[Mono-dev] CS0019 for value type != null

Marek Safar marek.safar at seznam.cz
Tue Apr 8 07:53:13 EDT 2008

Hello Andrés,
> Marek Safar wrote:
>> Hello Casey,
>>> I've noticed that on a recent SVN build of mono, I get a CS0019 error if
>>> I try to compare a value type against null. E.g.:
>>>   DateTime dt;
>>>   if (dt != null)
>>>     Console.WriteLine(dt);
>>> As far as I can tell, this is the correct behavior, since a value type
>>> can't be null. I'm concerned, though, because this behavior seems to
>>> have been introduced recently in SVN, AND it looks like MS's compiler
>>> doesn't reject this statement (well, I haven't seen it accept it, but
>>> this is existing code which apparently compiles fine under Visual
>>> Studio).
>> This code compiles correctly with the SVN HEAD version.
> IIRC this was a design flaw that some mono devs didn't agree about, 
> right? Is gmcs compiler at least reporting a warning about this? If not, 
> it would be interesting to do so although MS doesn't do it (in the past 
> I remember fixing some bugs in a MS.NET project because gmcs reported 
> more warnings than csc!).
Yes, gmcs does report a warning in this case.


More information about the Mono-devel-list mailing list