bug#50034: 28.0.50; elisp capf error "Wrong type argument: listp, elisp--witness--lisp"

bug#50034: 28.0.50; elisp capf error "Wrong type argument: listp, elisp--witness--lisp"

[Daniel Mendler]

Steps to reproduce:

1. Start "emacs -Q"
2. Enter "(defmacro foo bar" in the scratch buffer
3. Press M-<tab> to invoke 'completion-at-point'

The capf will throw the error "Wrong type argument: listp,
elisp--witness--lisp". This error will be shown on Emacs 27 and Emacs 28.

The input is nonsensical. I hit this while experimenting with my Corfu
completion UI package. A capf should never error in case no completion
is possible, such that another completion function of lower priority
registered in 'completion-at-point-functions' can take over.

Stack trace:

Debugger entered--Lisp error: (wrong-type-argument listp
elisp--witness--lisp)
  remq(&rest elisp--witness--lisp)
  elisp--local-variables-1(nil (lambda elisp--witness--lisp nil))
  #f(compiled-function (vars sexp) #<bytecode -0x8b1fe1acbf9337e>)(nil
(#'(lambda elisp--witness--lisp nil)))
  elisp--local-variables-1(nil #'(lambda elisp--witness--lisp nil))
  #f(compiled-function (vars sexp) #<bytecode -0x8b1fe1acbf9337e>)(nil
((cons 'macro #'(lambda elisp--witness--lisp nil))))
  elisp--local-variables-1(nil (cons 'macro #'(lambda
elisp--witness--lisp nil)))
  #f(compiled-function (vars sexp) #<bytecode -0x8b1fe1acbf9337e>)(nil
((defalias 'foo (cons 'macro #'(lambda elisp--witness--lisp nil)))))
  elisp--local-variables-1(nil (defalias 'foo (cons 'macro #'(lambda
elisp--witness--lisp nil))))
  elisp--local-variables()
  #f(compiled-function (string) #<bytecode 0x11ce5f9950685161>)(#("bar"
0 3 (fontified t)))
  #f(compiled-function (string pred action) #<bytecode
0x1441a5b45360593c>)(#("bar" 0 3 (fontified t)) nil nil)
  try-completion(#("bar" 0 3 (fontified t)) #f(compiled-function (string
pred action) #<bytecode 0x1441a5b45360593c>) nil)
  #f(compiled-function (table) #<bytecode
0x16347446532ce382>)(#f(compiled-function (string pred action)
#<bytecode 0x1441a5b45360593c>))
  mapcar(#f(compiled-function (table) #<bytecode 0x16347446532ce382>)
(#f(compiled-function (string pred action) #<bytecode
0x1441a5b45360593c>) #f(compiled-function (&rest args2) #<bytecode
-0xb6f918caeb61f7c>)))
  #f(compiled-function (string pred action) #<bytecode
0x129f647999b6137>)(#("bar" 0 3 (fontified t)) nil nil)
  try-completion(#("bar" 0 3 (fontified t)) #f(compiled-function (string
pred action) #<bytecode 0x129f647999b6137>) nil)
  completion-basic-try-completion(#("bar" 0 3 (fontified t))
#f(compiled-function (string pred action) #<bytecode 0x129f647999b6137>)
nil 3)
  #f(compiled-function (style) #<bytecode -0x1fb7ebf98eadbd47>)(basic)
  completion--some(#f(compiled-function (style) #<bytecode
-0x1fb7ebf98eadbd47>) (basic partial-completion emacs22))
  completion--nth-completion(1 #("bar" 0 3 (fontified t))
#f(compiled-function (string pred action) #<bytecode 0x129f647999b6137>)
nil 3 (metadata))
  completion-try-completion(#("bar" 0 3 (fontified t))
#f(compiled-function (string pred action) #<bytecode 0x129f647999b6137>)
nil 3 (metadata))
  completion--do-completion(#<marker at 160 in *scratch*> 163)
  completion--in-region-1(#<marker at 160 in *scratch*> 163)
  #f(compiled-function (start end collection predicate) #<bytecode
-0xf6d24f3ba2b80f7>)(#<marker at 160 in *scratch*> 163
#f(compiled-function (string pred action) #<bytecode 0x129f647999b6137>)
nil)
  apply(#f(compiled-function (start end collection predicate) #<bytecode
-0xf6d24f3ba2b80f7>) (#<marker at 160 in *scratch*> 163
#f(compiled-function (string pred action) #<bytecode 0x129f647999b6137>)
nil))
  #f(compiled-function (funs global args) #<bytecode
-0xbd1d687a6b6022>)(nil nil (#<marker at 160 in *scratch*> 163
#f(compiled-function (string pred action) #<bytecode 0x129f647999b6137>)
nil))
  completion--in-region(#<marker at 160 in *scratch*> 163
#f(compiled-function (string pred action) #<bytecode 0x129f647999b6137>)
nil)
  completion-in-region(#<marker at 160 in *scratch*> 163
#f(compiled-function (string pred action) #<bytecode 0x129f647999b6137>)
nil)
  completion-at-point()

