Extend the call site default argument expansion mechanism?

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On Tuesday, 15 May 2018 at 14:52:46 UTC, Steven Schveighoffer 
wrote:
>> 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

Yeah I tried it with opDispatch but it didn't work. I vaguely 
remember some changes being made to how lookup is done in the 
past year or so... but I can't find the PR in question.