PEGO
G085: Skip Positional Items for Action-Free Rules
A rule action reads its sequence's visible items by position. Typing those items is only needed when an action can read them.
Mechanism and Invariants
The checker types the whole rule body once, which reports every diagnostic and records every checked field and result. It types the visible top-level items again, each in a discarded capture scope, only for a rule with an action. Action-free rules skip that second pass; their value type comes from the body.
Scope and State
Default shared type checking before compilation/generation. No parser backend performs this analysis in its matching loop.
Reference Control
No maintained same-source control exists.
Evidence and Implementation
Record 101 measures complete type checking: 32,768 record captures fall from 18.57 to 9.74 ms and 131,243 to 103 allocations, and recursive captures fall by about 15% in time with 96% fewer allocated bytes. Unchanged example grammars check 2–8% faster.
Evidence records: 101.
Source owners: rule type checking.
The comparison policy distinguishes same-source controls, historical changes and full checkpoints.
Related mechanisms: G080.