cast(immutable) vs extra variable

[bearophile]

Jonathan M Davis:

> All in all, I think that it's pretty much always a bad idea to 
> have a struct
> with const or immutable members. It's just begging for 
> problems. Tail-const or
> tail-immutable is fine, because the members themselves aren't 
> const or
> immutable (just what they refer to), but having them be 
> directly const or immutable is a bad idea IMHO.

The Rust language has avoided this problem, you can copy struct 
instances with const fields. But you can't update their const 
fields.

Bye,
bearophile