diff --git a/analysis_options.yaml b/analysis_options.yaml
index 35b9e47300..3c2c466e20 100644
--- a/analysis_options.yaml
+++ b/analysis_options.yaml
@@ -113,7 +113,7 @@ linter:
     - prefer_collection_literals
     - prefer_conditional_assignment
     - prefer_const_constructors
-    # - prefer_const_constructors_in_immutables # not yet tested
+    - prefer_const_constructors_in_immutables
     # - prefer_constructors_over_static_methods # not yet tested
     - prefer_contains
     # - prefer_expression_function_bodies # conflicts with https://github.com/flutter/flutter/wiki/Style-guide-for-Flutter-repo#consider-using--for-short-functions-and-methods
diff --git a/analysis_options_repo.yaml b/analysis_options_repo.yaml
index eacdb1a510..29dbefb14b 100644
--- a/analysis_options_repo.yaml
+++ b/analysis_options_repo.yaml
@@ -107,7 +107,7 @@ linter:
     - prefer_collection_literals
     - prefer_conditional_assignment
     - prefer_const_constructors
-    # - prefer_const_constructors_in_immutables # not yet tested
+    - prefer_const_constructors_in_immutables
     # - prefer_constructors_over_static_methods # not yet tested
     - prefer_contains
     # - prefer_expression_function_bodies # conflicts with https://github.com/flutter/flutter/wiki/Style-guide-for-Flutter-repo#consider-using--for-short-functions-and-methods
diff --git a/packages/flutter/lib/src/cupertino/tab_scaffold.dart b/packages/flutter/lib/src/cupertino/tab_scaffold.dart
index 63e1fb2300..53d3c5db7b 100644
--- a/packages/flutter/lib/src/cupertino/tab_scaffold.dart
+++ b/packages/flutter/lib/src/cupertino/tab_scaffold.dart
@@ -172,7 +172,7 @@ class _CupertinoTabScaffoldState extends State<CupertinoTabScaffold> {
 /// An widget laying out multiple tabs with only one active tab being built
 /// at a time and on stage. Off stage tabs' animations are stopped.
 class _TabView extends StatefulWidget {
-  _TabView({
+  const _TabView({
     @required this.currentTabIndex,
     @required this.tabNumber,
     @required this.tabBuilder,
diff --git a/packages/flutter/lib/src/material/bottom_navigation_bar.dart b/packages/flutter/lib/src/material/bottom_navigation_bar.dart
index efa1e0dc07..5fd565b404 100644
--- a/packages/flutter/lib/src/material/bottom_navigation_bar.dart
+++ b/packages/flutter/lib/src/material/bottom_navigation_bar.dart
@@ -124,7 +124,7 @@ class BottomNavigationBar extends StatefulWidget {
 // This represents a single tile in the bottom navigation bar. It is intended
 // to go into a flex container.
 class _BottomNavigationTile extends StatelessWidget {
-  _BottomNavigationTile(
+  const _BottomNavigationTile(
     this.type,
     this.item,
     this.animation,
diff --git a/packages/flutter/lib/src/material/date_picker.dart b/packages/flutter/lib/src/material/date_picker.dart
index 60616e00c5..dff94601e1 100644
--- a/packages/flutter/lib/src/material/date_picker.dart
+++ b/packages/flutter/lib/src/material/date_picker.dart
@@ -158,7 +158,7 @@ class _DatePickerHeader extends StatelessWidget {
 }
 
 class _DateHeaderButton extends StatelessWidget {
-  _DateHeaderButton({
+  const _DateHeaderButton({
     Key key,
     this.onTap,
     this.color,
diff --git a/packages/flutter/lib/src/material/mergeable_material.dart b/packages/flutter/lib/src/material/mergeable_material.dart
index fa3a4aae69..822a14490e 100644
--- a/packages/flutter/lib/src/material/mergeable_material.dart
+++ b/packages/flutter/lib/src/material/mergeable_material.dart
@@ -617,7 +617,7 @@ class _MergeableMaterialState extends State<MergeableMaterial> with TickerProvid
 // The parent hierarchy can change and lead to the slice being
 // rebuilt. Using a global key solves the issue.
 class _MergeableMaterialSliceKey extends GlobalKey {
-  _MergeableMaterialSliceKey(this.value) : super.constructor();
+  const _MergeableMaterialSliceKey(this.value) : super.constructor();
 
   final LocalKey value;
 
