[Issue 12615] Warn against, and then deprecate old alias syntax

[via Digitalmars-d-bugs]

https://issues.dlang.org/show_bug.cgi?id=12615

--- Comment #16 from yebblies <yebblies at gmail.com> ---
(In reply to Mike from comment #14)
> 
> One of them needs to go,

I disagree.  Don't break all of my old code for no reason.

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