Subject: bug#21449: Emacs lisp mode: incorrect fontification of symbols containing escaped characters.

From: Alan Mackenzie <[email-masked]>
Date: Wed, 9 Sep 2015 20:10:42 +0000

Hello, Emacs.

In Emacs lisp mode, write something like:

    (defun fix-re--RA|RB->R\(A|B\) (foo bar) ...)
                           ^^^^^^^

.  The part of the symbol indicated remains unfontified.  This happens
because the fontification patterns in .../lisp/emacs-lisp/lisp-mode.el
dont't take account of escaped characters in symbol names.

By replacing lots of "\\(?:\\sw\\|\\s_\\)" by
"\\(?:\\sw\\|\\s_\\|\\\\.\\)", the fontification is repaired.

As a bonus, this fix makes imenu work properly with these symbols too.

Unfortunately, as yet the regular expression expressions "\\_<" and
"\\_>" don't work properly with these symbols.  To fix that would need
an amendment to .../src/regex.c, with possibly .../src/syntax.c needing
one too.  It feels like there really ought to be some major mode
dependent flag saying whether or not escaped characters are valid in
identifiers.  They are in Emacs lisp, but they're not in C.

Anyhow, here's the patch:

diff --git a/lisp/emacs-lisp/lisp-mode.el b/lisp/emacs-lisp/lisp-mode.el
index 8aa34c7..7be7cb3 100644
--- a/lisp/emacs-lisp/lisp-mode.el
+++ b/lisp/emacs-lisp/lisp-mode.el
@@ -110,7 +110,7 @@
                                 ;; CLOS and EIEIO
 				"defgeneric" "defmethod")
                               t))
-			   "\\s-+\\(\\(\\sw\\|\\s_\\)+\\)"))
+			   "\\s-+\\(\\(\\sw\\|\\s_\\|\\\\.\\)+\\)"))
 	 2)
    (list (purecopy "Variables")
 	 (purecopy (concat "^\\s-*("
@@ -122,11 +122,11 @@
                                 "defconstant"
 				"defparameter" "define-symbol-macro")
                               t))
-			   "\\s-+\\(\\(\\sw\\|\\s_\\)+\\)"))
+			   "\\s-+\\(\\(\\sw\\|\\s_\\|\\\\.\\)+\\)"))
 	 2)
    ;; For `defvar', we ignore (defvar FOO) constructs.
    (list (purecopy "Variables")
-	 (purecopy (concat "^\\s-*(defvar\\s-+\\(\\(\\sw\\|\\s_\\)+\\)"
+	 (purecopy (concat "^\\s-*(defvar\\s-+\\(\\(\\sw\\|\\s_\\|\\\\.\\)+\\)"
 			   "[[:space:]\n]+[^)]"))
 	 1)
    (list (purecopy "Types")
@@ -143,7 +143,7 @@
                                 ;; CLOS and EIEIO
                                 "defclass")
                               t))
-			   "\\s-+'?\\(\\(\\sw\\|\\s_\\)+\\)"))
+			   "\\s-+'?\\(\\(\\sw\\|\\s_\\|\\\\.\\)+\\)"))
 	 2))
 
