Issue 1:
What I Try to do

I use the AutomaticKeepAliveClientMixin in my widget , because I want to build a TabView with 4 pages and they can save self's state after scroll Automaticlly.

And I follow the issue #16445 , then switch my flutter channel to master , and yes , AutomaticKeepAlive works now , but I got a crush when I try to switch page 4 from page 1 directly after app launched.

Steps to Reproduce

Here is my demo code :

https://gist.github.com/debuggerx01/69668ff96926d4fddf7a51167045be5b

And I record a gif to show this problem:

Logs

I/flutter ( 6641): ══╡ EXCEPTION CAUGHT BY WIDGETS LIBRARY ╞═══════════════════════════════════════════════════════════
I/flutter ( 6641): The following assertion was thrown building NotificationListener<KeepAliveNotification>:
I/flutter ( 6641): 'package:flutter/src/rendering/object.dart': Failed assertion: line 2732 pos 14:
I/flutter ( 6641): '_debugUltimatePreviousSiblingOf(after, equals: _firstChild)': is not true.
I/flutter ( 6641):
I/flutter ( 6641): Either the assertion indicates an error in the framework itself, or we should provide substantially
I/flutter ( 6641): more information in this error message to help you determine and fix the underlying cause.
I/flutter ( 6641): In either case, please report this assertion by filing a bug on GitHub:
I/flutter ( 6641): https://github.com/flutter/flutter/issues/new
I/flutter ( 6641):
I/flutter ( 6641): When the exception was thrown, this was the stack:
I/flutter ( 6641): #2 _RenderSliverMultiBoxAdaptor&RenderSliver&ContainerRenderObjectMixin._insertIntoChildList (package:flutter/src/rendering/object.dart)
I/flutter ( 6641): #3 _RenderSliverMultiBoxAdaptor&RenderSliver&ContainerRenderObjectMixin.insert (package:flutter/src/rendering/object.dart:2766:5)
I/flutter ( 6641): #4 RenderSliverMultiBoxAdaptor.insert (package:flutter/src/rendering/sliver_multi_box_adaptor.dart:209:11)
I/flutter ( 6641): #5 SliverMultiBoxAdaptorElement.insertChildRenderObject (package:flutter/src/widgets/sliver.dart:849:18)
I/flutter ( 6641): #6 RenderObjectElement.attachRenderObject (package:flutter/src/widgets/framework.dart:4496:35)
I/flutter ( 6641): #7 RenderObjectElement.mount (package:flutter/src/widgets/framework.dart:4262:5)
I/flutter ( 6641): #8 SingleChildRenderObjectElement.mount (package:flutter/src/widgets/framework.dart:4636:11)
I/flutter ( 6641): #9 Element.inflateWidget (package:flutter/src/widgets/framework.dart:2890:14)
I/flutter ( 6641): #10 Element.updateChild (package:flutter/src/widgets/framework.dart:2693:12)
I/flutter ( 6641): #11 ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:3636:16)
I/flutter ( 6641): #12 Element.rebuild (package:flutter/src/widgets/framework.dart:3478:5)
I/flutter ( 6641): #13 ComponentElement._firstBuild (package:flutter/src/widgets/framework.dart:3605:5)
I/flutter ( 6641): #14 ComponentElement.mount (package:flutter/src/widgets/framework.dart:3600:5)
I/flutter ( 6641): #15 Element.inflateWidget (package:flutter/src/widgets/framework.dart:2890:14)
I/flutter ( 6641): #16 Element.updateChild (package:flutter/src/widgets/framework.dart:2693:12)
I/flutter ( 6641): #17 ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:3636:16)
I/flutter ( 6641): #18 Element.rebuild (package:flutter/src/widgets/framework.dart:3478:5)
I/flutter ( 6641): #19 ComponentElement._firstBuild (package:flutter/src/widgets/framework.dart:3605:5)
I/flutter ( 6641): #20 ComponentElement.mount (package:flutter/src/widgets/framework.dart:3600:5)
I/flutter ( 6641): #21 ParentDataElement.mount (package:flutter/src/widgets/framework.dart:3938:11)
I/flutter ( 6641): #22 Element.inflateWidget (package:flutter/src/widgets/framework.dart:2890:14)
I/flutter ( 6641): #23 Element.updateChild (package:flutter/src/widgets/framework.dart:2693:12)
I/flutter ( 6641): #24 ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:3636:16)
I/flutter ( 6641): #25 Element.rebuild (package:flutter/src/widgets/framework.dart:3478:5)
I/flutter ( 6641): #26 ComponentElement._firstBuild (package:flutter/src/widgets/framework.dart:3605:5)
I/flutter ( 6641): #27 StatefulElement._firstBuild (package:flutter/src/widgets/framework.dart:3752:11)
I/flutter ( 6641): #28 ComponentElement.mount (package:flutter/src/widgets/framework.dart:3600:5)
I/flutter ( 6641): #29 Element.inflateWidget (package:flutter/src/widgets/framework.dart:2890:14)
I/flutter ( 6641): #30 Element.updateChild (package:flutter/src/widgets/framework.dart:2693:12)
I/flutter ( 6641): #31 SliverMultiBoxAdaptorElement.performRebuild (package:flutter/src/widgets/sliver.dart:702:34)
