LibWeb: Remove inheritance of FormAssociatedElement from HTMLElement

HTMLObjectElement will need to be both a FormAssociatedElement and a
BrowsingContextContainer. Currently, both of these classes inherit from
HTMLElement. This can work in C++, but is generally frowned upon, and
doesn't play particularly well with the rest of LibWeb.

Instead, we can essentially revert commit 3bb5c62 to remove HTMLElement
from FormAssociatedElement's hierarchy. This means that objects such as
HTMLObjectElement individually inherit from FormAssociatedElement and
HTMLElement now.

Some caveats are:

* FormAssociatedElement still needs to know when the HTMLElement is
  inserted into and removed from the DOM. This hook is automatically
  injected via a macro now, while still allowing classes like
  HTMLInputElement to also know when the element is inserted.

* Casting from a DOM::Element to a FormAssociatedElement is now a
  sideways cast, rather than directly following an inheritance chain.
  This means static_cast cannot be used here; but we can safely use
  dynamic_cast since the only 2 instances of this already use RTTI to
  verify the cast.

Userland/Libraries/LibWeb/DOM/EventTarget.cpp

@@ -336,9 +336,11 @@ Bindings::CallbackType* EventTarget::get_current_value_of_event_handler(FlyStrin
         // 5. If element is not null and element has a form owner, let form owner be that form owner. Otherwise, let form owner be null.
         RefPtr<HTML::HTMLFormElement> form_owner;
         if (is<HTML::FormAssociatedElement>(element.ptr())) {
-            auto& form_associated_element = verify_cast<HTML::FormAssociatedElement>(*element);
-            if (form_associated_element.form())
-                form_owner = form_associated_element.form();
+            auto* form_associated_element = dynamic_cast<HTML::FormAssociatedElement*>(element.ptr());
+            VERIFY(form_associated_element);
+
+            if (form_associated_element->form())
+                form_owner = form_associated_element->form();
         }
 
         // 6. Let settings object be the relevant settings object of document.

Userland/Libraries/LibWeb/HTML/FormAssociatedElement.cpp

@@ -12,44 +12,49 @@
 #include <LibWeb/HTML/HTMLLegendElement.h>
 #include <LibWeb/HTML/HTMLSelectElement.h>
 #include <LibWeb/HTML/HTMLTextAreaElement.h>
+#include <LibWeb/HTML/Parser/HTMLParser.h>
 
 namespace Web::HTML {
 
 void FormAssociatedElement::set_form(HTMLFormElement* form)
 {
     if (m_form)
-        m_form->remove_associated_element({}, *this);
+        m_form->remove_associated_element({}, form_associated_element_to_html_element());
     m_form = form;
     if (m_form)
-        m_form->add_associated_element({}, *this);
+        m_form->add_associated_element({}, form_associated_element_to_html_element());
 }
 
 bool FormAssociatedElement::enabled() const
 {
     // https://html.spec.whatwg.org/multipage/form-control-infrastructure.html#concept-fe-disabled
+    auto const& html_element = const_cast<FormAssociatedElement&>(*this).form_associated_element_to_html_element();
 
     // A form control is disabled if any of the following conditions are met:
     // 1. The element is a button, input, select, textarea, or form-associated custom element, and the disabled attribute is specified on this element (regardless of its value).
     // FIXME: This doesn't check for form-associated custom elements.
-    if ((is<HTMLButtonElement>(this) || is<HTMLInputElement>(this) || is<HTMLSelectElement>(this) || is<HTMLTextAreaElement>(this)) && has_attribute(HTML::AttributeNames::disabled))
+    if ((is<HTMLButtonElement>(html_element) || is<HTMLInputElement>(html_element) || is<HTMLSelectElement>(html_element) || is<HTMLTextAreaElement>(html_element)) && html_element.has_attribute(HTML::AttributeNames::disabled))
         return false;
 