In GNU Emacs 28.0.50 (build 54, x86_64-pc-linux-gnu, GTK+ Version
3.24.5, cairo version 1.16.0)
 of 2021-08-12 built on projects
Windowing system distributor 'The X.Org Foundation', version 11.0.12004000
System Description: Debian GNU/Linux 10 (buster)

bug#50034: 28.0.50; elisp capf error "Wrong type argument: listp, elisp--witness--lisp"

[Lars Ingebrigtsen]

Daniel Mendler <mail@daniel-mendler.de> writes:

> Steps to reproduce:
>
> 1. Start "emacs -Q"
> 2. Enter "(defmacro foo bar" in the scratch buffer
> 3. Press M-<tab> to invoke 'completion-at-point'
>
> The capf will throw the error "Wrong type argument: listp,
> elisp--witness--lisp". This error will be shown on Emacs 27 and Emacs 28.

Slightly simpler repro:

(defmacro foo bar
M-: (elisp--local-variables) RET

It fails here:

                    (`(lambda ,args . ,body)
                     (elisp--local-variables-1
                      (append (remq '&optional (remq '&rest args)) vars)
                      (car (last body))))

where it expects args to be a list, but it's the symbol
`elisp--witness--lisp'.  I'm not quite sure what the correct fix is
here, so I've added Stefan to the CCs.  :-)

-- 
(domestic pets only, the antidote for overdose, milk.)
   bloggy blog: http://lars.ingebrigtsen.no

bug#50034: 28.0.50; elisp capf error "Wrong type argument: listp, elisp--witness--lisp"

[Lars Ingebrigtsen]

Lars Ingebrigtsen <larsi@gnus.org> writes:

>> 1. Start "emacs -Q"
>> 2. Enter "(defmacro foo bar" in the scratch buffer
>> 3. Press M-<tab> to invoke 'completion-at-point'
>>
>> The capf will throw the error "Wrong type argument: listp,
>> elisp--witness--lisp". This error will be shown on Emacs 27 and Emacs 28.
>
> Slightly simpler repro:
>
> (defmacro foo bar
> M-: (elisp--local-variables) RET
>
> It fails here:
>
>                     (`(lambda ,args . ,body)
>                      (elisp--local-variables-1
>                       (append (remq '&optional (remq '&rest args)) vars)
>                       (car (last body))))
>
> where it expects args to be a list, but it's the symbol
> `elisp--witness--lisp'.  I'm not quite sure what the correct fix is
> here, so I've added Stefan to the CCs.  :-)

One year later, this problem is still present in Emacs 29.  Stefan, do
you have any idea what the fix here should be?

bug#50034: 28.0.50; elisp capf error "Wrong type argument: listp, elisp--witness--lisp"

[Michael Heerdegen]

Lars Ingebrigtsen <larsi@gnus.org> writes:

> It fails here:
>
>                     (`(lambda ,args . ,body)
>                      (elisp--local-variables-1
>                       (append (remq '&optional (remq '&rest args)) vars)
>                       (car (last body))))

I have the impression that the clause before that is supposed to match
in this case (also see the FIXME).  It doesn't because the defmacro
macro expander adds an explicit `nil' body, i.e. the body is not empty
as assumed in that clause.

Michael.

bug#50034: 28.0.50; elisp capf error "Wrong type argument: listp, elisp--witness--lisp"

[Stefan Monnier via Bug reports for GNU Emacs, the Swiss army knife of text editors]

> Slightly simpler repro:
>
> (defmacro foo bar
> M-: (elisp--local-variables) RET
>
> It fails here:
>
>                     (`(lambda ,args . ,body)
>                      (elisp--local-variables-1
>                       (append (remq '&optional (remq '&rest args)) vars)
>                       (car (last body))))
>
> where it expects args to be a list, but it's the symbol
> `elisp--witness--lisp'.

Since the code can be completely non-sensical, `elisp--local-variables`
shouldn't presume that the arglist is indeed a list.  I installed the fix
below on `master`.


        Stefan


diff --git a/lisp/progmodes/elisp-mode.el b/lisp/progmodes/elisp-mode.el
index 0c4a9bfdbea..6d8ced7f220 100644
--- a/lisp/progmodes/elisp-mode.el
+++ b/lisp/progmodes/elisp-mode.el
@@ -383,7 +383,9 @@ elisp--local-variables-1
                      (setq sexp nil))
                     (`(lambda ,args . ,body)
                      (elisp--local-variables-1
-                      (append (remq '&optional (remq '&rest args)) vars)
+                      (let ((args (if (listp args) args)))
+                        ;; FIXME: Exit the loop if witness is in args.
+                        (append (remq '&optional (remq '&rest args)) vars))
                       (car (last body))))
                     (`(condition-case ,_ ,e) (elisp--local-variables-1 vars e))
                     (`(condition-case ,v ,_ . ,catches)