cast<NodeWrapper*>(wrap_impl(global_object, downcast<HTML::HTMLLegendElement>(node)));
+        return static_cast<NodeWrapper*>(wrap_impl(global_object, verify_cast<HTML::HTMLLegendElement>(node)));
     if (is<HTML::HTMLLIElement>(node))
-        return static_cast<NodeWrapper*>(wrap_impl(global_object, downcast<HTML::HTMLLIElement>(node)));
+        return static_cast<NodeWrapper*>(wrap_impl(global_object, verify_cast<HTML::HTMLLIElement>(node)));
     if (is<HTML::HTMLLinkElement>(node))
-        return static_cast<NodeWrapper*>(wrap_impl(global_object, downcast<HTML::HTMLLinkElement>(node)));
+        return static_cast<NodeWrapper*>(wrap_impl(global_object, verify_cast<HTML::HTMLLinkElement>(node)));
     if (is<HTML::HTMLMapElement>(node))
-        return static_cast<NodeWrapper*>(wrap_impl(global_object, downcast<HTML::HTMLMapElement>(node)));
+        return static_cast<NodeWrapper*>(wrap_impl(global_object, verify_cast<HTML::HTMLMapElement>(node)));
     if (is<HTML::HTMLMarqueeElement>(node))
-        return static_cast<NodeWrapper*>(wrap_impl(global_object, downcast<HTML::HTMLMarqueeElement>(node)));
+        return static_cast<NodeWrapper*>(wrap_impl(global_object, verify_cast<HTML::HTMLMarqueeElement>(node)));
     if (is<HTML::HTMLMenuElement>(node))
-        return static_cast<NodeWrapper*>(wrap_impl(global_object, downcast<HTML::HTMLMenuElement>(node)));
+        return static_cast<NodeWrapper*>(wrap_impl(global_object, verify_cast<HTML::HTMLMenuElement>(node)));
     if (is<HTML::HTMLMetaElement>(node))
-        return static_cast<NodeWrapper*>(wrap_impl(global_object, downcast<HTML::HTMLMetaElement>(node)));
+        return static_cast<NodeWrapper*>(wrap_impl(global_object, verify_cast<HTML::HTMLMetaElement>(node)));
     if (is<HTML::HTMLMeterElement>(node))
-        return static_cast<NodeWrapper*>(wrap_impl(global_object, downcast<HTML::HTMLMeterElement>(node)));
+        return static_cast<NodeWrapper*>(wrap_impl(global_object, verify_cast<HTML::HTMLMeterElement>(node)));
     if (is<HTML::HTMLModElement>(node))
-        return static_cast<NodeWrapper*>(wrap_impl(global_object, downcast<HTML::HTMLModElement>(node)));
+        return static_cast<NodeWrapper*>(wrap_impl(global_object, verify_cast<HTML::HTMLModElement>(node)));
     if (is<HTML::HTMLObjectElement>(node))
-        return static_cast<NodeWrapper*>(wrap_impl(global_object, downcast<HTML::HTMLObjectElement>(node)));
+        return static_cast<NodeWrapper*>(wrap_impl(global_object, verify_cast<HTML::HTMLObjectElement>(node)));
     if (is<HTML::HTMLOListElement>(node))
-        return static_cast<NodeWrapper*>(wrap_impl(global_object, downcast<HTML::HTMLOListElement>(node)));
+        return static_cast<NodeWrapper*>(wrap_impl(global_object, verify_cast<HTML::HTMLOListElement>(node)));
     if (is<HTML::HTMLOptGroupElement>(node))
-        return static_cast<NodeWrapper*>(wrap_impl(global_object, downcast<HTML::HTMLOptGroupElement>(node)));
+        return static_cast<NodeWrapper*>(wrap_impl(global_object, verify_cast<HTML::HTMLOptGroupElement>(node)));
     if (is<HTML::HTMLOptionElement>(node))
-        return static_cast<NodeWrapper*>(wrap_impl(global_object, downcast<HTML::HTMLOptionElement>(node)));
+        return static_cast<NodeWrapper*>(wrap_impl(global_object, verify_cast<HTML::HTMLOptionElement>(node)));
     if (is<HTML::HTMLOutputElement>(node))
-        return static_cast<NodeWrapper*>(wrap_impl(global_object, downcast<HTML::HTMLOutputElement>(node)));
+        return static_cast<NodeWrapper*>(wrap_impl(global_object, verify_cast<HTML::HTMLOutputElement>(node)));
     if (is<HTML::HTMLParagraphElement>(node))
-        return static_cast<NodeWrapper*>(wrap_impl(global_object, downcast<HTML::HTMLParagraphElement>(node)));
+        return static_cast<NodeWrapper*>(wrap_impl(global_object, verify_cast<HTML::HTMLParagraphElement>(node)));
     if (is<HTML::HTMLParamElement>(node))
-        return static_cast<NodeWrapper*>(wrap_impl(global_object, downcast<HTML::HTMLParamElement>(node)));
+        return static_cast<NodeWrapper*>(wrap_impl(global_object, verify_cast<HTML::HTMLParamElement>(node)));
     if (is<HTML::HTMLPictureElement>(node))
-        return static_cast<NodeWrapper*>(wrap_impl(global_object, downcast<HTML::HTMLPictureElement>(node)));
+        return static_cast<NodeWrapper*>(wrap_impl(global_object, verify_cast<HTML::HTMLPictureElement>(node)));
     if (is<HTML::HTMLPreElement>(node))
-        return static_cast<NodeWrapper*>(wrap_impl(global_object, downcast<HTML::HTMLPreElement>(node)));
+        return static_cast<NodeWrapper*>(wrap_impl(global_object, verify_cast<HTML::HTMLPreElement>(node)));
     if (is<HTML::HTMLProgressElement>(node))
-        return static_cast<NodeWrapper*>(wrap_impl(global_object, downcast<HTML::HTMLProgressElement>(node)));
+        return static_cast<NodeWrapper*>(wrap_impl(global_object, verify_cast<HTML::HTMLProgressElement>(node)));
     if (is<HTML::HTMLQuoteElement>(node))
-        return static_cast<NodeWrapper*>(wrap_impl(global_object, downcast<HTML::HTMLQuoteElement>(node)));
+        return static_cast<NodeWrapper*>(wrap_impl(global_object, verify_cast<HTML::HTMLQuoteElement>(node)));
     if (is<HTML::HTMLScriptElement>(node))
-        return static_cast<NodeWrapper*>(wrap_impl(global_object, downcast<HTML::HTMLScriptElement>(node)));
+        return static_cast<NodeWrapper*>(wrap_impl(global_object, verify_cast<HTML::HTMLScriptElement>(node)));
     if (is<HTML::HTMLSelectElement>(node))
-        return static_cast<NodeWrapper*>(wrap_impl(global_object, downcast<HTML::HTMLSelectElement>(node)));
+        return static_cast<NodeWrapper*>(wrap_impl(global_object, verify_cast<HTML::HTMLSelectElement>(node)));
     if (is<HTML::HTMLSlotElement>(node))
-        return static_cast<NodeWrapper*>(wrap_impl(global_object, downcast<HTML::HTMLSlotElement>(node)));
+        return static_cast<NodeWrapper*>(wrap_impl(global_object, verify_cast<HTML::HTMLSlotElement>(node)));
     if (is<HTML::HTMLSourceElement>(node))
-        return static_cast<NodeWrapper*>(wrap_impl(global_object, downcast<HTML::HTMLSourceElement>(node)));
+        return static_cast<NodeWrapper*>(wrap_impl(global_object, verify_cast<HTML::HTMLSourceElement>(node)));
     if (is<HTML::HTMLSpanElement>(node))
-        return static_cast<NodeWrapper*>(wrap_impl(global_object, downcast<HTML::HTMLSpanElement>(node)));
+        return static_cast<NodeWrapper*>(wrap_impl(global_object, verify_cast<HTML::HTMLSpanElement>(node)));
     if (is<HTML::HTMLStyleElement>(node))
-        return static_cast<NodeWrapper*>(wrap_impl(global_object, downcast<HTML::HTMLStyleElement>(node)));
+        return static_cast<NodeWrapper*>(wrap_impl(global_object, verify_cast<HTML::HTMLStyleElement>(node)));
     if (is<HTML::HTMLTableCaptionElement>(node))
-        return static_cast<NodeWrapper*>(wrap_impl(global_object, downcast<HTML::HTMLTableCaptionElement>(node)));
+        return static_cast<NodeWrapper*>(wrap_impl(global_object, verify_cast<HTML::HTMLTableCaptionElement>(node)));
     if (is<HTML::HTMLTableCellElement>(node))
-        return static_cast<NodeWrapper*>(wrap_impl(global_object, downcast<HTML::HTMLTableCellElement>(node)));
+        return static_cast<NodeWrapper*>(wrap_impl(global_object, verify_cast<HTML::HTMLTableCellElement>(node)));
     if (is<HTML::HTMLTableColElement>(node))
-        return static_cast<NodeWrapper*>(wrap_impl(global_object, downcast<HTML::HTMLTableColElement>(node)));
+        return static_cast<NodeWrapper*>(wrap_impl(global_object, verify_cast<HTML::HTMLTableColElement>(node)));
     if (is<HTML::HTMLTableElement>(node))
-        return static_cast<NodeWrapper*>(wrap_impl(global_object, downcast<HTML::HTMLTableElement>(node)));
+        return static_cast<NodeWrapper*>(wrap_impl(global_object, verify_cast<HTML::HTMLTableElement>(node)));
     if (is<HTML::HTMLTableRowElement>(node))
-        return static_cast<NodeWrapper*>(wrap_impl(global_object, downcast<HTML::HTMLTableRowElement>(node)));
+        return static_cast<NodeWrapper*>(wrap_impl(global_object, verify_cast<HTML::HTMLTableRowElement>(node)));
     if (is<HTML::HTMLTableSectionElement>(node))
-        return static_cast<NodeWrapper*>(wrap_impl(global_object, downcast<HTML::HTMLTableSectionElement>(node)));
+        return static_cast<NodeWrapper*>(wrap_impl(global_object, verify_cast<HTML::HTMLTableSectionElement>(node)));
     if (is<HTML::HTMLTemplateElement>(node))
-        return static_cast<NodeWrapper*>(wrap_impl(global_object, downcast<HTML::HTMLTemplateElement>(node)));
+        return static_cast<NodeWrapper*>(wrap_impl(global_object, verify_cast<HTML::HTMLTemplateElement>(node)));
     if (is<HTML::HTMLTextAreaElement>(node))
-        return static_cast<NodeWrapper*>(wrap_impl(global_object, downcast<HTML::HTMLTextAreaElement>(node)));
+        return static_cast<NodeWrapper*>(wrap_impl(global_object, verify_cast<HTML::HTMLTextAreaElement>(node)));
     if (is<HTML::HTMLTimeElement>(node))
-        return static_cast<NodeWrapper*>(wrap_impl(global_object, downcast<HTML::HTMLTimeElement>(node)));
+        return static_cast<NodeWrapper*>(wrap_impl(global_object, verify_cast<HTML::HTMLTimeElement>(node)));
     if (is<HTML::HTMLTitleElement>(node))
-        return static_cast<NodeWrapper*>(wrap_impl(global_object, downcast<HTML::HTMLTitleElement>(node)));
+        return static_cast<NodeWrapper*>(wrap_impl(global_object, verify_cast<HTML::HTMLTitleElement>(node)));
     if (is<HTML::HTMLTrackElement>(node))
-        return static_cast<NodeWrapper*>(wrap_impl(global_object, downcast<HTML::HTMLTrackElement>(node)));
+        return static_cast<NodeWrapper*>(wrap_impl(global_object, verify_cast<HTML::HTMLTrackElement>(node)));
     if (is<HTML::HTMLUListElement>(node))
-        return static_cast<NodeWrapper*>(wrap_impl(global_object, downcast<HTML::HTMLUListElement>(node)));
+        return static_cast<NodeWrapper*>(wrap_impl(global_object, verify_cast<HTML::HTMLUListElement>(node)));
     if (is<HTML::HTMLUnknownElement>(node))
-        return static_cast<NodeWrapper*>(wrap_impl(global_object, downcast<HTML::HTMLUnknownElement>(node)));
+        return static_cast<NodeWrapper*>(wrap_impl(global_object, verify_cast<HTML::HTMLUnknownElement>(node)));
     if (is<HTML::HTMLVideoElement>(node))
-        return static_cast<NodeWrapper*>(wrap_impl(global_object, downcast<HTML::HTMLVideoElement>(node)));
+        return static_cast<NodeWrapper*>(wrap_impl(global_object, verify_cast<HTML::HTMLVideoElement>(node)));
     if (is<HTML::HTMLElement>(node))
-        return static_cast<NodeWrapper*>(wrap_impl(global_object, downcast<HTML::HTMLElement>(node)));
+        return static_cast<NodeWrapper*>(wrap_impl(global_object, verify_cast<HTML::HTMLElement>(node)));
     if (is<SVG::SVGSVGElement>(node))
-        return static_cast<NodeWrapper*>(wrap_impl(global_object, downcast<SVG::SVGSVGElement>(node)));
+        return static_cast<NodeWrapper*>(wrap_impl(global_object, verify_cast<SVG::SVGSVGElement>(node)));
     if (is<SVG::SVGPathElement>(node))
-        return static_cast<NodeWrapper*>(wrap_impl(global_object, downcast<SVG::SVGPathElement>(node)));
+        return static_cast<NodeWrapper*>(wrap_impl(global_object, verify_cast<SVG::SVGPathElement>(node)));
     if (is<DOM::Element>(node))
-        return static_cast<NodeWrapper*>(wrap_impl(global_object, downcast<DOM::Element>(node)));
+        return static_cast<NodeWrapper*>(wrap_impl(global_object, verify_cast<DOM::Element>(node)));
     if (is<DOM::DocumentFragment>(node))
-        return static_cast<NodeWrapper*>(wrap_impl(global_object, downcast<DOM::DocumentFragment>(node)));
+        return static_cast<NodeWrapper*>(wrap_impl(global_object, verify_cast<DOM::DocumentFragment>(node)));
     if (is<DOM::Comment>(node))
-        return static_cast<NodeWrapper*>(wrap_impl(global_object, downcast<DOM::Comment>(node)));
+        return static_cast<NodeWrapper*>(wrap_impl(global_object, verify_cast<DOM::Comment>(node)));
     if (is<DOM::Text>(node))
-        return static_cast<NodeWrapper*>(wrap_impl(global_object, downcast<DOM::Text>(node)));
+        return static_cast<NodeWrapper*>(wrap_impl(global_object, verify_cast<DOM::Text>(node)));
     if (is<DOM::CharacterData>(node))
-        return static_cast<NodeWrapper*>(wrap_impl(global_object, downcast<DOM::CharacterData>(node)));
+        return static_cast<NodeWrapper*>(wrap_impl(global_object, verify_cast<DOM::CharacterData>(node)));
     return static_cast<NodeWrapper*>(wrap_impl(global_object, node));
 }
 

