fix doc-comment snippets (#25579)

dev/bots/test/analyze-sample-code-test-input/known_broken_documentation.dart

@@ -39,5 +39,5 @@
 /// new Opacity(
 ///   opacity: _visible ? 1.0 : 0.0,
 ///   child: const Text('Poor wandering ones!'),
-/// ),
+/// )
 /// ```

examples/catalog/lib/custom_a11y_traversal.dart

@@ -59,18 +59,18 @@ class RowColumnTraversal extends StatelessWidget {
   /// This function expresses the sort keys as a hierarchy, but it could just as
   /// easily have been a flat list:
   ///
-  /// ```
-  ///  Widget build(BuildContext context) {
-  ///    return new Semantics(
-  ///      sortOrder: new SemanticsSortOrder(
-  ///        keys: <SemanticsSortKey>[
-  ///          new OrdinalSortKey(columnOrder.toDouble()),
-  ///          new OrdinalSortKey(rowOrder.toDouble())
-  ///        ],
-  ///      ),
-  ///      child: child,
-  ///    );
-  ///  }
+  /// ```dart
+  /// Widget build(BuildContext context) {
+  ///   return new Semantics(
+  ///     sortOrder: new SemanticsSortOrder(
+  ///       keys: <SemanticsSortKey>[
+  ///         new OrdinalSortKey(columnOrder.toDouble()),
+  ///         new OrdinalSortKey(rowOrder.toDouble())
+  ///       ],
+  ///     ),
+  ///     child: child,
+  ///   );
+  /// }
   /// ```
   ///
   /// The resulting order is the same.

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

@@ -181,12 +181,12 @@ class MaterialApp extends StatefulWidget {
   /// ```dart
   /// import 'package:flutter_localizations/flutter_localizations.dart';
   /// MaterialApp(
-  ///  localizationsDelegates: [
-  ///    // ... app-specific localization delegate[s] here
-  ///    GlobalMaterialLocalizations.delegate,
-  ///    GlobalWidgetsLocalizations.delegate,
-  ///  ],
-  ///  supportedLocales: [
+  ///   localizationsDelegates: [
+  ///     // ... app-specific localization delegate[s] here
+  ///     GlobalMaterialLocalizations.delegate,
+  ///     GlobalWidgetsLocalizations.delegate,
+  ///   ],
+  ///   supportedLocales: [
   ///     const Locale('en', 'US'), // English
   ///     const Locale('he', 'IL'), // Hebrew
   ///     // ... other locales the app supports

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

@@ -79,47 +79,47 @@ enum BottomNavigationBarType {
 ///
 /// ```dart
 /// class MyHomePage extends StatefulWidget {
-///  MyHomePage({Key key}) : super(key: key);
+///   MyHomePage({Key key}) : super(key: key);
 ///
-///  @override
-///  _MyHomePageState createState() => _MyHomePageState();
+///   @override
+///   _MyHomePageState createState() => _MyHomePageState();
 /// }
 ///
 /// class _MyHomePageState extends State<MyHomePage> {
-///  int _selectedIndex = 1;
-///  final _widgetOptions = [
-///    Text('Index 0: Home'),
-///    Text('Index 1: Business'),
-///    Text('Index 2: School'),
-///  ];
+///   int _selectedIndex = 1;
+///   final _widgetOptions = [
+///     Text('Index 0: Home'),
+///     Text('Index 1: Business'),
+///     Text('Index 2: School'),
+///   ];
 ///
-///  @override
-///  Widget build(BuildContext context) {
-///    return Scaffold(
-///      appBar: AppBar(
-///        title: Text('BottomNavigationBar Sample'),
-///      ),
-///      body: Center(
-///        child: _widgetOptions.elementAt(_selectedIndex),
-///      ),
-///      bottomNavigationBar: BottomNavigationBar(
-///        items: <BottomNavigationBarItem>[
-///          BottomNavigationBarItem(icon: Icon(Icons.home), title: Text('Home')),
-///          BottomNavigationBarItem(icon: Icon(Icons.business), title: Text('Business')),
-///          BottomNavigationBarItem(icon: Icon(Icons.school), title: Text('School')),
-///        ],
-///        currentIndex: _selectedIndex,
-///        fixedColor: Colors.deepPurple,
-///        onTap: _onItemTapped,
-///      ),
-///    );
-///  }
+///   @override
+///   Widget build(BuildContext context) {
+///     return Scaffold(
+///       appBar: AppBar(
+///         title: Text('BottomNavigationBar Sample'),
+///       ),
+///       body: Center(
+///         child: _widgetOptions.elementAt(_selectedIndex),
+///       ),
+///       bottomNavigationBar: BottomNavigationBar(
+///         items: <BottomNavigationBarItem>[
+///           BottomNavigationBarItem(icon: Icon(Icons.home), title: Text('Home')),
+///           BottomNavigationBarItem(icon: Icon(Icons.business), title: Text('Business')),
+///           BottomNavigationBarItem(icon: Icon(Icons.school), title: Text('School')),
+///         ],
+///         currentIndex: _selectedIndex,
+///         fixedColor: Colors.deepPurple,
+///         onTap: _onItemTapped,
+///       ),
+///     );
+///   }
 ///
-///  void _onItemTapped(int index) {
-///    setState(() {
-///      _selectedIndex = index;
-///    });
-///  }
+///   void _onItemTapped(int index) {
+///     setState(() {
+///       _selectedIndex = index;
+///     });
+///   }
 /// }
 /// ```
 ///