diff --git a/packages/flutter/lib/src/material/tabs.dart b/packages/flutter/lib/src/material/tabs.dart
index c1be60ffa3..f5861b7012 100644
--- a/packages/flutter/lib/src/material/tabs.dart
+++ b/packages/flutter/lib/src/material/tabs.dart
@@ -433,7 +433,7 @@ class TabBar extends StatefulWidget implements PreferredSizeWidget {
   /// The [indicatorWeight] parameter defaults to 2, and must not be null.
   ///
   /// The [indicatorPadding] parameter defaults to [EdgeInsets.zero], and must not be null.
-  TabBar({
+  const TabBar({
     Key key,
     @required this.tabs,
     this.controller,
@@ -812,7 +812,7 @@ class TabBarView extends StatefulWidget {
   /// Creates a page view with one child per tab.
   ///
   /// The length of [children] must be the same as the [controller]'s length.
-  TabBarView({
+  const TabBarView({
     Key key,
     @required this.children,
     this.controller,
diff --git a/packages/flutter/lib/src/painting/rounded_rectangle_border.dart b/packages/flutter/lib/src/painting/rounded_rectangle_border.dart
index 2ade008afa..03213075b8 100644
--- a/packages/flutter/lib/src/painting/rounded_rectangle_border.dart
+++ b/packages/flutter/lib/src/painting/rounded_rectangle_border.dart
@@ -139,7 +139,7 @@ class RoundedRectangleBorder extends ShapeBorder {
 }
 
 class _RoundedRectangleToCircleBorder extends ShapeBorder {
-  _RoundedRectangleToCircleBorder({
+  const _RoundedRectangleToCircleBorder({
     this.side: BorderSide.none,
     this.borderRadius: BorderRadius.zero,
     @required this.circleness,
diff --git a/packages/flutter/lib/src/widgets/framework.dart b/packages/flutter/lib/src/widgets/framework.dart
index 6a41ceb20b..b53577b0e5 100644
--- a/packages/flutter/lib/src/widgets/framework.dart
+++ b/packages/flutter/lib/src/widgets/framework.dart
@@ -110,6 +110,7 @@ class _TypeLiteral<T> { Type get type => T; }
 /// A key that is only equal to itself.
 class UniqueKey extends LocalKey {
   /// Creates a key that is equal only to itself.
+  // ignore: prefer_const_constructors_in_immutables , never use const for this class
   UniqueKey();
 
   @override
@@ -175,7 +176,7 @@ abstract class GlobalKey<T extends State<StatefulWidget>> extends Key {
   ///
   /// The label is purely for debugging and not used for comparing the identity
   /// of the key.
-  factory GlobalKey({ String debugLabel }) = LabeledGlobalKey<T>._;
+  factory GlobalKey({ String debugLabel }) => new LabeledGlobalKey<T>(debugLabel);
 
   /// Creates a global key without a label.
   ///
@@ -323,11 +324,9 @@ class LabeledGlobalKey<T extends State<StatefulWidget>> extends GlobalKey<T> {
   /// Creates a global key with a debugging label.
   ///
   /// The label does not affect the key's identity.
+  // ignore: prefer_const_constructors_in_immutables , never use const for this class
   LabeledGlobalKey(this._debugLabel) : super.constructor();
 
-  // Used for forwarding the constructor from GlobalKey.
-  LabeledGlobalKey._({ String debugLabel }) : _debugLabel = debugLabel, super.constructor();
-
   final String _debugLabel;
 
   @override
diff --git a/packages/flutter/lib/src/widgets/sliver.dart b/packages/flutter/lib/src/widgets/sliver.dart
index 3989656be2..52f66d04c4 100644
--- a/packages/flutter/lib/src/widgets/sliver.dart
+++ b/packages/flutter/lib/src/widgets/sliver.dart
@@ -902,7 +902,7 @@ class KeepAlive extends ParentDataWidget<SliverMultiBoxAdaptorWidget> {
   /// Marks a child as needing to remain alive.
   ///
   /// The [child] and [keepAlive] arguments must not be null.
-  KeepAlive({
+  const KeepAlive({
     Key key,
     @required this.keepAlive,
     @required Widget child,
diff --git a/packages/flutter/test/material/feedback_test.dart b/packages/flutter/test/material/feedback_test.dart
index 9977316443..c741ab78c0 100644
--- a/packages/flutter/test/material/feedback_test.dart
+++ b/packages/flutter/test/material/feedback_test.dart
@@ -139,7 +139,7 @@ void main () {
 
