flutter-quill/example/lib/extensions/scaffold_messenger.dart

import 'package:flutter/material.dart'
    show ScaffoldMessenger, ScaffoldMessengerState, SnackBar;
import 'package:flutter/widgets.dart' show BuildContext, Text;

extension ScaffoldMessengerStateExt on ScaffoldMessengerState {
  void showText(String text) {
    showSnackBar(SnackBar(content: Text(text)));
  }
}

extension BuildContextExt on BuildContext {
  ScaffoldMessengerState get messenger => ScaffoldMessenger.of(this);
}