PEGO
A020: Node and List Slabs
Allocating each Node and child list individually creates many small heap objects. Parser-owned chunks amortize those allocations and collect repetition children before copying the published list once.
Mechanism and Invariants
newNode, node-list and field allocators carve storage from chunks. A result
retains the chunk containing its storage; returned cells cannot be recycled
merely because matching has finished. The temporary child stack is separate from
published child slices, whose capacity is constrained to avoid appends
overwriting a neighbor. Slab ownership trades fewer allocation objects for
possible retention of unused siblings.
Scope and State
Default in closure, both VMs and generated Go Node construction. Typed Go uses a distinct typed allocation policy. TypeScript arrays/objects do not implement these Go slabs.
Reference Control
No independent same-source Node/list slab-disable control is maintained. Typed object/list controls operate on typed output and do not disable Node chunks.
Evidence and Implementation
Record 006 reports JSON allocation counts from about 940k to 250k and 5–10% lower sampled timing for its combined node/list/frame change. Record 011 ports the storage to generated Go among other changes. These are historical combined results, not current slab-only effects or guarantees of low retained heap.
Evidence records: 006.
Source owners: parser.newNode, nodes, fields and kids, generated ptrSlab and node/list allocation.
The comparison policy distinguishes same-source controls, historical changes and full checkpoints.