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

@@ -265,6 +265,7 @@ class ButtonThemeData extends Diagnosticable {
 
   /// Simply a convenience that returns [minWidth] and [height] as a
   /// [BoxConstraints] object:
+  ///
   /// ```dart
   /// return BoxConstraints(
   ///   minWidth: minWidth,

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

@@ -151,7 +151,7 @@ class IconButton extends StatelessWidget {
   ///   color: Colors.blue,
   ///   onPressed: _handleTap,
   ///   icon: Icons.widgets,
-  /// ),
+  /// )
   /// ```
   final Color color;
 

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

@@ -68,7 +68,8 @@ enum ScriptCategory {
 /// `Typography(platform: platform)` which uses [englishLike2014],
 /// [dense2014] and [tall2014]. To use the 2018 text theme
 /// geometries, specify a typography value:
-/// ```
+///
+/// ```dart
 /// Typography(
 ///   platorm: platform,
 ///   englishLike: Typography.englishLike2018,

packages/flutter/lib/src/painting/decoration.dart

@@ -33,7 +33,7 @@ abstract class Decoration extends Diagnosticable {
   ///
   /// This is intended to be used as follows:
   /// ```dart
-  ///   assert(myDecoration.debugAssertIsValid());
+  /// assert(myDecoration.debugAssertIsValid());
   /// ```
   bool debugAssertIsValid() => true;
 

packages/flutter/lib/src/painting/image_provider.dart

@@ -700,8 +700,8 @@ class MemoryImage extends ImageProvider<MemoryImage> {
 /// it in the `assets` section:
 ///
 /// ```yaml
-///  assets:
-///    - packages/fancy_backgrounds/backgrounds/background1.png
+///   assets:
+///     - packages/fancy_backgrounds/backgrounds/background1.png
 /// ```
 ///
 /// The `lib/` is implied, so it should not be included in the asset path.

packages/flutter/lib/src/painting/image_resolution.dart

@@ -111,8 +111,8 @@ const String _kAssetManifestFileName = 'AssetManifest.json';
 /// it in the `assets` section:
 ///
 /// ```yaml
-///  assets:
-///    - packages/fancy_backgrounds/backgrounds/background1.png
+///   assets:
+///     - packages/fancy_backgrounds/backgrounds/background1.png
 /// ```
 ///
 /// The `lib/` is implied, so it should not be included in the asset path.

