replace simple empty Container with w & h with SizedBox (#54394)

* replace simple Container(w & h) with SizedBox

* address review comments

* address review comments

packages/flutter/lib/src/cupertino/action_sheet.dart

@@ -834,7 +834,7 @@ class _CupertinoAlertContentSection extends StatelessWidget {
     if (titleContentGroup.isEmpty) {
       return SingleChildScrollView(
         controller: scrollController,
-        child: Container(
+        child: const SizedBox(
           width: 0.0,
           height: 0.0,
         ),

packages/flutter/lib/src/cupertino/context_menu.dart

@@ -1036,7 +1036,7 @@ class _ContextMenuRouteStaticState extends State<_ContextMenuRouteStatic> with T
         ),
       ),
     );
-    final Container spacer = Container(
+    const SizedBox spacer = SizedBox(
       width: _kPadding,
       height: _kPadding,
     );

packages/flutter/lib/src/cupertino/dialog.dart

@@ -867,7 +867,7 @@ class _CupertinoAlertContentSection extends StatelessWidget {
     if (title == null && content == null) {
       return SingleChildScrollView(
         controller: scrollController,
-        child: Container(width: 0.0, height: 0.0),
+        child: const SizedBox(width: 0.0, height: 0.0),
       );
     }
 

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

@@ -175,7 +175,7 @@ class DataCell {
   }) : assert(child != null);
 
   /// A cell that has no content and has zero width and height.
-  static final DataCell empty = DataCell(Container(width: 0.0, height: 0.0));
+  static const DataCell empty = DataCell(SizedBox(width: 0.0, height: 0.0));
 
   /// The data for the row.
   ///

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

@@ -100,7 +100,7 @@ class _TextSelectionToolbarState extends State<_TextSelectionToolbar> with Ticke
 
     // If there is no option available, build an empty widget.
     if (items.isEmpty) {
-      return Container(width: 0.0, height: 0.0);
+      return const SizedBox(width: 0.0, height: 0.0);
     }
 
 

packages/flutter/test/cupertino/scaffold_test.dart

@@ -236,7 +236,7 @@ void main() {
   });
 
   testWidgets('Contents have automatic sliver padding between translucent bars', (WidgetTester tester) async {
-    final Container content = Container(height: 600.0, width: 600.0);
+    const SizedBox content = SizedBox(height: 600.0, width: 600.0);
 
     await tester.pumpWidget(
       CupertinoApp(
@@ -264,7 +264,7 @@ void main() {
                       middle: Text('Title'),
                     ),
                     child: ListView(
-                      children: <Widget>[
+                      children: const <Widget>[
                         content,
                       ],
                     ),

packages/flutter/test/cupertino/text_field_test.dart

@@ -3623,7 +3623,7 @@ void main() {
                     focusNode: focusNode,
                     expands: true,
                     maxLines: null,
-                    prefix: Container(
+                    prefix: const SizedBox(
                       height: 100,
                       width: 10,
                     ),
@@ -3676,7 +3676,7 @@ void main() {
                     focusNode: focusNode,
                     expands: true,
                     maxLines: null,
-                    prefix: Container(
+                    prefix: const SizedBox(
                       height: 100,
                       width: 10,
                     ),
@@ -3730,7 +3730,7 @@ void main() {
                     focusNode: focusNode,
                     expands: true,
                     maxLines: null,
-                    prefix: Container(
+                    prefix: const SizedBox(
                       height: 100,
                       width: 10,
                     ),
@@ -3784,7 +3784,7 @@ void main() {
                     focusNode: focusNode,
                     expands: true,
                     maxLines: null,
-                    prefix: Container(
+                    prefix: const SizedBox(
                       height: 100,
                       width: 10,
                     ),

packages/flutter/test/material/text_field_test.dart

@@ -1084,8 +1084,8 @@ void main() {
     await tester.pumpAndSettle();
     final RenderBox container = tester.renderObject(find.descendant(
       of: find.byType(FadeTransition),
-      matching: find.byType(Container),
-    ));
+      matching: find.byType(SizedBox),
+    ).first);
     expect(container.size, Size.zero);
   }, variant: const TargetPlatformVariant(<TargetPlatform>{ TargetPlatform.android, TargetPlatform.fuchsia, TargetPlatform.linux, TargetPlatform.windows }));
 
@@ -2252,7 +2252,7 @@ void main() {
     await tester.pumpWidget(containedTextFieldBuilder(
       counter: Container(height: counterHeight),
       labelText: 'I am labelText',
-      prefix: Container(
+      prefix: const SizedBox(
         width: 10,
         height: 60,
       ),

