Unable to parse extglob syntax in any context

[lkrms]

Real-world code assigns the expanded glob to an array variable, but the same parsing error prevails in both cases:

function check_pools() { (
    shopt -s nullglob extglob
    rm -fv /etc/php/*/fpm/pool.d/!(*.conf|*.orig|*.dpkg-dist)
); }

Enabling extglob in the global scope (as it is in production) makes no difference.

Thanks for your excellent work on Bash parsing!