Userland/Libraries/LibWeb/CSS/CSSStyleSheet.h

@@ -36,9 +36,9 @@ public:
     {
         for (auto& rule : m_rules)
             if (rule.type() == CSSRule::Type::Style) {
-                callback(downcast<CSSStyleRule>(rule));
+                callback(verify_cast<CSSStyleRule>(rule));
             } else if (rule.type() == CSSRule::Type::Import) {
-                const auto& import_rule = downcast<CSSImportRule>(rule);
+                const auto& import_rule = verify_cast<CSSImportRule>(rule);
                 if (import_rule.has_import_result())
                     import_rule.loaded_style_sheet()->for_each_effective_style_rule(callback);
             }
@@ -49,7 +49,7 @@ public:
     {
         for (auto& rule : m_rules)
             if (rule.type() == CSSRule::Type::Import) {
-                auto& import_rule = downcast<CSSImportRule>(rule);
+                auto& import_rule = verify_cast<CSSImportRule>(rule);
                 if (!import_rule.has_import_result()) {
                     callback(import_rule);
                     return true;

Userland/Libraries/LibWeb/CSS/SelectorEngine.cpp

@@ -212,7 +212,7 @@ static bool matches(const CSS::Selector& selector, int component_list_index, con
         for (auto* ancestor = element.parent(); ancestor; ancestor = ancestor->parent()) {
             if (!is<DOM::Element>(*ancestor))
                 continue;
-            if (matches(selector, component_list_index - 1, downcast<DOM::Element>(*ancestor)))
+            if (matches(selector, component_list_index - 1, verify_cast<DOM::Element>(*ancestor)))
                 return true;
         }
         return false;
@@ -220,7 +220,7 @@ static bool matches(const CSS::Selector& selector, int component_list_index, con
         VERIFY(component_list_index != 0);
         if (!element.parent() || !is<DOM::Element>(*element.parent()))
             return false;
-        return matches(selector, component_list_index - 1, downcast<DOM::Element>(*element.parent()));
+        return matches(selector, component_list_index - 1, verify_cast<DOM::Element>(*element.parent()));
     case CSS::Selector::ComplexSelector::Relation::AdjacentSibling:
         VERIFY(component_list_index != 0);
         if (auto* sibling = element.previous_element_sibling())

Userland/Libraries/LibWeb/CSS/StyleProperties.cpp

@@ -278,11 +278,11 @@ Optional<float> StyleProperties::flex_grow_factor() const
     auto value = property(CSS::PropertyID::FlexGrow);
     if (!value.has_value())
         return {};
-    if (value.value()->is_length() && downcast<CSS::LengthStyleValue>(value.value().ptr())->to_length().raw_value() == 0)
+    if (value.value()->is_length() && verify_cast<CSS::LengthStyleValue>(value.value().ptr())->to_length().raw_value() == 0)
         return { 0 };
     if (!value.value()->is_numeric())
         return {};
-    auto numeric = downcast<CSS::NumericStyleValue>(value.value().ptr());
+    auto numeric = verify_cast<CSS::NumericStyleValue>(value.value().ptr());
     return numeric->value();
 }
 
@@ -291,11 +291,11 @@ Optional<float> StyleProperties::flex_shrink_factor() const
     auto value = property(CSS::PropertyID::FlexShrink);
     if (!value.has_value())
         return {};
-    if (value.value()->is_length() && downcast<CSS::LengthStyleValue>(value.value().ptr())->to_length().raw_value() == 0)
+    if (value.value()->is_length() && verify_cast<CSS::LengthStyleValue>(value.value().ptr())->to_length().raw_value() == 0)
         return { 0 };
     if (!value.value()->is_numeric())
         return {};
-    auto numeric = downcast<CSS::NumericStyleValue>(value.value().ptr());
+    auto numeric = verify_cast<CSS::NumericStyleValue>(value.value().ptr());
     return numeric->value();
 }
 

Userland/Libraries/LibWeb/DOM/Document.cpp

@@ -188,7 +188,7 @@ HTML::HTMLHtmlElement* Document::html_element()
 {
     auto* html = document_element();
     if (is<HTML::HTMLHtmlElement>(html))
-        return downcast<HTML::HTMLHtmlElement>(html);
+        return verify_cast<HTML::HTMLHtmlElement>(html);
     return nullptr;
 }
 
@@ -423,7 +423,7 @@ static void update_style_recursively(DOM::Node& node)
     node.for_each_child([&](auto& child) {
         if (child.needs_style_update()) {
             if (is<Element>(child))
-                downcast<Element>(child).recompute_style();
+                verify_cast<Element>(child).recompute_style();
             child.set_needs_style_update(false);
         }
         if (child.child_needs_style_update()) {
@@ -836,7 +836,7 @@ ExceptionOr<NonnullRefPtr<Node>> Document::adopt_node_binding(NonnullRefPtr<Node
     if (is<ShadowRoot>(*node))
         return DOM::HierarchyRequestError::create("Cannot adopt a shadow root into a document");
 
-    if (is<DocumentFragment>(*node) && downcast<DocumentFragment>(*node).host())
+    if (is<DocumentFragment>(*node) && verify_cast<DocumentFragment>(*node).host())
         return node;
 
     adopt_node(*node);

Userland/Libraries/LibWeb/DOM/Element.cpp

@@ -290,7 +290,7 @@ String Element::inner_html() const
     Function<void(const Node&)> recurse = [&](auto& node) {
         for (auto* child = node.first_child(); child; child = child->next_sibling()) {
             if (child->is_element()) {
-                auto& element = downcast<Element>(*child);
+                auto& element = verify_cast<Element>(*child);
                 builder.append('<');
                 builder.append(element.local_name());
                 element.for_each_attribute([&](auto& name, auto& value) {
@@ -311,7 +311,7 @@ String Element::inner_html() const
                 builder.append('>');
             }
             if (child->is_text()) {
-                auto& text = downcast<Text>(*child);
+                auto& text = verify_cast<Text>(*child);
                 builder.append(escape_string(text.data(), false));
             }
             // FIXME: Also handle Comment, ProcessingInstruction, DocumentType

Userland/Libraries/LibWeb/DOM/Event.cpp

@@ -18,11 +18,11 @@ void Event::append_to_path(EventTarget& invocation_target, RefPtr<EventTarget> s
     bool root_of_closed_tree = false;
 
     if (is<Node>(invocation_target)) {
-        auto& invocation_target_node = downcast<Node>(invocation_target);
+        auto& invocation_target_node = verify_cast<Node>(invocation_target);
         if (is<ShadowRoot>(invocation_target_node.root()))
             invocation_target_in_shadow_tree = true;
         if (is<ShadowRoot>(invocation_target_node)) {
-            auto& invocation_target_shadow_root = downcast<ShadowRoot>(invocation_target_node);
+            auto& invocation_target_shadow_root = verify_cast<ShadowRoot>(invocation_target_node);
             root_of_closed_tree = invocation_target_shadow_root.closed();
         }
     }

Userland/Libraries/LibWeb/DOM/EventDispatcher.cpp

@@ -35,14 +35,14 @@ static EventTarget* retarget(EventTarget* left, [[maybe_unused]] EventTarget* ri
         if (!is<Node>(left))
             return left;
 
-        auto* left_node = downcast<Node>(left);
+        auto* left_node = verify_cast<Node>(left);
         auto* left_root = left_node->root();
         if (!is<ShadowRoot>(left_root))
             return left;
 
         // FIXME: If right is a node and left’s root is a shadow-including inclusive ancestor of right, return left.
 