I/flutter ( 6641): #32 SliverMultiBoxAdaptorElement.update (package:flutter/src/widgets/sliver.dart:671:7)
I/flutter ( 6641): #33 Element.updateChild (package:flutter/src/widgets/framework.dart:2682:15)
I/flutter ( 6641): #34 RenderObjectElement.updateChildren (package:flutter/src/widgets/framework.dart:4362:32)
I/flutter ( 6641): #35 MultiChildRenderObjectElement.update (package:flutter/src/widgets/framework.dart:4752:17)
I/flutter ( 6641): #36 _ViewportElement.update (package:flutter/src/widgets/viewport.dart:187:11)
I/flutter ( 6641): #37 Element.updateChild (package:flutter/src/widgets/framework.dart:2682:15)
I/flutter ( 6641): #38 ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:3636:16)
I/flutter ( 6641): #39 Element.rebuild (package:flutter/src/widgets/framework.dart:3478:5)
I/flutter ( 6641): #40 ProxyElement.update (package:flutter/src/widgets/framework.dart:3892:5)
I/flutter ( 6641): #41 Element.updateChild (package:flutter/src/widgets/framework.dart:2682:15)
I/flutter ( 6641): #42 SingleChildRenderObjectElement.update (package:flutter/src/widgets/framework.dart:4644:14)
I/flutter ( 6641): #43 Element.updateChild (package:flutter/src/widgets/framework.dart:2682:15)
I/flutter ( 6641): #44 SingleChildRenderObjectElement.update (package:flutter/src/widgets/framework.dart:4644:14)
I/flutter ( 6641): #45 Element.updateChild (package:flutter/src/widgets/framework.dart:2682:15)
I/flutter ( 6641): #46 SingleChildRenderObjectElement.update (package:flutter/src/widgets/framework.dart:4644:14)
I/flutter ( 6641): #47 Element.updateChild (package:flutter/src/widgets/framework.dart:2682:15)
I/flutter ( 6641): #48 SingleChildRenderObjectElement.update (package:flutter/src/widgets/framework.dart:4644:14)
I/flutter ( 6641): #49 Element.updateChild (package:flutter/src/widgets/framework.dart:2682:15)
I/flutter ( 6641): #50 ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:3636:16)
I/flutter ( 6641): #51 Element.rebuild (package:flutter/src/widgets/framework.dart:3478:5)
I/flutter ( 6641): #52 StatefulElement.update (package:flutter/src/widgets/framework.dart:3782:5)
I/flutter ( 6641): #53 Element.updateChild (package:flutter/src/widgets/framework.dart:2682:15)
I/flutter ( 6641): #54 SingleChildRenderObjectElement.update (package:flutter/src/widgets/framework.dart:4644:14)
I/flutter ( 6641): #55 Element.updateChild (package:flutter/src/widgets/framework.dart:2682:15)
I/flutter ( 6641): #56 SingleChildRenderObjectElement.update (package:flutter/src/widgets/framework.dart:4644:14)
I/flutter ( 6641): #57 Element.updateChild (package:flutter/src/widgets/framework.dart:2682:15)
I/flutter ( 6641): #58 SingleChildRenderObjectElement.update (package:flutter/src/widgets/framework.dart:4644:14)
I/flutter ( 6641): #59 Element.updateChild (package:flutter/src/widgets/framework.dart:2682:15)
I/flutter ( 6641): #60 SingleChildRenderObjectElement.update (package:flutter/src/widgets/framework.dart:4644:14)
I/flutter ( 6641): #61 Element.updateChild (package:flutter/src/widgets/framework.dart:2682:15)
I/flutter ( 6641): #62 ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:3636:16)
I/flutter ( 6641): #63 Element.rebuild (package:flutter/src/widgets/framework.dart:3478:5)
I/flutter ( 6641): #64 StatelessElement.update (package:flutter/src/widgets/framework.dart:3685:5)
I/flutter ( 6641): #65 Element.updateChild (package:flutter/src/widgets/framework.dart:2682:15)
I/flutter ( 6641): #66 ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:3636:16)
I/flutter ( 6641): #67 Element.rebuild (package:flutter/src/widgets/framework.dart:3478:5)
I/flutter ( 6641): #68 StatefulElement.update (package:flutter/src/widgets/framework.dart:3782:5)
I/flutter ( 6641): #69 Element.updateChild (package:flutter/src/widgets/framework.dart:2682:15)
I/flutter ( 6641): #70 ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:3636:16)
I/flutter ( 6641): #71 Element.rebuild (package:flutter/src/widgets/framework.dart:3478:5)
I/flutter ( 6641): #72 StatefulElement.update (package:flutter/src/widgets/framework.dart:3782:5)
I/flutter ( 6641): #73 Element.updateChild (package:flutter/src/widgets/framework.dart:2682:15)
I/flutter ( 6641): #74 ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:3636:16)
I/flutter ( 6641): #75 Element.rebuild (package:flutter/src/widgets/framework.dart:3478:5)
I/flutter ( 6641): #76 StatelessElement.update (package:flutter/src/widgets/framework.dart:3685:5)
I/flutter ( 6641): #77 Element.updateChild (package:flutter/src/widgets/framework.dart:2682:15)
I/flutter ( 6641): #78 ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:3636:16)
