This came up internally - pytype supports `ellipsis` as a global definition in type stubs, and the poster was wondering how portable it was (seeing as how it's not directly accessible in python itself). Are other type checkers okay with `ellipsis` used as a type?
I think there would be a good case for special-casing Ellipsis like None, i.e., to allow annotating Ellipsis values with just Ellipsis rather than ellipsis.
Both Ellipsis and None are singleton objects, and aside from type-checking there is no need to refer to their types (which are somewhat of an implementation detail).