Extend the call site default argument expansion mechanism?

[Steven Schveighoffer]

On 5/15/18 10:26 AM, Yuxuan Shui wrote:
> On Tuesday, 15 May 2018 at 13:59:37 UTC, jmh530 wrote:
>> On Tuesday, 15 May 2018 at 13:16:21 UTC, Steven Schveighoffer wrote:
>>> [snip]
>>>
>>> Hm... neat idea. Somehow, opDispatch can probably be used to make 
>>> this work even more generically (untested):
>>>
>>> struct WithAlloc(alias alloc)
>>> {
>>>    auto opDispatch(string s, Args...)(auto ref Args args) if 
>>> (__traits(compiles, mixin(s ~ "(args, alloc)")))
>>>    {
>>>       mixin("return " ~ s ~ "(args, alloc);");
>>>    }
>>> }
>>>
>>> -Steve
>>
>> Example:
>> https://run.dlang.io/is/RV2xIH
> 
> Sadly with(WithAlloc!alloc) doesn't work. (If you have to use 
> withAlloc.func everywhere, it kind of destroy the point, doesn't it?)

It seems opDispatch isn't being used in the with statement. That seems 
like a bug, or maybe a limitation. I'm not sure how "with" works, but I 
assumed it would try calling as a member, and then if it doesn't work, 
try the call normally. Probably it's checking to see if it has that 
member first.

Annoying...

-Steve