Look for cased character classes when deciding on case-fold-search, #'isearch lisp/ChangeLog addition: 2015-03-11 Aidan Kehoe <kehoea@parhasard.net> * isearch-mode.el: * isearch-mode.el (isearch-fix-case): Use the new #'no-case-regexp-p function if treating ISEARCH-STRING as a regular expression; otherwise, use the [[:upper:]] character class. * isearch-mode.el (isearch-no-upper-case-p): Removed. * isearch-mode.el (with-caps-disable-folding): Removed. These two haven't been used since 1998. * occur.el (occur-1): Use #'no-case-regexp-p here. * replace.el (perform-replace): Don't use #'no-upper-case-p, use #'no-case-regexp-p or (string-match "[[:upper:]]" ...) as appropriate. * simple.el: * simple.el (no-upper-case-p): Removed. This did two different things, and its secondary function (examining regular expressions) just became much more complicated; move the regular expression functionality to its own function, use character classes when examining non-regular-expressions instead. The code to look for character classes, and the design decision that this should be done, are from GNU, thank you Stefan Monnier. * simple.el (no-case-regexp-p): New. Given a REGEXP, return non-nil if it has nothing to suggest an interactive user wants a case-sensitive search. * simple.el (with-search-caps-disable-folding): * simple.el (with-interactive-search-caps-disable-folding): Update both these macros to use #'no-case-regexp-p.

--- a/lisp/occur.el	Wed Mar 11 15:06:05 2015 +0000
+++ b/lisp/occur.el	Wed Mar 11 18:06:15 2015 +0000
@@ -394,8 +394,7 @@
 	(let ((count (occur-engine
 		      regexp active-bufs occur-buf
 		      (or nlines list-matching-lines-default-context-lines)
-		      (and case-fold-search
-			   (no-upper-case-p regexp t))
+		      (and case-fold-search (no-case-regexp-p regexp))
 		      list-matching-lines-buffer-name-face
 		      nil list-matching-lines-face t)))
 	  (let* ((bufcount (length active-bufs))