-        auto* left_shadow_root = downcast<ShadowRoot>(left_root);
+        auto* left_shadow_root = verify_cast<ShadowRoot>(left_root);
         left = left_shadow_root->host();
     }
 }
@@ -76,7 +76,7 @@ bool EventDispatcher::inner_invoke(Event& event, Vector<EventTarget::EventListen
         RefPtr<Event> current_event;
 
         if (is<Bindings::WindowObject>(global)) {
-            auto& bindings_window_global = downcast<Bindings::WindowObject>(global);
+            auto& bindings_window_global = verify_cast<Bindings::WindowObject>(global);
             auto& window_impl = bindings_window_global.impl();
             current_event = window_impl.current_event();
             if (!invocation_target_in_shadow_tree)
@@ -97,7 +97,7 @@ bool EventDispatcher::inner_invoke(Event& event, Vector<EventTarget::EventListen
 
         event.set_in_passive_listener(false);
         if (is<Bindings::WindowObject>(global)) {
-            auto& bindings_window_global = downcast<Bindings::WindowObject>(global);
+            auto& bindings_window_global = verify_cast<Bindings::WindowObject>(global);
             auto& window_impl = bindings_window_global.impl();
             window_impl.set_current_event(current_event);
         }
@@ -162,7 +162,7 @@ bool EventDispatcher::dispatch(NonnullRefPtr<EventTarget> target, NonnullRefPtr<
         target_override = target;
     } else {
         // NOTE: This can be done because legacy_target_override is only set for events targeted at Window.
-        target_override = downcast<Window>(*target).document();
+        target_override = verify_cast<Window>(*target).document();
     }
 
     RefPtr<EventTarget> activation_target;
@@ -232,13 +232,13 @@ bool EventDispatcher::dispatch(NonnullRefPtr<EventTarget> target, NonnullRefPtr<
         VERIFY(clear_targets_struct.has_value());
 
         if (is<Node>(clear_targets_struct.value().shadow_adjusted_target.ptr())) {
-            auto& shadow_adjusted_target_node = downcast<Node>(*clear_targets_struct.value().shadow_adjusted_target);
+            auto& shadow_adjusted_target_node = verify_cast<Node>(*clear_targets_struct.value().shadow_adjusted_target);
             if (is<ShadowRoot>(shadow_adjusted_target_node.root()))
                 clear_targets = true;
         }
 
         if (!clear_targets && is<Node>(clear_targets_struct.value().related_target.ptr())) {
-            auto& related_target_node = downcast<Node>(*clear_targets_struct.value().related_target);
+            auto& related_target_node = verify_cast<Node>(*clear_targets_struct.value().related_target);
             if (is<ShadowRoot>(related_target_node.root()))
                 clear_targets = true;
         }
@@ -246,7 +246,7 @@ bool EventDispatcher::dispatch(NonnullRefPtr<EventTarget> target, NonnullRefPtr<
         if (!clear_targets) {
             for (auto touch_target : clear_targets_struct.value().touch_target_list) {
                 if (is<Node>(*touch_target.ptr())) {
-                    auto& touch_target_node = downcast<Node>(*touch_target.ptr());
+                    auto& touch_target_node = verify_cast<Node>(*touch_target.ptr());
                     if (is<ShadowRoot>(touch_target_node.root())) {
                         clear_targets = true;
                         break;

Userland/Libraries/LibWeb/DOM/Node.cpp

@@ -51,8 +51,8 @@ Node::~Node()
 const HTML::HTMLAnchorElement* Node::enclosing_link_element() const
 {
     for (auto* node = this; node; node = node->parent()) {
-        if (is<HTML::HTMLAnchorElement>(*node) && downcast<HTML::HTMLAnchorElement>(*node).has_attribute(HTML::AttributeNames::href))
-            return downcast<HTML::HTMLAnchorElement>(node);
+        if (is<HTML::HTMLAnchorElement>(*node) && verify_cast<HTML::HTMLAnchorElement>(*node).has_attribute(HTML::AttributeNames::href))
+            return verify_cast<HTML::HTMLAnchorElement>(node);
     }
     return nullptr;
 }
@@ -65,8 +65,8 @@ const HTML::HTMLElement* Node::enclosing_html_element() const
 const HTML::HTMLElement* Node::enclosing_html_element_with_attribute(const FlyString& attribute) const
 {
     for (auto* node = this; node; node = node->parent()) {
-        if (is<HTML::HTMLElement>(*node) && downcast<HTML::HTMLElement>(*node).has_attribute(attribute))
-            return downcast<HTML::HTMLElement>(node);
+        if (is<HTML::HTMLElement>(*node) && verify_cast<HTML::HTMLElement>(*node).has_attribute(attribute))
+            return verify_cast<HTML::HTMLElement>(node);
     }
     return nullptr;
 }
@@ -83,7 +83,7 @@ String Node::text_content() const
 void Node::set_text_content(const String& content)
 {
     if (is_text()) {
-        downcast<Text>(this)->set_data(content);
+        verify_cast<Text>(this)->set_data(content);
     } else {
         remove_all_children();
         append_child(document().create_text_node(content));
@@ -123,9 +123,9 @@ String Node::child_text_content() const
         return String::empty();
 
     StringBuilder builder;
-    downcast<ParentNode>(*this).for_each_child([&](auto& child) {
+    verify_cast<ParentNode>(*this).for_each_child([&](auto& child) {
         if (is<Text>(child))
-            builder.append(downcast<Text>(child).text_content());
+            builder.append(verify_cast<Text>(child).text_content());
     });
     return builder.build();
 }
@@ -142,7 +142,7 @@ Node* Node::shadow_including_root()
 {
     auto node_root = root();
     if (is<ShadowRoot>(node_root))
-        return downcast<ShadowRoot>(node_root)->host()->shadow_including_root();
+        return verify_cast<ShadowRoot>(node_root)->host()->shadow_including_root();
     return node_root;
 }
 
@@ -155,14 +155,14 @@ Element* Node::parent_element()
 {
     if (!parent() || !is<Element>(parent()))
         return nullptr;
-    return downcast<Element>(parent());
+    return verify_cast<Element>(parent());
 }
 
 const Element* Node::parent_element() const
 {
     if (!parent() || !is<Element>(parent()))
         return nullptr;
-    return downcast<Element>(parent());
+    return verify_cast<Element>(parent());
 }
 
 // https://dom.spec.whatwg.org/#concept-node-ensure-pre-insertion-validity
@@ -187,7 +187,7 @@ ExceptionOr<void> Node::ensure_pre_insertion_validity(NonnullRefPtr<Node> node,
 
     if (is<Document>(this)) {
         if (is<DocumentFragment>(*node)) {
-            auto node_element_child_count = downcast<DocumentFragment>(*node).child_element_count();
+            auto node_element_child_count = verify_cast<DocumentFragment>(*node).child_element_count();
             if ((node_element_child_count > 1 || node->has_child_of_type<Text>())
                 || (node_element_child_count == 1 && (has_child_of_type<Element>() || is<DocumentType>(child.ptr()) /* FIXME: or child is non-null and a doctype is following child. */))) {
                 return DOM::HierarchyRequestError::create("Invalid node type for insertion");
@@ -209,7 +209,7 @@ void Node::insert_before(NonnullRefPtr<Node> node, RefPtr<Node> child, bool supp
 {
     NonnullRefPtrVector<Node> nodes;
     if (is<DocumentFragment>(*node))
-        nodes = downcast<DocumentFragment>(*node).child_nodes();
+        nodes = verify_cast<DocumentFragment>(*node).child_nodes();
     else
         nodes.append(node);
 
@@ -369,7 +369,7 @@ ExceptionOr<NonnullRefPtr<Node>> Node::replace_child(NonnullRefPtr<Node> node, N
 
     if (is<Document>(this)) {
         if (is<DocumentFragment>(*node)) {
-            auto node_element_child_count = downcast<DocumentFragment>(*node).child_element_count();
+            auto node_element_child_count = verify_cast<DocumentFragment>(*node).child_element_count();
             if ((node_element_child_count > 1 || node->has_child_of_type<Text>())
                 || (node_element_child_count == 1 && (first_child_of_type<Element>() != child /* FIXME: or a doctype is following child. */))) {
                 return DOM::HierarchyRequestError::create("Invalid node type for insertion");
@@ -411,7 +411,7 @@ NonnullRefPtr<Node> Node::clone_node(Document* document, bool clone_children) co
         document = m_document;
     RefPtr<Node> copy;
     if (is<Element>(this)) {
-        auto& element = *downcast<Element>(this);
+        auto& element = *verify_cast<Element>(this);
         auto qualified_name = QualifiedName(element.local_name(), element.prefix(), element.namespace_());
         auto element_copy = adopt_ref(*new Element(*document, move(qualified_name)));
         element.for_each_attribute([&](auto& name, auto& value) {
@@ -419,7 +419,7 @@ NonnullRefPtr<Node> Node::clone_node(Document* document, bool clone_children) co
         });
         copy = move(element_copy);
     } else if (is<Document>(this)) {
-        auto document_ = downcast<Document>(this);
+        auto document_ = verify_cast<Document>(this);
         auto document_copy = Document::create(document_->url());
         document_copy->set_encoding(document_->encoding());
         document_copy->set_content_type(document_->content_type());
@@ -428,22 +428,22 @@ NonnullRefPtr<Node> Node::clone_node(Document* document, bool clone_children) co
         // FIXME: Set type ("xml" or "html")
         copy = move(document_copy);
     } else if (is<DocumentType>(this)) {
-        auto document_type = downcast<DocumentType>(this);
+        auto document_type = verify_cast<DocumentType>(this);
         auto document_type_copy = adopt_ref(*new DocumentType(*document));
         document_type_copy->set_name(document_type->name());
         document_type_copy->set_public_id(document_type->public_id());
         document_type_copy->set_system_id(document_type->system_id());
         copy = move(document_type_copy);
     } else if (is<Text>(this)) {
-        auto text = downcast<Text>(this);
+        auto text = verify_cast<Text>(this);
         auto text_copy = adopt_ref(*new Text(*document, text->data()));
         copy = move(text_copy);
     } else if (is<Comment>(this)) {
-        auto comment = downcast<Comment>(this);
+        auto comment = verify_cast<Comment>(this);
         auto comment_copy = adopt_ref(*new Comment(*document, comment->data()));
         copy = move(comment_copy);
     } else if (is<ProcessingInstruction>(this)) {
-        auto processing_instruction = downcast<ProcessingInstruction>(this);
+        auto processing_instruction = verify_cast<ProcessingInstruction>(this);
         auto processing_instruction_copy = adopt_ref(*new ProcessingInstruction(*document, processing_instruction->data(), processing_instruction->target()));
         copy = move(processing_instruction_copy);
     } else {
@@ -490,7 +490,7 @@ JS::Object* Node::create_wrapper(JS::GlobalObject& global_object)
 void Node::removed_last_ref()
 {
     if (is<Document>(*this)) {
-        downcast<Document>(*this).removed_last_ref();
+        verify_cast<Document>(*this).removed_last_ref();
         return;
     }
     m_deletion_has_begun = true;
@@ -534,8 +534,8 @@ void Node::inserted()
 ParentNode* Node::parent_or_shadow_host()
 {
     if (is<ShadowRoot>(*this))
-        return downcast<ShadowRoot>(*this).host();
-    return downcast<ParentNode>(parent());
+        return verify_cast<ShadowRoot>(*this).host();
+    return verify_cast<ParentNode>(parent());
 }
 