packages/flutter/test/material/tooltip_test.dart

@@ -61,7 +61,7 @@ void main() {
                         padding: const EdgeInsets.all(5.0),
                         verticalOffset: 20.0,
                         preferBelow: false,
-                        child: Container(
+                        child: const SizedBox(
                           width: 0.0,
                           height: 0.0,
                         ),
@@ -118,7 +118,7 @@ void main() {
                         padding: const EdgeInsets.all(5.0),
                         verticalOffset: 20.0,
                         preferBelow: false,
-                        child: Container(
+                        child: const SizedBox(
                           width: 0.0,
                           height: 0.0,
                         ),
@@ -172,7 +172,7 @@ void main() {
                         padding: const EdgeInsets.all(0.0),
                         verticalOffset: 100.0,
                         preferBelow: false,
-                        child: Container(
+                        child: const SizedBox(
                           width: 0.0,
                           height: 0.0,
                         ),
@@ -228,7 +228,7 @@ void main() {
                         padding: const EdgeInsets.all(0.0),
                         verticalOffset: 100.0,
                         preferBelow: false,
-                        child: Container(
+                        child: const SizedBox(
                           width: 0.0,
                           height: 0.0,
                         ),
@@ -295,7 +295,7 @@ void main() {
                         padding: const EdgeInsets.all(0.0),
                         verticalOffset: 100.0,
                         preferBelow: true,
-                        child: Container(
+                        child: const SizedBox(
                           width: 0.0,
                           height: 0.0,
                         ),
@@ -350,7 +350,7 @@ void main() {
                         padding: const EdgeInsets.all(0.0),
                         verticalOffset: 10.0,
                         preferBelow: true,
-                        child: Container(
+                        child: const SizedBox(
                           width: 0.0,
                           height: 0.0,
                         ),
@@ -407,7 +407,7 @@ void main() {
                         padding: const EdgeInsets.all(0.0),
                         verticalOffset: 10.0,
                         preferBelow: true,
-                        child: Container(
+                        child: const SizedBox(
                           width: 0.0,
                           height: 0.0,
                         ),
@@ -458,7 +458,7 @@ void main() {
                   message: tooltipText,
                   padding: const EdgeInsets.all(0.0),
                   margin: const EdgeInsets.all(_customMarginValue),
-                  child: Container(
+                  child: const SizedBox(
                     width: 0.0,
                     height: 0.0,
                   ),
@@ -654,7 +654,7 @@ void main() {
                 return Tooltip(
                   key: key,
                   message: tooltipText,
-                  child: Container(
+                  child: const SizedBox(
                     width: 0.0,
                     height: 0.0,
                   ),
@@ -696,7 +696,7 @@ void main() {
                   key: key,
                   decoration: customDecoration,
                   message: tooltipText,
-                  child: Container(
+                  child: const SizedBox(
                     width: 0.0,
                     height: 0.0,
                   ),
@@ -780,12 +780,12 @@ void main() {
     await gesture.moveTo(Offset.zero);
 
     await tester.pumpWidget(
-      MaterialApp(
+      const MaterialApp(
         home: Center(
           child: Tooltip(
             message: tooltipText,
             waitDuration: waitDuration,
-            child: Container(
+            child: SizedBox(
               width: 100.0,
               height: 100.0,
             ),
@@ -838,7 +838,7 @@ void main() {
                       child: Tooltip(
                         key: key,
                         message: tooltipText,
-                        child: Container(width: 10.0, height: 10.0),
+                        child: const SizedBox(width: 10.0, height: 10.0),
                       ),
                     ),
                   ],

packages/flutter/test/material/tooltip_theme_test.dart

@@ -119,7 +119,7 @@ void main() {
                         child: Tooltip(
                           key: key,
                           message: tooltipText,
-                          child: Container(
+                          child: const SizedBox(
                             width: 0.0,
                             height: 0.0,
                           ),
@@ -177,7 +177,7 @@ void main() {
                         child: Tooltip(
                           key: key,
                           message: tooltipText,
-                          child: Container(
+                          child: const SizedBox(
                             width: 0.0,
                             height: 0.0,
                           ),
@@ -237,7 +237,7 @@ void main() {
                         child: Tooltip(
                           key: key,
                           message: tooltipText,
-                          child: Container(
+                          child: const SizedBox(
                             width: 0.0,
                             height: 0.0,
                           ),
@@ -306,7 +306,7 @@ void main() {
                         child: Tooltip(
                           key: key,
                           message: tooltipText,
-                          child: Container(
+                          child: const SizedBox(
                             width: 0.0,
                             height: 0.0,
                           ),
@@ -377,7 +377,7 @@ void main() {
                         child: Tooltip(
                           key: key,
                           message: tooltipText,
-                          child: Container(
+                          child: const SizedBox(
                             width: 0.0,
                             height: 0.0,
                           ),
@@ -434,7 +434,7 @@ void main() {
                         child: Tooltip(
                           key: key,
                           message: tooltipText,
-                          child: Container(
+                          child: const SizedBox(
                             width: 0.0,
                             height: 0.0,
                           ),
@@ -486,7 +486,7 @@ void main() {
                   child: Tooltip(
                     key: key,
                     message: tooltipText,
-                    child: Container(
+                    child: const SizedBox(
                       width: 0.0,
                       height: 0.0,
                     ),
@@ -542,7 +542,7 @@ void main() {
                   child: Tooltip(
                     key: key,
                     message: tooltipText,
-                    child: Container(
+                    child: const SizedBox(
                       width: 0.0,
                       height: 0.0,
                     ),
@@ -662,7 +662,7 @@ void main() {
                   return Tooltip(
                     key: key,
                     message: tooltipText,
-                    child: Container(
+                    child: const SizedBox(
                       width: 0.0,
                       height: 0.0,
                     ),
@@ -704,7 +704,7 @@ void main() {
                   return Tooltip(
                     key: key,
                     message: tooltipText,
-                    child: Container(
+                    child: const SizedBox(
                       width: 0.0,
                       height: 0.0,
                     ),
@@ -837,10 +837,10 @@ void main() {
               waitDuration: customWaitDuration,
             ),
           ),
-          child: Center(
+          child: const Center(
             child: Tooltip(
               message: tooltipText,
-              child: Container(
+              child: SizedBox(
                 width: 100.0,
                 height: 100.0,
               ),
@@ -878,13 +878,13 @@ void main() {
     await gesture.moveTo(Offset.zero);
 
