bug#29165: 26.0.90; can't use some code byte-compiled under emacs 24

[Noam Postavsky <npostavs@users.sourceforge.net>]

tags 29165 + notabug
quit

Ken Raeburn <raeburn@permabit.com> writes:

>     (defun* foobar (init-fun test-fun cleanup-fun
>                              &optional &key

> Use Emacs 24.3 to byte-compile the file.
> 
> Start the Emacs 26 pretest, and load the .elc file.

>     Debugger entered--Lisp error: (invalid-function #f(compiled-function (init-fun test-fun cleanup-fun &optional &rest --cl-rest--) "Blah blah blah" 

> It appears that the eval.c code of 26.0.90 doesn't like to see &optional
> and &rest together in the argument list of a compiled function.

Yes, see Bug#24912 and Bug#24913.

> But in this case, the byte compiler from version 24 does generate
> that.  In version 25, only &rest is put into the list.

It's not the byte compiler specifically, the defun* macro (aka cl-defun)
expands &key into &rest, so the expansion has &optional &rest.  At any
rate, using &optional is meaningless there, so the solution is just to
remove it.

We should perhaps put something about throwing error on '&option &rest'
into NEWS though.