[Mono-dev] Generic Constraints Regression in 2.8

[Marek Safar]

Hello,

Could you please fill a bug report.

Thanks
Marek

> Except that Y is constrained to be of type Z and so is guaranteed to 
> be a reference type.
>
> On Mon, Nov 15, 2010 at 12:30 AM, Bojan Rajkovic 
> <severedcross at gmail.com <mailto:severedcross at gmail.com>> wrote:
>
>     On Nov 14, 2010, at 10:16 PM, Tom Philpot wrote:
>
>>     The following code compiled with a warning on Mono 2.7 (as of
>>     147679)  but has  an error in 2.8.
>>
>>     namespace Application
>>     {
>>     public class Z {}
>>
>>     public class A<X, Y>
>>     where Y : Z
>>     where X : Y
>>     {
>>     protected void SomeOperation(Y y)
>>     {
>>     X x = y as X;
>>     }
>>     }
>>
>>     public class Foo { public static void Main() {} }
>>     }
>>
>>     /opt/mono-2.8/bin/gmcs CS0413Regression.cs
>>     CS0413Regression.cs(12,33): error CS0413: The `as' operator
>>     cannot be used with a non-reference type parameter `X'. Consider
>>     adding `class' or a reference type constraint
>>     Compilation failed: 1 error(s), 0 warnings
>>
>>     /opt/mono-r147679/bin/gmcs CS0413Regression.cs
>>     CS0413Regression.cs(12,27): warning CS0219: The variable `x' is
>>     assigned but its value is never used
>>     Compilation succeeded - 1 warning(s)
>
>     The error message here is the correct thing to do—as casts are
>     only valid with reference types, because they can result in null,
>     which is invalid for a value type. If this raised only a warning
>     in gmcs earlier, it was a bug.
>
>     —Bojan
>
>>
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>
>
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>
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