[Issue 19532] chunkBy assert error involving non-forward input ranges.

[d-bugmail at puremagic.com]

https://issues.dlang.org/show_bug.cgi?id=19532

--- Comment #6 from Jon Degenhardt <jrdemail2000-dlang at yahoo.com> ---
PR 6841 (https://github.com/dlang/phobos/pull/6841)

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