I don't know when this type became 'unit' but I guess it's done.

Should probably replace the multitude of nil occurrences in libsyntax and librustc with unit, at some point.

Having unit and unit as types is not friendly to dyslexics.

Having unit and unit

And your typo there is more evidence. :)

I agree with @crazymykl, I think this should get more discussion.

The type theory name for this type is the Unit type, so naming it unit seems the correct thing to do. nil always struck me as a bad name for it because it means something different than it does in pretty much every programming language that as a nil. The potential confusion with uint is unfortunate, but since the type isn't actually called unit in the type system, it's called (), I think it's ok.

Maybe it should be preferred to write () where possible, with a parenthetical mentioning it is pronounced unit/nil where appropriate.