Function map_temp_error_message 

pub fn map_temp_error_message(
    err_msg: &str,
    tmp_path: &Path,
    expanded_lines: &[String],
    mapping: &[usize],
    orig_path: &Path,
) -> (String, Option<usize>)

Map a temporary expanded-file error message back to the original file path and line; returns (mapped_message, optional original line number).