Must ranges support `r1 = r2;`?

[Jack Stouffer]

On Monday, 16 April 2018 at 16:15:30 UTC, H. S. Teoh wrote:
> I could come up with some pretty pathological range types for 
> stress-testing, if you want.  (These are actual range types 
> I've used in my own code, I didn't set out to break Phobos, but 
> it turned out that Phobos makes many unstated assumptions that 
> explode in your face when given a more unusual instance of a 
> range. There used to be (and may still be) a lot of places that 
> essentially assumes built-in array semantics, and that blew up 
> in ugly ways when handed something else that's nevertheless 
> still a valid range.)

It would be awesome to have these as range types in 
std.internal.test.dummyrange. Then they could be used in tests 
throughout Phobos.