I/flutter ( 6641): #79 Element.rebuild (package:flutter/src/widgets/framework.dart:3478:5)
I/flutter ( 6641): #80 StatefulElement.update (package:flutter/src/widgets/framework.dart:3782:5)
I/flutter ( 6641): #81 Element.updateChild (package:flutter/src/widgets/framework.dart:2682:15)
I/flutter ( 6641): #82 ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:3636:16)
I/flutter ( 6641): #83 Element.rebuild (package:flutter/src/widgets/framework.dart:3478:5)
I/flutter ( 6641): #84 StatelessElement.update (package:flutter/src/widgets/framework.dart:3685:5)
I/flutter ( 6641): #85 Element.updateChild (package:flutter/src/widgets/framework.dart:2682:15)
I/flutter ( 6641): #86 ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:3636:16)
I/flutter ( 6641): #87 Element.rebuild (package:flutter/src/widgets/framework.dart:3478:5)
I/flutter ( 6641): #88 BuildOwner.buildScope (package:flutter/src/widgets/framework.dart:2225:33)
I/flutter ( 6641): #89 _WidgetsFlutterBinding&BindingBase&GestureBinding&ServicesBinding&SchedulerBinding&PaintingBinding&RendererBinding&WidgetsBinding.drawFrame (package:flutter/src/widgets/binding.dart:621:20)
I/flutter ( 6641): #90 _WidgetsFlutterBinding&BindingBase&GestureBinding&ServicesBinding&SchedulerBinding&PaintingBinding&RendererBinding._handlePersistentFrameCallback (package:flutter/src/rendering/binding.dart:208:5)
I/flutter ( 6641): #91 _WidgetsFlutterBinding&BindingBase&GestureBinding&ServicesBinding&SchedulerBinding._invokeFrameCallback (package:flutter/src/scheduler/binding.dart:990:15)
I/flutter ( 6641): #92 _WidgetsFlutterBinding&BindingBase&GestureBinding&ServicesBinding&SchedulerBinding.handleDrawFrame (package:flutter/src/scheduler/binding.dart:930:9)
I/flutter ( 6641): #93 _WidgetsFlutterBinding&BindingBase&GestureBinding&ServicesBinding&SchedulerBinding._handleDrawFrame (package:flutter/src/scheduler/binding.dart:842:5)
I/flutter ( 6641): #94 _invoke (dart:ui/hooks.dart:120:13)
I/flutter ( 6641): #95 _drawFrame (dart:ui/hooks.dart:109:3)
I/flutter ( 6641): (elided 2 frames from class _AssertionError)
I/flutter ( 6641): ════════════════════════════════════════════════════════════════════════════════════════════════════
I/flutter ( 6641): Another exception was thrown: 'package:flutter/src/rendering/object.dart': Failed assertion: line 2732 pos 14: '_debugUltimatePreviousSiblingOf(after, equals: _firstChild)': is not true.
I/flutter ( 6641): Another exception was thrown: 'package:flutter/src/rendering/object.dart': Failed assertion: line 2732 pos 14: '_debugUltimatePreviousSiblingOf(after, equals: _firstChild)': is not true.
I/flutter ( 6641): Another exception was thrown: 'package:flutter/src/rendering/object.dart': Failed assertion: line 2732 pos 14: '_debugUltimatePreviousSiblingOf(after, equals: _firstChild)': is not true.
I/flutter ( 6641): Another exception was thrown: 'package:flutter/src/widgets/framework.dart': Failed assertion: line 3480 pos 14: 'owner._debugCurrentBuildTarget == this': is not true.
I/flutter ( 6641): Another exception was thrown: 'package:flutter/src/widgets/framework.dart': Failed assertion: line 3480 pos 14: 'owner._debugCurrentBuildTarget == this': is not true.
I/flutter ( 6641): Another exception was thrown: 'package:flutter/src/widgets/framework.dart': Failed assertion: line 3480 pos 14: 'owner._debugCurrentBuildTarget == this': is not true.
I/flutter ( 6641): Another exception was thrown: 'package:flutter/src/widgets/framework.dart': Failed assertion: line 3480 pos 14: 'owner._debugCurrentBuildTarget == this': is not true.
I/flutter ( 6641): Another exception was thrown: 'package:flutter/src/widgets/framework.dart': Failed assertion: line 3480 pos 14: 'owner._debugCurrentBuildTarget == this': is not true.
I/flutter ( 6641): Another exception was thrown: 'package:flutter/src/widgets/framework.dart': Failed assertion: line 3480 pos 14: 'owner._debugCurrentBuildTarget == this': is not true.
I/flutter ( 6641): Another exception was thrown: 'package:flutter/src/widgets/framework.dart': Failed assertion: line 3480 pos 14: 'owner._debugCurrentBuildTarget == this': is not true.
I/flutter ( 6641): Another exception was thrown: 'package:flutter/src/widgets/framework.dart': Failed assertion: line 3480 pos 14: 'owner._debugCurrentBuildTarget == this': is not true.
I/flutter ( 6641): Another exception was thrown: 'package:flutter/src/widgets/framework.dart': Failed assertion: line 3480 pos 14: 'owner._debugCurrentBuildTarget == this': is not true.
I/flutter ( 6641): Another exception was thrown: The _ScaffoldLayout custom multichild layout delegate forgot to lay out the following children:`

