Repro of DartPad issue #2286

main.dart

import 'package:flutter/material.dart';
import 'package:google_fonts/google_fonts.dart';

void main() => runApp(
  MaterialApp(
    title: 'Flutter Demo',
    theme: ThemeData(
      primarySwatch: Colors.blue,
      textTheme: TextTheme(
        headline1: GoogleFonts.oswald(
          fontSize: 35,
        ),
        headline2: GoogleFonts.lato(
          fontSize: 25,
          fontStyle: FontStyle.italic,
        ),
      ),
    ),
    home: const MyHomePage(title: 'Flutter Demo Home Page'),
  ),
);

class MyHomePage extends StatefulWidget {
  const MyHomePage({Key? key, required this.title}) : super(key: key);

  final String title;

  @override
  State<MyHomePage> createState() => _MyHomePageState();
}

class _MyHomePageState extends State<MyHomePage> {
  int _counter = 0;

  void _incrementCounter() {
    setState(() {
      _counter++;
    });
  }

  @override
  Widget build(BuildContext context) {
    final TextStyle headline1 = Theme.of(context).textTheme.headline1!;
    final TextStyle headline2 = Theme.of(context).textTheme.headline2!;
    
    return Scaffold(
      appBar: AppBar(
        title: Text(widget.title),
      ),
      body: Center(
        child: Column(
          mainAxisAlignment: MainAxisAlignment.center,
          children: [
            Text(
              'You have pushed the button this many times:',
              style: headline1,
              textAlign: TextAlign.center,
            ),
            Text(
              '$_counter',
              style: headline2,
            ),
          ],
        ),
      ),
      floatingActionButton: FloatingActionButton(
        onPressed: _incrementCounter,
        tooltip: 'Increment',
        child: const Icon(Icons.add),
      ),
    );
  }
}