I will disagree with conropl on what you would see if you put on the EF-S lens on your full frame. I will speculate a bit. You would most likely just see black after you broke your mirror. Or maybe a error message on your lcd telling you the camera no longer functions.
That is why I said "if" you could put an EF-S on a FF camera.
5DS R, 1D X, 7D, Sigma 10-20mm f/4-5.6, 24mm f/1.4L II, 16-35mm f/4L IS, 24-105mm f/4L, 50mm f/1.8, 100mm Macro f/2.8L, 70-200mm f/2.8L IS II, 100-400mm f/4.5-5.6L, 580EX-II flickr