## Flutter Doctor
`flutter doctor -v
[✓] Flutter (Channel master, v0.2.12-pre.15, on Linux, locale zh_CN.UTF-8)
• Flutter version 0.2.12-pre.15 at /home/debuggerx/flutter
• Framework revision da9e1a4aca (3 小时前), 2018-04-11 20:50:25 -0700
• Engine revision 4db7a00677
• Dart version 2.0.0-dev.47.0.flutter-4126459025

[✓] Android toolchain - develop for Android devices (Android SDK 27.0.3)
• Android SDK at /opt/android-sdk
• Android NDK at /opt/android-sdk/ndk-bundle
• Platform android-27, build-tools 27.0.3
• ANDROID_HOME = /opt/android-sdk
• Java binary at: /opt/android-studio/jre/bin/java
• Java version openjdk version "1.8.0_152-release"
• All Android licenses accepted.

[✓] Android Studio (version 3.1)
• Android Studio at /opt/android-studio
• Flutter plugin version 23.2.2
• Dart plugin version 173.4700
• Java version openjdk version "1.8.0_152-release"

[!] IntelliJ IDEA Ultimate Edition (version 2016.2)
• IntelliJ at /home/debuggerx/idea
✗ Flutter plugin not installed; this adds Flutter specific functionality.
✗ Dart plugin not installed; this adds Dart specific functionality.
• For information about installing plugins, see
https://flutter.io/intellij-setup/#installing-the-plugins
✗ This install is older than the minimum recommended version of 2017.1.0.

[!] IntelliJ IDEA Ultimate Edition (version 2017.2)
• IntelliJ at /opt/idea
✗ Flutter plugin not installed; this adds Flutter specific functionality.
• Dart plugin version 172.4343.25
• For information about installing plugins, see
https://flutter.io/intellij-setup/#installing-the-plugins

[✓] Connected devices (1 available)
• Custom Phone, 7 1 0, API 25, 768x1280 • 192.168.56.101:5555 • android-x86 • Android 7.1.1 (API 25)

Issue 2:
Steps to Reproduce

I have a PageView that contains the top level widgets for my app, with switching between them controlled by a BottomNavBar. As per @Hixie's advice in the chat, I am adding AutomaticKeepAliveClientMixin to these top level widgets so the PageView won't recycle them and will preserve state. After I added this to the main widget that contains a network loaded ListView, on occasion when switching back to this ListView from another tab I get this failed assertion in the framework.

