x:DataType in MarkupExtension.ProvideValue

[doublecount]

x:DataType is used in XAML to set the the scope for databindings. MarkupExtensions are helpers to enhance the XAML, but x:DataType seems not available there (at least I did not manage to get it).

It would be convenient and powerful if x:DataType would be accessible when a MarkupExtension is resolved. This way, a MarkupExtension could profit from all present metadata that is available, just as CompiledBinding does.

public class MyMarkup: MarkupExtension
{
    public override object ProvideValue(IServiceProvider serviceProvider)
    {
        // wanted: serviceProvider.DataType
        return null;
    }
}