[Issue 18263] selective import with same name masks out this reference in mixin template

[d-bugmail at puremagic.com]

https://issues.dlang.org/show_bug.cgi?id=18263

--- Comment #5 from FeepingCreature <default_357-line at yahoo.de> ---
Good point! I'd prefer to wait until the actual deprecation goes through, but
at least there's some hint towards what is happening now.

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