Logs

══╡ EXCEPTION CAUGHT BY WIDGETS LIBRARY ╞═══════════════════════════════════════════════════════════
The following assertion was thrown building NotificationListener<KeepAliveNotification>:
'package:flutter/src/rendering/object.dart': Failed assertion: line 3031 pos 14:
'_debugUltimatePreviousSiblingOf(after, equals: _firstChild)': is not true.
Either the assertion indicates an error in the framework itself, or we should provide substantially
more information in this error message to help you determine and fix the underlying cause.
In either case, please report this assertion by filing a bug on GitHub:
https://github.com/flutter/flutter/issues/new
When the exception was thrown, this was the stack:
#2 RenderSliver&ContainerRenderObjectMixin._insertIntoChildList (package:flutter/src/rendering/object.dart:3031:14)
#3 RenderSliver&ContainerRenderObjectMixin.insert (package:flutter/src/rendering/object.dart:3065:5)
#4 RenderSliverMultiBoxAdaptor.insert (package:flutter/src/rendering/sliver_multi_box_adaptor.dart:193:17)
#5 SliverMultiBoxAdaptorElement.insertChildRenderObject (package:flutter/src/widgets/sliver.dart:840:18)
#6 RenderObjectElement.attachRenderObject (package:flutter/src/widgets/framework.dart:4380:35)
#7 RenderObjectElement.mount (package:flutter/src/widgets/framework.dart:4151:5)
#8 SingleChildRenderObjectElement.mount (package:flutter/src/widgets/framework.dart:4515:16)
#9 Element.inflateWidget (package:flutter/src/widgets/framework.dart:2882:14)
#10 Element.updateChild (package:flutter/src/widgets/framework.dart:2685:12)
#11 ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:3546:16)
#12 Element.rebuild (package:flutter/src/widgets/framework.dart:3435:5)
#13 ComponentElement._firstBuild (package:flutter/src/widgets/framework.dart:3514:5)
#14 ComponentElement.mount (package:flutter/src/widgets/framework.dart:3509:5)
#15 Element.inflateWidget (package:flutter/src/widgets/framework.dart:2882:14)
#16 Element.updateChild (package:flutter/src/widgets/framework.dart:2685:12)
#17 ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:3546:16)
#18 Element.rebuild (package:flutter/src/widgets/framework.dart:3435:5)
#19 ComponentElement._firstBuild (package:flutter/src/widgets/framework.dart:3514:5)
#20 ComponentElement.mount (package:flutter/src/widgets/framework.dart:3509:5)
#21 ParentDataElement.mount (package:flutter/src/widgets/framework.dart:3827:16)
#22 Element.inflateWidget (package:flutter/src/widgets/framework.dart:2882:14)
#23 Element.updateChild (package:flutter/src/widgets/framework.dart:2685:12)
#24 ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:3546:16)
#25 Element.rebuild (package:flutter/src/widgets/framework.dart:3435:5)
#26 ComponentElement._firstBuild (package:flutter/src/widgets/framework.dart:3514:5)
#27 StatefulElement._firstBuild (package:flutter/src/widgets/framework.dart:3652:22)
#28 ComponentElement.mount (package:flutter/src/widgets/framework.dart:3509:5)
#29 Element.inflateWidget (package:flutter/src/widgets/framework.dart:2882:14)
#30 Element.updateChild (package:flutter/src/widgets/framework.dart:2685:12)
#31 SliverMultiBoxAdaptorElement.performRebuild (package:flutter/src/widgets/sliver.dart:696:34)
#32 SliverMultiBoxAdaptorElement.update (package:flutter/src/widgets/sliver.dart:665:7)
#33 Element.updateChild (package:flutter/src/widgets/framework.dart:2674:15)
#34 RenderObjectElement.updateChildren (package:flutter/src/widgets/framework.dart:4250:32)
#35 MultiChildRenderObjectElement.update (package:flutter/src/widgets/framework.dart:4631:17)
#36 _ViewportElement.update (package:flutter/src/widgets/viewport.dart:150:17)
#37 Element.updateChild (package:flutter/src/widgets/framework.dart:2674:15)
#38 ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:3546:16)
#39 Element.rebuild (package:flutter/src/widgets/framework.dart:3435:5)
#40 ProxyElement.update (package:flutter/src/widgets/framework.dart:3781:5)
#41 Element.updateChild (package:flutter/src/widgets/framework.dart:2674:15)
#42 SingleChildRenderObjectElement.update (package:flutter/src/widgets/framework.dart:4523:14)
#43 Element.updateChild (package:flutter/src/widgets/framework.dart:2674:15)
#44 SingleChildRenderObjectElement.update (package:flutter/src/widgets/framework.dart:4523:14)
#45 Element.updateChild (package:flutter/src/widgets/framework.dart:2674:15)
#46 SingleChildRenderObjectElement.update (package:flutter/src/widgets/framework.dart:4523:14)
#47 Element.updateChild (package:flutter/src/widgets/framework.dart:2674:15)
#48 ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:3546:16)
#49 Element.rebuild (package:flutter/src/widgets/framework.dart:3435:5)
#50 StatefulElement.update (package:flutter/src/widgets/framework.dart:3671:5)
#51 Element.updateChild (package:flutter/src/widgets/framework.dart:2674:15)
#52 ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:3546:16)
#53 Element.rebuild (package:flutter/src/widgets/framework.dart:3435:5)
#54 StatefulElement.update (package:flutter/src/widgets/framework.dart:3671:5)
#55 Element.updateChild (package:flutter/src/widgets/framework.dart:2674:15)
#56 ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:3546:16)
#57 Element.rebuild (package:flutter/src/widgets/framework.dart:3435:5)
#58 StatelessElement.update (package:flutter/src/widgets/framework.dart:3596:5)
#59 Element.updateChild (package:flutter/src/widgets/framework.dart:2674:15)
#60 ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:3546:16)
#61 Element.rebuild (package:flutter/src/widgets/framework.dart:3435:5)
#62 StatefulElement.update (package:flutter/src/widgets/framework.dart:3671:5)
#63 Element.updateChild (package:flutter/src/widgets/framework.dart:2674:15)
#64 ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:3546:16)
#65 Element.rebuild (package:flutter/src/widgets/framework.dart:3435:5)
#66 ProxyElement.update (package:flutter/src/widgets/framework.dart:3781:5)
#67 Element.updateChild (package:flutter/src/widgets/framework.dart:2674:15)
#68 RenderObjectElement.updateChildren (package:flutter/src/widgets/framework.dart:4250:32)
#69 MultiChildRenderObjectElement.update (package:flutter/src/widgets/framework.dart:4631:17)
#70 Element.updateChild (package:flutter/src/widgets/framework.dart:2674:15)
#71 ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:3546:16)
#72 Element.rebuild (package:flutter/src/widgets/framework.dart:3435:5)
