bug#30039: 26.0.90; [26.1] Making my code warning free is impossible with when-let

[Noam Postavsky]

Damien Cassou <damien@cassou.me> writes:

> I try to make all my packages warning free by setting
> byte-compile-error-on-warn and running the byte compiler during
> continuous integration. I do that for both Emacs 25 and Emacs 26. This
> has become impossible with Emacs 26 because when-let is deprecated but
> it’s replacement does not exist in Emacs 25.

Couldn't you do

(eval-when-compile
  (unless (fboundp 'when-let*)
    (defalias 'when-let* 'when-let)))