presto-main/src/main/java/io/prestosql/type/SmallintOperators.java/SmallintOperators/castToVarchar
class SmallintOperators:    @ScalarOperator(CAST)
    @LiteralParameters("x")
    @SqlType("varchar(x)")
    public static Slice castToVarchar(@SqlType(StandardTypes.SMALLINT) long value)
    {
        // todo optimize me
        return utf8Slice(String.valueOf(value));
    }