[PATCH] Disallow empty "or" type specifier

[Pietro Cerutti]

Hi all,

the attached patch makes the `(or)` type specifier invalid, as opposed 
to being simplified to `*`.
This is more consistent with the mathematical interpretation of an empty 
(sum) type being the bottom type having no inhabitants.
This is very explicit in OCaml, for example, where the empty type is 
literally a sum (variant) of 0 types: `type t = |`.

--
Pietro Cerutti
I have pledged to give 10% of income to effective charities
and invite you to join me - https://givingwhatwecan.org

0001-Disallow-empty-or-type-specifier.patch
Description: Text document