 NonnullRefPtrVector<Node> Node::child_nodes() const
@@ -595,7 +595,7 @@ u16 Node::compare_document_position(RefPtr<Node> other)
 // https://dom.spec.whatwg.org/#concept-tree-host-including-inclusive-ancestor
 bool Node::is_host_including_inclusive_ancestor_of(const Node& other) const
 {
-    return is_inclusive_ancestor_of(other) || (is<DocumentFragment>(other.root()) && downcast<DocumentFragment>(other.root())->host() && is_inclusive_ancestor_of(*downcast<DocumentFragment>(other.root())->host().ptr()));
+    return is_inclusive_ancestor_of(other) || (is<DocumentFragment>(other.root()) && verify_cast<DocumentFragment>(other.root())->host() && is_inclusive_ancestor_of(*verify_cast<DocumentFragment>(other.root())->host().ptr()));
 }
 
 // https://dom.spec.whatwg.org/#dom-node-ownerdocument

Userland/Libraries/LibWeb/DOM/NonDocumentTypeChildNode.h

@@ -19,7 +19,7 @@ public:
     {
         for (auto* sibling = static_cast<NodeType*>(this)->previous_sibling(); sibling; sibling = sibling->previous_sibling()) {
             if (is<Element>(*sibling))
-                return downcast<Element>(sibling);
+                return verify_cast<Element>(sibling);
         }
         return nullptr;
     }
@@ -28,7 +28,7 @@ public:
     {
         for (auto* sibling = static_cast<NodeType*>(this)->next_sibling(); sibling; sibling = sibling->next_sibling()) {
             if (is<Element>(*sibling))
-                return downcast<Element>(sibling);
+                return verify_cast<Element>(sibling);
         }
         return nullptr;
     }
@@ -37,7 +37,7 @@ public:
     {
         for (auto* node = static_cast<NodeType*>(this)->next_in_pre_order(); node; node = node->next_in_pre_order()) {
             if (is<Element>(*node))
-                return downcast<Element>(node);
+                return verify_cast<Element>(node);
         }
         return nullptr;
     }

Userland/Libraries/LibWeb/DOM/Position.cpp

@@ -34,7 +34,7 @@ bool Position::increment_offset()
     if (!is<DOM::Text>(*m_node))
         return false;
 
-    auto& node = downcast<DOM::Text>(*m_node);
+    auto& node = verify_cast<DOM::Text>(*m_node);
     auto text = Utf8View(node.data());
 
     for (auto iterator = text.begin(); !iterator.done(); ++iterator) {
@@ -53,7 +53,7 @@ bool Position::decrement_offset()
     if (m_offset == 0 || !is<DOM::Text>(*m_node))
         return false;
 
-    auto& node = downcast<DOM::Text>(*m_node);
+    auto& node = verify_cast<DOM::Text>(*m_node);
     auto text = Utf8View(node.data());
 
     size_t last_smaller_offset = 0;
@@ -76,7 +76,7 @@ bool Position::offset_is_at_end_of_node() const
     if (!is<DOM::Text>(*m_node))
         return false;
 
-    auto& node = downcast<DOM::Text>(*m_node);
+    auto& node = verify_cast<DOM::Text>(*m_node);
     auto text = node.data();
     return m_offset == text.length();
 }

Userland/Libraries/LibWeb/DOM/ShadowRoot.cpp

@@ -19,7 +19,7 @@ ShadowRoot::ShadowRoot(Document& document, Element& host)
 EventTarget* ShadowRoot::get_parent(const Event& event)
 {
     if (!event.composed()) {
-        auto& events_first_invocation_target = downcast<Node>(*event.path().first().invocation_target);
+        auto& events_first_invocation_target = verify_cast<Node>(*event.path().first().invocation_target);
         if (events_first_invocation_target.root() == this)
             return nullptr;
     }

Userland/Libraries/LibWeb/DOMTreeModel.cpp

@@ -110,10 +110,10 @@ GUI::Variant DOMTreeModel::data(const GUI::ModelIndex& index, GUI::ModelRole rol
     }
     if (role == GUI::ModelRole::Display) {
         if (node.is_text())
-            return with_whitespace_collapsed(downcast<DOM::Text>(node).data());
+            return with_whitespace_collapsed(verify_cast<DOM::Text>(node).data());
         if (!node.is_element())
             return node.node_name();
-        auto& element = downcast<DOM::Element>(node);
+        auto& element = verify_cast<DOM::Element>(node);
         StringBuilder builder;
         builder.append('<');
         builder.append(element.local_name());

Userland/Libraries/LibWeb/Dump.cpp

@@ -40,19 +40,19 @@ void dump_tree(StringBuilder& builder, const DOM::Node& node)
     for (int i = 0; i < indent; ++i)
         builder.append("  ");
     if (is<DOM::Element>(node)) {
-        builder.appendff("<{}", downcast<DOM::Element>(node).local_name());
-        downcast<DOM::Element>(node).for_each_attribute([&](auto& name, auto& value) {
+        builder.appendff("<{}", verify_cast<DOM::Element>(node).local_name());
+        verify_cast<DOM::Element>(node).for_each_attribute([&](auto& name, auto& value) {
             builder.appendff(" {}={}", name, value);
         });
         builder.append(">\n");
     } else if (is<DOM::Text>(node)) {
-        builder.appendff("\"{}\"\n", downcast<DOM::Text>(node).data());
+        builder.appendff("\"{}\"\n", verify_cast<DOM::Text>(node).data());
     } else {
         builder.appendff("{}\n", node.node_name());
     }
     ++indent;
-    if (is<DOM::Element>(node) && downcast<DOM::Element>(node).shadow_root()) {
-        dump_tree(*downcast<DOM::Element>(node).shadow_root());
+    if (is<DOM::Element>(node) && verify_cast<DOM::Element>(node).shadow_root()) {
+        dump_tree(*verify_cast<DOM::Element>(node).shadow_root());
     }
     if (is<DOM::ParentNode>(node)) {
         if (!is<HTML::HTMLTemplateElement>(node)) {
@@ -60,7 +60,7 @@ void dump_tree(StringBuilder& builder, const DOM::Node& node)
                 dump_tree(child);
             });
         } else {
-            auto& template_element = downcast<HTML::HTMLTemplateElement>(node);
+            auto& template_element = verify_cast<HTML::HTMLTemplateElement>(node);
             dump_tree(template_element.content());
         }
     }
@@ -84,13 +84,13 @@ void dump_tree(StringBuilder& builder, const Layout::Node& layout_node, bool sho
     if (layout_node.is_anonymous())
         tag_name = "(anonymous)";
     else if (is<DOM::Element>(layout_node.dom_node()))
-        tag_name = downcast<DOM::Element>(*layout_node.dom_node()).local_name();
+        tag_name = verify_cast<DOM::Element>(*layout_node.dom_node()).local_name();
     else
         tag_name = layout_node.dom_node()->node_name();
 
     String identifier = "";
     if (layout_node.dom_node() && is<DOM::Element>(*layout_node.dom_node())) {
-        auto& element = downcast<DOM::Element>(*layout_node.dom_node());
+        auto& element = verify_cast<DOM::Element>(*layout_node.dom_node());
         StringBuilder builder;
         auto id = element.attribute(HTML::AttributeNames::id);
         if (!id.is_empty()) {
@@ -139,7 +139,7 @@ void dump_tree(StringBuilder& builder, const Layout::Node& layout_node, bool sho
             builder.appendff(" @{:p}", &layout_node);
         builder.append("\n");
     } else {
-        auto& box = downcast<Layout::Box>(layout_node);
+        auto& box = verify_cast<Layout::Box>(layout_node);
         builder.appendff("{}{}{} <{}{}{}{}> ",
             box_color_on,
             box.class_name().substring_view(13),
@@ -231,13 +231,13 @@ void dump_tree(StringBuilder& builder, const Layout::Node& layout_node, bool sho
         }
     }
 
-    if (show_specified_style && layout_node.dom_node() && layout_node.dom_node()->is_element() && downcast<DOM::Element>(layout_node.dom_node())->specified_css_values()) {
+    if (show_specified_style && layout_node.dom_node() && layout_node.dom_node()->is_element() && verify_cast<DOM::Element>(layout_node.dom_node())->specified_css_values()) {
         struct NameAndValue {
             String name;
             String value;
         };
         Vector<NameAndValue> properties;
-        downcast<DOM::Element>(*layout_node.dom_node()).specified_css_values()->for_each_property([&](auto property_id, auto& value) {
+        verify_cast<DOM::Element>(*layout_node.dom_node()).specified_css_values()->for_each_property([&](auto property_id, auto& value) {
             properties.append({ CSS::string_from_property_id(property_id), value.to_string() });
         });
         quick_sort(properties, [](auto& a, auto& b) { return a.name < b.name; });
@@ -417,10 +417,10 @@ void dump_rule(StringBuilder& builder, const CSS::CSSRule& rule)
     builder.appendff("{}:\n", rule.class_name());
     switch (rule.type()) {
     case CSS::CSSRule::Type::Style:
-        dump_style_rule(builder, downcast<const CSS::CSSStyleRule>(rule));
+        dump_style_rule(builder, verify_cast<const CSS::CSSStyleRule>(rule));
         break;
     case CSS::CSSRule::Type::Import:
-        dump_import_rule(builder, downcast<const CSS::CSSImportRule>(rule));
+        dump_import_rule(builder, verify_cast<const CSS::CSSImportRule>(rule));
         break;
     default:
         VERIFY_NOT_REACHED();

