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Headstart overlaps Rust crate checks by emitting metadata early

github.com 5 min read Editor score 7/10

Headstart lets dependent crates begin checking against early interface metadata while upstream crates continue checking function bodies; failed builds still report errors. The approach exposes a concrete way to trade some wasted work and memory for shorter build waits.

What

Headstart changes Rust compilation so dependent crates can start before their dependencies finish checking function bodies.

How

rustc writes early metadata after checking interfaces; cargo starts dependents from it, then waits for full metadata before code generation.

Why it matters

Overlapping crate checks can reduce build time and idle CPU capacity in large Rust workspaces, at the cost of extra memory and discarded work.

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