PEGO
A040: Action Operand Scratch
Actions and predicates need evaluation contexts, argument windows and constructor field lists. Reusing invocation-local scratch avoids allocating those containers for every expression.
Mechanism and Invariants
The parser keeps an evaluation context, expression stack, one-element action buffer and operator locals. Evaluators push operands above the current stack height and restore it after nested evaluation. Built-ins and constructors cannot retain these temporary windows; published values receive separate ownership. Lambda environments that must survive a nested call keep their own context. Cleanup on failed predicates must drop any gathered children and construction tracking.
Scope and State
Default reusable action plumbing in closure, both VMs and generated Go Node/typed Go. TypeScript reuses a per-parser action context and evaluation storage where its runtime permits; it does not pool a parser across separate calls. Direct typed code can eliminate some context use entirely.
Reference Control
No common same-source scratch-off control isolates all action buffers. Whole-input parser pooling and concat fusion are separate mechanisms with different lifetimes.
Evidence and Implementation
Records 010/014/015/027/028 measure successive changes. For example, VM JSON allocation counts fall from 292k to 147k in 014, and closure Operators Rule action plumbing from about 40.6k to 0.6k in 027. These are historical backend/workload-specific comparisons, not one combined or current effect estimate.
Evidence records: 014, 015, 027, 028.
Source owners: evalCtx, termEvaluator,
vmProgram.eval, parser.estack and operator locals, generated ActCtx, typed evaluation scratch, Parser action context.
The comparison policy distinguishes same-source controls, historical changes and full checkpoints.