Must ranges support `r1 = r2;`?

[ag0aep6g]

On 03/25/2018 01:49 AM, Jonathan M Davis wrote:
> assignment really isn't part of the range API. I don't think that any of the
> range traits even test that assignment works on any level. So, it could be
> argued that generic, range-based functions simply shouldn't ever be
> assigning one range to another.
So we have to remove all range assignments from generic code. Ugh.

The first three: https://github.com/dlang/phobos/pull/6346