Function syntax::diagnostics::metadata::output_metadata

pub fn output_metadata(
    ecx: &ExtCtxt, 
    prefix: &str, 
    name: &str, 
    err_map: &ErrorMap
) -> Result<(), Box<dyn Error>>

Write metadata for the errors in err_map to disk, to a file corresponding to prefix/name.

For our current purposes the prefix is the target architecture and the name is a crate name. If an error occurs steps will be taken to ensure that no file is created.