over_react_invalid_render_return_type

The return value of a component render() method must be ReactElement, Fragment, string, number, boolean, null, or an Iterable of those types

GOOD:

@override
render() {
  return Dom.div()(
    'Hi there',
  );
}

GOOD:

@override
render() {
  return Fragment()(
    Dom.div()(
      NavItem()('Nav'in it, you know?'),
    ),
    (Dom.button()..type = 'button')('Click me'),
  );
}

GOOD:

@override
render() {
  return null;
}

BAD:

@override
render() {
  return {
    'foo': 'bar',
  };
}