What about looking at it from quantum and uncertainty principle angles...
How can you ever truly know if something is dark? That would mean that you have to observe it and in order to observe it, interact with it. And then you get into trouble with the uncertainty principle. You can only say with certain probabilties particles of certain energies exist or dont exist within some defined spacetime. In other words there is some probability a certain volume of space located in the center of the sun is "dark."