More fun with autodecoding

[Nicholas Wilson]

On Tuesday, 11 September 2018 at 13:08:46 UTC, Steven 
Schveighoffer wrote:
> On 9/10/18 7:00 PM, Nicholas Wilson wrote:
>> On Monday, 10 September 2018 at 20:44:46 UTC, Andrei 
>> Alexandrescu wrote:
>>> On 9/10/18 12:46 PM, Steven Schveighoffer wrote:
>>>> On 9/10/18 8:58 AM, Steven Schveighoffer wrote:
>>>>> I'll have to figure out why my specialized range doesn't 
>>>>> allow splitting based on " ".
>>>>
>>>> And the answer is: I'm an idiot. Forgot to define empty :) 
>>>> Also my slicing operator accepted ints and not size_t.
>>>
>>> I guess a better error message would be in order.
>> 
>> https://github.com/dlang/DIPs/pull/131 will help narrow down 
>> the cause.
>
> While this would help eventually, I'd prefer something that 
> just transforms all the existing code into useful error 
> messages. See my response to Andrei.
>
> -Steve

Please tell me where to get one of those!

But yeah, that DIP will tell you that has slicing is you problem 
straight away. Extracting useful information to present to the 
user on why hasSlicing!R is false is much trickier for the same 
reason that providing useful information in the current template 
constraint format is hard: it is a bunch of potentially 
unstructured logic that has already been const-folded in order to 
evaluate it in the first place, so you can't re-evaluate it 
without flushing the template cache.

That's not to say that the situation can't be improved beyond 
what the DIP specifies, but I haven't had any brilliant ideas 
(and the Idea for that DIP was stolen from someone else anyway).