head const (again), but for free?

[sighoya]

On Wednesday, 13 January 2021 at 19:42:14 UTC, Meta wrote:
> I can see the value in head-immutable, in terms of type system 
> guarantees, but not head-const.

I think they are both worthwhile and if we provide one of them we 
should also provide the other combinations. They are already 
mentioned in the D documentation with comparison to C++.

One point for head const aka "final" would be to align to C#/Java 
though a weak one.