UFCS functions with both pointers and refs

[Q. Schroll]

On Tuesday, 15 December 2020 at 20:38:04 UTC, Dave P. wrote:
> The use case would be to define extension methods on a struct 
> outside of where the struct is defined. The extension method 
> mutates the state of the struct, so I want to ensure I am 
> modifying the original struct and not a copy. If it’s a method 
> and I call it on a pointer to the struct, the pointer will get 
> auto-dereferenced and everything is great. So my question is 
> that if I want an extension method as a free function, do I 
> have to write both the version whose first argument is a 
> pointer to the struct and the version whose first argument is a 
> ref, or is there some keyword or other technique so that the 
> pointer gets auto-dereferenced the same way as if it were a 
> method. It sounds like the answer is no and I have to write a 
> version that just dereferences the pointer and calls the ref 
> version.

Now it's coming together.

The easiest way to do this is using an overload taking a `ref` 
(non-pointer) value and another taking a pointer (by copy, I 
guess).

     R f(ref T value, Ts args) { /* doing the actual work */ }
     R f(T* ptr, Ts args) { f(*p, args); } // manually dereference

You cannot get around doing the actual `f`, and the addition 
isn't that big. I think that's the best solution unless you have 
to deal with non-copyable types among Ts. Then you need to 
forward those properly.
I couldn't really do better using one template instead of this 
simple overload. (Certainly a template can be made, but it is 
clearly not the better solution.)