     await tester.pumpWidget(
-      MaterialApp(
+      const MaterialApp(
         home: TooltipTheme(
-          data: const TooltipThemeData(waitDuration: customWaitDuration),
+          data: TooltipThemeData(waitDuration: customWaitDuration),
           child: Center(
             child: Tooltip(
               message: tooltipText,
-              child: Container(
+              child: SizedBox(
                 width: 100.0,
                 height: 100.0,
               ),
@@ -922,10 +922,10 @@ void main() {
               showDuration: customShowDuration,
             ),
           ),
-          child: Center(
+          child: const Center(
             child: Tooltip(
               message: tooltipText,
-              child: Container(
+              child: SizedBox(
                 width: 100.0,
                 height: 100.0,
               ),
@@ -952,13 +952,13 @@ void main() {
   testWidgets('Tooltip showDuration - TooltipTheme', (WidgetTester tester) async {
     const Duration customShowDuration = Duration(milliseconds: 3000);
     await tester.pumpWidget(
-      MaterialApp(
+      const MaterialApp(
         home: TooltipTheme(
-          data: const TooltipThemeData(showDuration: customShowDuration),
+          data: TooltipThemeData(showDuration: customShowDuration),
           child: Center(
             child: Tooltip(
               message: tooltipText,
-              child: Container(
+              child: SizedBox(
                 width: 100.0,
                 height: 100.0,
               ),

packages/flutter/test/widgets/align_test.dart

@@ -44,51 +44,51 @@ void main() {
   });
 
   testWidgets('Align control test (LTR)', (WidgetTester tester) async {
-    await tester.pumpWidget(Directionality(
+    await tester.pumpWidget(const Directionality(
       textDirection: TextDirection.ltr,
       child: Align(
-        child: Container(width: 100.0, height: 80.0),
+        child: SizedBox(width: 100.0, height: 80.0),
         alignment: AlignmentDirectional.topStart,
       ),
     ));
 
-    expect(tester.getTopLeft(find.byType(Container)).dx, 0.0);
-    expect(tester.getBottomRight(find.byType(Container)).dx, 100.0);
+    expect(tester.getTopLeft(find.byType(SizedBox)).dx, 0.0);
+    expect(tester.getBottomRight(find.byType(SizedBox)).dx, 100.0);
 
-    await tester.pumpWidget(Directionality(
+    await tester.pumpWidget(const Directionality(
       textDirection: TextDirection.ltr,
       child: Align(
-        child: Container(width: 100.0, height: 80.0),
+        child: SizedBox(width: 100.0, height: 80.0),
         alignment: Alignment.topLeft,
       ),
     ));
 
-    expect(tester.getTopLeft(find.byType(Container)).dx, 0.0);
-    expect(tester.getBottomRight(find.byType(Container)).dx, 100.0);
+    expect(tester.getTopLeft(find.byType(SizedBox)).dx, 0.0);
+    expect(tester.getBottomRight(find.byType(SizedBox)).dx, 100.0);
   });
 
   testWidgets('Align control test (RTL)', (WidgetTester tester) async {
-    await tester.pumpWidget(Directionality(
+    await tester.pumpWidget(const Directionality(
       textDirection: TextDirection.rtl,
       child: Align(
-        child: Container(width: 100.0, height: 80.0),
+        child: SizedBox(width: 100.0, height: 80.0),
         alignment: AlignmentDirectional.topStart,
       ),
     ));
 
-    expect(tester.getTopLeft(find.byType(Container)).dx, 700.0);
-    expect(tester.getBottomRight(find.byType(Container)).dx, 800.0);
+    expect(tester.getTopLeft(find.byType(SizedBox)).dx, 700.0);
+    expect(tester.getBottomRight(find.byType(SizedBox)).dx, 800.0);
 
-    await tester.pumpWidget(Directionality(
+    await tester.pumpWidget(const Directionality(
       textDirection: TextDirection.ltr,
       child: Align(
-        child: Container(width: 100.0, height: 80.0),
+        child: SizedBox(width: 100.0, height: 80.0),
         alignment: Alignment.topLeft,
       ),
     ));
 
