Function parse_dep_info 

pub fn parse_dep_info(
    pkg_root: &Path,
    build_root: &Path,
    dep_info: &Path,
) -> CargoResult<Option<RustcDepInfo>>

Parses Cargo’s internal EncodedDepInfo structure that was previously serialized to disk.

Note that this is not rustc’s *.d files.

Also note that rustc’s *.d files are translated to Cargo-specific EncodedDepInfo files after compilations have finished in translate_dep_info.

Returns None if the file is corrupt or couldn’t be read from disk. This indicates that the crate should likely be rebuilt.