     // 2. The element is a descendant of a fieldset element whose disabled attribute is specified, and is not a descendant of that fieldset element's first legend element child, if any.
-    auto* fieldset_ancestor = first_ancestor_of_type<HTMLFieldSetElement>();
+    auto* fieldset_ancestor = html_element.first_ancestor_of_type<HTMLFieldSetElement>();
     if (fieldset_ancestor && fieldset_ancestor->has_attribute(HTML::AttributeNames::disabled)) {
         auto* first_legend_element_child = fieldset_ancestor->first_child_of_type<HTMLLegendElement>();
-        if (!first_legend_element_child || !is_descendant_of(*first_legend_element_child))
+        if (!first_legend_element_child || !html_element.is_descendant_of(*first_legend_element_child))
             return false;
     }
 
     return true;
 }
 
-// https://html.spec.whatwg.org/multipage/form-control-infrastructure.html#association-of-controls-and-forms:nodes-are-inserted
-void FormAssociatedElement::inserted()
+void FormAssociatedElement::set_parser_inserted(Badge<HTMLParser>)
 {
-    HTMLElement::inserted();
+    m_parser_inserted = true;
+}
 
+// https://html.spec.whatwg.org/multipage/form-control-infrastructure.html#association-of-controls-and-forms:nodes-are-inserted
+void FormAssociatedElement::form_node_was_inserted()
+{
     // 1. If the form-associated element's parser inserted flag is set, then return.
     if (m_parser_inserted)
         return;
@@ -59,18 +64,18 @@ void FormAssociatedElement::inserted()
 }
 
 // https://html.spec.whatwg.org/multipage/form-control-infrastructure.html#association-of-controls-and-forms:nodes-are-removed
-void FormAssociatedElement::removed_from(DOM::Node* node)
+void FormAssociatedElement::form_node_was_removed()
 {
-    HTMLElement::removed_from(node);
-
     // 1. If the form-associated element has a form owner and the form-associated element and its form owner are no longer in the same tree, then reset the form owner of the form-associated element.
-    if (m_form && &root() != &m_form->root())
+    if (m_form && &form_associated_element_to_html_element().root() != &m_form->root())
         reset_form_owner();
 }
 
 // https://html.spec.whatwg.org/multipage/form-control-infrastructure.html#reset-the-form-owner
 void FormAssociatedElement::reset_form_owner()
 {
+    auto& html_element = form_associated_element_to_html_element();
+
     // Although these aren't in the "reset form owner" algorithm, these here as they are triggers for this algorithm:
     // FIXME: When a listed form-associated element's form attribute is set, changed, or removed, then the user agent must reset the form owner of that element.
     // FIXME: When a listed form-associated element has a form attribute and the ID of any of the elements in the tree changes, then the user agent must reset the form owner of that form-associated element.
@@ -85,8 +90,8 @@ void FormAssociatedElement::reset_form_owner()
     //    - element's form owner is its nearest form element ancestor after the change to the ancestor chain
     //    then do nothing, and return.
     if (m_form
-        && (!is_listed() || !has_attribute(HTML::AttributeNames::form))
-        && first_ancestor_of_type<HTMLFormElement>() == m_form.ptr()) {
+        && (!is_listed() || !html_element.has_attribute(HTML::AttributeNames::form))
+        && html_element.first_ancestor_of_type<HTMLFormElement>() == m_form.ptr()) {
         return;
     }
 
@@ -94,10 +99,10 @@ void FormAssociatedElement::reset_form_owner()
     set_form(nullptr);
 
     // 4. If element is listed, has a form content attribute, and is connected, then:
-    if (is_listed() && has_attribute(HTML::AttributeNames::form) && is_connected()) {
+    if (is_listed() && html_element.has_attribute(HTML::AttributeNames::form) && html_element.is_connected()) {
         // 1. If the first element in element's tree, in tree order, to have an ID that is identical to element's form content attribute's value, is a form element, then associate the element with that form element.
-        auto form_value = attribute(HTML::AttributeNames::form);
-        root().for_each_in_inclusive_subtree_of_type<HTMLFormElement>([this, &form_value](HTMLFormElement& form_element) mutable {
+        auto form_value = html_element.attribute(HTML::AttributeNames::form);
+        html_element.root().for_each_in_inclusive_subtree_of_type<HTMLFormElement>([this, &form_value](HTMLFormElement& form_element) mutable {
             if (form_element.attribute(HTML::AttributeNames::id) == form_value) {
                 set_form(&form_element);
                 return IterationDecision::Break;
@@ -109,7 +114,7 @@ void FormAssociatedElement::reset_form_owner()
 
     // 5. Otherwise, if element has an ancestor form element, then associate element with the nearest such ancestor form element.
     else {
-        auto* form_ancestor = first_ancestor_of_type<HTMLFormElement>();
+        auto* form_ancestor = html_element.first_ancestor_of_type<HTMLFormElement>();
         if (form_ancestor)
             set_form(form_ancestor);
     }

