Selfless

A Selfless reference is one which might be the same as some reference not created at the same instant.

There are two kinds of Selflessness:

transparent selfless
Those references whose sameness is defined by the sameness of their response to __optUncall/0.

A consequence of this is that such objects are immutable in a way (Frozen): they cannot change their behavior except due to being composed of mutable objects, where "composed of" means that the objects are exposed in __optUncall.

opaque selfless
Opaque selfless objects are such as characters and SturdyRefs. XXX explain further