A12Pointer
One exact A12 DocumentPointer: an ordered list of A12PathPart, with A12's derived views over it.
The shape is the owner's. DocumentPointer holds List<PathPart> and derives fullName() and repetitionIndexes() from it. This type used to be a pair of parallel names/repetitions lists, which is a shape A12 does not have — the parallel lists appear only as factory arguments there (DocumentPointer.of(fullName, repetitions)), never as the value's state.
Repetition domain, measured against DocumentPointerImpl's constructor: every index >= 1, except the last, which may also be A12PointerFormat.LAST_PART_ZERO to address A12's RepetitionsV2 slot. Nothing negative is representable; a repetition that could not be resolved to a row belongs to A12PartiallyKnownMultiPointer.
Zero parts is legal. That is A12's root pointer: DocumentPointerImpl.parseFullName("") returns an empty part list and the class displays that value as (empty DocumentPointer), a display name no illegal value gets. Rejecting it would invent a shape stricter than A12's.
Construction goes through of, and never through a generated copy(): the parts list is snapshotted, so a data class would be unable to validate-and-snapshot in one step (init cannot reassign a val constructor property) and its copy() would hand back an unchecked value.
Properties
The parts, in order — DocumentPointer.getPathParts(). Immutable and independent of the caller's list.
DocumentPointer.repetitionIndexes(). Immutable, like pathParts, rather than a fresh mutable copy.