message: fix(Symbol.iterator): correctly handle case where Symbol constructor itself is not defined
diff: -
  +export function getSymbolIterator(): symbol {
  /* NOTE: Warning users that they don't have a Symbol.iterator
  polyfill. We don't want to throw on this, because it's not required
  by the library. However it will provide clues to users on older
  browsers why things like `from(iterable)` doesn't work. */
  -if (!Symbol || !Symbol.iterator) {
  - console.warn('RxJS: Symbol.observable does not exist');
  + if (typeof Symbol !== 'function' || !Symbol.iterator) {
  + console.warn('RxJS: Symbol.iterator does not exist, so things like from(iterable) won\'t work');
  + return '@@iterator' as any;
  + }
  +
  + return Symbol.iterator;
  }
  -/** The native Symbol.iterator instance or a string */
  -export const iterator = Symbol && Symbol.iterator || '@@iterator';
  +export const iterator = getSymbolIterator();
  /**
  * @deprecated use {@link iterator} instead
  