[Mono-dev] Compiler bug with Generics and where constraints

John Anderson sontek at gmail.com
Mon Jul 16 20:13:35 EDT 2007

On 7/16/07, Adar Wesley <adar.wesley at gmail.com> wrote:
> Hi John,
> It seams to me there is a problem with the code.  (I don't know if it
> worked before)
> In
>    1. protected static T
>    GetBusinessQueryObjectFromReader<T>(IDataReader reader)
>    2. 74             where T : BusinessQueryObject, new()
> The generic parameter T is contained.  However in:
> public override T[] GetQueryObjects<T>(string query, params
> QueryParameter[] parameters)
> T is not constrained.
> When you try to call GetBusinessQueryObjectFromReader<T>(IDataReader
> reader)
> from within GetQueryObjects<T> with the same generic parameter you get the
> error.
> Either add the same constraint on T in the decleration of
> GetQueryObjects<T> or remove
> the constraint from GetBusinessQueryObjectFromReader<T>.

The constraint is inherited and you can't add a constraint to a method that
you are overriding (because you inherited it)

but I found the actual cause of the problem, Its when passing the generic
type through an anonymous delegate.
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