#73 ProxyElement.update (package:flutter/src/widgets/framework.dart:3781:5)
#74 Element.updateChild (package:flutter/src/widgets/framework.dart:2674:15)
#75 ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:3546:16)
#76 Element.rebuild (package:flutter/src/widgets/framework.dart:3435:5)
#77 StatefulElement.update (package:flutter/src/widgets/framework.dart:3671:5)
#78 Element.updateChild (package:flutter/src/widgets/framework.dart:2674:15)
#79 SingleChildRenderObjectElement.update (package:flutter/src/widgets/framework.dart:4523:14)
#80 Element.updateChild (package:flutter/src/widgets/framework.dart:2674:15)
#81 ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:3546:16)
#82 Element.rebuild (package:flutter/src/widgets/framework.dart:3435:5)
#83 StatelessElement.update (package:flutter/src/widgets/framework.dart:3596:5)
#84 Element.updateChild (package:flutter/src/widgets/framework.dart:2674:15)
#85 SingleChildRenderObjectElement.update (package:flutter/src/widgets/framework.dart:4523:14)
#86 Element.updateChild (package:flutter/src/widgets/framework.dart:2674:15)
#87 ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:3546:16)
#88 Element.rebuild (package:flutter/src/widgets/framework.dart:3435:5)
#89 StatefulElement.update (package:flutter/src/widgets/framework.dart:3671:5)
#90 Element.updateChild (package:flutter/src/widgets/framework.dart:2674:15)
#91 ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:3546:16)
#92 Element.rebuild (package:flutter/src/widgets/framework.dart:3435:5)
#93 StatefulElement.update (package:flutter/src/widgets/framework.dart:3671:5)
#94 Element.updateChild (package:flutter/src/widgets/framework.dart:2674:15)
#95 ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:3546:16)
#96 Element.rebuild (package:flutter/src/widgets/framework.dart:3435:5)
#97 ProxyElement.update (package:flutter/src/widgets/framework.dart:3781:5)
#98 Element.updateChild (package:flutter/src/widgets/framework.dart:2674:15)
#99 ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:3546:16)
#100 Element.rebuild (package:flutter/src/widgets/framework.dart:3435:5)
#101 ProxyElement.update (package:flutter/src/widgets/framework.dart:3781:5)
#102 Element.updateChild (package:flutter/src/widgets/framework.dart:2674:15)
#103 ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:3546:16)
#104 Element.rebuild (package:flutter/src/widgets/framework.dart:3435:5)
#105 StatefulElement.update (package:flutter/src/widgets/framework.dart:3671:5)
#106 Element.updateChild (package:flutter/src/widgets/framework.dart:2674:15)
#107 ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:3546:16)
#108 Element.rebuild (package:flutter/src/widgets/framework.dart:3435:5)
#109 BuildOwner.buildScope (package:flutter/src/widgets/framework.dart:2260:33)
#110 BindingBase&SchedulerBinding&GestureBinding&ServicesBinding&RendererBinding&WidgetsBinding.drawFrame (package:flutter/src/widgets/binding.dart:503:20)
#111 BindingBase&SchedulerBinding&GestureBinding&ServicesBinding&RendererBinding._handlePersistentFrameCallback (package:flutter/src/rendering/binding.dart:189:5)
#112 BindingBase&SchedulerBinding._invokeFrameCallback (package:flutter/src/scheduler/binding.dart:695:15)
#113 BindingBase&SchedulerBinding.handleDrawFrame (package:flutter/src/scheduler/binding.dart:643:9)
#114 _invoke (file:///b/build/slave/Mac_Engine/build/src/flutter/lib/ui/hooks.dart:86)
#115 _drawFrame (file:///b/build/slave/Mac_Engine/build/src/flutter/lib/ui/hooks.dart:75)
(elided 2 frames from class _AssertionError)
════════════════════════════════════════════════════════════════════════════════════════════════════
Another exception was thrown: 'package:flutter/src/rendering/object.dart': Failed assertion: line 3031 pos 14: '_debugUltimatePreviousSiblingOf(after, equals: _firstChild)': is not true.
Another exception was thrown: 'package:flutter/src/rendering/object.dart': Failed assertion: line 3031 pos 14: '_debugUltimatePreviousSiblingOf(after, equals: _firstChild)': is not true.
Another exception was thrown: 'package:flutter/src/widgets/framework.dart': Failed assertion: line 3437 pos 14: 'owner._debugCurrentBuildTarget == this': is not true.
Another exception was thrown: 'package:flutter/src/widgets/framework.dart': Failed assertion: line 3437 pos 14: 'owner._debugCurrentBuildTarget == this': is not true.
Another exception was thrown: 'package:flutter/src/widgets/framework.dart': Failed assertion: line 3437 pos 14: 'owner._debugCurrentBuildTarget == this': is not true.
Another exception was thrown: 'package:flutter/src/widgets/framework.dart': Failed assertion: line 3437 pos 14: 'owner._debugCurrentBuildTarget == this': is not true.
Another exception was thrown: 'package:flutter/src/widgets/framework.dart': Failed assertion: line 3437 pos 14: 'owner._debugCurrentBuildTarget == this': is not true.
Another exception was thrown: 'package:flutter/src/widgets/framework.dart': Failed assertion: line 3437 pos 14: 'owner._debugCurrentBuildTarget == this': is not true.
Another exception was thrown: 'package:flutter/src/widgets/framework.dart': Failed assertion: line 3437 pos 14: 'owner._debugCurrentBuildTarget == this': is not true.
Another exception was thrown: 'package:flutter/src/widgets/framework.dart': Failed assertion: line 3437 pos 14: 'owner._debugCurrentBuildTarget == this': is not true.
Another exception was thrown: 'package:flutter/src/widgets/framework.dart': Failed assertion: line 3437 pos 14: 'owner._debugCurrentBuildTarget == this': is not true.
Another exception was thrown: 'package:flutter/src/widgets/framework.dart': Failed assertion: line 3437 pos 14: 'owner._debugCurrentBuildTarget == this': is not true.
Another exception was thrown: 'package:flutter/src/widgets/framework.dart': Failed assertion: line 3437 pos 14: 'owner._debugCurrentBuildTarget == this': is not true.
Another exception was thrown: 'package:flutter/src/widgets/framework.dart': Failed assertion: line 3437 pos 14: 'owner._debugCurrentBuildTarget == this': is not true.
Another exception was thrown: 'package:flutter/src/widgets/framework.dart': Failed assertion: line 3437 pos 14: 'owner._debugCurrentBuildTarget == this': is not true.
Another exception was thrown: 'package:flutter/src/widgets/framework.dart': Failed assertion: line 3437 pos 14: 'owner._debugCurrentBuildTarget == this': is not true.

