Add __traits(canCall) and __traits(resolve)

[Paul Backus]

On Tuesday, 29 July 2025 at 02:11:22 UTC, Steven Schveighoffer 
wrote:
> On Saturday, 26 July 2025 at 02:27:08 UTC, Steven Schveighoffer 
> wrote:
>
>> ## `__traits(resolve, expression)`
>
> I was informed that opend has a feature similar to this 
> proposal:
>
> __traits(resolveFunctionCall, overloadSet, argTypes...)
>
> While similar, it's not exactly what I want. Because it's not 
> as natural as "what would you do if I wrote this expression".

Also, taking a list of types instead of an actual argument list 
means that you cannot distinguish between by-`ref` and by-value 
overloads of the same function.