completion in var=$(cmd1) cmd2 <tab>

[Raphaël Droz]

Example:
$ var=$(id) foo <tab>
completes with completion matches from id(1)

This is problematic for cases like:
LD_LIBRARY_PATH=$(find ...) cmd --<tab>
where options are those from find(1).

I didn't looked deeper but I guess the faulty part is in
_rl_find_completion_word() which, as its name suggest, *should* find the
word to be completed instead of returning rl_point as-is (14 in the
above case) [ *fp, *dp quoting-related variable are correctly set
to 0 though ]

please not that `id`, instead of $(id), is treated as 'id' would be
so the internal filename completion is used instead of the programmable
completion (which is also wrong but is probably another issue)

regards