packages/flutter/lib/src/scheduler/binding.dart

@@ -513,7 +513,7 @@ mixin SchedulerBinding on BindingBase, ServicesBinding {
   /// To call this function, use the following code:
   ///
   /// ```dart
-  ///   SchedulerBinding.debugPrintTransientCallbackRegistrationStack();
+  /// SchedulerBinding.debugPrintTransientCallbackRegistrationStack();
   /// ```
   static void debugPrintTransientCallbackRegistrationStack() {
     assert(() {

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

@@ -79,10 +79,10 @@ class Icon extends StatelessWidget {
   /// Typically, a material design color will be used, as follows:
   ///
   /// ```dart
-  ///  Icon(
-  ///    icon: Icons.widgets,
-  ///    color: Colors.blue.shade400,
-  ///  ),
+  /// Icon(
+  ///   icon: Icons.widgets,
+  ///   color: Colors.blue.shade400,
+  /// )
   /// ```
   final Color color;
 

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

@@ -368,8 +368,8 @@ class Image extends StatefulWidget {
   /// specify it in the assets section:
   ///
   /// ```yaml
-  ///  assets:
-  ///    - packages/fancy_backgrounds/backgrounds/background1.png
+  ///   assets:
+  ///     - packages/fancy_backgrounds/backgrounds/background1.png
   /// ```
   ///
   /// The `lib/` is implied, so it should not be included in the asset path.

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

@@ -595,18 +595,18 @@ class NavigatorObserver {
 ///
 /// ```dart
 /// class MyApp extends StatelessWidget {
-///  @override
-///  Widget build(BuildContext context) {
-///    return MaterialApp(
-///      // ...some parameters omitted...
-///      // MaterialApp contains our top-level Navigator
-///      initialRoute: '/',
-///      routes: {
-///        '/': (BuildContext context) => HomePage(),
-///        '/signup': (BuildContext context) => SignUpPage(),
-///      },
-///    );
-///  }
+///   @override
+///   Widget build(BuildContext context) {
+///     return MaterialApp(
+///       // ...some parameters omitted...
+///       // MaterialApp contains our top-level Navigator
+///       initialRoute: '/',
+///       routes: {
+///         '/': (BuildContext context) => HomePage(),
+///         '/signup': (BuildContext context) => SignUpPage(),
+///       },
+///     );
+///   }
 /// }
 ///
 /// class SignUpPage extends StatelessWidget {

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

@@ -117,6 +117,7 @@ class AndroidView extends StatefulWidget {
   ///
   /// For example, with the following setup vertical drags will not be dispatched to the Android
   /// view as the vertical drag gesture is claimed by the parent [GestureDetector].
+  ///
   /// ```dart
   /// GestureDetector(
   ///   onVerticalDragStart: (DragStartDetails d) {},
@@ -125,8 +126,10 @@ class AndroidView extends StatefulWidget {
   ///   ),
   /// )
   /// ```
+  ///
   /// To get the [AndroidView] to claim the vertical drag gestures we can pass a vertical drag
   /// gesture recognizer factory in [gestureRecognizers] e.g:
+  ///
   /// ```dart
   /// GestureDetector(
   ///   onVerticalDragStart: (DragStartDetails details) {},
@@ -247,6 +250,7 @@ class UiKitView extends StatefulWidget {
   ///
   /// For example, with the following setup vertical drags will not be dispatched to the UIKit
   /// view as the vertical drag gesture is claimed by the parent [GestureDetector].
+  ///
   /// ```dart
   /// GestureDetector(
   ///   onVerticalDragStart: (DragStartDetails details) {},
@@ -255,8 +259,10 @@ class UiKitView extends StatefulWidget {
   ///   ),
   /// )
   /// ```
+  ///
   /// To get the [UiKitView] to claim the vertical drag gestures we can pass a vertical drag
   /// gesture recognizer factory in [gestureRecognizers] e.g:
+  ///
   /// ```dart
   /// GestureDetector(
   ///   onVerticalDragStart: (DragStartDetails details) {},

