I am trying to run this code example https://pub.dev/packages/flutter_adaptive_scaffold/example
but the code does not compile showing Undefined name 'WidgetStateProperty'.

Have tried restarting VS Code and flutter clean/get – not helpful.

Also, tried to copy WidgetStateProperty class into my project, but then I got WidgetState is not a type.

I searched and found this issue https://github.com/hiddify/hiddify-next/issues/946 which seems to be somehow similar but not helpful.

I am on Windows using the latest versions of VS Code, Dart and Flutter

Flutter (Channel stable, 3.22.2, on Microsoft Windows [Version 10.0.19045.4412], locale en-US)

Any ideas?