Emitting metadata early makes building/checking Rust up to twice as fast ---- - 8 hours ago | 51 points | 8 comments - URL: https://github.com/PowderworksCode/headstart - Discussions: https://news.ycombinator.com/item?id=49951218 - Summary: The GitHub repository "headstart" by PowderworksCode introduces a tool that allows dependent Rust crates to start compiling before their dependencies finish type-checking. It works by having rustc write early metadata files after interface checking, enabling cargo to begin dependent crates sooner. For `cargo check`, dependents run to completion on early metadata; for `cargo build`, they analyze early metadata and wait for full metadata before code generation. The project includes patches for rustc and cargo, with performance improvements up to 54% faster for check and 42% for build on 16-core machines. It provides setup scripts, test scripts for error handling, incremental builds, and benchmarks. The repository contains documentation on design, results, and readiness, along with a suite of scripts to measure performance across real projects. The tool aims to reduce idle cores during compilation without changing diagnostics or exit statuses.