Userland/Libraries/LibWeb/HTML/HTMLElement.cpp

@@ -110,7 +110,7 @@ String HTMLElement::inner_text()
     Function<void(const Layout::Node&)> recurse = [&](auto& node) {
         for (auto* child = node.first_child(); child; child = child->next_sibling()) {
             if (is<Layout::TextNode>(child))
-                builder.append(downcast<Layout::TextNode>(*child).text_for_rendering());
+                builder.append(verify_cast<Layout::TextNode>(*child).text_for_rendering());
             if (is<Layout::BreakNode>(child))
                 builder.append('\n');
             recurse(*child);

Userland/Libraries/LibWeb/HTML/HTMLFormElement.cpp

@@ -98,7 +98,7 @@ void HTMLFormElement::submit_form(RefPtr<HTMLElement> submitter, bool from_submi
     Vector<URLQueryParam> parameters;
 
     for_each_in_inclusive_subtree_of_type<HTMLInputElement>([&](auto& node) {
-        auto& input = downcast<HTMLInputElement>(node);
+        auto& input = verify_cast<HTMLInputElement>(node);
         if (!input.name().is_null() && (input.type() != "submit" || &input == submitter))
             parameters.append({ input.name(), input.value() });
         return IterationDecision::Continue;

Userland/Libraries/LibWeb/HTML/HTMLStyleElement.cpp

@@ -30,7 +30,7 @@ void HTMLStyleElement::children_changed()
     StringBuilder builder;
     for_each_child([&](auto& child) {
         if (is<DOM::Text>(child))
-            builder.append(downcast<DOM::Text>(child).text_content());
+            builder.append(verify_cast<DOM::Text>(child).text_content());
     });
     m_css_loader.load_from_text(builder.to_string());
 

Userland/Libraries/LibWeb/HTML/HTMLTableElement.cpp

@@ -84,7 +84,7 @@ RefPtr<HTMLTableSectionElement> HTMLTableElement::t_head()
 {
     for (auto* child = first_child(); child; child = child->next_sibling()) {
         if (is<HTMLTableSectionElement>(*child)) {
-            auto table_section_element = &downcast<HTMLTableSectionElement>(*child);
+            auto table_section_element = &verify_cast<HTMLTableSectionElement>(*child);
             if (table_section_element->tag_name() == TagNames::thead)
                 return table_section_element;
         }
@@ -110,7 +110,7 @@ DOM::ExceptionOr<void> HTMLTableElement::set_t_head(HTMLTableSectionElement& the
         if (is<HTMLTableCaptionElement>(*child))
             continue;
         if (is<HTMLTableColElement>(*child)) {
-            auto table_col_element = &downcast<HTMLTableColElement>(*child);
+            auto table_col_element = &verify_cast<HTMLTableColElement>(*child);
             if (table_col_element->tag_name() == TagNames::colgroup)
                 continue;
         }
@@ -141,7 +141,7 @@ NonnullRefPtr<HTMLTableSectionElement> HTMLTableElement::create_t_head()
         if (is<HTMLTableCaptionElement>(*child))
             continue;
         if (is<HTMLTableColElement>(*child)) {
-            auto table_col_element = &downcast<HTMLTableColElement>(*child);
+            auto table_col_element = &verify_cast<HTMLTableColElement>(*child);
             if (table_col_element->tag_name() == TagNames::colgroup)
                 continue;
         }
@@ -168,7 +168,7 @@ RefPtr<HTMLTableSectionElement> HTMLTableElement::t_foot()
 {
     for (auto* child = first_child(); child; child = child->next_sibling()) {
         if (is<HTMLTableSectionElement>(*child)) {
-            auto table_section_element = &downcast<HTMLTableSectionElement>(*child);
+            auto table_section_element = &verify_cast<HTMLTableSectionElement>(*child);
             if (table_section_element->tag_name() == TagNames::tfoot)
                 return table_section_element;
         }
@@ -228,7 +228,7 @@ NonnullRefPtr<HTMLTableSectionElement> HTMLTableElement::create_t_body()
         if (!is<HTMLElement>(*child))
             continue;
         if (is<HTMLTableSectionElement>(*child)) {
-            auto table_section_element = &downcast<HTMLTableSectionElement>(*child);
+            auto table_section_element = &verify_cast<HTMLTableSectionElement>(*child);
             if (table_section_element->tag_name() == TagNames::tbody) {
                 // We have found an element which is a <tbody> we'll insert after this
                 child_to_append_after = child->next_sibling();

Userland/Libraries/LibWeb/HTML/Parser/HTMLDocumentParser.cpp

@@ -411,7 +411,7 @@ HTMLDocumentParser::AdjustedInsertionLocation HTMLDocumentParser::find_appropria
         auto last_table = m_stack_of_open_elements.last_element_with_tag_name(HTML::TagNames::table);
         if (last_template.element && (!last_table.element || last_template.index > last_table.index)) {
             // This returns the template content, so no need to check the parent is a template.
-            return { downcast<HTMLTemplateElement>(last_template.element)->content(), nullptr };
+            return { verify_cast<HTMLTemplateElement>(last_template.element)->content(), nullptr };
         }
         if (!last_table.element) {
             VERIFY(m_parsing_fragment);
@@ -428,7 +428,7 @@ HTMLDocumentParser::AdjustedInsertionLocation HTMLDocumentParser::find_appropria
     }
 
     if (is<HTMLTemplateElement>(*adjusted_insertion_location.parent))
-        return { downcast<HTMLTemplateElement>(*adjusted_insertion_location.parent).content(), nullptr };
+        return { verify_cast<HTMLTemplateElement>(*adjusted_insertion_location.parent).content(), nullptr };
 
     return adjusted_insertion_location;
 }
@@ -497,7 +497,7 @@ void HTMLDocumentParser::handle_before_head(HTMLToken& token)
 
     if (token.is_start_tag() && token.tag_name() == HTML::TagNames::head) {
         auto element = insert_html_element(token);
-        m_head_element = downcast<HTMLHeadElement>(*element);
+        m_head_element = verify_cast<HTMLHeadElement>(*element);
         m_insertion_mode = InsertionMode::InHead;
         return;
     }
@@ -512,7 +512,7 @@ void HTMLDocumentParser::handle_before_head(HTMLToken& token)
     }
 
 AnythingElse:
-    m_head_element = downcast<HTMLHeadElement>(*insert_html_element(HTMLToken::make_start_tag(HTML::TagNames::head)));
+    m_head_element = verify_cast<HTMLHeadElement>(*insert_html_element(HTMLToken::make_start_tag(HTML::TagNames::head)));
     m_insertion_mode = InsertionMode::InHead;
     process_using_the_rules_for(InsertionMode::InHead, token);
     return;
@@ -583,7 +583,7 @@ void HTMLDocumentParser::handle_in_head(HTMLToken& token)
     if (token.is_start_tag() && token.tag_name() == HTML::TagNames::script) {
         auto adjusted_insertion_location = find_appropriate_place_for_inserting_node();
         auto element = create_element_for(token, Namespace::HTML);
-        auto& script_element = downcast<HTMLScriptElement>(*element);
+        auto& script_element = verify_cast<HTMLScriptElement>(*element);
         script_element.set_parser_document({}, document());
         script_element.set_non_blocking({}, false);
 
@@ -706,7 +706,7 @@ DOM::Text* HTMLDocumentParser::find_character_insertion_node()
     if (adjusted_insertion_location.parent->is_document())
         return nullptr;
     if (adjusted_insertion_location.parent->last_child() && adjusted_insertion_location.parent->last_child()->is_text())
-        return downcast<DOM::Text>(adjusted_insertion_location.parent->last_child());
+        return verify_cast<DOM::Text>(adjusted_insertion_location.parent->last_child());
     auto new_text_node = adopt_ref(*new DOM::Text(document(), ""));
     adjusted_insertion_location.parent->append_child(new_text_node);
     return new_text_node;
@@ -1268,7 +1268,7 @@ void HTMLDocumentParser::handle_in_body(HTMLToken& token)
             close_a_p_element();
         auto element = insert_html_element(token);
         if (!m_stack_of_open_elements.contains(HTML::TagNames::template_))
-            m_form_element = downcast<HTMLFormElement>(*element);
+            m_form_element = verify_cast<HTMLFormElement>(*element);
         return;
     }
 
@@ -1877,7 +1877,7 @@ void HTMLDocumentParser::handle_text(HTMLToken& token)
     if (token.is_end_of_file()) {
         log_parse_error();
         if (current_node().local_name() == HTML::TagNames::script)
-            downcast<HTMLScriptElement>(current_node()).set_already_started({}, true);
+            verify_cast<HTMLScriptElement>(current_node()).set_already_started({}, true);
         m_stack_of_open_elements.pop();
         m_insertion_mode = m_original_insertion_mode;
         process_using_the_rules_for(m_insertion_mode, token);
@@ -1887,7 +1887,7 @@ void HTMLDocumentParser::handle_text(HTMLToken& token)
         // Make sure the <script> element has up-to-date text content before preparing the script.
         flush_character_insertions();
 
-        NonnullRefPtr<HTMLScriptElement> script = downcast<HTMLScriptElement>(current_node());
+        NonnullRefPtr<HTMLScriptElement> script = verify_cast<HTMLScriptElement>(current_node());
         m_stack_of_open_elements.pop();
         m_insertion_mode = m_original_insertion_mode;
         // FIXME: Handle tokenizer insertion point stuff here.
@@ -2289,7 +2289,7 @@ void HTMLDocumentParser::handle_in_table(HTMLToken& token)
             return;
         }
 
-        m_form_element = downcast<HTMLFormElement>(*insert_html_element(token));
+        m_form_element = verify_cast<HTMLFormElement>(*insert_html_element(token));
 
         // FIXME: See previous FIXME, as this is the same situation but for form.
         m_stack_of_open_elements.pop();
@@ -3025,7 +3025,7 @@ NonnullRefPtrVector<DOM::Node> HTMLDocumentParser::parse_html_fragment(DOM::Elem
 
     for (auto* form_candidate = &context_element; form_candidate; form_candidate = form_candidate->parent_element()) {
         if (is<HTMLFormElement>(*form_candidate)) {
-            parser.m_form_element = downcast<HTMLFormElement>(*form_candidate);
+            parser.m_form_element = verify_cast<HTMLFormElement>(*form_candidate);
             break;
         }
     }

