Extend the call site default argument expansion mechanism?

[jmh530]

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