PEGO
G170: Typed Framed Cuts
Cut-bearing unfinished LR and Operators Rule bodies can use structural emission without moving runtime frame ownership.
Mechanism and Invariants
Each body initializes lexical cut state from incoming p.cut and publishes it
on both returns. Choice, optional and repetition scopes remain separate;
lookahead resets discard its cut. Repetition restores the full mark before cut
failure drops collected values. Incompatible layouts remain general.
Scope and State
Applied by default only to eligible generated typed Go bodies. Node parsing/recognition, closure, VMs and TypeScript retain their separate routes.
Reference Control
No generation option selects an alternative for this mechanism. Typed Go
output comes from the Flow IR printer, and its generated parsers are compared
with the engine oracle in the internal/engine tests.
Evidence and Implementation
Record 081 measures large same-generator LR and Operators Rule fixtures at about 0.889–0.943 of reference time, with unchanged allocations. The small Operators Rule Bytes case is 0.4% slower at its median. These eligibility-specific gains and costs do not establish a broad speedup or recovery support by this selector alone.
Evidence records: 081.
Source owners: typed structural emitter, framed body emission.
The comparison policy distinguishes same-source controls, historical changes and full checkpoints.