Userland/Libraries/LibWeb/InProcessWebView.cpp

@@ -81,7 +81,7 @@ void InProcessWebView::select_all()
 
     int last_layout_node_index_in_node = 0;
     if (is<Layout::TextNode>(*last_layout_node))
-        last_layout_node_index_in_node = downcast<Layout::TextNode>(*last_layout_node).text_for_rendering().length() - 1;
+        last_layout_node_index_in_node = verify_cast<Layout::TextNode>(*last_layout_node).text_for_rendering().length() - 1;
 
     layout_root->set_selection({ { first_layout_node, 0 }, { last_layout_node, last_layout_node_index_in_node } });
     update();

Userland/Libraries/LibWeb/Layout/BlockBox.cpp

@@ -88,11 +88,11 @@ HitTestResult BlockBox::hit_test(const Gfx::IntPoint& position, HitTestType type
     HitTestResult last_good_candidate;
     for (auto& line_box : m_line_boxes) {
         for (auto& fragment : line_box.fragments()) {
-            if (is<Box>(fragment.layout_node()) && downcast<Box>(fragment.layout_node()).stacking_context())
+            if (is<Box>(fragment.layout_node()) && verify_cast<Box>(fragment.layout_node()).stacking_context())
                 continue;
             if (enclosing_int_rect(fragment.absolute_rect()).contains(position)) {
                 if (is<BlockBox>(fragment.layout_node()))
-                    return downcast<BlockBox>(fragment.layout_node()).hit_test(position, type);
+                    return verify_cast<BlockBox>(fragment.layout_node()).hit_test(position, type);
                 return { fragment.layout_node(), fragment.text_index_at(position.x()) };
             }
             if (fragment.absolute_rect().top() <= position.y())

Userland/Libraries/LibWeb/Layout/BlockBox.h

@@ -21,10 +21,10 @@ public:
 
     virtual HitTestResult hit_test(const Gfx::IntPoint&, HitTestType) const override;
 
-    BlockBox* previous_sibling() { return downcast<BlockBox>(Node::previous_sibling()); }
-    const BlockBox* previous_sibling() const { return downcast<BlockBox>(Node::previous_sibling()); }
-    BlockBox* next_sibling() { return downcast<BlockBox>(Node::next_sibling()); }
-    const BlockBox* next_sibling() const { return downcast<BlockBox>(Node::next_sibling()); }
+    BlockBox* previous_sibling() { return verify_cast<BlockBox>(Node::previous_sibling()); }
+    const BlockBox* previous_sibling() const { return verify_cast<BlockBox>(Node::previous_sibling()); }
+    BlockBox* next_sibling() { return verify_cast<BlockBox>(Node::next_sibling()); }
+    const BlockBox* next_sibling() const { return verify_cast<BlockBox>(Node::next_sibling()); }
 
     template<typename Callback>
     void for_each_fragment(Callback);

Userland/Libraries/LibWeb/Layout/BlockFormattingContext.cpp

@@ -72,7 +72,7 @@ void BlockFormattingContext::compute_width(Box& box)
 
     if (is<ReplacedBox>(box)) {
         // FIXME: This should not be done *by* ReplacedBox
-        auto& replaced = downcast<ReplacedBox>(box);
+        auto& replaced = verify_cast<ReplacedBox>(box);
         replaced.prepare_for_replaced_layout();
         compute_width_for_block_level_replaced_element_in_normal_flow(replaced);
         return;
@@ -304,7 +304,7 @@ float BlockFormattingContext::compute_theoretical_height(const Box& box)
     // Then work out what the height is, based on box type and CSS properties.
     float height = 0;
     if (is<ReplacedBox>(box)) {
-        height = compute_height_for_replaced_element(downcast<ReplacedBox>(box));
+        height = compute_height_for_replaced_element(verify_cast<ReplacedBox>(box));
     } else {
         if (box.computed_values().height().is_undefined_or_auto()
             || (computed_values.height().is_percentage() && !containing_block.computed_values().height().is_absolute())) {
@@ -410,10 +410,10 @@ void BlockFormattingContext::layout_block_level_children(Box& box, LayoutMode la
         // FIXME: This should be factored differently. It's uncool that we mutate the tree *during* layout!
         //        Instead, we should generate the marker box during the tree build.
         if (is<ListItemBox>(child_box))
-            downcast<ListItemBox>(child_box).layout_marker();
+            verify_cast<ListItemBox>(child_box).layout_marker();
 
         content_height = max(content_height, child_box.effective_offset().y() + child_box.height() + child_box.box_model().margin_box().bottom);
-        content_width = max(content_width, downcast<Box>(child_box).width());
+        content_width = max(content_width, verify_cast<Box>(child_box).width());
         return IterationDecision::Continue;
     });
 
@@ -526,7 +526,7 @@ void BlockFormattingContext::layout_initial_containing_block(LayoutMode layout_m
 {
     auto viewport_rect = context_box().browsing_context().viewport_rect();
 
-    auto& icb = downcast<Layout::InitialContainingBlockBox>(context_box());
+    auto& icb = verify_cast<Layout::InitialContainingBlockBox>(context_box());
     icb.build_stacking_context_tree();
 
     icb.set_width(viewport_rect.width());
@@ -551,7 +551,7 @@ static Gfx::FloatRect rect_in_coordinate_space(const Box& box, const Box& contex
     Gfx::FloatRect rect = box.margin_box_as_relative_rect();
     for (auto* ancestor = box.parent(); ancestor; ancestor = ancestor->parent()) {
         if (is<Box>(*ancestor)) {
-            auto offset = downcast<Box>(*ancestor).effective_offset();
+            auto offset = verify_cast<Box>(*ancestor).effective_offset();
             rect.translate_by(offset);
         }
         if (ancestor == &context_box)

Userland/Libraries/LibWeb/Layout/Box.cpp

@@ -50,7 +50,7 @@ void Box::paint(PaintContext& context, PaintPhase phase)
         context.painter().draw_rect(enclosing_int_rect(content_rect), Color::Magenta);
     }
 
-    if (phase == PaintPhase::FocusOutline && dom_node() && dom_node()->is_element() && downcast<DOM::Element>(*dom_node()).is_focused()) {
+    if (phase == PaintPhase::FocusOutline && dom_node() && dom_node()->is_element() && verify_cast<DOM::Element>(*dom_node()).is_focused()) {
         context.painter().draw_rect(enclosing_int_rect(absolute_rect()), context.palette().focus_outline());
     }
 }
@@ -347,7 +347,7 @@ StackingContext* Box::enclosing_stacking_context()
     for (auto* ancestor = parent(); ancestor; ancestor = ancestor->parent()) {
         if (!is<Box>(ancestor))
             continue;
-        auto& ancestor_box = downcast<Box>(*ancestor);
+        auto& ancestor_box = verify_cast<Box>(*ancestor);
         if (!ancestor_box.establishes_stacking_context())
             continue;
         VERIFY(ancestor_box.stacking_context());

Userland/Libraries/LibWeb/Layout/BreakNode.h

@@ -16,7 +16,7 @@ public:
     BreakNode(DOM::Document&, HTML::HTMLBRElement&);
     virtual ~BreakNode() override;
 
-    const HTML::HTMLBRElement& dom_node() const { return downcast<HTML::HTMLBRElement>(*Node::dom_node()); }
+    const HTML::HTMLBRElement& dom_node() const { return verify_cast<HTML::HTMLBRElement>(*Node::dom_node()); }
 
 private:
     virtual void split_into_lines(InlineFormattingContext&, LayoutMode) override;

Userland/Libraries/LibWeb/Layout/FormattingContext.cpp

@@ -254,7 +254,7 @@ float FormattingContext::tentative_width_for_replaced_element(const ReplacedBox&
 void FormattingContext::compute_width_for_absolutely_positioned_element(Box& box)
 {
     if (is<ReplacedBox>(box))
-        compute_width_for_absolutely_positioned_replaced_element(downcast<ReplacedBox>(box));
+        compute_width_for_absolutely_positioned_replaced_element(verify_cast<ReplacedBox>(box));
     else
         compute_width_for_absolutely_positioned_non_replaced_element(box);
 }
@@ -262,7 +262,7 @@ void FormattingContext::compute_width_for_absolutely_positioned_element(Box& box
 void FormattingContext::compute_height_for_absolutely_positioned_element(Box& box)
 {
     if (is<ReplacedBox>(box))
-        compute_height_for_absolutely_positioned_replaced_element(downcast<ReplacedBox>(box));
+        compute_height_for_absolutely_positioned_replaced_element(verify_cast<ReplacedBox>(box));
     else
         compute_height_for_absolutely_positioned_non_replaced_element(box);
 }

Userland/Libraries/LibWeb/Layout/FrameBox.h

@@ -19,8 +19,8 @@ public:
     virtual void paint(PaintContext&, PaintPhase) override;
     virtual void prepare_for_replaced_layout() override;
 
-    const HTML::HTMLIFrameElement& dom_node() const { return downcast<HTML::HTMLIFrameElement>(ReplacedBox::dom_node()); }
-    HTML::HTMLIFrameElement& dom_node() { return downcast<HTML::HTMLIFrameElement>(ReplacedBox::dom_node()); }
+    const HTML::HTMLIFrameElement& dom_node() const { return verify_cast<HTML::HTMLIFrameElement>(ReplacedBox::dom_node()); }
+    HTML::HTMLIFrameElement& dom_node() { return verify_cast<HTML::HTMLIFrameElement>(ReplacedBox::dom_node()); }
 
 private:
     virtual void did_set_rect() override;

Userland/Libraries/LibWeb/Layout/ImageBox.cpp

@@ -60,7 +60,7 @@ void ImageBox::prepare_for_replaced_layout()
     }
 
     if (renders_as_alt_text()) {
-        auto& image_element = downcast<HTML::HTMLImageElement>(dom_node());
+        auto& image_element = verify_cast<HTML::HTMLImageElement>(dom_node());
         auto& font = Gfx::FontDatabase::default_font();
         auto alt = image_element.alt();
         if (alt.is_empty())
@@ -88,7 +88,7 @@ void ImageBox::paint(PaintContext& context, PaintPhase phase)
 
     if (phase == PaintPhase::Foreground) {
         if (renders_as_alt_text()) {
-            auto& image_element = downcast<HTML::HTMLImageElement>(dom_node());
+            auto& image_element = verify_cast<HTML::HTMLImageElement>(dom_node());
             context.painter().set_font(Gfx::FontDatabase::default_font());
             Gfx::StylePainter::paint_frame(context.painter(), enclosing_int_rect(absolute_rect()), context.palette(), Gfx::FrameShape::Container, Gfx::FrameShadow::Sunken, 2);
             auto alt = image_element.alt();

