NBMsgPack060: UnusedDataPacket member should have a property shape

A property or field typed as the special UnusedDataPacket type must have a property shape generated for it by PolyType. This is done by default for public members, but other members must have PropertyShapeAttribute applied (without setting its Ignore property to true of course).

Example violation

The following class has the special property defined as private but without a PropertyShapeAttribute:

public class Person
{
    public required string Name { get; set; }

    private UnusedDataPacket Extension { get; set; } // NBMsgPack060
}

Resolution

Add the PropertyShapeAttribute:

public class Person
{
    public required string Name { get; set; }

    [PropertyShape]
    private UnusedDataPacket Extension { get; set; }
}