Example from 'Cutting the stateful boilerplate' using likely Dart features (primary constructors, inferred `required`, `override`)

stateful_boilerplate_plain.dart

import 'package:flutter/material.dart';

// Assumptions:
//  * Dart has primary constructors.
//  * Dart supports `override`, and override inference
//    is considered appropriate.
//  * The named parameter `String name` can omit `required`
//    because it is inferred.

void main() {
  runApp(const App(name: 'Dash'));
}

class const App(String name) {
  override build(context) {
    return MaterialApp(
      home: Counter(
        name: name,
        startValue: 10,
      ),
    );
  }
}

class const Counter({
  super.key,
  String name,
  int startValue = 0,
}): assert(startValue >= 0) extends StatefulWidget {
  override State<Counter> createState() => _CounterState();
}

class _CounterState extends State<Counter> {
  int _count = 0;

  override build(context) {
    return Scaffold(
      appBar: AppBar(title: Text('Hello ${widget.name}')),
      floatingActionButton: FloatingActionButton(
        onPressed: () {
          setState(() {
            _count += 1;
          });
        },
      ),
      body: Center(
        child: Text('Count: ${widget.startValue + _count}'),
      ),
    );
  }
}

It might still be convenient to use a macro @Stateful to generate createState and add the superclass:

@Stateful(_CounterState)
class const Counter({
  super.key,
  String name,
  int startValue = 0,
}): assert(startValue >= 0);