anchor.diff:  }
   
   class _SignInPageState extends State<SignInPage> {
  +  User user;
  +
  +  @override
  +  void initState() {
  +    _auth.userChanges().listen((event) => setState(() => user = event));
  +    super.initState();
  +  }
  +
     @override
     Widget build(BuildContext context) {
       return Scaffold(
  
positive.code:   // Example code for sign out.
    Future<void> _signOut() async {
      await _auth.signOut();
    }
  }
  
  
negative.code:         return ListView(
            padding: const EdgeInsets.all(8),
            children: <Widget>[
              _UserInfoCard(user),
              _EmailPasswordForm(),
              _EmailLinkSignInSection(),
              _AnonymouslySignInSection(),
  