[m-dev.] discussion about the implementation of compact type representations

[Mark Brown]

Hi Zoltan,

> On Mon, 30 Oct 2017 09:25:27 +1100 (AEDT), "Zoltan Somogyi" <zoltan.somogyi at runbox.com> wrote:
>>
>> I propose that for types with a single function symbol of arity 1,
>
>> - If the argument of the function symbol has an existential type,
>>   that should not be an error, but should make the type NOT a notag type.

How about if it's an existentially typed dummy type, such as

  :- type foo ---> some [T] foo(unit(T)).

If there's just a type_info in there, that could also be considered
notag. Is it worth including this case?

Mark