mutable keyword

[Jack Applegame via Digitalmars-d-learn]

On Saturday, 21 May 2016 at 21:49:23 UTC, Jonathan M Davis wrote:
> Rebindable is in kind of a weird grey area. It involves a 
> union, not casting, and it's only ever mutating the class 
> reference, not the object itself. Certainly, if it mutated the 
> object, it would be undefined behavior, but it's just mutating 
> the reference - but then again, the type system itself doesn't 
> really differentiate between the two. So, I suspect that what 
> it comes down to is that Rebindable is doing something that you 
> really shouldn't, but because it's using a union rather than a 
> cast, and it's so limited in what it's mutating, its behavior 
> is effectively defined in the sense that the compiler has no 
> leeway, but's probably still technically undefined. I don't 
> know what Walter would say though. Certainly, if casting were 
> involved, it would be undefined behavior without question, and 
> it's not the sort of thing that you should be doing in your own 
> code.
>
> [...]

I agree. But I think we need something that allows *logical* 
const and immutable.
Strict binding constness to physical memory constancy is not 
always necessary and sometimes even harmful.