-    expect(tester.getTopLeft(find.byType(Container)).dx, 0.0);
-    expect(tester.getBottomRight(find.byType(Container)).dx, 100.0);
+    expect(tester.getTopLeft(find.byType(SizedBox)).dx, 0.0);
+    expect(tester.getBottomRight(find.byType(SizedBox)).dx, 100.0);
   });
 
   testWidgets('Shrink wraps in finite space', (WidgetTester tester) async {
@@ -97,7 +97,7 @@ void main() {
       SingleChildScrollView(
         child: Align(
           key: alignKey,
-          child: Container(
+          child: const SizedBox(
             width: 10.0,
             height: 10.0,
           ),

packages/flutter/test/widgets/box_decoration_test.dart

@@ -112,7 +112,7 @@ Future<void> main() async {
         child: Container(
           key: key,
           decoration: BoxDecoration(border: Border.all(width: 10.0)),
-          child: Container(
+          child: const SizedBox(
             width: 25.0,
             height: 25.0,
           ),

packages/flutter/test/widgets/column_test.dart

@@ -338,9 +338,9 @@ void main() {
     await tester.pumpWidget(Center(
       child: Column(
         key: flexKey,
-        children: <Widget>[
-          Container(width: 100.0, height: 100.0),
-          Container(width: 100.0, height: 150.0),
+        children: const <Widget>[
+          SizedBox(width: 100.0, height: 100.0),
+          SizedBox(width: 100.0, height: 150.0),
         ],
       ),
     ));
@@ -353,9 +353,9 @@ void main() {
       child: Column(
         key: flexKey,
         mainAxisSize: MainAxisSize.min,
-        children: <Widget>[
-          Container(width: 100.0, height: 100.0),
-          Container(width: 100.0, height: 150.0),
+        children: const <Widget>[
+          SizedBox(width: 100.0, height: 100.0),
+          SizedBox(width: 100.0, height: 150.0),
         ],
       ),
     ));
@@ -729,9 +729,9 @@ void main() {
       child: Column(
         key: flexKey,
         verticalDirection: VerticalDirection.up,
-        children: <Widget>[
-          Container(width: 100.0, height: 100.0),
-          Container(width: 100.0, height: 150.0),
+        children: const <Widget>[
+          SizedBox(width: 100.0, height: 100.0),
+          SizedBox(width: 100.0, height: 150.0),
         ],
       ),
     ));
@@ -745,9 +745,9 @@ void main() {
         key: flexKey,
         mainAxisSize: MainAxisSize.min,
         verticalDirection: VerticalDirection.up,
-        children: <Widget>[
-          Container(width: 100.0, height: 100.0),
-          Container(width: 100.0, height: 150.0),
+        children: const <Widget>[
+          SizedBox(width: 100.0, height: 100.0),
+          SizedBox(width: 100.0, height: 150.0),
         ],
       ),
     ));

packages/flutter/test/widgets/composited_transform_test.dart

@@ -20,7 +20,7 @@ void main() {
               top: 456.0,
               child: CompositedTransformTarget(
                 link: link,
-                child: Container(height: 10.0, width: 10.0),
+                child: const SizedBox(height: 10.0, width: 10.0),
               ),
             ),
             Positioned(

packages/flutter/test/widgets/custom_multi_child_layout_test.dart

@@ -49,8 +49,8 @@ Widget buildFrame(MultiChildLayoutDelegate delegate) {
   return Center(
     child: CustomMultiChildLayout(
       children: <Widget>[
-        LayoutId(id: 0, child: Container(width: 150.0, height: 100.0)),
-        LayoutId(id: 1, child: Container(width: 100.0, height: 200.0)),
+        LayoutId(id: 0, child: const SizedBox(width: 150.0, height: 100.0)),
+        LayoutId(id: 1, child: const SizedBox(width: 100.0, height: 200.0)),
       ],
       delegate: delegate,
     ),
@@ -225,13 +225,13 @@ void main() {
             id: 0,
             child: CustomMultiChildLayout(
               children: <Widget>[
-                LayoutId(id: 0, child: Container(width: 150.0, height: 100.0)),
-                LayoutId(id: 1, child: Container(width: 100.0, height: 200.0)),
+                LayoutId(id: 0, child: const SizedBox(width: 150.0, height: 100.0)),
+                LayoutId(id: 1, child: const SizedBox(width: 100.0, height: 200.0)),
               ],
               delegate: delegate,
             ),
           ),
-          LayoutId(id: 1, child: Container(width: 100.0, height: 200.0)),
+          LayoutId(id: 1, child: const SizedBox(width: 100.0, height: 200.0)),
         ],
         delegate: delegate,
       ),

packages/flutter/test/widgets/custom_paint_test.dart

@@ -195,7 +195,7 @@ void main() {
     expect(target.currentContext.size, const Size(800.0, 600.0));
 
     await tester.pumpWidget(Center(
-      child: CustomPaint(key: target, child: Container(height: 0.0, width: 0.0)),
+      child: CustomPaint(key: target, child: const SizedBox(height: 0.0, width: 0.0)),
     ));
     expect(target.currentContext.size, Size.zero);
 