Userland/Libraries/LibWeb/HTML/FormAssociatedElement.h

@@ -8,11 +8,39 @@
 
 #include <AK/WeakPtr.h>
 #include <LibWeb/Forward.h>
-#include <LibWeb/HTML/HTMLElement.h>
 
 namespace Web::HTML {
 
-class FormAssociatedElement : public HTMLElement {
+// Form-associated elements should invoke this macro to inject overidden FormAssociatedElement and HTMLElement
+// methods as needed. If your class wished to override an HTMLElement method that is overidden here, use the
+// following methods instead:
+//
+//    HTMLElement::inserted() -> Use form_associated_element_was_inserted()
+//    HTMLElement::removed_from() -> Use form_associated_element_was_removed()
+//
+#define FORM_ASSOCIATED_ELEMENT(ElementBaseClass, ElementClass)             \
+private:                                                                    \
+    virtual HTMLElement& form_associated_element_to_html_element() override \
+    {                                                                       \
+        static_assert(IsBaseOf<HTMLElement, ElementClass>);                 \
+        return *this;                                                       \
+    }                                                                       \
+                                                                            \
+    virtual void inserted() override                                        \
+    {                                                                       \
+        ElementBaseClass::inserted();                                       \
+        form_node_was_inserted();                                           \
+        form_associated_element_was_inserted();                             \
+    }                                                                       \
+                                                                            \
+    virtual void removed_from(DOM::Node* node) override                     \
+    {                                                                       \
+        ElementBaseClass::removed_from(node);                               \
+        form_node_was_removed();                                            \
+        form_associated_element_was_removed(node);                          \
+    }
+
+class FormAssociatedElement {
 public:
     HTMLFormElement* form() { return m_form; }
     HTMLFormElement const* form() const { return m_form; }
@@ -21,7 +49,7 @@ public:
 
     bool enabled() const;
 
-    void set_parser_inserted(Badge<HTMLParser>) { m_parser_inserted = true; }
+    void set_parser_inserted(Badge<HTMLParser>);
 
     // https://html.spec.whatwg.org/multipage/forms.html#category-listed
     virtual bool is_listed() const { return false; }
@@ -35,14 +63,18 @@ public:
     // https://html.spec.whatwg.org/multipage/forms.html#category-autocapitalize
     virtual bool is_auto_capitalize_inheriting() const { return false; }
 
-protected:
-    FormAssociatedElement(DOM::Document& document, DOM::QualifiedName qualified_name)
-        : HTMLElement(document, move(qualified_name))
-    {
-    }
+    virtual HTMLElement& form_associated_element_to_html_element() = 0;
 
+protected:
+    FormAssociatedElement() = default;
     virtual ~FormAssociatedElement() = default;
 
+    virtual void form_associated_element_was_inserted() { }
+    virtual void form_associated_element_was_removed(DOM::Node*) { }
+
+    void form_node_was_inserted();
+    void form_node_was_removed();
+
 private:
     WeakPtr<HTMLFormElement> m_form;
 
@@ -50,10 +82,6 @@ private:
     bool m_parser_inserted { false };
 
     void reset_form_owner();
-
-    // ^DOM::Node
-    virtual void inserted() override;
-    virtual void removed_from(DOM::Node*) override;
 };
 
 }

Userland/Libraries/LibWeb/HTML/HTMLButtonElement.cpp

@@ -11,7 +11,7 @@
 namespace Web::HTML {
 
 HTMLButtonElement::HTMLButtonElement(DOM::Document& document, DOM::QualifiedName qualified_name)
-    : FormAssociatedElement(document, move(qualified_name))
+    : HTMLElement(document, move(qualified_name))
 {
     // https://html.spec.whatwg.org/multipage/form-elements.html#the-button-element:activation-behaviour
     activation_behavior = [this](auto&) {

Userland/Libraries/LibWeb/HTML/HTMLButtonElement.h

@@ -7,6 +7,7 @@
 #pragma once
 
 #include <LibWeb/HTML/FormAssociatedElement.h>
+#include <LibWeb/HTML/HTMLElement.h>
 
 namespace Web::HTML {
 
@@ -15,7 +16,11 @@ namespace Web::HTML {
     __ENUMERATE_HTML_BUTTON_TYPE_ATTRIBUTE(reset, Reset)   \
     __ENUMERATE_HTML_BUTTON_TYPE_ATTRIBUTE(button, Button)
 
