Analyzer doesn't detect changes in l10n Flutter tool.

Describe the bug https://flutter.dev/docs/development/accessibility-and-localization/internationalization

In Flutter 1.22, a new tool for generating translations was released. This tool generates a synthetic package in the root .dart_tool/flutter_gen/l10n_gen and updates the code when flutter run is running and the arb template file changes .

But the new code generated inside that package is not reanalyzed and saw an error like if the methods inside the package don’t exists. Once the file .dart_tool/flutter_gen/l10n_gen/app_localizations.dart is opened the error disapears.

To Reproduce Steps to reproduce the behavior:

1. Follow the steps at https://flutter.dev/docs/development/accessibility-and-localization/internationalization

Screenshots If applicable, add screenshots to help explain your problem.

Versions (please complete the following information):

• VS Code version: 1.52.1
• Dart extension version: 3.18.1
• Dart/Flutter SDK version: Channel dev, 1.26.0-8.0.pre, on macOS 11.1 20C69 darwin-x64, locale es-E

[DanTup]

@orestesgaolin the fix above should have shipped in stable releases quite some time ago, but perhaps you’re still seeing #3438? The fix for that was in the Dart SDK, but looks like it wasn’t in v2.16 (the current stable), so I’d expect it to be in the next major Dart/Flutter release.

I think it’s probably already in the Flutter beta channel, as that reports 2.17.0-69.2.beta for the Dart SDK and the commit above includes the tag 2.17.0-20.0.dev.

[DanTup]

I’ve updated https://dart-review.googlesource.com/c/sdk/+/179776 to only handle .dart_tool (I’m not aware of any dot-folders package:build writes to outside of that, but more can be added if that’s not true).