packages/flutter/test/widgets/drawer_test.dart

@@ -97,7 +97,7 @@ void main() {
               onEnter: (_) { logs.add('enter'); },
               onHover: (_) { logs.add('hover'); },
               onExit: (_) { logs.add('exit'); },
-              child: Container(width: 10, height: 10),
+              child: const SizedBox(width: 10, height: 10),
             ),
           ),
         ),

packages/flutter/test/widgets/ensure_visible_test.dart

@@ -384,7 +384,7 @@ void main() {
       Widget buildSliver(int i) {
         return SliverToBoxAdapter(
           key: ValueKey<int>(i),
-          child: Container(width: 200.0, height: 200.0),
+          child: const SizedBox(width: 200.0, height: 200.0),
         );
       }
 

packages/flutter/test/widgets/flow_test.dart

@@ -119,9 +119,9 @@ void main() {
     await tester.pumpWidget(
       Flow(
         delegate: DuplicatePainterOpacityFlowDelegate(1.0),
-        children: <Widget>[
-          Container(width: 100.0, height: 100.0),
-          Container(width: 100.0, height: 100.0),
+        children: const <Widget>[
+          SizedBox(width: 100.0, height: 100.0),
+          SizedBox(width: 100.0, height: 100.0),
         ],
       ),
     );
@@ -142,8 +142,8 @@ void main() {
     await tester.pumpWidget(
       Flow(
         delegate: OpacityFlowDelegate(opacity),
-        children: <Widget>[
-          Container(width: 100.0, height: 100.0),
+        children: const <Widget>[
+          SizedBox(width: 100.0, height: 100.0),
         ],
       ),
     );

packages/flutter/test/widgets/heroes_test.dart

@@ -40,13 +40,13 @@ final Map<String, WidgetBuilder> routes = <String, WidgetBuilder>{
     child: ListView(
       key: homeRouteKey,
       children: <Widget>[
-        Container(height: 100.0, width: 100.0),
+        const SizedBox(height: 100.0, width: 100.0),
         Card(child: Hero(
           tag: 'a',
           transitionOnUserGestures: transitionFromUserGestures,
           child: Container(height: 100.0, width: 100.0, key: firstKey),
         )),
-        Container(height: 100.0, width: 100.0),
+        const SizedBox(height: 100.0, width: 100.0),
         FlatButton(
           child: const Text('two'),
           onPressed: () { Navigator.pushNamed(context, '/two'); },
@@ -70,13 +70,13 @@ final Map<String, WidgetBuilder> routes = <String, WidgetBuilder>{
           child: const Text('pop'),
           onPressed: () { Navigator.pop(context); },
         ),
-        Container(height: 150.0, width: 150.0),
+        const SizedBox(height: 150.0, width: 150.0),
         Card(child: Hero(
           tag: 'a',
           transitionOnUserGestures: transitionFromUserGestures,
           child: Container(height: 150.0, width: 150.0, key: secondKey),
         )),
-        Container(height: 150.0, width: 150.0),
+        const SizedBox(height: 150.0, width: 150.0),
         FlatButton(
           child: const Text('three'),
           onPressed: () { Navigator.push(context, ThreeRoute()); },
@@ -96,7 +96,7 @@ final Map<String, WidgetBuilder> routes = <String, WidgetBuilder>{
           child: const Text('pop'),
           onPressed: () { Navigator.pop(context); },
         ),
-        Container(height: 150.0, width: 150.0),
+        const SizedBox(height: 150.0, width: 150.0),
         Card(
           child: Padding(
             padding: const EdgeInsets.only(left: 50.0),
@@ -107,7 +107,7 @@ final Map<String, WidgetBuilder> routes = <String, WidgetBuilder>{
             ),
           ),
         ),
-        Container(height: 150.0, width: 150.0),
+        const SizedBox(height: 150.0, width: 150.0),
         FlatButton(
           child: const Text('three'),
           onPressed: () { Navigator.push(context, ThreeRoute()); },
@@ -137,9 +137,9 @@ class ThreeRoute extends MaterialPageRoute<void> {
           key: routeThreeKey,
           child: ListView(
             children: <Widget>[
-              Container(height: 200.0, width: 200.0),
+              const SizedBox(height: 200.0, width: 200.0),
               Card(child: Hero(tag: 'a', child: Container(height: 200.0, width: 200.0, key: thirdKey))),
-              Container(height: 200.0, width: 200.0),
+              const SizedBox(height: 200.0, width: 200.0),
             ],
           ),
         );
@@ -718,7 +718,7 @@ Future<void> main() async {
                   return Card(
                     child: routeIncludesHero
                       ? Hero(tag: 'H', child: Container(key: routeHeroKey, height: 200.0, width: 200.0))
-                      : Container(height: 200.0, width: 200.0),
+                      : const SizedBox(height: 200.0, width: 200.0),
                   );
                 },
               ),

packages/flutter/test/widgets/implicit_semantics_test.dart

@@ -189,7 +189,7 @@ void main() {
               Semantics(
                 label: 'node 1',
                 selected: true,
-                child: Container(
+                child: const SizedBox(
                   width: 10.0,
                   height: 10.0,
                 ),
@@ -197,7 +197,7 @@ void main() {
               Semantics(
                 label: 'node 2',
                 selected: true,
-                child: Container(
+                child: const SizedBox(
                   width: 10.0,
                   height: 10.0,
                 ),
@@ -205,7 +205,7 @@ void main() {
               Semantics(
                 label: 'node 3',
                 selected: true,
-                child: Container(
+                child: const SizedBox(
                   width: 10.0,
                   height: 10.0,
                 ),

packages/flutter/test/widgets/list_body_test.dart

@@ -7,15 +7,15 @@ import 'package:flutter/src/painting/basic_types.dart';
 import 'package:flutter_test/flutter_test.dart';
 import 'package:flutter/widgets.dart';
 
