presto-parser/src/main/java/io/prestosql/sql/parser/SqlParser.java/SqlParser/exitDigitIdentifier
class SqlParser:        @Override
        public void exitDigitIdentifier(SqlBaseParser.DigitIdentifierContext context)
        {
            Token token = context.DIGIT_IDENTIFIER().getSymbol();
            throw new ParsingException(
                    "identifiers must not start with a digit; surround the identifier with double quotes",
                    null,
                    token.getLine(),
                    token.getCharPositionInLine());
        }