isInputRange as a __traits ?

[user1234]

On Saturday, 7 October 2017 at 10:59:02 UTC, Jonathan M Davis 
wrote:
> On Saturday, October 07, 2017 10:46:05 user1234 via
>> > Why? What would we gain from that?
>>
>> I've replied in another answer, so again, the idea is to save 
>> a bit of time spent to compile.
>
> I very much doubt Walter would consider that a good enough 
> reason. And it would make more sense to try and improve 
> template processing in general than to try and speed things up 
> by avoiding one template. In general, __traits does stuff that 
> you can't check with a library, and we _can_ check in the case 
> of isInputRange. At this point, if something can be done in a 
> library, it's almost a guarantee that it won't be added to the 
> language. A _really_ strong argument is needed for why 
> something should be in the language rather than a library if it 
> can be done in a library with the language as-is.
>
> - Jonathan M Davis

Yes i understand the reasoning but the compiler has **already** 
the ability to check input ranges. For now it's just for 
aggregates (and even those who are input ranges by their alias 
this).