enum.diff

diff --git a/lib/web_ui/lib/src/engine/semantics/label_and_value.dart b/lib/web_ui/lib/src/engine/semantics/label_and_value.dart
index 843c4dedda..74ccc08d2a 100644
--- a/lib/web_ui/lib/src/engine/semantics/label_and_value.dart
+++ b/lib/web_ui/lib/src/engine/semantics/label_and_value.dart
@@ -16,7 +16,7 @@ import 'semantics.dart';
 /// respect the `aria-label` without a [DomText] node. Crawlers typically do not
 /// need this information, as they primarily scan visible text, which is
 /// communicated in semantics as leaf text and heading nodes.
-enum LabelRepresentation {
+sealed class LabelRepresentation {
   /// Represents the label as an `aria-label` attribute.
   ///
   /// This representation is the most efficient as all it does is pass a string
@@ -27,7 +27,7 @@ enum LabelRepresentation {
   /// role) JAWS on Windows. However, this role is still the most common, as it
   /// applies to all container nodes, and many ARIA roles (e.g. checkboxes,
   /// radios, scrollables, sliders).
-  ariaLabel(AriaLabelRepresentation),
+  static const LabelRepresentation ariaLabel = _AriaLabel();

   /// Represents the label as a [DomText] node.
   ///
@@ -37,7 +37,7 @@ enum LabelRepresentation {
   ///
   /// This representation is compatible with most web crawlers, and it is the
   /// best option for certain ARIA roles, such as buttons, links, and headings.
-  domText(DomTextRepresentation),
+  static const LabelRepresentation domText = _DomText();

   /// Represents the label as a sized span.
   ///
@@ -45,17 +45,38 @@ enum LabelRepresentation {
   /// need to be laid out to compute the right size. It is compatible with most
   /// web crawlers, and it is the best options for certain ARIA roles, such as
   /// the implicit "generic" role used for plain text (not headings).
-  sizedSpan(SizedSpanRepresentation);
-
-  const LabelRepresentation(this.implementation);
+  static const LabelRepresentation sizedSpan = _SizedSpan();

   /// The type used to implement this representation.
-  final Type implementation;
+  LabelRepresentationBehavior createBehavior(PrimaryRoleManager owner);
+}
+
+final class _AriaLabel implements LabelRepresentation {
+  const _AriaLabel();
+
+  @override
+  LabelRepresentationBehavior createBehavior(PrimaryRoleManager owner) => AriaLabelRepresentation._(owner);
+}
+
+final class _DomText implements LabelRepresentation {
+  const _DomText();
+
+  @override
+  LabelRepresentationBehavior createBehavior(PrimaryRoleManager owner) => DomTextRepresentation._(owner);
+}
+
+final class _SizedSpan implements LabelRepresentation {
+  const _SizedSpan();
+
+  @override
+  LabelRepresentationBehavior createBehavior(PrimaryRoleManager owner) => SizedSpanRepresentation._(owner);
 }

 /// Provides a DOM behavior for a [LabelRepresentation].
 abstract final class LabelRepresentationBehavior {
-  LabelRepresentationBehavior(this.owner);
+  LabelRepresentationBehavior(this.kind, this.owner);
+
+  final LabelRepresentation kind;

   /// The role manager that this label representation is attached to.
   final PrimaryRoleManager owner;
@@ -103,7 +124,7 @@ abstract final class LabelRepresentationBehavior {
 ///
 ///     <flt-semantics aria-label="Hello, World!"></flt-semantics>
 final class AriaLabelRepresentation extends LabelRepresentationBehavior {
-  AriaLabelRepresentation._(super.owner);
+  AriaLabelRepresentation._(PrimaryRoleManager owner) : super(LabelRepresentation.ariaLabel, owner);

   String? _previousLabel;

@@ -137,7 +158,7 @@ final class AriaLabelRepresentation extends LabelRepresentationBehavior {
 /// no ARIA role set, or the role does not size the element, then the
 /// [SizedSpanRepresentation] representation can be used.
 final class DomTextRepresentation extends LabelRepresentationBehavior {
-  DomTextRepresentation._(super.owner);
+  DomTextRepresentation._(PrimaryRoleManager owner) : super(LabelRepresentation.domText, owner);

   DomText? _domText;
   String? _previousLabel;
@@ -200,7 +221,7 @@ typedef _Measurement = ({
 /// Text scaling is used to control the size of the screen reader focus ring.
 /// This is used for plain text nodes (e.g. paragraphs of text).
 final class SizedSpanRepresentation extends LabelRepresentationBehavior {
-  SizedSpanRepresentation._(super.owner) {
+  SizedSpanRepresentation._(PrimaryRoleManager owner) : super(LabelRepresentation.sizedSpan, owner) {
     _domText.style
       // `inline-block` is needed for two reasons:
       // - It supports measuring the true size of the text. Pure `block` would
@@ -423,13 +444,9 @@ class LabelAndValue extends RoleManager {
       : preferredRepresentation;

     LabelRepresentationBehavior? representation = _representation;
-    if (representation == null || representation.runtimeType != effectiveRepresentation.implementation) {
+    if (representation == null || representation.kind != effectiveRepresentation) {
       representation?.cleanUp();
-      _representation = representation = switch (effectiveRepresentation) {
-        LabelRepresentation.ariaLabel => AriaLabelRepresentation._(owner),
-        LabelRepresentation.domText => DomTextRepresentation._(owner),
-        LabelRepresentation.sizedSpan => SizedSpanRepresentation._(owner),
-      };
+      _representation = representation = effectiveRepresentation.createBehavior(owner);
     }
     return representation;
   }