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Have 'cl-case' warn about suspicious cases

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* lisp/emacs-lisp/cl-macs.el (cl-case): Warn if the user passes a nil
key list (which would never match).  Warn about quoted symbols that
should probably be unquoted.

* test/lisp/emacs-lisp/cl-macs-tests.el (cl-case-warning): New unit
test (bug#51368).
This commit is contained in:
Philipp Stephani 2022-09-13 17:12:57 +02:00 • committed by Lars Ingebrigtsen
parent 6d8f5161ea
commit fffa53ff1a
2 changed files with 47 additions and 0 deletions
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15
lisp/emacs-lisp/cl-macs.el
View file

@ -788,6 +788,21 @@ compared by `eql'.
((eq (car c) 'cl--ecase-error-flag)
`(error "cl-ecase failed: %s, %s"
,temp ',(reverse head-list)))
((null (car c))
(macroexp-warn-and-return
"Case nil will never match"
nil 'suspicious))
((and (consp (car c)) (not (cddar c))
(memq (caar c) '(quote function)))
(macroexp-warn-and-return
(format-message
(concat "Case %s will match `%s'. If "
"that's intended, write %s "
"instead. Otherwise, don't "
"quote `%s'.")
(car c) (caar c) (list (cadar c) (caar c))
(cadar c))
`(cl-member ,temp ',(car c)) 'suspicious))
((listp (car c))
(setq head-list (append (car c) head-list))
`(cl-member ,temp ',(car c)))

32
test/lisp/emacs-lisp/cl-macs-tests.el
View file

@ -25,6 +25,8 @@
(require 'cl-macs)
(require 'edebug)
(require 'ert)
(require 'ert-x)
(require 'pcase)
;;;; cl-loop tests -- many adapted from Steele's CLtL2
@ -758,4 +760,34 @@ collection clause."
(should (equal (cdr error)
'("Misplaced t or `otherwise' clause")))))))
(ert-deftest cl-case-warning ()
"Test that `cl-case' and `cl-ecase' warn about suspicious
constructs."
(pcase-dolist (`(,case . ,message)
`((nil . "Case nil will never match")
('nil . ,(concat "Case 'nil will match `quote'. "
"If that's intended, write "
"(nil quote) instead. "
"Otherwise, don't quote `nil'."))
('t . ,(concat "Case 't will match `quote'. "
"If that's intended, write "
"(t quote) instead. "
"Otherwise, don't quote `t'."))
('foo . ,(concat "Case 'foo will match `quote'. "
"If that's intended, write "
"(foo quote) instead. "
"Otherwise, don't quote `foo'."))
(#'foo . ,(concat "Case #'foo will match "
"`function'. If that's "
"intended, write (foo function) "
"instead. Otherwise, don't "
"quote `foo'."))))
(dolist (macro '(cl-case cl-ecase))
(let ((form `(,macro val (,case 1))))
(ert-info ((prin1-to-string form) :prefix "Form: ")
(ert-with-message-capture messages
(macroexpand form)
(should (equal messages
(concat "Warning: " message "\n")))))))))
;;; cl-macs-tests.el ends here