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Allow &rest' or &optional' without following variable (Bug#29165)

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This is sometimes convenient when writing macros, so that the empty
variable case doesn't need to be handled specially.  Older versions of
Emacs accepted this in some cases (especially the interpreter in Emacs
25 and below was very accepting).

                            |   interpreted/compiled   |
| arglist                   | 25 & earlier | 26  | 27  |
|---------------------------+--------------+-----+-----|
| (&rest)                   | y/n          | n/n | y/y |
| (&rest &rest)             | y/n          | n/n | n/n |
| (&rest &rest x)           | y/n          | n/n | n/n |
| (&rest x &rest)           | y/n          | n/n | n/n |
| (&rest x &rest y)         | y/n          | n/n | n/n |
|---------------------------+--------------+-----+-----|
| (&optional)               | y/n          | n/n | y/y |
| (&optional &optional)     | y/n          | n/n | n/n |
| (&optional x &optional)   | y/n          | n/n | n/n |
| (&optional x &optional y) | y/y          | n/n | n/n |
|---------------------------+--------------+-----+-----|
| (&optional &rest)         | y/n          | n/n | y/y |
| (&optional x &rest)       | y/n          | n/n | y/y |
| (&optional &rest y)       | y/y          | n/n | y/y |
|---------------------------+--------------+-----+-----|
| (&rest &optional)         | y/n          | n/n | n/n |
| (&rest &optional y)       | y/n          | n/n | n/n |
| (&rest x &optional y)     | y/n          | n/n | n/n |

The values in the table above can be produced with the following code:

(with-current-buffer (get-buffer-create "*ck-args*")
  (erase-buffer)
  (dolist (arglist '((&rest)
                     (&rest &rest)
                     (&rest &rest x)
                     (&rest x &rest)
                     (&rest x &rest y)
                     (&optional)
                     (&optional &optional)
                     (&optional x &optional)
                     (&optional x &optional y)
                     (&optional &rest)
                     (&optional x &rest)
                     (&optional &rest y)
                     (&rest &optional)
                     (&rest &optional y)
                     (&rest x &optional y)))
    (insert
     (format "%c/%c\n"
             (condition-case err
                 (progn (funcall `(lambda ,arglist 'ok))
                        ?y)
               (error ?n))
             (condition-case err
                 (progn (byte-compile-check-lambda-list arglist)
                        ?y)
               (error ?n))))
    (display-buffer (current-buffer))))

* src/eval.c (funcall_lambda):
* lisp/emacs-lisp/bytecomp.el (byte-compile-check-lambda-list): Don't
check for missing variables after `&rest' and `&optional'.
* test/src/eval-tests.el (eval-tests--bugs-24912-and-24913)
(eval-tests-accept-empty-optional-rest): Update tests accordingly.
* etc/NEWS: Update announcement accordingly.
* doc/lispref/functions.texi (Argument List): Update manual to
indicate that variable names are optional.
This commit is contained in:
Noam Postavsky 2018-01-20 11:27:23 -05:00
parent d73d1384aa
commit 1d47d777ef
5 changed files with 33 additions and 19 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

4
doc/lispref/functions.texi
View File

@ -371,8 +371,8 @@ keyword @code{&rest} before one final argument.
@example
@group
(@var{required-vars}@dots{}
@r{[}&optional @var{optional-vars}@dots{}@r{]}
@r{[}&rest @var{rest-var}@r{]})
@r{[}&optional @r{[}@var{optional-vars}@dots{}@r{]}@r{]}
@r{[}&rest @r{[}@var{rest-var}@r{]}@r{]})
@end group
@end example

7
etc/NEWS
View File

@ -380,6 +380,13 @@ backslash. For example:
(read "‘smart") => (invalid-read-syntax "strange quote" "‘")
(read "\\‘smart") == (intern "‘smart")
+++
** Omitting variables after '&optional' and '&rest' is now allowed.
For example (defun foo (&optional)) is no longer an error. This is
sometimes convenient when writing macros. See the ChangeLog entry
titled "Allow `&rest' or `&optional' without following variable" for a
full listing of which arglists are accepted across versions.
** Internal parsing commands now use syntax-ppss and disregard
open-paren-in-column-0-is-defun-start. This affects mostly things like
forward-comment, scan-sexps, and forward-sexp when parsing backward.

