cargoLock = builtins.fromTOML (builtins.readFile ./Cargo.lock);

  getCrates = cargoLock:
    mapAttrsToList
      (name: value:
        let m = builtins.match "checksum ([^ ]+) ([^ ]+).*" name;
        in if m == null then
          throw ("Don't know how to handle metadata '${name}'")
        else {
           name = elemAt m 0;
           version = elemAt m 1;
           sha256 = value;
         })
      cargoLock.metadata;

  fetchCrates = cargoLock:
    map
      ({ name, version, sha256 }: fetchurl
        { name = "${name}-${version}.tar.gz";
          url = "https://crates.io/api/v1/crates/${name}/${version}/download";
          inherit sha256;
        })
      (getCrates cargoLock);