function warnOnInvalidKey(child, knownKeys) {
    {
      if (typeof child !== 'object' || child === null) {
        return knownKeys;
      }
      switch (child.$$typeof) {
        case REACT_ELEMENT_TYPE:
        case REACT_PORTAL_TYPE:
          warnForMissingKey(child);
          var key = child.key;
          if (typeof key !== 'string') {
            break;
          }
          if (knownKeys === null) {
            knownKeys = new Set();
            knownKeys.add(key);
            break;
          }
          if (!knownKeys.has(key)) {
            knownKeys.add(key);
            break;
          }
          warning$1(false, 'Encountered two children with the same key, `%s`. ' + 'Keys should be unique so that components maintain their identity ' + 'across updates. Non-unique keys may cause children to be ' + 'duplicated and/or omitted — the behavior is unsupported and ' + 'could change in a future version.', key);
          break;
        default:
          break;
      }
    }
    return knownKeys;
  }