Blocks that emit light have shadows on sides

Blocks that emit light have shadows on sides. They shouldn't, because they create light, light that should be stronger than the shadow being cast. I made glowstone pure white to display it best. This happens in the new snapshots too.

Mediafire link to resource pack: http://www.mediafire.com/download/t1vp2ulk28juin4/Default+Resource+Pack+%2815w47c%29.zip (didn't make it, just changed pumpkin and glowstone)