A single non-blank leaf in a resulting ratchet tree that is new or was
re-signed relative to a parent tree, paired with its true MLS leaf index.
parentLeaf is the prior occupant of the same MLS leaf index in the parent
tree (Phase 9, UPD-01): the leaf a caller compares this changed leaf's
account identity against. It is undefined exactly when the parent node at
that index was absent or not a leaf — a brand-new or previously-blank slot
— meaning there is no prior identity to preserve (an Add into a freed slot
legitimately has a different identity than whoever occupied the slot
before it was removed).
A single non-blank leaf in a resulting ratchet tree that is new or was re-signed relative to a parent tree, paired with its true MLS leaf index.
parentLeafis the prior occupant of the same MLS leaf index in the parent tree (Phase 9, UPD-01): the leaf a caller compares this changed leaf's account identity against. It isundefinedexactly when the parent node at that index was absent or not a leaf — a brand-new or previously-blank slot — meaning there is no prior identity to preserve (an Add into a freed slot legitimately has a different identity than whoever occupied the slot before it was removed).