If a plugin has set Swift 6 as the swift-tools-version or the swiftLanguageModes, it will fail with error:

Conformance of 'MyPlugin' to protocol 'FlutterPlugin' crosses into main actor-isolated code and can cause data races

Example:
https://github.com/spencerccf/app_settings/blob/111a15c4dca6fa9e094fca027ca27bdcd903c9e5/ios/app_settings/Package.swift#L1

Steps to repro:

1. flutter create my_app && cd my_app
2. flutter pub add app_settings
3. flutter build ios