The NaN of types (in D)

[Imperatorn]

On Sunday, 11 October 2020 at 13:11:28 UTC, Stefan Koch wrote:
> On Sunday, 11 October 2020 at 12:46:53 UTC, Imperatorn wrote:
>> On Sunday, 11 October 2020 at 12:18:59 UTC, Stefan Koch wrote:
>>> [...]
>>
>> Shouldn't this be the universe. The empty set is "there is no 
>> _", while the "opposite" ¬∅ of the empty set is the universe?
>
> The universe would be __type. (because it can hold any type in 
> U)
> If you set the __type.init to be __type; (And that's how it 
> used to be)
>
> The that means you cannot distinguish between a function 
> returning __type.
> (Assuming your type function gives you the return type of a 
> function)
> And the programmer having messed up the and forgot to set the 
> value.
>
> Therefore you need an initial value which cannot possibly be a 
> valid type anywhere.
> Hence a type which is no valid type is needed.

Oh, I see. I mis-read the question