Analyzing /Users/matt/code/flutter/kudos...
lint • Don't import implementation files from another package at lib/feed.dart:5:8 • implementation_imports
lint • Close instances of `dart.core.Sink` at lib/feed.dart:26:26 • close_sinks
lint • Don't explicitly initialize variables to null at lib/loading_list_view.dart:23:5 • avoid_init_to_null
lint • Don't import implementation files from another package at lib/post.dart:3:8 • implementation_imports
hint • Unused import at lib/application.dart:4:8 • unused_import
hint • Unused import at lib/feed.dart:2:8 • unused_import
hint • Unused import at lib/feed.dart:5:8 • unused_import
hint • Unused import at lib/feed.dart:7:8 • unused_import
hint • Unused import at lib/feed.dart:12:8 • unused_import
hint • Unused import at lib/feed.dart:13:8 • unused_import
hint • This method overrides a method annotated as @mustCallSuper in 'State', but does not invoke the overridden method at lib/feed.dart:29:8 • must_call_super
hint • This method overrides a method annotated as @mustCallSuper in 'State', but does not invoke the overridden method at lib/feed.dart:40:8 • must_call_super
hint • The type parameter 'widgetAdapter' is annotated with @required but only named parameters without default value can be annotated with it at lib/loading_list_view.dart:23:5 • invalid_required_param
hint • Unused import at lib/main.dart:6:8 • unused_import
hint • The value of the field '_counter' isn't used at lib/main.dart:56:7 • unused_field
hint • This method overrides a method annotated as @mustCallSuper in 'State', but does not invoke the overridden method at lib/main.dart:63:8 • must_call_super
hint • This method overrides a method annotated as @mustCallSuper in 'State', but does not invoke the overridden method at lib/main.dart:71:8 • must_call_super
hint • The method '_incrementCounter' isn't used at lib/main.dart:76:8 • unused_element
hint • Unused import at lib/post.dart:7:8 • unused_import
hint • This class inherits from a class marked as @immutable, and therefore should be immutable (all instance fields must be final) at lib/post.dart:10:7 • must_be_immutable
hint • This class inherits from a class marked as @immutable, and therefore should be immutable (all instance fields must be final) at lib/post.dart:34:7 • must_be_immutable
hint • The value of the local variable 'plainText' isn't used at lib/post.dart:71:10 • unused_local_variable
hint • This class inherits from a class marked as @immutable, and therefore should be immutable (all instance fields must be final) at lib/post.dart:112:7 • must_be_immutable
hint • This class inherits from a class marked as @immutable, and therefore should be immutable (all instance fields must be final) at lib/post.dart:160:7 • must_be_immutable
hint • This class inherits from a class marked as @immutable, and therefore should be immutable (all instance fields must be final) at lib/profile.dart:10:7 • must_be_immutable
hint • This method overrides a method annotated as @mustCallSuper in 'State', but does not invoke the overridden method at lib/profile.dart:27:10 • must_call_super
hint • This class inherits from a class marked as @immutable, and therefore should be immutable (all instance fields must be final) at lib/profile.dart:145:7 • must_be_immutable
hint • The class '_KudosEarned' isn't used at lib/profile.dart:218:7 • unused_element
hint • Unused import at lib/send_photo.dart:5:8 • unused_import
hint • Unused import at lib/usersearch.dart:6:8 • unused_import
hint • Unused import at lib/usersearch.dart:7:8 • unused_import
hint • This method overrides a method annotated as @mustCallSuper in 'State', but does not invoke the overridden method at lib/usersearch.dart:25:10 • must_call_super
32 issues found.