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

@@ -297,11 +297,11 @@ class ScrollController extends ChangeNotifier {
 ///       controller: _trackingScrollController,
 ///       children: List<Widget>.generate(100, (int i) => Text('page 0 item $i')).toList(),
 ///     ),
-///    ListView(
-///      controller: _trackingScrollController,
-///      children: List<Widget>.generate(200, (int i) => Text('page 1 item $i')).toList(),
-///    ),
-///    ListView(
+///     ListView(
+///       controller: _trackingScrollController,
+///       children: List<Widget>.generate(200, (int i) => Text('page 1 item $i')).toList(),
+///     ),
+///     ListView(
 ///      controller: _trackingScrollController,
 ///      children: List<Widget>.generate(300, (int i) => Text('page 2 item $i')).toList(),
 ///     ),

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

@@ -41,6 +41,7 @@ class ScrollPhysics {
   /// ScrollPhysics that has [ancestor] as its parent.
   ///
   /// This method is typically used to define [applyTo] methods like:
+  ///
   /// ```dart
   /// FooScrollPhysics applyTo(ScrollPhysics ancestor) {
   ///   return FooScrollPhysics(parent: buildParent(ancestor));

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

@@ -337,7 +337,6 @@ class Text extends StatelessWidget {
   ///
   /// ```dart
   /// Text(r'$$', semanticsLabel: 'Double dollars')
-  ///
   /// ```
   final String semanticsLabel;
 

packages/flutter/test/rendering/mock_canvas.dart

@@ -28,7 +28,7 @@ import 'recording_canvas.dart';
 /// To specify the pattern, call the methods on the returned object. For example:
 ///
 /// ```dart
-///  expect(myRenderObject, paints..circle(radius: 10.0)..circle(radius: 20.0));
+/// expect(myRenderObject, paints..circle(radius: 10.0)..circle(radius: 20.0));
 /// ```
 ///
 /// This particular pattern would verify that the render object `myRenderObject`

packages/flutter/test/widgets/semantics_tester.dart

@@ -495,6 +495,7 @@ class SemanticsTester {
   ///   ));
   ///   semantics.dispose();
   /// });
+  /// ```
   ///
   /// At this point the unit test should automatically pass because it was
   /// generated from the actual [SemanticsNode]s. Next time the semantics tree

packages/flutter_driver/lib/src/driver/driver.dart

@@ -601,12 +601,12 @@ class FlutterDriver {
   ///
   /// ```dart
   /// test('enters text in a text field', () async {
-  ///  var textField = find.byValueKey('enter-text-field');
-  ///  await driver.tap(textField);  // acquire focus
-  ///  await driver.enterText('Hello!');  // enter text
-  ///  await driver.waitFor(find.text('Hello!'));  // verify text appears on UI
-  ///  await driver.enterText('World!');  // enter another piece of text
-  ///  await driver.waitFor(find.text('World!'));  // verify new text appears
+  ///   var textField = find.byValueKey('enter-text-field');
+  ///   await driver.tap(textField);  // acquire focus
+  ///   await driver.enterText('Hello!');  // enter text
+  ///   await driver.waitFor(find.text('Hello!'));  // verify text appears on UI
+  ///   await driver.enterText('World!');  // enter another piece of text
+  ///   await driver.waitFor(find.text('World!'));  // verify new text appears
   /// });
   /// ```
   Future<void> enterText(String text, { Duration timeout }) async {

packages/flutter_test/lib/src/widget_tester.dart

@@ -59,11 +59,11 @@ typedef WidgetTesterCallback = Future<void> Function(WidgetTester widgetTester);
 /// ## Sample code
 ///
 /// ```dart
-///     testWidgets('MyWidget', (WidgetTester tester) async {
-///       await tester.pumpWidget(new MyWidget());
-///       await tester.tap(find.text('Save'));
-///       expect(find.text('Success'), findsOneWidget);
-///     });
+/// testWidgets('MyWidget', (WidgetTester tester) async {
+///   await tester.pumpWidget(new MyWidget());
+///   await tester.tap(find.text('Save'));
+///   expect(find.text('Success'), findsOneWidget);
+/// });
 /// ```
 @isTest
 void testWidgets(String description, WidgetTesterCallback callback, {