-class HTMLButtonElement final : public FormAssociatedElement {
+class HTMLButtonElement final
+    : public HTMLElement
+    , public FormAssociatedElement {
+    FORM_ASSOCIATED_ELEMENT(HTMLElement, HTMLButtonElement)
+
 public:
     using WrapperType = Bindings::HTMLButtonElementWrapper;
 

Userland/Libraries/LibWeb/HTML/HTMLFieldSetElement.cpp

@@ -9,7 +9,7 @@
 namespace Web::HTML {
 
 HTMLFieldSetElement::HTMLFieldSetElement(DOM::Document& document, DOM::QualifiedName qualified_name)
-    : FormAssociatedElement(document, move(qualified_name))
+    : HTMLElement(document, move(qualified_name))
 {
 }
 

Userland/Libraries/LibWeb/HTML/HTMLFieldSetElement.h

@@ -7,10 +7,15 @@
 #pragma once
 
 #include <LibWeb/HTML/FormAssociatedElement.h>
+#include <LibWeb/HTML/HTMLElement.h>
 
 namespace Web::HTML {
 
-class HTMLFieldSetElement final : public FormAssociatedElement {
+class HTMLFieldSetElement final
+    : public HTMLElement
+    , public FormAssociatedElement {
+    FORM_ASSOCIATED_ELEMENT(HTMLElement, HTMLFieldSetElement)
+
 public:
     using WrapperType = Bindings::HTMLFieldSetElementWrapper;
 

Userland/Libraries/LibWeb/HTML/HTMLImageElement.cpp

@@ -18,7 +18,7 @@
 namespace Web::HTML {
 
 HTMLImageElement::HTMLImageElement(DOM::Document& document, DOM::QualifiedName qualified_name)
-    : FormAssociatedElement(document, move(qualified_name))
+    : HTMLElement(document, move(qualified_name))
     , m_image_loader(*this)
 {
     m_image_loader.on_load = [this] {

Userland/Libraries/LibWeb/HTML/HTMLImageElement.h

@@ -10,11 +10,16 @@
 #include <AK/OwnPtr.h>
 #include <LibGfx/Forward.h>
 #include <LibWeb/HTML/FormAssociatedElement.h>
+#include <LibWeb/HTML/HTMLElement.h>
 #include <LibWeb/Loader/ImageLoader.h>
 
 namespace Web::HTML {
 
-class HTMLImageElement final : public FormAssociatedElement {
+class HTMLImageElement final
+    : public HTMLElement
+    , public FormAssociatedElement {
+    FORM_ASSOCIATED_ELEMENT(HTMLElement, HTMLImageElement)
+
 public:
     using WrapperType = Bindings::HTMLImageElementWrapper;
 

Userland/Libraries/LibWeb/HTML/HTMLInputElement.cpp

@@ -21,7 +21,7 @@
 namespace Web::HTML {
 
 HTMLInputElement::HTMLInputElement(DOM::Document& document, DOM::QualifiedName qualified_name)
-    : FormAssociatedElement(document, move(qualified_name))
+    : HTMLElement(document, move(qualified_name))
     , m_value(String::empty())
 {
     activation_behavior = [this](auto&) {
@@ -215,7 +215,7 @@ bool HTMLInputElement::is_focusable() const
 
 void HTMLInputElement::parse_attribute(FlyString const& name, String const& value)
 {
-    FormAssociatedElement::parse_attribute(name, value);
+    HTMLElement::parse_attribute(name, value);
     if (name == HTML::AttributeNames::checked) {
         // When the checked content attribute is added, if the control does not have dirty checkedness,
         // the user agent must set the checkedness of the element to true
@@ -245,7 +245,7 @@ HTMLInputElement::TypeAttributeState HTMLInputElement::parse_type_attribute(Stri
 
 void HTMLInputElement::did_remove_attribute(FlyString const& name)
 {
-    FormAssociatedElement::did_remove_attribute(name);
+    HTMLElement::did_remove_attribute(name);
     if (name == HTML::AttributeNames::checked) {
         // When the checked content attribute is removed, if the control does not have dirty checkedness,
         // the user agent must set the checkedness of the element to false.
@@ -310,7 +310,7 @@ String HTMLInputElement::value_sanitization_algorithm(String value) const
     return value;
 }
 