Flutter Doctor

[✓] Flutter (on Mac OS X 10.12.6 16G29, locale en-US, channel alpha)
• Flutter at /Users/matt/code/flutter/flutter
• Framework revision b156a0f054 (3 weeks ago), 2017-08-11 22:01:40 -0700
• Engine revision fef7d827d6
• Tools Dart version 1.25.0-dev.9.0

[✓] Android toolchain - develop for Android devices (Android SDK 25.0.3)
• Android SDK at /Users/matt/code/android/android
• Platform android-25, build-tools 25.0.3
• Java binary at: /Applications/Android Studio.app/Contents/jre/jdk/Contents/Home/bin/java
• Java version OpenJDK Runtime Environment (build 1.8.0_112-release-b06)

[✓] iOS toolchain - develop for iOS devices (Xcode 8.3.3)
• Xcode at /Applications/Xcode.app/Contents/Developer
• Xcode 8.3.3, Build version 8E3004b
• ios-deploy 1.9.1
• CocoaPods version 1.3.1

[✓] Android Studio (version 2.3)
• Android Studio at /Applications/Android Studio.app/Contents
• Java version OpenJDK Runtime Environment (build 1.8.0_112-release-b06)

[✓] IntelliJ IDEA Ultimate Edition (version 2017.2.2)
• Flutter plugin version 16.0
• Dart plugin version 172.3757.55

[✓] Connected devices
• iPhone 6s • 3DF999CB-1CD6-4649-8187-DDEFBDB14DFA • ios • iOS 10.3 (simulator)

For more information about diagnosing and reporting Flutter bugs, please see https://flutter.io/bug-reports/.