const defendSyncArgs = (args, methodGuard, label) => {
  const { argGuards, optionalArgGuards, restArgGuard } = methodGuard;
  const paramsPattern = M.splitArray(
    argGuards,
    optionalArgGuards,
    restArgGuard,
  );
  const positionalGuards = [...argGuards, ...(optionalArgGuards || [])];
  const numPositionalArgs = Math.min(positionalGuards.length, args.length);
  const startOfRawArgs = isRawValueGuard(restArgGuard) ? numPositionalArgs : undefined;
  const cookedArgs = args.slice(0, startOfRawArgs);
  for (let i = 0; i < numPositionalArgs; i += 1) {
    if (isRawValueGuard(positionalGuards[i])) {
      // Replace the raw argument with something innocuous as a
      // placeholder to be matched by the raw value guard without
      // hardening the caller's argument.
      cookedArgs[i] = null;
    }
  }
  mustMatch(harden(cookedArgs), paramsPattern, label);
};

// ...
    // Note purposeful use of `this` and concise method syntax
    syncMethod(...args) {
      defendSyncArgs(args, methodGuard, label);
      const result = apply(method, this, args);
      if (!isRawValueGuard(returnGuard)) {
        // Only harden non-raw return values.
        mustMatch(harden(result), returnGuard, `${label}: result`);
      }
      return result;
    },