[Issue 19441] alias this causes partial assignment

[d-bugmail at puremagic.com]

https://issues.dlang.org/show_bug.cgi?id=19441

--- Comment #4 from Andrei Alexandrescu <andrei at erdani.com> ---
Great you guys. I think it's best to qualify this as an wrong-code bug so we
don't go through a deprecation cycle. OK?

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