There are some situations in which a segment scope is created out of thin air (e.g. w/o an arena):

* Segments created from an array
* Segments created from a buffer
* Segments obtained from a loader lookup

In such cases we create a fresh scope. The problem with this approach is that if we create multiple segments backed by the same underlying resource, their scope are not equal (even though their lifetime obviously is).

The scope implementation returned in these cases should take into account the underlying resource, so that a more appropriate behavior for equals can be implemented.