Sink

The containers between the root and the current element, by IDENTITY: equals/hashCode are caller code that recurses over the structure being walked, so equality would blow the stack this protects.

v is on the chain for the duration of body. A walk that repaired nothing stands where it already reads as v.toString() (SELF_RENDERING), and is rolled back for v's own format everywhere else. Removed on the way out: the same list twice as SIBLINGS is not a cycle. Depth is measured here rather than per element, since only a container can be descended into — a scalar sitting at the limit is a leaf, and reads as itself.

Tried BEFORE the container branches: a boxed unsigned array implements java.util.Collection, so walked as one it would repair nothing and fall back to the signed storage its toString() prints.

Append v's rendering, containing whatever its toString() throws.

Append v's rendering — a repair, or its own toString() — and answer whether it was a repair.

owner is what joins the chain; items is what gets rendered — the same object for a collection, an array view for an array, its components for a tuple. Its [a, b] is AbstractCollection's and its (a, b) the tuples', to the character: SELF_RENDERING lets an unchanged walk stand on that.

AbstractMap's own {k=v, k2=v2}, so a walked map reads the same as an unwalked one — and SELF_RENDERING counts on it: change the format and an unchanged walk no longer IS toString().