frontmatter - The Rust Unstable Book

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# `frontmatter`

The tracking issue for this feature is: #136889

The `frontmatter` feature allows an extra metadata block at the top of files for consumption by external tools. For example, it can be used by `cargo-script` files to specify dependencies.

    #!/usr/bin/env -S cargo -Zscript
    ---
    [dependencies]
    libc = "0.2.172"
    ---
    #![feature(frontmatter)]
    mod libc { pub type c_int = i32; }

    fn main() {
        let x: libc::c_int = 1i32;
    }