63. A Smaller Node

• Node was 120 bytes: two name strings (Type, Rule), int positions, the text, children, fields and flags. The pair of names now sits behind one pointer to an interned kind (nodeKind; rules precompute the kinds they give their nodes, and programs those of the grammar's types, so a parse never looks one up), and Start and End are int32: 88 bytes. This changes the API: Type() and Rule() are methods, and positions are int32 (Go accepts them as slice indexes; arithmetic with ints needs a conversion). JSON and String output are unchanged (MarshalJSON writes the same members).
• Measured beforehand with a synthetic tree of 400,000 nodes: building −15%, node memory −22%, walking −7%, a GC with the tree live unchanged; int32 positions alone saved nothing, since a chunk of 256 nodes of 112 bytes falls into the same allocation size class as one of 120 bytes.
• Effect (min of 6 interleaved runs, Apple M3 Max): allocation per parse −11% to −20% (JSON 13.0 → 10.8 MB, XML 16.4 → 13.5 MB, CSV 7.1 → 5.7 MB, streams 168 → 152 MB); time within ±3% on every workload and backend.