[Mono-dev] [PATCH] The big "as" cast cleanup

[Juraj Skripsky]

Hi Rodrigo,

SelectSingleNode ("cp") returns an XmlElement if an element <cp> is
found or null otherwise. So the explicit cast should be no problem here.
XPaths like "@someAttribute" or "count(...)" would of course be a
different story.

- Juraj


On Tue, 2008-01-08 at 12:25 -0200, Rodrigo Kumpera wrote:
> Hi Juraj,
> 
> @@ -326,7 +324,7 @@
>                          Console.Error.WriteLine ("WARNING: {0} is not
> supported for now.", el.FirstChild.LocalName);
>                          continue;
>                      } 
> -                    XmlElement cpElem = el.SelectSingleNode ("cp") as
> XmlElement;
> +                    XmlElement cpElem =
> (XmlElement)el.SelectSingleNode ("cp");
>                      string v = ""; 
>                      if (cpElem != null)
>                          v = new string ((char) (int.Parse (
> 
> 
> Here there is an explicit test if cpElem is null, this could mean that
> the code expect the cast to fail. Isn't that a possibility? 
> 
> 
> Rodrigo
> 
> 
> On Jan 8, 2008 11:49 AM, Juraj Skripsky <js at hotfeet.ch> wrote:
>         Hello,
>         
>         After getting annoyed by NullReferenceExceptions which turned
>         out to be
>         ClassCastExceptions in disguise, I've decided to clean up the
>         code in
>         mcs/class/corlib with regard to wrong/unnecessary uses of the
>         "as" cast 
>         operator.
>         
>         Reasons for the clean up:
>         -------------------------
>         - NullRefExceptions are thrown where ClassCastException should
>         be. With
>         explicit casts, the later is thrown at the right spot and
>         gives you more 
>         info.
>         - Personally, I consider the use of the "as" operator to be
>         confusing /
>         irritating in those cases where a explicit cast is sufficient.
>         
>         The following links also describe the problems with the "as"
>         operator: 
>         http://www.winterdom.com/weblog/2006/09/27/CastingOperatorsAndToString.aspx
>         http://blog.mattwynne.net/2007/09/04/casting-with-as-in-c/
>         
>         The performance of explicit casts and "as" casts are pretty
>         much the
>         same on Mono and MS.NET (see and run attached test program). 
>         
>         Attached is a patch (including ChangeLog entries).
>         All unit tests pass.
>         
>         Please review.
>         
>         - Juraj
>         
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