 class TestWidget extends StatelessWidget {
 
-  TestWidget({
+  const TestWidget({
     this.tapHandler: nullHandler,
     this.longPressHandler: nullHandler,
   });
diff --git a/packages/flutter/test/widgets/automatic_keep_alive_test.dart b/packages/flutter/test/widgets/automatic_keep_alive_test.dart
index a82e093bd0..17b9626a27 100644
--- a/packages/flutter/test/widgets/automatic_keep_alive_test.dart
+++ b/packages/flutter/test/widgets/automatic_keep_alive_test.dart
@@ -7,7 +7,7 @@ import 'package:flutter/widgets.dart';
 import 'package:flutter_test/flutter_test.dart';
 
 class Leaf extends StatefulWidget {
-  Leaf({ Key key, this.child }) : super(key: key);
+  const Leaf({ Key key, this.child }) : super(key: key);
   final Widget child;
   @override
   _LeafState createState() => new _LeafState();
@@ -222,8 +222,8 @@ void main() {
               child: new Container(
                 height: 400.0,
                 child: new Stack(children: <Widget>[
-                  new Leaf(key: const GlobalObjectKey<_LeafState>(0), child: const Placeholder()),
-                  new Leaf(key: const GlobalObjectKey<_LeafState>(1), child: const Placeholder()),
+                  const Leaf(key: const GlobalObjectKey<_LeafState>(0), child: const Placeholder()),
+                  const Leaf(key: const GlobalObjectKey<_LeafState>(1), child: const Placeholder()),
                 ]),
               ),
             ),
@@ -298,8 +298,8 @@ void main() {
               child: new Container(
                 height: 400.0,
                 child: new Stack(children: <Widget>[
-                  new Leaf(key: const GlobalObjectKey<_LeafState>(0), child: const Placeholder()),
-                  new Leaf(key: const GlobalObjectKey<_LeafState>(1), child: const Placeholder()),
+                  const Leaf(key: const GlobalObjectKey<_LeafState>(0), child: const Placeholder()),
+                  const Leaf(key: const GlobalObjectKey<_LeafState>(1), child: const Placeholder()),
                 ]),
               ),
             ),
@@ -307,8 +307,8 @@ void main() {
               child: new Container(
                 height: 400.0,
                 child: new Stack(children: <Widget>[
-                  new Leaf(key: const GlobalObjectKey<_LeafState>(2), child: const Placeholder()),
-                  new Leaf(key: const GlobalObjectKey<_LeafState>(3), child: const Placeholder()),
+                  const Leaf(key: const GlobalObjectKey<_LeafState>(2), child: const Placeholder()),
+                  const Leaf(key: const GlobalObjectKey<_LeafState>(3), child: const Placeholder()),
                 ]),
               ),
             ),
@@ -316,8 +316,8 @@ void main() {
               child: new Container(
                 height: 400.0,
                 child: new Stack(children: <Widget>[
-                  new Leaf(key: const GlobalObjectKey<_LeafState>(4), child: const Placeholder()),
-                  new Leaf(key: const GlobalObjectKey<_LeafState>(5), child: const Placeholder()),
+                  const Leaf(key: const GlobalObjectKey<_LeafState>(4), child: const Placeholder()),
+                  const Leaf(key: const GlobalObjectKey<_LeafState>(5), child: const Placeholder()),
                 ]),
               ),
             ),
@@ -350,7 +350,7 @@ void main() {
             child: new Container(
               height: 400.0,
               child: new Stack(children: <Widget>[
-                new Leaf(key: const GlobalObjectKey<_LeafState>(1), child: const Placeholder()),
+                const Leaf(key: const GlobalObjectKey<_LeafState>(1), child: const Placeholder()),
               ]),
             ),
           ),
@@ -358,8 +358,8 @@ void main() {
             child: new Container(
               height: 400.0,
               child: new Stack(children: <Widget>[
-                new Leaf(key: const GlobalObjectKey<_LeafState>(2), child: const Placeholder()),
-                new Leaf(key: const GlobalObjectKey<_LeafState>(3), child: const Placeholder()),
+                const Leaf(key: const GlobalObjectKey<_LeafState>(2), child: const Placeholder()),
+                const Leaf(key: const GlobalObjectKey<_LeafState>(3), child: const Placeholder()),
               ]),
             ),
           ),
@@ -367,9 +367,9 @@ void main() {
             child: new Container(
               height: 400.0,
               child: new Stack(children: <Widget>[
-                new Leaf(key: const GlobalObjectKey<_LeafState>(4), child: const Placeholder()),
-                new Leaf(key: const GlobalObjectKey<_LeafState>(5), child: const Placeholder()),
-                new Leaf(key: const GlobalObjectKey<_LeafState>(0), child: const Placeholder()),
+                const Leaf(key: const GlobalObjectKey<_LeafState>(4), child: const Placeholder()),
+                const Leaf(key: const GlobalObjectKey<_LeafState>(5), child: const Placeholder()),
+                const Leaf(key: const GlobalObjectKey<_LeafState>(0), child: const Placeholder()),
               ]),
             ),
           ),
@@ -409,8 +409,8 @@ void main() {
             child: new Container(
               height: 400.0,
               child: new Stack(children: <Widget>[
-                new Leaf(key: const GlobalObjectKey<_LeafState>(1), child: const Placeholder()),
-                new Leaf(key: const GlobalObjectKey<_LeafState>(2), child: const Placeholder()),
+                const Leaf(key: const GlobalObjectKey<_LeafState>(1), child: const Placeholder()),
+                const Leaf(key: const GlobalObjectKey<_LeafState>(2), child: const Placeholder()),
               ]),
             ),
           ),
@@ -425,10 +425,10 @@ void main() {
             child: new Container(
               height: 400.0,
               child: new Stack(children: <Widget>[
-                new Leaf(key: const GlobalObjectKey<_LeafState>(3), child: const Placeholder()),
-                new Leaf(key: const GlobalObjectKey<_LeafState>(4), child: const Placeholder()),
-                new Leaf(key: const GlobalObjectKey<_LeafState>(5), child: const Placeholder()),
-                new Leaf(key: const GlobalObjectKey<_LeafState>(0), child: const Placeholder()),
+                const Leaf(key: const GlobalObjectKey<_LeafState>(3), child: const Placeholder()),
+                const Leaf(key: const GlobalObjectKey<_LeafState>(4), child: const Placeholder()),
+                const Leaf(key: const GlobalObjectKey<_LeafState>(5), child: const Placeholder()),
+                const Leaf(key: const GlobalObjectKey<_LeafState>(0), child: const Placeholder()),
               ]),
             ),
           ),
diff --git a/packages/flutter/test/widgets/keep_alive_test.dart b/packages/flutter/test/widgets/keep_alive_test.dart
index baf455d8a9..6dbdc732a1 100644
--- a/packages/flutter/test/widgets/keep_alive_test.dart
+++ b/packages/flutter/test/widgets/keep_alive_test.dart
@@ -8,7 +8,7 @@ import 'package:flutter_test/flutter_test.dart';
 import 'package:flutter/widgets.dart';
 
