docs: protected AstParameters params() throws ScanException, ParseException {
  		consumeToken(LPAREN);
  		List<AstNode> l = Collections.emptyList();
  		AstNode v = expr(false);
  		if (v != null) {
  			l = new ArrayList<AstNode>();
  			l.add(v);
  			while (token.getSymbol() == COMMA) {
  				consumeToken();
  				l.add(expr(true));
  			}
  		}
  		consumeToken(RPAREN);
  		return new AstParameters(l);
  	}