I've noticed upon switching the lamp types in the new release candidate for Blender 2.8, that the size property for the Sun type is missing. Is that feature removed?
The sun is not an infinitely far away object with no size clearly. It has a size, and although small, does create slightly fuzzy shadows even in a completely clear atmosphere.
I believe that Angle is referring to the angular size of the sun as seen from the surface of the planet, an average of 0.53 degrees should be accurate enough. You can use the same figure for a Moon light too.
Doing this gives hard shadows close up, that grow less distinct with distance.