What code is relevant in your area, that is the question! Some places use the IRC as-written, while others use an amended or modified version, or something else, or nothing at all! If you're not clear about what, if any, local code requirements pertain to your project, call the appropriate department having jurisdiction over your project and get the information straight from the horse's mouth.

FWIW, here's what's required if one is simply following the 2015 International Residential Code:

SECTIONP2717
DISHWASHING MACHINES

P2717.1 Protection of water supply.

The water supply to a dishwasher shall be protected against backflow by an air gap complying with ASME A112.1.3 or A112.1.2 that is installed integrally within the machine or a backflow preventer in accordance with Section P2902.

P2717.2 Sink and dishwasher.

The combined discharge from a dishwasher and a one- or two-compartment sink, with or without a food-waste disposer, shall be served by a trap of not less than 11/2 inches (38 mm) in outside diameter. The dishwasher discharge pipe or tubing shall rise to the underside of the counter and be fastened or otherwise held in that position before connecting to the head of the food-waste disposer or to a wye fitting in the sink tailpiece.

I don't live in IL but I do have a single sink, disposal and dishwasher. Mine is installed using the last method - high loop under sink.

Plumb your single bowl sink with no disposal and pass inspection, then install a disposal with a connection to your dishwasher. I'm all for code, but this is lunacy.

I am going to call and ask the city for the verbiage. Maybe this contractor isn't knowledgeable in how to work it, since the other contractors I have been talking to haven't brought it up.

Sammy my problem is this is all Greek to me. I have no idea how the plumbing all works, which is why I'm not installing the sink myself! From what you have posted it sounds like there is likely a work around, which is good, though it concerns me more than a little that this contractor (or his plumber??) isn't aware of how to do it. Armed with a better understanding I can talk through it with him when he comes back with his quote.

Does the Illinois Plumbing Code even apply to your remodel?

Based on the definitions in the Illinois Plumbing Code, I would interpret Domestic Dishwasher (Private Residence) to apply only to dishwashers installed in residences located in hotels or motels.

"Private" or "Private Use": In the classification of plumbing fixtures, private applies to fixtures in residences, apartments and private bathrooms of hotels or motels where the fixtures are intended for the use of a single family or an individual; handwashing stations (lavatories) within residents' rooms, within shared or common resident restrooms, or designated for staff use only in hospitals/long-term care units/mental health facilities, and hand-washing stations where food is being prepared.

Does your brain hurt yet? Mine does. It's sh*t like this that really brings it home for me just how overly complicated things are when it comes to governmental regulations. I mean, if a person of above average intelligence finds it confusing, how in the world is someone of average or below average intelligence supposed to understand it and comply? I feel the same way about the tax code, btw. :)

Why not just install the disposal after inspection? There is no rule against that. Garbage disposals do not require government inspection in order to be installed. You do not need to pull a permit to put one in. Do what Joseph Corlett said and be done with it. There are enough hard things to do in life without trying to comply with silliness, which I suspect in the end your disposal would pass inspection anyway because tons of people have single bowls and disposals.

Rita - that is certainly an option and if necessary I would do that. If there is a way to just have it all done up front during the remodel and it be compliant I would rather that than have to hire a plumber after the fact. It is a good thought that I hadn't come up with before Joseph mentioned it though so I will definitely keep it as a back up plan.