Fix errors in examples (#87962)

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

@@ -44,7 +44,7 @@ import 'theme_data.dart';
 ///     ),
 ///   ),
 /// )
-///```
+/// ```
 ///
 /// In this case the background color for all other button states would fallback
 /// to the ElevatedButton’s default values. To unconditionally set the button's
@@ -56,7 +56,7 @@ import 'theme_data.dart';
 ///     backgroundColor: MaterialStateProperty.all<Color>(Colors.green),
 ///   ),
 /// )
-///```
+/// ```
 ///
 /// Configuring a ButtonStyle directly makes it possible to very
 /// precisely control the button’s visual attributes for all states.
@@ -77,7 +77,7 @@ import 'theme_data.dart';
 /// TextButton(
 ///   style: TextButton.styleFrom(primary: Colors.green),
 /// )
-///```
+/// ```
 ///
 /// To configure all of the application's text buttons in the same
 /// way, specify the overall theme's `textButtonTheme`:
@@ -90,7 +90,7 @@ import 'theme_data.dart';
 ///   ),
 ///   home: MyAppHome(),
 /// )
-///```
+/// ```
 /// See also:
 ///
 ///  * [TextButtonTheme], the theme for [TextButton]s.

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

@@ -109,7 +109,7 @@ import 'theme_data.dart';
 ///   final String label;
 ///   final EdgeInsets padding;
 ///   final bool value;
-///   final Function onChanged;
+///   final ValueChanged<bool> onChanged;
 ///
 ///   @override
 ///   Widget build(BuildContext context) {
@@ -135,7 +135,7 @@ import 'theme_data.dart';
 ///           Checkbox(
 ///             value: value,
 ///             onChanged: (bool? newValue) {
-///               onChanged(newValue);
+///               onChanged(newValue!);
 ///             },
 ///           ),
 ///         ],
@@ -190,7 +190,7 @@ import 'theme_data.dart';
 ///   final String label;
 ///   final EdgeInsets padding;
 ///   final bool value;
-///   final Function onChanged;
+///   final ValueChanged<bool> onChanged;
 ///
 ///   @override
 ///   Widget build(BuildContext context) {
@@ -206,7 +206,7 @@ import 'theme_data.dart';
 ///             Checkbox(
 ///               value: value,
 ///               onChanged: (bool? newValue) {
-///                 onChanged(newValue);
+///                 onChanged(newValue!);
 ///               },
 ///             ),
 ///           ],

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

@@ -120,7 +120,7 @@ import 'theme_data.dart';
 ///   final EdgeInsets padding;
 ///   final bool groupValue;
 ///   final bool value;
-///   final Function onChanged;
+///   final ValueChanged<bool> onChanged;
 ///
 ///   @override
 ///   Widget build(BuildContext context) {
@@ -132,7 +132,7 @@ import 'theme_data.dart';
 ///             groupValue: groupValue,
 ///             value: value,
 ///             onChanged: (bool? newValue) {
-///               onChanged(newValue);
+///               onChanged(newValue!);
 ///             }
 ///           ),
 ///           RichText(
@@ -221,7 +221,7 @@ import 'theme_data.dart';
 ///   final EdgeInsets padding;
 ///   final bool groupValue;
 ///   final bool value;
-///   final Function onChanged;
+///   final ValueChanged<bool> onChanged;
 ///
 ///   @override
 ///   Widget build(BuildContext context) {
@@ -239,7 +239,7 @@ import 'theme_data.dart';
 ///               groupValue: groupValue,
 ///               value: value,
 ///               onChanged: (bool? newValue) {
-///                 onChanged(newValue);
+///                 onChanged(newValue!);
 ///               },
 ///             ),
 ///             Text(label),

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

@@ -112,7 +112,7 @@ enum _SwitchListTileType { material, adaptive }
 ///   final String label;
 ///   final EdgeInsets padding;
 ///   final bool value;
-///   final Function onChanged;
+///   final ValueChanged<bool> onChanged;
 ///
 ///   @override
 ///   Widget build(BuildContext context) {
@@ -193,7 +193,7 @@ enum _SwitchListTileType { material, adaptive }
 ///   final String label;
 ///   final EdgeInsets padding;
 ///   final bool value;
-///   final Function onChanged;
+///   final ValueChanged<bool> onChanged;
 ///
 ///   @override
 ///   Widget build(BuildContext context) {

packages/flutter/lib/src/widgets/implicit_animations.dart

@@ -1139,7 +1139,7 @@ class _AnimatedAlignState extends AnimatedWidgetBaseState<AnimatedAlign> {
 ///     ),
 ///   );
 /// }
-///```
+/// ```
 /// {@end-tool}
 ///
 /// See also:

packages/flutter/lib/src/widgets/preferred_size.dart

@@ -94,7 +94,7 @@ abstract class PreferredSizeWidget implements Widget {
 ///   }
 /// }
 /// ```
-///```dart
+/// ```dart
 /// Widget build(BuildContext context) {
 ///   return Scaffold(
 ///     appBar: PreferredSize(

packages/flutter/lib/src/widgets/scroll_notification_observer.dart

@@ -50,7 +50,7 @@ class _ListenerEntry extends LinkedListEntry<_ListenerEntry> {
 /// To remove the listener from a [ScrollNotificationObserver] ancestor:
 /// ```dart
 /// ScrollNotificationObserver.of(context).removeListener(listener);
-///```
+/// ```
 ///
 /// Stateful widgets that share an ancestor [ScrollNotificationObserver] typically
 /// add a listener in [State.didChangeDependencies] (removing the old one

packages/flutter_driver/lib/src/extension/extension.dart

@@ -163,7 +163,7 @@ class _DriverBinding extends BindingBase with SchedulerBinding, ServicesBinding,
 ///
 ///   final int times;
 /// }
-///```
+/// ```
 ///
 /// ```dart
 /// class SomeCommandResult extends Result {

packages/flutter_tools/lib/src/asset.dart

@@ -28,12 +28,12 @@ const String kFontManifestJson = 'FontManifest.json';
 /// The effect of adding `uses-material-design: true` to the pubspec is to insert
 /// the following snippet into the asset manifest:
 ///
-///```yaml
+/// ```yaml
 /// material:
 ///   - family: MaterialIcons
 ///     fonts:
 ///       - asset: fonts/MaterialIcons-Regular.otf
-///```
+/// ```
 const List<Map<String, Object>> kMaterialFonts = <Map<String, Object>>[
   <String, Object>{
     'family': 'MaterialIcons',