Class type & : class & causes recursiveness

What causes this issue?

You want to allocate a class to another class. However, this would make
a class subordinate to itself in the hierarchy. Recursiveness is not
allowed.

System Response

The system issues an error message and will not allow you to continue with this transaction until the error is resolved.

How to fix this error?

Choose another class.

Error message extract from SAP system. Copyright SAP SE.