StatelessWidget & StatelessElement as a StatefulWidget

stateless.dart

import 'package:flutter/widgets.dart';

class Example extends StatelessWidget {
  const Example({super.key});

  @override
  StatelessElement createElement() => ExampleElement(this);

  @override
  Widget build(BuildContext context) => const Placeholder();
}

class ExampleElement extends StatelessElement {
  ExampleElement(this.widget) : super(widget);

  @override
  StatelessWidget widget;

  @override
  void mount(Element? parent, Object? newSlot) {
    super.mount(parent, newSlot);
    print('initState');
  }

  @override
  void update(covariant Example newWidget) {
    super.update(newWidget);
    print('didUpdateWidget');
  }

  @override
  void unmount() {
    print('dispose');
    super.unmount();
  }

  void setState(VoidCallback fn) {
    fn();
    markNeedsBuild();
  }

  @override
  Widget build() => widget.build(this);
}