message: stricter Symbol support check
diff: @@ -41,7 +41,9 @@ export function isNative (Ctor: Function): boolean {
  return /native code/.test(Ctor.toString())
  }
  -export const hasSymbol = typeof Symbol !== 'undefined' && isNative(Symbol)
  +export const hasSymbol =
  + typeof Symbol !== 'undefined' && isNative(Symbol) &&
  + typeof Reflect !== 'undefined' && isNative(Reflect.ownKeys)
  /**
  * Defer a task to execute it asynchronously.
  