-void HTMLInputElement::inserted()
+void HTMLInputElement::form_associated_element_was_inserted()
 {
     create_shadow_tree_if_needed();
 }

Userland/Libraries/LibWeb/HTML/HTMLInputElement.h

@@ -37,7 +37,11 @@ namespace Web::HTML {
     __ENUMERATE_HTML_INPUT_TYPE_ATTRIBUTE(reset, ResetButton)                 \
     __ENUMERATE_HTML_INPUT_TYPE_ATTRIBUTE(button, Button)
 
-class HTMLInputElement final : public FormAssociatedElement {
+class HTMLInputElement final
+    : public HTMLElement
+    , public FormAssociatedElement {
+    FORM_ASSOCIATED_ELEMENT(HTMLElement, HTMLInputElement)
+
 public:
     using WrapperType = Bindings::HTMLInputElementWrapper;
 
@@ -92,12 +96,12 @@ public:
     // https://html.spec.whatwg.org/multipage/forms.html#category-autocapitalize
     virtual bool is_auto_capitalize_inheriting() const override { return true; }
 
+    virtual void form_associated_element_was_inserted() override;
+
     // ^HTMLElement
     // https://html.spec.whatwg.org/multipage/forms.html#category-label
     virtual bool is_labelable() const override { return type_state() != TypeAttributeState::Hidden; }
 
-    virtual void inserted() override;
-
 private:
     // ^DOM::EventTarget
     virtual void did_receive_focus() override;

Userland/Libraries/LibWeb/HTML/HTMLObjectElement.cpp

@@ -15,7 +15,7 @@
 namespace Web::HTML {
 
 HTMLObjectElement::HTMLObjectElement(DOM::Document& document, DOM::QualifiedName qualified_name)
-    : FormAssociatedElement(document, move(qualified_name))
+    : HTMLElement(document, move(qualified_name))
 {
 }
 

Userland/Libraries/LibWeb/HTML/HTMLObjectElement.h

@@ -9,13 +9,17 @@
 #include <LibCore/Forward.h>
 #include <LibGfx/Forward.h>
 #include <LibWeb/HTML/FormAssociatedElement.h>
+#include <LibWeb/HTML/HTMLElement.h>
 #include <LibWeb/Loader/ImageLoader.h>
 
 namespace Web::HTML {
 
 class HTMLObjectElement final
-    : public FormAssociatedElement
+    : public HTMLElement
+    , public FormAssociatedElement
     , public ResourceClient {
+    FORM_ASSOCIATED_ELEMENT(HTMLElement, HTMLObjectElement)
+
 public:
     using WrapperType = Bindings::HTMLObjectElementWrapper;
 

Userland/Libraries/LibWeb/HTML/HTMLOutputElement.cpp

@@ -9,7 +9,7 @@
 namespace Web::HTML {
 
 HTMLOutputElement::HTMLOutputElement(DOM::Document& document, DOM::QualifiedName qualified_name)
-    : FormAssociatedElement(document, move(qualified_name))
+    : HTMLElement(document, move(qualified_name))
 {
 }
 

Userland/Libraries/LibWeb/HTML/HTMLOutputElement.h

@@ -8,10 +8,15 @@
 #pragma once
 
 #include <LibWeb/HTML/FormAssociatedElement.h>
+#include <LibWeb/HTML/HTMLElement.h>
 
 namespace Web::HTML {
 
-class HTMLOutputElement final : public FormAssociatedElement {
+class HTMLOutputElement final
+    : public HTMLElement
+    , public FormAssociatedElement {
+    FORM_ASSOCIATED_ELEMENT(HTMLElement, HTMLOutputElement)
+
 public:
     using WrapperType = Bindings::HTMLOutputElementWrapper;
 

Userland/Libraries/LibWeb/HTML/HTMLSelectElement.cpp

@@ -13,7 +13,7 @@
 namespace Web::HTML {
 
 HTMLSelectElement::HTMLSelectElement(DOM::Document& document, DOM::QualifiedName qualified_name)
-    : FormAssociatedElement(document, move(qualified_name))
+    : HTMLElement(document, move(qualified_name))
 {
 }
 

