Feature Request / Improvement

I think I have somewhat of an idea on how to do this, so far have added the following to parser.py:

CAST = CaselessKeyword("cast")
cast_expression = (CAST + "(" + column + "as" + identifier + Suppress(")")).set_results_name("cast")

# would need something special for the set_parse_action

I am wondering a couple of things:
Do we need a new class CastableReference or something? Worth expanding on the Reference class? And once that is done, how would we propagate the new type (Im assuming we need some way to go from a string to an IcebergType of the string the user has put into the cast operation) into the scan?

This was spawned from #170

Happy to work on this, just would be awesome to get some context