hint‑mostly‑unused compiler hint

// This program demonstrates the hint-mostly-unused feature.
// It does not compile on stable Rust; it requires nightly with
// the -Zprofile-hint-mostly-unused flag and a crate that
// declares hints.mostly-unused = true in its Cargo.toml.

fn main() {
    // The body is irrelevant; the point is that the compiler
    // will skip generating code for unused items in dependencies
    // that are marked as mostly unused.
    println!("If you build with -Zprofile-hint-mostly-unused, \
             compile time may be reduced for large crates.");
}