Userland/Libraries/LibWeb/HTML/HTMLSelectElement.h

@@ -14,7 +14,11 @@
 
 namespace Web::HTML {
 
-class HTMLSelectElement final : public FormAssociatedElement {
+class HTMLSelectElement final
+    : public HTMLElement
+    , public FormAssociatedElement {
+    FORM_ASSOCIATED_ELEMENT(HTMLElement, HTMLSelectElement)
+
 public:
     using WrapperType = Bindings::HTMLSelectElementWrapper;
 

Userland/Libraries/LibWeb/HTML/HTMLTextAreaElement.cpp

@@ -9,7 +9,7 @@
 namespace Web::HTML {
 
 HTMLTextAreaElement::HTMLTextAreaElement(DOM::Document& document, DOM::QualifiedName qualified_name)
-    : FormAssociatedElement(document, move(qualified_name))
+    : HTMLElement(document, move(qualified_name))
 {
 }
 

Userland/Libraries/LibWeb/HTML/HTMLTextAreaElement.h

@@ -8,10 +8,15 @@
 #pragma once
 
 #include <LibWeb/HTML/FormAssociatedElement.h>
+#include <LibWeb/HTML/HTMLElement.h>
 
 namespace Web::HTML {
 
-class HTMLTextAreaElement final : public FormAssociatedElement {
+class HTMLTextAreaElement final
+    : public HTMLElement
+    , public FormAssociatedElement {
+    FORM_ASSOCIATED_ELEMENT(HTMLElement, HTMLTextAreaElement)
+
 public:
     using WrapperType = Bindings::HTMLTextAreaElementWrapper;
 

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

@@ -632,14 +632,17 @@ NonnullRefPtr<DOM::Element> HTMLParser::create_element_for(HTMLToken const& toke
     //     then associate element with the form element pointed to by the form element pointer and set element's parser inserted flag.
     // FIXME: Check if the element is not a form-associated custom element.
     if (is<FormAssociatedElement>(*element)) {
-        auto& form_associated_element = static_cast<FormAssociatedElement&>(*element);
+        auto* form_associated_element = dynamic_cast<FormAssociatedElement*>(element.ptr());
+        VERIFY(form_associated_element);
+
+        auto& html_element = form_associated_element->form_associated_element_to_html_element();
 
         if (m_form_element
             && !m_stack_of_open_elements.contains(HTML::TagNames::template_)
-            && (!form_associated_element.is_listed() || !form_associated_element.has_attribute(HTML::AttributeNames::form))
+            && (!form_associated_element->is_listed() || !html_element.has_attribute(HTML::AttributeNames::form))
             && &intended_parent.root() == &m_form_element->root()) {
-            form_associated_element.set_form(m_form_element);
-            form_associated_element.set_parser_inserted({});
+            form_associated_element->set_form(m_form_element);
+            form_associated_element->set_parser_inserted({});
         }
     }
 

Userland/Libraries/LibWeb/Layout/FormAssociatedLabelableNode.h

@@ -8,18 +8,19 @@
 
 #include <LibWeb/Forward.h>
 #include <LibWeb/HTML/FormAssociatedElement.h>
+#include <LibWeb/HTML/HTMLElement.h>
 #include <LibWeb/Layout/LabelableNode.h>
 
 namespace Web::Layout {
 
 class FormAssociatedLabelableNode : public LabelableNode {
 public:
-    const HTML::FormAssociatedElement& dom_node() const { return static_cast<const HTML::FormAssociatedElement&>(LabelableNode::dom_node()); }
-    HTML::FormAssociatedElement& dom_node() { return static_cast<HTML::FormAssociatedElement&>(LabelableNode::dom_node()); }
+    const HTML::FormAssociatedElement& dom_node() const { return dynamic_cast<const HTML::FormAssociatedElement&>(LabelableNode::dom_node()); }
+    HTML::FormAssociatedElement& dom_node() { return dynamic_cast<HTML::FormAssociatedElement&>(LabelableNode::dom_node()); }
 
 protected:
     FormAssociatedLabelableNode(DOM::Document& document, HTML::FormAssociatedElement& element, NonnullRefPtr<CSS::StyleProperties> style)
-        : LabelableNode(document, element, move(style))
+        : LabelableNode(document, element.form_associated_element_to_html_element(), move(style))
     {
     }