message: make sure we do not discard information on the Ok exit side
diff: @@ -262,7 +262,7 @@ fn main() {
  })
  .and_then(|result| result);
  let exit_code = match result {
  - Ok(_) => rustc_driver::EXIT_SUCCESS,
  + Ok(()) => rustc_driver::EXIT_SUCCESS,
  Err(_) => rustc_driver::EXIT_FAILURE,
  };
  std::process::exit(exit_code);
  