-final List<Widget> children = <Widget>[
-  Container(width: 200.0, height: 150.0),
-  Container(width: 200.0, height: 150.0),
-  Container(width: 200.0, height: 150.0),
-  Container(width: 200.0, height: 150.0),
+const List<Widget> children = <Widget>[
+  SizedBox(width: 200.0, height: 150.0),
+  SizedBox(width: 200.0, height: 150.0),
+  SizedBox(width: 200.0, height: 150.0),
+  SizedBox(width: 200.0, height: 150.0),
 ];
 
 void expectRects(WidgetTester tester, List<Rect> expected) {
-  final Finder finder = find.byType(Container);
+  final Finder finder = find.byType(SizedBox);
   finder.precache();
   final List<Rect> actual = <Rect>[];
   for (int i = 0; i < expected.length; ++i) {

packages/flutter/test/widgets/listener_deprecated_test.dart

@@ -122,7 +122,7 @@ void main() {
       await tester.pumpWidget(
         Center(
           child: Listener(
-            child: Container(
+            child: const SizedBox(
               width: 100.0,
               height: 100.0,
             ),
@@ -152,7 +152,7 @@ void main() {
       await tester.pumpWidget(
         Center(
           child: Listener(
-            child: Container(
+            child: const SizedBox(
               width: 100.0,
               height: 100.0,
             ),
@@ -170,8 +170,8 @@ void main() {
       expect(enter, isNotNull);
       expect(enter.position, equals(const Offset(400.0, 300.0)));
       expect(exit, isNull);
-      await tester.pumpWidget(Center(
-        child: Container(
+      await tester.pumpWidget(const Center(
+        child: SizedBox(
           width: 100.0,
           height: 100.0,
         ),
@@ -284,7 +284,7 @@ void main() {
           children: <Widget>[
             Listener(
               key: key1,
-              child: Container(
+              child: const SizedBox(
                 width: 100.0,
                 height: 100.0,
               ),
@@ -294,7 +294,7 @@ void main() {
             ),
             Listener(
               key: key2,
-              child: Container(
+              child: const SizedBox(
                 width: 100.0,
                 height: 100.0,
               ),
@@ -561,7 +561,7 @@ void main() {
             onPointerEnter: (PointerEnterEvent e) => enter.add(e),
             onPointerHover: (PointerHoverEvent e) => hover.add(e),
             onPointerExit: (PointerExitEvent e) => exit.add(e),
-            child: Container(
+            child: const SizedBox(
               height: 100.0,
               width: 100.0,
             ),
@@ -574,7 +574,7 @@ void main() {
       await gesture.addPointer(location: Offset.zero);
       addTearDown(() => gesture?.removePointer());
       await tester.pumpAndSettle();
-      await gesture.moveTo(tester.getCenter(find.byType(Container)));
+      await gesture.moveTo(tester.getCenter(find.byType(SizedBox)));
 
       expect(enter.length, 1);
       expect(enter.single.position, const Offset(400.0, 300.0));

