[Issue 20009] isForwardRange doesn't work with alias range this or inheritance

[d-bugmail at puremagic.com]

https://issues.dlang.org/show_bug.cgi?id=20009

--- Comment #4 from shove <shove at 163.com> ---
(In reply to Ali Ak from comment #3)
> Why mark this invalid? Are interfaces and alias this'd ranges not supposed
> to work?

Misread the title and misoperate it. I'm sorry.

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