Auto-completion and snippets inside StatefulWidget do not work

[r-i-c-o]

Auto-completion and snippets do not work inside "State" class for methods like "initState", "dispose", "setState" etc.

Steps to Reproduce

1. create stateful widget
2. start typing "initState" or "setState" methods inside "State" class

Version info

Please paste the output of running flutter doctor -v here
[√] Flutter (Channel stable, 3.0.1, on Microsoft Windows [Version 10.0.19043.1706], locale ru-RU)
• Flutter version 3.0.1 at D:~\AppData\Roaming\flutter
• Upstream repository https://github.com/flutter/flutter.git
• Framework revision fb57da5f94 (7 days ago), 2022-05-19 15:50:29 -0700
• Engine revision caaafc5604
• Dart version 2.17.1
• DevTools version 2.12.2

Checking Android licenses is taking an unexpectedly long time...[√] Android toolchain - develop for Android devices (Android SDK version 31.0.0)
• Android SDK at D:~\AppData\Local\Android\Sdk
• Platform android-31, build-tools 31.0.0
• Java binary at: D:\Programs\Android\Android Studio\jre\bin\java
• Java version OpenJDK Runtime Environment (build 11.0.12+7-b1504.28-7817840)
• All Android licenses accepted.

[X] Chrome - develop for the web (Cannot find Chrome executable at .\Google\Chrome\Application\chrome.exe)
! Cannot find Chrome. Try setting CHROME_EXECUTABLE to a Chrome executable.

[√] Visual Studio - develop for Windows (Visual Studio Community 2022 17.1.5)
• Visual Studio at D:\Programs\Microsoft Visual Studio\2022\Community
• Visual Studio Community 2022 version 17.1.32414.318
• Windows 10 SDK version 10.0.19041.0

[√] Android Studio (version 2020.3)
• Android Studio at D:\Programs\Android Studio
• Flutter plugin can be installed from:
https://plugins.jetbrains.com/plugin/9212-flutter
• Dart plugin can be installed from:
https://plugins.jetbrains.com/plugin/6351-dart
• Java version OpenJDK Runtime Environment (build 11.0.11+9-b60-7590822)

[√] Android Studio (version 2021.2)
• Android Studio at D:\Programs\Android\Android Studio
• Flutter plugin can be installed from:
https://plugins.jetbrains.com/plugin/9212-flutter
• Dart plugin can be installed from:
https://plugins.jetbrains.com/plugin/6351-dart
• Java version OpenJDK Runtime Environment (build 11.0.12+7-b1504.28-7817840)

[√] HTTP Host Availability
• All required HTTP hosts are available

[stevemessick]

Dup of #6167. Tracked as dart-lang/sdk#49027