Prevent dubious argument lists

See Bug#24912 and Bug#24913.

* src/eval.c (funcall_lambda): Detect more dubious argument lists.
* lisp/emacs-lisp/bytecomp.el (byte-compile-check-lambda-list): Detect
more dubious argument lists.
* test/src/eval-tests.el (eval-tests--bugs-24912-and-24913): Add unit
test.

1 files changed, 5 insertions, 2 deletions

diff --git a/lisp/emacs-lisp/bytecomp.el b/lisp/emacs-lisp/bytecomp.el
index 428e21c7a39..85daa43eaed 100644
--- a/lisp/emacs-lisp/bytecomp.el
+++ b/lisp/emacs-lisp/bytecomp.el
@@ -2672,8 +2672,11 @@ If FORM is a lambda or a macro, byte-compile it as a function."
                (when (cddr list)
                  (error "Garbage following &rest VAR in lambda-list")))
               ((eq arg '&optional)
-               (unless (cdr list)
-                 (error "Variable name missing after &optional")))
+               (when (or (null (cdr list))
+                         (memq (cadr list) '(&optional &rest)))
+                 (error "Variable name missing after &optional"))
+               (when (memq '&optional (cddr list))
+                 (error "Duplicate &optional")))
               ((memq arg vars)
                (byte-compile-warn "repeated variable %s in lambda-list" arg))
               (t