foreach() behavior on ranges

[Alexandru Ermicioi]

On Wednesday, 25 August 2021 at 11:04:35 UTC, Steven 
Schveighoffer wrote:
> It never has called `save`. It makes a copy, which is almost 
> always the equivalent `save` implementation.
>
> -Steve

Really?

Then what is the use for .save method then?
The only reason I can find is that you can't declare constructors 
in interfaces hence the use of the .save method instead of copy 
constructor for defining forward ranges.

We have now two ways of doing the same thing, which can cause 
confusion. Best would be then for ranges to hide copy constructor 
under private modifier (or disable altoghether), and force other 
range wrappers call .save always, including foreach since by not 
doing so we introduce difference in behavior between ref and 
value forward ranges (for foreach use).