Long version: <https://issues.dlang.org/show_bug.cgi?id=18657>
("std.range and std.algorithm can't handle refRange").
Short version: With two `std.range.RefRange`s, `r1 = r2;` does not what
other Phobos code expects.
Question is: Who's at fault? Where do I fix this? Do ranges have to
support assignment as expected - even though std.range doesn't mention
it? Or should range-handling code never do that - even though it comes
naturally and is widespread currently?
- Must ranges support `r1 = r2;`? ag0aep6g via Digitalmars-d
-