Function |move|, in Rust (take 1)

gistfile1.txt

fn move(from: string, to: string, options: move_options, policy: issue_policy): bool {
  // Handle options.no_overwrite
  if (options.no_overwrite) {
    alt(file::open(to, O_WRONLY, 0, report_error_as_sum)) {
       {ok} {
         close(ok, ignore_error); // Could be removed with some RAII mechanism
       }
       {ko: {errno}} if errno == EACCESS {
         ret policy.report(/*destination exists*/);
       }
       {ko: {errno}} {
         // Do nothing
       }
       x {
        // Any other kind of error
        ret policy.report(x); 
       }
    }
  }

  // Attempt to rename file
  alt (file::rename(from, to, report_error_as_sum)) {
    {ok} { ret policy.success(ok); }
    {ko: {errno}} if errno != EXDEV {
      ret policy.report({errno: errno});
    }
    _ {}
  }

  file::copy(from, to, propagate_error);
  file::remove(from, propagate_error);

  ret policy.success();
}