parser = regexpParserOn(new StringReader(tail), stream);
} catch (IOException e) {
// TODO: better exception type?
throw new RuntimeException(e);
}
LinkedListTree ast = AS3FragmentParser.tree(parser.regexpLiteral());
tail = parser.getInputTail();
// skip over the regexp in the original, underlying CharStream
cs.seek(cs.index() + (initialTailLength - tail.length()));
LinkedListTokenSource source = (LinkedListTokenSource)stream.getTokenSource();
stream.setTokenSource(source); // cause any remembered RegexpSimple state to be dropped