Re: Has eval-and-compile changed in emacs 27?

[Stefan Monnier]

>> That one's easy: the way the warning works is that when we process
>> a `eval-when-compile` we look at the `load-history` to see the functions
>> that have been defined during execution of its body, and then we remember
>> those as "only available now but maybe not at runtime".
>>
>> If that loaded `cl-lib`, then a subsequent (require 'cl-lib) will be
>> a no-op and won't "unremember" the corresponding functions.
>
> This sounds like nightmare :(
>
> Is this new in Emacs 27?

No, it was new back when we added the "not known to exist at run-time",
i.e. a long time ago.

> What prompted the change?

We found it useful to try and warn the users when they did
(eval-when-compile (require FOO)) but FOO was also needed at run time.


        Stefan