function getPropertyNames(properties) {
  var names = [];
  for (var i = 0; i < properties.length; i++) {
    var property = properties[i];
    if (property.type === Syntax.SpreadProperty) {
      continue;
    }
    if (property.type === Syntax.Identifier) {
      names.push(property.name);
    } else {
      names.push(property.key.name);
    }
  }
  return names;
}
Desugars ES7 rest properties into ES5 object iteration.