packages/flutter/test/widgets/mouse_region_test.dart

@@ -119,7 +119,7 @@ void main() {
     PointerExitEvent exit;
     await tester.pumpWidget(Center(
       child: MouseRegion(
-        child: Container(
+        child: const SizedBox(
           width: 100.0,
           height: 100.0,
         ),
@@ -149,7 +149,7 @@ void main() {
     PointerExitEvent exit;
     await tester.pumpWidget(Center(
       child: MouseRegion(
-        child: Container(
+        child: const SizedBox(
           width: 100.0,
           height: 100.0,
         ),
@@ -179,7 +179,7 @@ void main() {
     PointerExitEvent exit;
     await tester.pumpWidget(Center(
       child: MouseRegion(
-        child: Container(
+        child: const SizedBox(
           width: 100.0,
           height: 100.0,
         ),
@@ -214,8 +214,8 @@ void main() {
     PointerEnterEvent enter;
     PointerHoverEvent move;
     PointerExitEvent exit;
-    await tester.pumpWidget(Center(
-      child: Container(
+    await tester.pumpWidget(const Center(
+      child: SizedBox(
         width: 100.0,
         height: 100.0,
       ),
@@ -230,7 +230,7 @@ void main() {
     expect(exit, isNull);
     await tester.pumpWidget(Center(
       child: MouseRegion(
-        child: Container(
+        child: const SizedBox(
           width: 100.0,
           height: 100.0,
         ),
@@ -252,7 +252,7 @@ void main() {
     PointerExitEvent exit;
     await tester.pumpWidget(Center(
       child: MouseRegion(
-        child: Container(
+        child: const SizedBox(
           width: 100.0,
           height: 100.0,
         ),
@@ -269,8 +269,8 @@ void main() {
     move = null;
     enter = null;
     exit = null;
-    await tester.pumpWidget(Center(
-      child: Container(
+    await tester.pumpWidget(const Center(
+      child: SizedBox(
         width: 100.0,
         height: 100.0,
       ),
@@ -287,7 +287,7 @@ void main() {
     await tester.pumpWidget(Container(
       alignment: Alignment.center,
       child: MouseRegion(
-        child: Container(
+        child: const SizedBox(
           width: 100.0,
           height: 100.0,
         ),
@@ -306,7 +306,7 @@ void main() {
     await tester.pumpWidget(Container(
       alignment: Alignment.topLeft,
       child: MouseRegion(
-        child: Container(
+        child: const SizedBox(
           width: 100.0,
           height: 100.0,
         ),
@@ -329,7 +329,7 @@ void main() {
     await tester.pumpWidget(Container(
       alignment: Alignment.center,
       child: MouseRegion(
-        child: Container(
+        child: const SizedBox(
           width: 100.0,
           height: 100.0,
         ),
@@ -348,7 +348,7 @@ void main() {
     await tester.pumpWidget(Container(
       alignment: Alignment.topLeft,
       child: MouseRegion(
-        child: Container(
+        child: const SizedBox(
           width: 100.0,
           height: 100.0,
         ),
@@ -471,7 +471,7 @@ void main() {
         children: <Widget>[
           MouseRegion(
             key: key1,
-            child: Container(
+            child: const SizedBox(
               width: 100.0,
               height: 100.0,
             ),
@@ -481,7 +481,7 @@ void main() {
           ),
           MouseRegion(
             key: key2,
-            child: Container(
+            child: const SizedBox(
               width: 100.0,
               height: 100.0,
             ),
@@ -842,7 +842,7 @@ void main() {
           onEnter: (PointerEnterEvent e) => enter.add(e),
           onHover: (PointerHoverEvent e) => hover.add(e),
           onExit: (PointerExitEvent e) => exit.add(e),
-          child: Container(
+          child: const SizedBox(
             height: 100.0,
             width: 100.0,
           ),
@@ -855,7 +855,7 @@ void main() {
     await gesture.addPointer(location: Offset.zero);
     addTearDown(() => gesture?.removePointer());
     await tester.pumpAndSettle();
-    await gesture.moveTo(tester.getCenter(find.byType(Container)));
+    await gesture.moveTo(tester.getCenter(find.byType(SizedBox)));
 
     expect(enter.length, 1);
     expect(enter.single.position, const Offset(400.0, 300.0));
@@ -1286,7 +1286,7 @@ void main() {
                 onEnter: (_) { bottomRegionIsHovered = true; },
                 onHover: (_) { bottomRegionIsHovered = true; },
                 onExit: (_) { bottomRegionIsHovered = true; },
-                child: Container(
+                child: const SizedBox(
                   width: 10,
                   height: 10,
                 ),
@@ -1456,7 +1456,7 @@ void main() {
   testWidgets('No new frames are scheduled when mouse moves without triggering callbacks', (WidgetTester tester) async {
     await tester.pumpWidget(Center(
       child: MouseRegion(
-        child: Container(
+        child: const SizedBox(
           width: 100.0,
           height: 100.0,
         ),

packages/flutter/test/widgets/reparent_state_test.dart

@@ -231,7 +231,7 @@ void main() {
       textDirection: TextDirection.ltr,
       children: <Widget>[
         StateMarker(key: key),
-        Container(width: 100.0, height: 100.0),
+        const SizedBox(width: 100.0, height: 100.0),
       ],
     ));
 
@@ -241,7 +241,7 @@ void main() {
     await tester.pumpWidget(Stack(
       textDirection: TextDirection.ltr,
       children: <Widget>[
-        Container(width: 100.0, height: 100.0),
+        const SizedBox(width: 100.0, height: 100.0),
         StateMarker(key: key),
       ],
     ));
@@ -253,7 +253,7 @@ void main() {
       textDirection: TextDirection.ltr,
       children: <Widget>[
         StateMarker(key: key),
-        Container(width: 100.0, height: 100.0),
+        const SizedBox(width: 100.0, height: 100.0),
       ],
     ));
 
@@ -267,9 +267,9 @@ void main() {
     await tester.pumpWidget(Stack(
       textDirection: TextDirection.ltr,
       children: <Widget>[
-        Container(width: 100.0, height: 100.0),
+        const SizedBox(width: 100.0, height: 100.0),
         StateMarker(key: key),
-        Container(width: 100.0, height: 100.0),
+        const SizedBox(width: 100.0, height: 100.0),
       ],
     ));
 