11
lisp/emacs-lisp/bytecomp.el
View File

@ -2737,15 +2737,12 @@ If FORM is a lambda or a macro, byte-compile it as a function."
(macroexp--const-symbol-p arg t))
(error "Invalid lambda variable %s" arg))
((eq arg '&rest)
(unless (cdr list)
(error "&rest without variable name"))
(when (cddr list)
(error "Garbage following &rest VAR in lambda-list")))
(error "Garbage following &rest VAR in lambda-list"))
(when (memq (cadr list) '(&optional &rest))
(error "%s following &rest in lambda-list" (cadr list))))
((eq arg '&optional)
(when (or (null (cdr list))
(memq (cadr list) '(&optional &rest)))
(error "Variable name missing after &optional"))
(when (memq '&optional (cddr list))
(when (memq '&optional (cdr list))
(error "Duplicate &optional")))
((memq arg vars)
(byte-compile-warn "repeated variable %s in lambda-list" arg))

10
src/eval.c
View File

@ -3035,7 +3035,6 @@ funcall_lambda (Lisp_Object fun, ptrdiff_t nargs,
emacs_abort ();
i = optional = rest = 0;
bool previous_optional_or_rest = false;
for (; CONSP (syms_left); syms_left = XCDR (syms_left))
{
maybe_quit ();
@ -3046,17 +3045,15 @@ funcall_lambda (Lisp_Object fun, ptrdiff_t nargs,
if (EQ (next, Qand_rest))
{
if (rest || previous_optional_or_rest)
if (rest)
xsignal1 (Qinvalid_function, fun);
rest = 1;
previous_optional_or_rest = true;
}
else if (EQ (next, Qand_optional))
{
if (optional || rest || previous_optional_or_rest)
if (optional || rest)
xsignal1 (Qinvalid_function, fun);
optional = 1;
previous_optional_or_rest = true;
}
else
{
@ -3080,11 +3077,10 @@ funcall_lambda (Lisp_Object fun, ptrdiff_t nargs,
else
/* Dynamically bind NEXT. */
specbind (next, arg);
previous_optional_or_rest = false;
}
}
if (!NILP (syms_left) || previous_optional_or_rest)
if (!NILP (syms_left))
xsignal1 (Qinvalid_function, fun);
else if (i < nargs)
xsignal2 (Qwrong_number_of_arguments, fun, make_number (nargs));

20
test/src/eval-tests.el
View File

@ -37,8 +37,7 @@
(ert-deftest eval-tests--bugs-24912-and-24913 ()
"Check that Emacs doesn't accept weird argument lists.
Bug#24912 and Bug#24913."
(dolist (args '((&optional) (&rest) (&optional &rest) (&rest &optional)
(&optional &rest a) (&optional a &rest)
(dolist (args '((&rest &optional)
(&rest a &optional) (&rest &optional a)
(&optional &optional) (&optional &optional a)
(&optional a &optional b)
@ -47,7 +46,22 @@ Bug#24912 and Bug#24913."
(should-error (eval `(funcall (lambda ,args)) t) :type 'invalid-function)
(should-error (byte-compile-check-lambda-list args))
(let ((byte-compile-debug t))
(should-error (eval `(byte-compile (lambda ,args)) t)))))
(ert-info ((format "bytecomp: args = %S" args))
(should-error (eval `(byte-compile (lambda ,args)) t))))))
(ert-deftest eval-tests-accept-empty-optional-rest ()
"Check that Emacs accepts empty &optional and &rest arglists.
Bug#24912."
(dolist (args '((&optional) (&rest) (&optional &rest)
(&optional &rest a) (&optional a &rest)))
(let ((fun `(lambda ,args 'ok)))
(ert-info ("eval")
(should (eq (funcall (eval fun t)) 'ok)))
(ert-info ("byte comp check")
(byte-compile-check-lambda-list args))
(ert-info ("bytecomp")
(let ((byte-compile-debug t))
(should (eq (funcall (byte-compile fun)) 'ok)))))))
(dolist (form '(let let*))