 class Leaf extends StatefulWidget {
-  Leaf({ Key key, this.child }) : super(key: key);
+  const Leaf({ Key key, this.child }) : super(key: key);
   final Widget child;
   @override
   _LeafState createState() => new _LeafState();
diff --git a/packages/flutter/test/widgets/nested_scroll_view_test.dart b/packages/flutter/test/widgets/nested_scroll_view_test.dart
index 0d528fe18d..ec4fe92cc2 100644
--- a/packages/flutter/test/widgets/nested_scroll_view_test.dart
+++ b/packages/flutter/test/widgets/nested_scroll_view_test.dart
@@ -37,7 +37,7 @@ Widget buildTest({ ScrollController controller, String title:'TTTTTTTT' }) {
                   pinned: true,
                   expandedHeight: 200.0,
                   forceElevated: innerBoxIsScrolled,
-                  bottom: new TabBar(
+                  bottom: const TabBar(
                     tabs: const <Tab>[
                       const Tab(text: 'AA'),
                       const Tab(text: 'BB'),
diff --git a/packages/flutter_localizations/test/basics_test.dart b/packages/flutter_localizations/test/basics_test.dart
index 52d3c2b485..da81575e9c 100644
--- a/packages/flutter_localizations/test/basics_test.dart
+++ b/packages/flutter_localizations/test/basics_test.dart
@@ -11,11 +11,11 @@ void main() {
     await tester.pumpWidget(new MaterialApp( // Creates the outer Localizations widget.
       home: new ListView(
         children: <Widget>[
-          new LocalizationTracker(key: const ValueKey<String>('outer')),
+          const LocalizationTracker(key: const ValueKey<String>('outer')),
           new Localizations(
             locale: const Locale('zh', 'CN'),
             delegates: GlobalMaterialLocalizations.delegates,
-            child: new LocalizationTracker(key: const ValueKey<String>('inner')),
+            child: const LocalizationTracker(key: const ValueKey<String>('inner')),
           ),
         ],
       ),
@@ -65,7 +65,7 @@ class _DummyLocalizationsDelegate extends LocalizationsDelegate<DummyLocalizatio
 class DummyLocalizations {}
 
 class LocalizationTracker extends StatefulWidget {
-  LocalizationTracker({Key key}) : super(key: key);
+  const LocalizationTracker({Key key}) : super(key: key);
 
   @override
   State<StatefulWidget> createState() => new LocalizationTrackerState();