Add toggled semantics to `ToggleButtons` (#106096)

packages/flutter/lib/src/material/toggle_buttons.dart

@@ -790,6 +790,7 @@ class ToggleButtons extends StatelessWidget {
       return MergeSemantics(
         child: Semantics(
           container: true,
+          toggled: isSelected[index],
           enabled: onPressed != null,
           child: _InputPadding(
             minSize: minPaddingSize,

packages/flutter/test/material/toggle_buttons_test.dart

@@ -2006,6 +2006,7 @@ void main() {
                 SemanticsFlag.isButton,
                 SemanticsFlag.isEnabled,
                 SemanticsFlag.hasEnabledState,
+                SemanticsFlag.hasToggledState,
                 SemanticsFlag.isFocusable,
               ],
               actions: <SemanticsAction>[
@@ -2018,6 +2019,7 @@ void main() {
                 SemanticsFlag.isButton,
                 SemanticsFlag.isEnabled,
                 SemanticsFlag.hasEnabledState,
+                SemanticsFlag.hasToggledState,
                 SemanticsFlag.isFocusable,
               ],
               actions: <SemanticsAction>[
@@ -2030,6 +2032,7 @@ void main() {
                 SemanticsFlag.isButton,
                 SemanticsFlag.isEnabled,
                 SemanticsFlag.hasEnabledState,
+                SemanticsFlag.hasToggledState,
                 SemanticsFlag.isFocusable,
               ],
               actions: <SemanticsAction>[
@@ -2045,6 +2048,65 @@ void main() {
       ),
     );
 
+    semantics.dispose();
+  });
+
+    testWidgets('Toggle buttons have correct semantics', (WidgetTester tester) async {
+    final SemanticsTester semantics = SemanticsTester(tester);
+
+    await tester.pumpWidget(
+      Material(
+        child: boilerplate(
+          child: ToggleButtons(
+            isSelected: const <bool>[false, true],
+            onPressed: (int index) {},
+            children: const <Widget>[
+              Icon(Icons.check),
+              Icon(Icons.access_alarm),
+            ],
+          ),
+        ),
+      ),
+    );
+
+    expect(
+      semantics,
+      hasSemantics(
+        TestSemantics.root(
+          children: <TestSemantics>[
+            TestSemantics(
+              flags: <SemanticsFlag>[
+                SemanticsFlag.isButton,
+                SemanticsFlag.isEnabled,
+                SemanticsFlag.hasEnabledState,
+                SemanticsFlag.hasToggledState,
+                SemanticsFlag.isFocusable,
+              ],
+              actions: <SemanticsAction>[
+                SemanticsAction.tap,
+              ],
+            ),
+            TestSemantics(
+              flags: <SemanticsFlag>[
+                SemanticsFlag.isButton,
+                SemanticsFlag.isEnabled,
+                SemanticsFlag.hasEnabledState,
+                SemanticsFlag.isToggled,
+                SemanticsFlag.hasToggledState,
+                SemanticsFlag.isFocusable,
+              ],
+              actions: <SemanticsAction>[
+                SemanticsAction.tap,
+              ],
+            ),
+          ],
+        ),
+        ignoreId: true,
+        ignoreRect: true,
+        ignoreTransform: true,
+      ),
+    );
+
     semantics.dispose();
   });
 }