Userland/Libraries/LibWeb/Layout/InlineFormattingContext.cpp

@@ -75,7 +75,7 @@ void InlineFormattingContext::run(Box&, LayoutMode layout_mode)
     containing_block().for_each_child([&](auto& child) {
         VERIFY(child.is_inline());
         if (is<Box>(child) && child.is_absolutely_positioned()) {
-            layout_absolutely_positioned_element(downcast<Box>(child));
+            layout_absolutely_positioned_element(verify_cast<Box>(child));
             return;
         }
 
@@ -181,14 +181,14 @@ void InlineFormattingContext::run(Box&, LayoutMode layout_mode)
 void InlineFormattingContext::dimension_box_on_line(Box& box, LayoutMode layout_mode)
 {
     if (is<ReplacedBox>(box)) {
-        auto& replaced = downcast<ReplacedBox>(box);
+        auto& replaced = verify_cast<ReplacedBox>(box);
         replaced.set_width(compute_width_for_replaced_element(replaced));
         replaced.set_height(compute_height_for_replaced_element(replaced));
         return;
     }
 
     if (box.is_inline_block()) {
-        auto& inline_block = const_cast<BlockBox&>(downcast<BlockBox>(box));
+        auto& inline_block = const_cast<BlockBox&>(verify_cast<BlockBox>(box));
 
         if (inline_block.computed_values().width().is_undefined_or_auto()) {
             auto result = calculate_shrink_to_fit_widths(inline_block);

Userland/Libraries/LibWeb/Layout/LineBox.cpp

@@ -27,7 +27,7 @@ void LineBox::add_fragment(Node& layout_node, int start, int length, float width
     m_width += width;
 
     if (is<Box>(layout_node))
-        downcast<Box>(layout_node).set_containing_line_box_fragment(m_fragments.last());
+        verify_cast<Box>(layout_node).set_containing_line_box_fragment(m_fragments.last());
 }
 
 void LineBox::trim_trailing_whitespace()

Userland/Libraries/LibWeb/Layout/LineBoxFragment.cpp

@@ -41,7 +41,7 @@ StringView LineBoxFragment::text() const
 {
     if (!is<TextNode>(layout_node()))
         return {};
-    return downcast<TextNode>(layout_node()).text_for_rendering().substring_view(m_start, m_length);
+    return verify_cast<TextNode>(layout_node()).text_for_rendering().substring_view(m_start, m_length);
 }
 
 const Gfx::FloatRect LineBoxFragment::absolute_rect() const
@@ -56,7 +56,7 @@ int LineBoxFragment::text_index_at(float x) const
 {
     if (!is<TextNode>(layout_node()))
         return 0;
-    auto& layout_text = downcast<TextNode>(layout_node());
+    auto& layout_text = verify_cast<TextNode>(layout_node());
     auto& font = layout_text.font();
     Utf8View view(text());
 

Userland/Libraries/LibWeb/Layout/Node.cpp

@@ -150,7 +150,7 @@ void Node::set_needs_display()
 Gfx::FloatPoint Node::box_type_agnostic_position() const
 {
     if (is<Box>(*this))
-        return downcast<Box>(*this).absolute_position();
+        return verify_cast<Box>(*this).absolute_position();
     VERIFY(is_inline());
     Gfx::FloatPoint position;
     if (auto* block = containing_block()) {

Userland/Libraries/LibWeb/Layout/Node.h

@@ -158,13 +158,13 @@ public:
     void for_each_child_in_paint_order(Callback callback) const
     {
         for_each_child([&](auto& child) {
-            if (is<Box>(child) && downcast<Box>(child).stacking_context())
+            if (is<Box>(child) && verify_cast<Box>(child).stacking_context())
                 return;
             if (!child.is_positioned())
                 callback(child);
         });
         for_each_child([&](auto& child) {
-            if (is<Box>(child) && downcast<Box>(child).stacking_context())
+            if (is<Box>(child) && verify_cast<Box>(child).stacking_context())
                 return;
             if (child.is_positioned())
                 callback(child);

Userland/Libraries/LibWeb/Layout/ReplacedBox.h

@@ -16,8 +16,8 @@ public:
     ReplacedBox(DOM::Document&, DOM::Element&, NonnullRefPtr<CSS::StyleProperties>);
     virtual ~ReplacedBox() override;
 
-    const DOM::Element& dom_node() const { return downcast<DOM::Element>(*Node::dom_node()); }
-    DOM::Element& dom_node() { return downcast<DOM::Element>(*Node::dom_node()); }
+    const DOM::Element& dom_node() const { return verify_cast<DOM::Element>(*Node::dom_node()); }
+    DOM::Element& dom_node() { return verify_cast<DOM::Element>(*Node::dom_node()); }
 
     bool has_intrinsic_width() const { return m_has_intrinsic_width; }
     bool has_intrinsic_height() const { return m_has_intrinsic_height; }

Userland/Libraries/LibWeb/Layout/SVGGraphicsBox.cpp

@@ -19,7 +19,7 @@ void SVGGraphicsBox::before_children_paint(PaintContext& context, PaintPhase pha
     if (phase != PaintPhase::Foreground)
         return;
 
-    auto& graphics_element = downcast<SVG::SVGGraphicsElement>(dom_node());
+    auto& graphics_element = verify_cast<SVG::SVGGraphicsElement>(dom_node());
 
     if (graphics_element.fill_color().has_value())
         context.svg_context().set_fill_color(graphics_element.fill_color().value());

Userland/Libraries/LibWeb/Layout/SVGPathBox.h

@@ -16,7 +16,7 @@ public:
     SVGPathBox(DOM::Document&, SVG::SVGPathElement&, NonnullRefPtr<CSS::StyleProperties>);
     virtual ~SVGPathBox() override = default;
 
-    SVG::SVGPathElement& dom_node() { return downcast<SVG::SVGPathElement>(SVGGraphicsBox::dom_node()); }
+    SVG::SVGPathElement& dom_node() { return verify_cast<SVG::SVGPathElement>(SVGGraphicsBox::dom_node()); }
 
     virtual void prepare_for_replaced_layout() override;
     virtual void paint(PaintContext& context, PaintPhase phase) override;

Userland/Libraries/LibWeb/Layout/SVGSVGBox.h

@@ -16,7 +16,7 @@ public:
     SVGSVGBox(DOM::Document&, SVG::SVGSVGElement&, NonnullRefPtr<CSS::StyleProperties>);
     virtual ~SVGSVGBox() override = default;
 
-    SVG::SVGSVGElement& dom_node() { return downcast<SVG::SVGSVGElement>(SVGGraphicsBox::dom_node()); }
+    SVG::SVGSVGElement& dom_node() { return verify_cast<SVG::SVGSVGElement>(SVGGraphicsBox::dom_node()); }
 
     virtual void prepare_for_replaced_layout() override;
 

Userland/Libraries/LibWeb/Layout/TableCellBox.cpp

@@ -28,7 +28,7 @@ size_t TableCellBox::colspan() const
 {
     if (!dom_node())
         return 1;
-    return downcast<DOM::Element>(*dom_node()).attribute(HTML::AttributeNames::colspan).to_uint().value_or(1);
+    return verify_cast<DOM::Element>(*dom_node()).attribute(HTML::AttributeNames::colspan).to_uint().value_or(1);
 }
 
 float TableCellBox::width_of_logical_containing_block() const

Userland/Libraries/LibWeb/Layout/TextNode.cpp

@@ -261,7 +261,7 @@ void TextNode::handle_mousedown(Badge<EventHandler>, const Gfx::IntPoint& positi
 {
     if (!parent() || !is<Label>(*parent()))
         return;
-    downcast<Label>(*parent()).handle_mousedown_on_label({}, position, button);
+    verify_cast<Label>(*parent()).handle_mousedown_on_label({}, position, button);
     browsing_context().event_handler().set_mouse_event_tracking_layout_node(this);
 }
 
@@ -273,7 +273,7 @@ void TextNode::handle_mouseup(Badge<EventHandler>, const Gfx::IntPoint& position
     // NOTE: Changing the state of the DOM node may run arbitrary JS, which could disappear this node.
     NonnullRefPtr protect = *this;
 
-    downcast<Label>(*parent()).handle_mouseup_on_label({}, position, button);
+    verify_cast<Label>(*parent()).handle_mouseup_on_label({}, position, button);
     browsing_context().event_handler().set_mouse_event_tracking_layout_node(nullptr);
 }
 
@@ -281,7 +281,7 @@ void TextNode::handle_mousemove(Badge<EventHandler>, const Gfx::IntPoint& positi
 {
     if (!parent() || !is<Label>(*parent()))
         return;
-    downcast<Label>(*parent()).handle_mousemove_on_label({}, position, button);
+    verify_cast<Label>(*parent()).handle_mousemove_on_label({}, position, button);
 }
 
 TextNode::ChunkIterator::ChunkIterator(StringView const& text, LayoutMode layout_mode, bool wrap_lines, bool wrap_breaks)

Userland/Libraries/LibWeb/Layout/TreeBuilder.cpp

@@ -103,13 +103,13 @@ void TreeBuilder::create_layout_tree(DOM::Node& dom_node)
         }
     }
 
-    auto* shadow_root = is<DOM::Element>(dom_node) ? downcast<DOM::Element>(dom_node).shadow_root() : nullptr;
+    auto* shadow_root = is<DOM::Element>(dom_node) ? verify_cast<DOM::Element>(dom_node).shadow_root() : nullptr;
 
     if ((dom_node.has_children() || shadow_root) && layout_node->can_have_children()) {
-        push_parent(downcast<NodeWithStyle>(*layout_node));
+        push_parent(verify_cast<NodeWithStyle>(*layout_node));
         if (shadow_root)
             create_layout_tree(*shadow_root);
-        downcast<DOM::ParentNode>(dom_node).for_each_child([&](auto& dom_child) {
+        verify_cast<DOM::ParentNode>(dom_node).for_each_child([&](auto& dom_child) {
             create_layout_tree(dom_child);
         });
         pop_parent();
@@ -121,7 +121,7 @@ RefPtr<Node> TreeBuilder::build(DOM::Node& dom_node)
     if (dom_node.parent()) {
         // We're building a partial layout tree, so start by building up the stack of parent layout nodes.
         for (auto* ancestor = dom_node.parent()->layout_node(); ancestor; ancestor = ancestor->parent())
-            m_parent_stack.prepend(downcast<NodeWithStyle>(ancestor));
+            m_parent_stack.prepend(verify_cast<NodeWithStyle>(ancestor));
     }
 
     create_layout_tree(dom_node);

