On Wed, May 6, 2020 at 2:04 PM Eli Zaretskii <eliz@gnu.org> wrote:
> 'apply' is a very popular function, and is used very widely.  I won't
> be surprised if there were more of these usage cases that would be
> broken by such a change in the signature.

> Can we instead identify the problematic usage and signal an error?

Yes. What we also have to do is fix the documentation, and fix the
byte optimizer.

Here's a first suggestion. I'd particularly appreciate hints on better
wording for the documentation.