[Issue 17440] Nullable.nullify() resets referenced object

[d-bugmail at puremagic.com]

https://issues.dlang.org/show_bug.cgi?id=17440

--- Comment #14 from Chris Paulson-Ellis <chris at edesix.com> ---
Also - to emphasise what was said in comment 11 - let me just say that it took
me *3 days* to find that the cause of a mysterious crash in my code was the
destroy in nullify().

At the very least, the documentation for Nullable should contain a prominent
warning that nullify() will invalidate your class references.

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