Function passableSymbolForName

If name is a string that could have been produced by nameForPassableSymbol, return the symbol argument it was produced to represent.

If name does not begin with "@@", then just the corresponding registered symbol, Symbol.for(name). If name is "@@" followed by a well known symbol's property name on Symbol such "@@iterator", return that well known symbol such as Symbol.iterator Ifnamebegins with"@@@@"it encodes the registered symbol whose name begins with"@@"instead. Otherwise, if name begins with"@@"` it may encode a registered symbol from a future version of JavaScript, but it is not one we can decode yet, so throw.