export default function(node, {evaluate, scope}) {
  const unary = (arg) => {
    switch (node.operator) {
      case '+'     : return +arg;
      case '-'     : return -arg;
      case '!'     : return !arg;
      case '~'     : return ~arg;
      case 'typeof': return typeof arg;
      case 'void'  : return undefined;
      // case 'delete': ...
      /* v8 ignore next 2 */
      default:
        throw new Error(`operator not implemented: ${node.operator}`);
    }
  };
  const arg = evaluate(node.argument, {scope});
  if (arg.async) {
    return {
      async: true,
      value: Promise.resolve(arg.value).then(unary),
    };
  }
  return {async: false, value: unary(arg.value)};
}