FirebaseAuth: How are the errors reported

[kroikie]

Hi,
Im currently writing a sample project using FirebaseAuth. When looking at teh sourcecode I see:

 /// Tries to create a new user account with the given email address and password.
  ///
  /// If successful, it also signs the user in into the app and updates
  /// the [onAuthStateChanged] stream.
  ///
  /// Errors:
  ///   • `ERROR_WEAK_PASSWORD` - If the password is not strong enough.
  ///   • `ERROR_INVALID_EMAIL` - If the email address is malformed.
  ///   • `ERROR_EMAIL_ALREADY_IN_USE` - If the email is already in use by a different account.
  Future<FirebaseUser> createUserWithEmailAndPassword({
    @required String email,
    @required String password,
  }) async {
    assert(email != null);
    assert(password != null);
    final Map<String, dynamic> data =
        await channel.invokeMapMethod<String, dynamic>(
      'createUserWithEmailAndPassword',
      <String, String>{'email': email, 'password': password, 'app': app.name},
    );
    final FirebaseUser currentUser = FirebaseUser._(data, app);
    return currentUser;
  }

My question is how are the named erros reported? The method only returns a FirebaseUser and no Exception is thrown in the function. What am I missing?
Thanks
Thomas