SELF_RENDERING

Whether a class's toString() prints exactly what an unchanged walk of it printed, so the walk can stand in for it: the JDK's stock printers — AbstractCollection's [a, b], AbstractMap's {k=v}, the formats Sink.walk and Sink.walkMap copy (their (this ...) never meets an unchanged walk: a self-reference is a CYCLE) — and Pair/Triple, final, whose (a, b) is the tuple walk's own.

By the DECLARING class, not is: extending AbstractList says nothing of who overrides toString() further down. Every other format keeps the rollback, even one that only LOOKS the same — a wrong guess costs a wrong line, caution a second pass. A ClassValue: the reflection runs once per class, and a snippet's class still unloads with its loader. A class reflection cannot read answers false — the rollback again.