interface Something {
    i int
}

struct Some {
    i int
}

struct App {
mut:
    count u8
}

fn (mut self App) next[T](input T) string {
    $if T is Something {
        return 'Something'
    } $else $if T is f64 {
        return 'f64'
    } $else {
        panic('${typeof(T.typ).name} is not supported')
    }
    panic('Unreachable')
}

fn test_comptime_if_is_interface() {
    mut app := App{}
    assert app.next(Something(Some{1})) == 'Something'
    assert app.next(1.0) == 'f64'
}