It wasn't all that long ago that the only realistic way to have a useful electric car was to build one yourself. I know three people who did just that. It seems reasonable, given the advances in motor, battery, and solar tech, that a reasonably determined person could build a solar one today. It probably wouldn't be able to drive on the solar panels directly, but that's not necessary.
In fact, that's my backup plan should the day come when I can no longer get used cars that are old enough to avoid connectivity.
Not like the one in the reddit post, though. That is, as one commenter pointed out, a death trap. Better to modify an existing car.