Porting a Python PEG parser to Rust in 72 hours, and actually proving it worked
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Porting a PEG parser to Rust with proof is deeply technical and relevant to open source and infrastructure.
A team ported the pure-Python PEG packrat parser parsimonious to Rust in 72 hours, achieving 20,041 differential fuzz cases with zero divergences, 84/84 upstream tests passing unmodified, and a cold start latency drop from 23ms to 2ms. The key design decision was modeling expressions as an Arc-wrapped enum keyed by pointer identity (Arc::as_ptr) rather than trait objects, enabling correct packrat memoization without deep clones. The port ships as a single 2.1MB static binary with zero unsafe blocks and peak memory reduced from ~13MB to ~6.7MB.