bug#30626: 26.0.91; Crash when traversing a `stream-of-directory-files'

[Noam Postavsky]

John Mastro <john.b.mastro@gmail.com> writes:

> (let* ((stream0 (stream-range 1 1000000))
>        (stream stream0))
>   (setq stream0 nil) ;; <<< Inserted by compiler
>   (while (not (stream-empty-p stream))
>     (cl-callf stream-rest stream)))
>
> If the code does reference stream0 later, locals clearing can't help
> you, but that's considered a "if it hurts, don't do it" situation.
>
> This probably isn't practical for Emacs, especially since it could only
> work for byte-compiled code, but thought the prior art may be of
> interest.

Not sure how doable this solution is, but the fact that it works only
for byte-compiled code seems fine to me.  The interpreted case is doomed
to fail anyway since the interpreter doesn't prune redundant variables
from closures.