@@ -280,7 +280,7 @@ void main() {
       textDirection: TextDirection.ltr,
       children: <Widget>[
         Container(width: 100.0, height: 100.0, child: StateMarker(key: key)),
-        Container(width: 100.0, height: 100.0),
+        const SizedBox(width: 100.0, height: 100.0),
       ],
     ));
 
@@ -290,9 +290,9 @@ void main() {
     await tester.pumpWidget(Stack(
       textDirection: TextDirection.ltr,
       children: <Widget>[
-        Container(width: 100.0, height: 100.0),
+        const SizedBox(width: 100.0, height: 100.0),
         StateMarker(key: key),
-        Container(width: 100.0, height: 100.0),
+        const SizedBox(width: 100.0, height: 100.0),
       ],
     ));
 
@@ -302,7 +302,7 @@ void main() {
     await tester.pumpWidget(Stack(
       textDirection: TextDirection.ltr,
       children: <Widget>[
-        Container(width: 100.0, height: 100.0),
+        const SizedBox(width: 100.0, height: 100.0),
         Container(width: 100.0, height: 100.0, child: StateMarker(key: key)),
       ],
     ));
@@ -313,9 +313,9 @@ void main() {
     await tester.pumpWidget(Stack(
       textDirection: TextDirection.ltr,
       children: <Widget>[
-        Container(width: 100.0, height: 100.0),
+        const SizedBox(width: 100.0, height: 100.0),
         StateMarker(key: key),
-        Container(width: 100.0, height: 100.0),
+        const SizedBox(width: 100.0, height: 100.0),
       ],
     ));
 

packages/flutter/test/widgets/scroll_events_test.dart

@@ -20,8 +20,8 @@ Widget _buildScroller({ List<String> log }) {
       }
       return false;
     },
-    child: SingleChildScrollView(
-      child: Container(width: 1000.0, height: 1000.0),
+    child: const SingleChildScrollView(
+      child: SizedBox(width: 1000.0, height: 1000.0),
     ),
   );
 }

packages/flutter/test/widgets/semantics_test.dart

@@ -312,14 +312,14 @@ void main() {
             children: <Widget>[
               Semantics(
                 value: 'value one',
-                child: Container(
+                child: const SizedBox(
                   height: 10.0,
                   width: 10.0,
                 ),
               ),
               Semantics(
                 value: 'value two',
-                child: Container(
+                child: const SizedBox(
                   height: 10.0,
                   width: 10.0,
                 ),

packages/flutter/test/widgets/shader_mask_test.dart

@@ -19,8 +19,8 @@ Shader createShader(Rect bounds) {
 
 void main() {
   testWidgets('Can be constructed', (WidgetTester tester) async {
-    final Widget child = Container(width: 100.0, height: 100.0);
-    await tester.pumpWidget(ShaderMask(child: child, shaderCallback: createShader));
+    const Widget child = SizedBox(width: 100.0, height: 100.0);
+    await tester.pumpWidget(const ShaderMask(child: child, shaderCallback: createShader));
   }, skip: isBrowser);
 
   testWidgets('Bounds rect includes offset', (WidgetTester tester) async {
@@ -37,7 +37,7 @@ void main() {
         height: 400.0,
         child: ShaderMask(
           shaderCallback: recordShaderBounds,
-          child: Container(width: 100.0, height: 100.0),
+          child: const SizedBox(width: 100.0, height: 100.0),
         ),
       ),
     );

packages/flutter/test/widgets/simple_semantics_test.dart

@@ -44,7 +44,7 @@ void main() {
       home: Center(
         child: Semantics(
           label: 'Hello!',
-          child: Container(
+          child: const SizedBox(
             width: 10.0,
             height: 10.0,
           ),

packages/flutter/test/widgets/single_child_scroll_view_test.dart

@@ -581,8 +581,9 @@ void main() {
                   children: List<Widget>.generate(10, (int y) {
                     return Row(
                       children: children[y] = List<Widget>.generate(10, (int x) {
-                        return Container(
-                          height: 100.0,
+                        // nonconst is used below to avoid const constructor and to force a new instance
+                        return SizedBox(
+                          height: nonconst(100.0),
                           width: 100.0,
                         );
                       }),

packages/flutter/test/widgets/stack_test.dart

@@ -412,15 +412,15 @@ void main() {
         textDirection: TextDirection.ltr,
         child: Center(
           child: Stack(
-            children: <Widget>[
-              Container(
+            children: const <Widget>[
+              SizedBox(
                 width: 100.0,
                 height: 100.0,
               ),
               Positioned(
                 top: 0.0,
                 left: 0.0,
-                child: Container(
+                child: SizedBox(
                   width: 200.0,
                   height: 200.0,
                 ),
@@ -442,15 +442,15 @@ void main() {
         child: Center(
           child: Stack(
             overflow: Overflow.visible,
-            children: <Widget>[
-              Container(
+            children: const <Widget>[
+              SizedBox(
                 width: 100.0,
                 height: 100.0,
               ),
               Positioned(
                 top: 0.0,
                 left: 0.0,
-                child: Container(
+                child: SizedBox(
                   width: 200.0,
                   height: 200.0,
                 ),