오류 ../../../.pub-cache/hosted/pub.dev/watcher-1.0.2/lib/src/constructable_file_system_event.dart:7:57: Error: The class 'FileSystemEvent' can't be extended, implemented, or mixed in outside of its library because it's a sealed class. Dart 을 업그레이드 해주니 해결 dart pub upgrade 해결 : https://github.com/dart-lang/sdk/issues/52570 Watcher fails with `class 'FileSystemEvent' can't be extended`, for dart, no..