I have a subclass of OrderedCollection, which adds some instance variables.

Poking around in the collection classes, I find that sometimes
self copyEmpty is used to make an empty collection, and sometimes
self species new: 0.

The basic problem is that if you have a subclass of OrderedCollection
(or any other SequenceableCollection) that adds instance variables,
*sometimes* a selection or slicing method will return an empty result
that has its additional instance variables appropriately set up, and
simetimes it will return a non-empty result that _doesn't_ have its
additional isntance variables appropriately set up.

The problem is that using
    self species new: (size)
to return a copy of part of a sequence doesn't provide information about
the additional instance variables.

I was wondering about a refactoring where there would be a new method

    copySansContentsForSize: size
        "Subclasses of existing sequenceable collections that add
         instance variables should override this to set up those
         variables in the new object."
        ^self species new: size

and having the methods that now call
    self species new: newSize
call
    self copySansContentsForSize: newSize
instead.

Before doing this, is there any agreed way to decide which selection/
filtering/slicing methods should return OrderdCollections and which
should return objects of the new subclass?