[Issue 15793] Change !is error to warning

[via Digitalmars-d-bugs]

https://issues.dlang.org/show_bug.cgi?id=15793

Jonathan M Davis <issues.dlang at jmdavisProg.com> changed:

           What    |Removed                     |Added
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                 CC|                            |issues.dlang at jmdavisProg.co
                   |                            |m

--- Comment #2 from Jonathan M Davis <issues.dlang at jmdavisProg.com> ---
It's still more efficient to use is null or !is null, and it's what code really
should be doing, but making it an error to use == null or != null is arguably a
bit much.

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