Mutable ForwardRange save() method not callable using const object

[Timoses]

On Tuesday, 4 September 2018 at 14:26:44 UTC, Steven 
Schveighoffer wrote:
> [...]
> As general advice, I wouldn't expect const to work well with 
> Ranges anyway -- const ranges are useless (you can't iterate 
> them). So not much code is expecting to handle const, including 
> the wrappers that Phobos provides.

Thanks, that sounds like some good advice. I've actually bumped 
into this right after when I had an immutable range which was 
supposed to fill in its cache when being iterated.
My argument for why this should work is that "from the outside of 
the range" it is immutable, since accessing via opIndex will 
always give the same value.
... In the end, that'll lead nowhere. The immutable attribute 
would become a "promise" rather than an enforcement (or too hard 
for the compiler to enforce).


Thanks for the clarification, Steve!