I'm not sure this belongs in the cheatsheet, since the cheatsheet is meant to be a quick reference for common types, and the type of an empty tuple is definitely not a common need. Maybe there isn't a better place for it though.

Maybe there isn't a better place for it though.

There is "Common issues" section. Maybe this discussion can be put there?

I doubt it's a common issue either. :)

Maybe it should be in https://mypy.readthedocs.io/en/latest/builtin_types.html, which is currently missing Tuple.

I think adding various forms of tuples to https://mypy.readthedocs.io/en/latest/builtin_types.html is a good idea, but I like adding this to the cheat sheets too (many people use just the cheat sheet for reference, and this is definitely an issue where everyone needs help).