Userland/Libraries/LibWeb/LayoutTreeModel.cpp

@@ -108,7 +108,7 @@ GUI::Variant LayoutTreeModel::data(const GUI::ModelIndex& index, GUI::ModelRole
     }
     if (role == GUI::ModelRole::Display) {
         if (is<Layout::TextNode>(node))
-            return String::formatted("TextNode: {}", with_whitespace_collapsed(downcast<Layout::TextNode>(node).text_for_rendering()));
+            return String::formatted("TextNode: {}", with_whitespace_collapsed(verify_cast<Layout::TextNode>(node).text_for_rendering()));
         StringBuilder builder;
         builder.append(node.class_name());
         builder.append(' ');
@@ -117,7 +117,7 @@ GUI::Variant LayoutTreeModel::data(const GUI::ModelIndex& index, GUI::ModelRole
         } else if (!node.dom_node()->is_element()) {
             builder.append(node.dom_node()->node_name());
         } else {
-            auto& element = downcast<DOM::Element>(*node.dom_node());
+            auto& element = verify_cast<DOM::Element>(*node.dom_node());
             builder.append('<');
             builder.append(element.local_name());
             element.for_each_attribute([&](auto& name, auto& value) {

Userland/Libraries/LibWeb/Loader/FrameLoader.cpp

@@ -277,7 +277,7 @@ void FrameLoader::resource_did_load()
     if (auto* host_element = browsing_context().host_element()) {
         // FIXME: Perhaps in the future we'll have a better common base class for <frame> and <iframe>
         VERIFY(is<HTML::HTMLIFrameElement>(*host_element));
-        downcast<HTML::HTMLIFrameElement>(*host_element).nested_browsing_context_did_load({});
+        verify_cast<HTML::HTMLIFrameElement>(*host_element).nested_browsing_context_did_load({});
     }
 
     if (auto* page = browsing_context().page())

Userland/Libraries/LibWeb/Page/BrowsingContext.cpp

@@ -165,7 +165,7 @@ void BrowsingContext::scroll_to_anchor(const String& fragment)
         auto candidates = document()->get_elements_by_name(fragment);
         for (auto& candidate : candidates->collect_matching_elements()) {
             if (is<HTML::HTMLAnchorElement>(*candidate)) {
-                element = downcast<HTML::HTMLAnchorElement>(*candidate);
+                element = verify_cast<HTML::HTMLAnchorElement>(*candidate);
                 break;
             }
         }
@@ -181,7 +181,7 @@ void BrowsingContext::scroll_to_anchor(const String& fragment)
 
     Gfx::FloatRect float_rect { layout_node.box_type_agnostic_position(), { (float)viewport_rect().width(), (float)viewport_rect().height() } };
     if (is<Layout::Box>(layout_node)) {
-        auto& layout_box = downcast<Layout::Box>(layout_node);
+        auto& layout_box = verify_cast<Layout::Box>(layout_node);
         auto padding_box = layout_box.box_model().padding_box();
         float_rect.translate_by(-padding_box.left, -padding_box.top);
     }
@@ -244,13 +244,13 @@ String BrowsingContext::selected_text() const
     if (selection.start().layout_node == selection.end().layout_node) {
         if (!is<Layout::TextNode>(*selection.start().layout_node))
             return "";
-        return downcast<Layout::TextNode>(*selection.start().layout_node).text_for_rendering().substring(selection.start().index_in_node, selection.end().index_in_node - selection.start().index_in_node);
+        return verify_cast<Layout::TextNode>(*selection.start().layout_node).text_for_rendering().substring(selection.start().index_in_node, selection.end().index_in_node - selection.start().index_in_node);
     }
 
     // Start node
     auto layout_node = selection.start().layout_node;
     if (is<Layout::TextNode>(*layout_node)) {
-        auto& text = downcast<Layout::TextNode>(*layout_node).text_for_rendering();
+        auto& text = verify_cast<Layout::TextNode>(*layout_node).text_for_rendering();
         builder.append(text.substring(selection.start().index_in_node, text.length() - selection.start().index_in_node));
     }
 
@@ -258,7 +258,7 @@ String BrowsingContext::selected_text() const
     layout_node = layout_node->next_in_pre_order();
     while (layout_node && layout_node != selection.end().layout_node) {
         if (is<Layout::TextNode>(*layout_node))
-            builder.append(downcast<Layout::TextNode>(*layout_node).text_for_rendering());
+            builder.append(verify_cast<Layout::TextNode>(*layout_node).text_for_rendering());
         else if (is<Layout::BreakNode>(*layout_node) || is<Layout::BlockBox>(*layout_node))
             builder.append('\n');
 
@@ -268,7 +268,7 @@ String BrowsingContext::selected_text() const
     // End node
     VERIFY(layout_node == selection.end().layout_node);
     if (is<Layout::TextNode>(*layout_node)) {
-        auto& text = downcast<Layout::TextNode>(*layout_node).text_for_rendering();
+        auto& text = verify_cast<Layout::TextNode>(*layout_node).text_for_rendering();
         builder.append(text.substring(0, selection.end().index_in_node));
     }
 

Userland/Libraries/LibWeb/Page/EditEventHandler.cpp

@@ -39,8 +39,8 @@ void EditEventHandler::handle_delete_character_after(const DOM::Position& cursor
 // This method is quite convoluted but this is necessary to make editing feel intuitive.
 void EditEventHandler::handle_delete(DOM::Range& range)
 {
-    auto* start = downcast<DOM::Text>(range.start_container());
-    auto* end = downcast<DOM::Text>(range.end_container());
+    auto* start = verify_cast<DOM::Text>(range.start_container());
+    auto* end = verify_cast<DOM::Text>(range.end_container());
 
     if (start == end) {
         StringBuilder builder;
@@ -100,7 +100,7 @@ void EditEventHandler::handle_delete(DOM::Range& range)
 void EditEventHandler::handle_insert(DOM::Position position, u32 code_point)
 {
     if (is<DOM::Text>(*position.node())) {
-        auto& node = downcast<DOM::Text>(*position.node());
+        auto& node = verify_cast<DOM::Text>(*position.node());
 
         StringBuilder builder;
         builder.append(node.data().substring_view(0, position.offset()));

Userland/Libraries/LibWeb/Page/EventHandler.cpp

@@ -158,7 +158,7 @@ bool EventHandler::handle_mouseup(const Gfx::IntPoint& position, unsigned button
     if (result.layout_node && result.layout_node->dom_node()) {
         RefPtr<DOM::Node> node = result.layout_node->dom_node();
         if (is<HTML::HTMLIFrameElement>(*node)) {
-            if (auto* subframe = downcast<HTML::HTMLIFrameElement>(*node).nested_browsing_context())
+            if (auto* subframe = verify_cast<HTML::HTMLIFrameElement>(*node).nested_browsing_context())
                 return subframe->event_handler().handle_mouseup(position.translated(compute_mouse_event_offset({}, *result.layout_node)), button, modifiers);
             return false;
         }
@@ -202,7 +202,7 @@ bool EventHandler::handle_mousedown(const Gfx::IntPoint& position, unsigned butt
             return false;
 
         if (is<HTML::HTMLIFrameElement>(*node)) {
-            if (auto* subframe = downcast<HTML::HTMLIFrameElement>(*node).nested_browsing_context())
+            if (auto* subframe = verify_cast<HTML::HTMLIFrameElement>(*node).nested_browsing_context())
                 return subframe->event_handler().handle_mousedown(position.translated(compute_mouse_event_offset({}, *result.layout_node)), button, modifiers);
             return false;
         }
@@ -219,7 +219,7 @@ bool EventHandler::handle_mousedown(const Gfx::IntPoint& position, unsigned butt
         return true;
 
     if (button == GUI::MouseButton::Right && is<HTML::HTMLImageElement>(*node)) {
-        auto& image_element = downcast<HTML::HTMLImageElement>(*node);
+        auto& image_element = verify_cast<HTML::HTMLImageElement>(*node);
         auto image_url = image_element.document().complete_url(image_element.src());
         if (auto* page = m_frame.page())
             page->client().page_did_request_image_context_menu(m_frame.to_top_level_position(position), image_url, "", modifiers, image_element.bitmap());
@@ -299,7 +299,7 @@ bool EventHandler::handle_mousemove(const Gfx::IntPoint& position, unsigned butt
         RefPtr<DOM::Node> node = result.layout_node->dom_node();
 
         if (node && is<HTML::HTMLIFrameElement>(*node)) {
-            if (auto* subframe = downcast<HTML::HTMLIFrameElement>(*node).nested_browsing_context())
+            if (auto* subframe = verify_cast<HTML::HTMLIFrameElement>(*node).nested_browsing_context())
                 return subframe->event_handler().handle_mousemove(position.translated(compute_mouse_event_offset({}, *result.layout_node)), buttons, modifiers);
             return false;
         }

Userland/Libraries/LibWeb/Painting/StackingContext.cpp

@@ -107,7 +107,7 @@ HitTestResult StackingContext::hit_test(const Gfx::IntPoint& position, HitTestTy
     } else {
         // NOTE: InitialContainingBlockBox::hit_test() merely calls StackingContext::hit_test()
         //       so we call its base class instead.
-        result = downcast<InitialContainingBlockBox>(m_box).BlockBox::hit_test(position, type);
+        result = verify_cast<InitialContainingBlockBox>(m_box).BlockBox::hit_test(position, type);
     }
 
     int z_index = m_box.computed_values().z_index().value_or(0);

Userland/Libraries/LibWeb/TreeNode.h

@@ -263,7 +263,7 @@ public:
     {
         for (auto* node = first_child(); node; node = node->next_sibling()) {
             if (is<U>(node))
-                callback(downcast<U>(*node));
+                callback(verify_cast<U>(*node));
         }
     }
 
@@ -284,7 +284,7 @@ public:
     {
         for (auto* sibling = next_sibling(); sibling; sibling = sibling->next_sibling()) {
             if (is<U>(*sibling))
-                return &downcast<U>(*sibling);
+                return &verify_cast<U>(*sibling);
         }
         return nullptr;
     }
@@ -300,7 +300,7 @@ public:
     {
         for (auto* sibling = previous_sibling(); sibling; sibling = sibling->previous_sibling()) {
             if (is<U>(*sibling))
-                return &downcast<U>(*sibling);
+                return &verify_cast<U>(*sibling);
         }
         return nullptr;
     }
@@ -322,7 +322,7 @@ public:
     {
         for (auto* child = first_child(); child; child = child->next_sibling()) {
             if (is<U>(*child))
-                return &downcast<U>(*child);
+                return &verify_cast<U>(*child);
         }
         return nullptr;
     }
@@ -332,7 +332,7 @@ public:
     {
         for (auto* child = last_child(); child; child = child->previous_sibling()) {
             if (is<U>(*child))
-                return &downcast<U>(*child);
+                return &verify_cast<U>(*child);
         }
         return nullptr;
     }
@@ -354,7 +354,7 @@ public:
     {
         for (auto* ancestor = parent(); ancestor; ancestor = ancestor->parent()) {
             if (is<U>(*ancestor))
-                return &downcast<U>(*ancestor);
+                return &verify_cast<U>(*ancestor);
         }
         return nullptr;
     }