Infinite loop in bash glob matching

[Zoltán Herczeg]

Hi,

bash enter an infinite loop for this glob:

ls @(@()).

I have been trying to create a bash glob regex converter. It would be great if 
somebody (privately) could explain me  how !() and invalid [] expressions 
exactly work. I have questions such as:

ls a[[:alpha:][:abm]

Why does this match to a: and nothing else (e.g. am or a[mm )?

Regards,
Zoltan