Thank you for the review.

I believe there is one more issue. In the following example:

  compdef '_sequence _wanted tag expl desc compadd - 1 2 3' foo

the `tag` is not known to _sequence yet. So a user can't ignore matches
using e.g.

  zstyle ':completion:*:foo:*:tag' ignored-patterns 2 '2,*' '*,2,*' '*,2'

which is a bit inconsistent. I'd have fixed it by merging _sequence
patterns with _comp_ignore in _description, but that would be too much
code changes for a small gain.

For now, I suggest to ignore -F and its argument in order to fix the
`command not found: -F` error (patch attached).