Generality creep

[ag0aep6g]

On 28.03.19 12:12, Andrei Alexandrescu wrote:
> See also the related issue: https://issues.dlang.org/show_bug.cgi?id=18657
> 
> Indeed so, thanks. The entire thing with ranges whereby save() does 
> something else than a mere copy has been a mistake and supporting it has 
> been an expensive distraction.

`save` is a red herring with regards to issue 18657.

The problem isn't RefRange.save, it's RefRange.opAssign. The issue 
manifests often in implementations of `save`, but that's just because 
they *assign* the result of `save` over an existing range.

Note that there's no `save` call in issue 18657's third example (`choose`).

The question is whether ranges are allowed to implement opAssign like 
RefRange does. If so, all of Phobos needs fixing to avoid calling 
opAssign. If not, RefRange.opAssign should be removed.