Implicit x:DataType is ignored, if InheritDataTypeFromItems.AncestorType doesn't have an exact match

[maxkatz6]

x:DataType is implicitly assumed from the DataGrid.ItemsSource thanks to this attribute defined on the base column class: https://github.com/AvaloniaUI/Avalonia/blob/master/src/Avalonia.Controls.DataGrid/DataGridBoundColumn.cs#L28

It seems compiled doesn't respect AncestorType-delivered types and only expects exact match.
As a workaround, I would recommend explicitly setting x:DataType on these columns.

This specific line should be replaced

Avalonia/src/Markup/Avalonia.Markup.Xaml.Loader/CompilerExtensions/Transformers/AvaloniaXamlIlDataContextTypeTransformer.cs

Line 95 in ead6ac8

.FirstOrDefault(n => n.Type.GetClrType().FullName == xamlType.FullName);

-     .FirstOrDefault(n => n.Type.GetClrType().FullName == xamlType.FullName);
+     .FirstOrDefault(n => xamlType.IsAssignableFrom(n.Type.GetClrType()));

If anybody can make a quick change and simple unit test, it will be really helpful.

Originally posted by @maxkatz6 in #18186 (comment)