dart fix: always_declare_return_types

Author: M-Ahal

example/lib/cupertino_date_picker.dart

@@ -2,7 +2,7 @@ import 'package:flutter/cupertino.dart';
 import 'package:flutter/material.dart';
 import 'package:flutter_platform_widgets/flutter_platform_widgets.dart';
 
-showDatePickerWithCustomCupertinoStateful(BuildContext context) async {
+Future<void> showDatePickerWithCustomCupertinoStateful(BuildContext context) async {
   final now = DateUtils.dateOnly(DateTime.now());
   final firstDate = now.subtract(const Duration(days: 100));
   final lastDate = now.add(const Duration(days: 100));
@@ -23,7 +23,7 @@ showDatePickerWithCustomCupertinoStateful(BuildContext context) async {
   }
 }
 
-showDatePickerWithCustomCupertino(BuildContext context) async {
+Future<void> showDatePickerWithCustomCupertino(BuildContext context) async {
   final now = DateUtils.dateOnly(DateTime.now());
   final firstDate = now.subtract(const Duration(days: 100));
   final lastDate = now.add(const Duration(days: 100));
@@ -61,7 +61,7 @@ showDatePickerWithCustomCupertino(BuildContext context) async {
   }
 }
 
-_showResultDialog(BuildContext context, String text) {
+void _showResultDialog(BuildContext context, String text) {
   showPlatformDialog(
     context: context,
     builder: (_) => PlatformAlertDialog(

example/lib/platform_page.dart.dart

@@ -431,7 +431,7 @@ ThemeMode _cycleThemeMode(ThemeMode? mode) {
   }
 }
 
-_showDatePicker(BuildContext context) async {
+Future<void> _showDatePicker(BuildContext context) async {
   final now = DateUtils.dateOnly(DateTime.now());
   final date = await showPlatformDatePicker(
     context: context,
@@ -445,7 +445,7 @@ _showDatePicker(BuildContext context) async {
   }
 }
 
-_showExampleDialog(BuildContext context, String text) {
+void _showExampleDialog(BuildContext context, String text) {
   showPlatformDialog(
     context: context,
     builder: (_) => PlatformAlertDialog(
@@ -467,7 +467,7 @@ _showExampleDialog(BuildContext context, String text) {
   );
 }
 
-_showPopupSheet(BuildContext context, String text) {
+void _showPopupSheet(BuildContext context, String text) {
   showPlatformModalSheet(
     context: context,
     builder: (_) => PlatformWidget(

example/lib/tab_impl_page.dart

@@ -69,7 +69,7 @@ class TabImplementationPage extends StatelessWidget {
   }
 }
 
-_openPage(
+void _openPage(
   BuildContext context,
   WidgetBuilder pageToDisplayBuilder,
   TargetPlatform platform,

lib/src/platform_app.dart

@@ -468,7 +468,7 @@ class PlatformApp extends PlatformWidgetBase<CupertinoApp, MaterialApp> {
         cupertinoRouter = cupertino;
 
   @override
-  createMaterialWidget(BuildContext context) {
+  MaterialApp createMaterialWidget(BuildContext context) {
     final dataRouter = materialRouter?.call(context, platform(context));
 
     if (routeInformationParser != null ||
@@ -617,7 +617,7 @@ class PlatformApp extends PlatformWidgetBase<CupertinoApp, MaterialApp> {
   }
 
   @override
-  createCupertinoWidget(BuildContext context) {
+  CupertinoApp createCupertinoWidget(BuildContext context) {
     final dataRouter = cupertinoRouter?.call(context, platform(context));
 
     if (routeInformationParser != null ||