bug#24913: 25.1.50; Emacs accepts undocumented and confusing combinations of &optional and &rest in argument lists

[Philipp Stephani]

Philipp Stephani <p.stephani2@gmail.com> schrieb am Mi., 9. Nov. 2016 um 22:19 Uhr:

For example:

(funcall (lambda (&optional &rest &rest &optional x) (list x)) 'a)
=> ((a))

Obviously here the &rest keyword "wins", but I think that's overly
confusing.  Such an argument list is most likely a programmer mistake,
and should signal an error to make the programmer aware of the mistake.

Here's a patch that detects such argument lists. 

0001-Prevent-dubious-argument-lists.txt
Description: Text document