main.dart

class Test {
  late Object? x = null;
  
  void talk() {
     print("value: $x");
  }
}

void main() {  
  Test()..talk();
}

pubspec.yaml

name: quickfix
description: A sample command-line application.
version: 1.0.0
# repository: https://github.com/my_org/my_repo

environment:
  sdk: ^3.4.0

# Add regular dependencies here.
dependencies:
  # path: ^1.8.0

dev_dependencies:
  lints: ^3.0.0
  test: ^1.24.0