   "Imenu generic expression for Lisp mode.  See `imenu-generic-expression'.")
@@ -220,7 +220,7 @@
 (defun lisp--el-match-keyword (limit)
   ;; FIXME: Move to elisp-mode.el.
   (catch 'found
-    (while (re-search-forward "(\\(\\(?:\\sw\\|\\s_\\)+\\)\\_>" limit t)
+    (while (re-search-forward "(\\(\\(?:\\sw\\|\\s_\\|\\\\.\\)+\\)\\_>" limit t)
       (let ((sym (intern-soft (match-string 1))))
 	(when (or (special-form-p sym)
 		  (and (macrop sym)
@@ -349,7 +349,7 @@
                   ;; Any whitespace and defined object.
                   "[ \t']*"
                   "\\(([ \t']*\\)?" ;; An opening paren.
-                  "\\(\\(setf\\)[ \t]+\\(?:\\sw\\|\\s_\\)+\\|\\(?:\\sw\\|\\s_\\)+\\)?")
+                  "\\(\\(setf\\)[ \t]+\\(?:\\sw\\|\\s_\\|\\\\.\\)+\\|\\(?:\\sw\\|\\s_\\|\\\\.\\)+\\)?")
           (1 font-lock-keyword-face)
           (3 (let ((type (get (intern-soft (match-string 1)) 'lisp-define-type)))
                (cond ((eq type 'var) font-lock-variable-name-face)
@@ -373,7 +373,7 @@
                   ;; Any whitespace and defined object.
                   "[ \t']*"
                   "\\(([ \t']*\\)?" ;; An opening paren.
-                  "\\(\\(setf\\)[ \t]+\\(?:\\sw\\|\\s_\\)+\\|\\(?:\\sw\\|\\s_\\)+\\)?")
+                  "\\(\\(setf\\)[ \t]+\\(?:\\sw\\|\\s_\\|\\\\.\\)+\\|\\(?:\\sw\\|\\s_\\|\\\\.\\)+\\)?")
           (1 font-lock-keyword-face)
           (3 (let ((type (get (intern-soft (match-string 1)) 'lisp-define-type)))
                (cond ((eq type 'var) font-lock-variable-name-face)
@@ -395,22 +395,22 @@
          (lisp--el-match-keyword . 1)
          ;; Exit/Feature symbols as constants.
          (,(concat "(\\(catch\\|throw\\|featurep\\|provide\\|require\\)\\_>"
-                   "[ \t']*\\(\\(?:\\sw\\|\\s_\\)+\\)?")
+                   "[ \t']*\\(\\(?:\\sw\\|\\s_\\|\\\\.\\)+\\)?")
            (1 font-lock-keyword-face)
            (2 font-lock-constant-face nil t))
          ;; Erroneous structures.
          (,(concat "(" el-errs-re "\\_>")
            (1 font-lock-warning-face))
          ;; Words inside \\[] tend to be for `substitute-command-keys'.
-         ("\\\\\\\\\\[\\(\\(?:\\sw\\|\\s_\\)+\\)\\]"
+         ("\\\\\\\\\\[\\(\\(?:\\sw\\|\\s_\\|\\\\.\\)+\\)\\]"
           (1 font-lock-constant-face prepend))
          ;; Words inside ‘’ and '' and `' tend to be symbol names.
-         ("['`‘]\\(\\(?:\\sw\\|\\s_\\)\\(?:\\sw\\|\\s_\\)+\\)['’]"
+         ("['`‘]\\(\\(?:\\sw\\|\\s_\\|\\\\.\\)\\(?:\\sw\\|\\s_\\|\\\\.\\)+\\)['’]"
           (1 font-lock-constant-face prepend))
          ;; Constant values.
-         ("\\_<:\\(?:\\sw\\|\\s_\\)+\\_>" 0 font-lock-builtin-face)
+         ("\\_<:\\(?:\\sw\\|\\s_\\|\\\\.\\)+\\_>" 0 font-lock-builtin-face)
          ;; ELisp and CLisp `&' keywords as types.
-         ("\\_<\\&\\(?:\\sw\\|\\s_\\)+\\_>" . font-lock-type-face)
+         ("\\_<\\&\\(?:\\sw\\|\\s_\\|\\\\.\\)+\\_>" . font-lock-type-face)
          ;; ELisp regexp grouping constructs
          (,(lambda (bound)
              (catch 'found
@@ -447,19 +447,19 @@
          (,(concat "(" cl-kws-re "\\_>") . 1)
          ;; Exit/Feature symbols as constants.
          (,(concat "(\\(catch\\|throw\\|provide\\|require\\)\\_>"
-                   "[ \t']*\\(\\(?:\\sw\\|\\s_\\)+\\)?")
+                   "[ \t']*\\(\\(?:\\sw\\|\\s_\\|\\\\.\\)+\\)?")
            (1 font-lock-keyword-face)
            (2 font-lock-constant-face nil t))
          ;; Erroneous structures.
          (,(concat "(" cl-errs-re "\\_>")
            (1 font-lock-warning-face))
          ;; Words inside ‘’ and '' and `' tend to be symbol names.
-         ("['`‘]\\(\\(?:\\sw\\|\\s_\\)\\(?:\\sw\\|\\s_\\)+\\)['’]"
+         ("['`‘]\\(\\(?:\\sw\\|\\s_\\|\\\\.\\)\\(?:\\sw\\|\\s_\\|\\\\.\\)+\\)['’]"
           (1 font-lock-constant-face prepend))
          ;; Constant values.
-         ("\\_<:\\(?:\\sw\\|\\s_\\)+\\_>" 0 font-lock-builtin-face)
+         ("\\_<:\\(?:\\sw\\|\\s_\\|\\\\.\\)+\\_>" 0 font-lock-builtin-face)
          ;; ELisp and CLisp `&' keywords as types.
-         ("\\_<\\&\\(?:\\sw\\|\\s_\\)+\\_>" . font-lock-type-face)
+         ("\\_<\\&\\(?:\\sw\\|\\s_\\|\\\\.\\)+\\_>" . font-lock-type-face)
          ;; This is too general -- rms.
          ;; A user complained that he has functions whose names start with `do'
          ;; and that they get the wrong color.
@@ -482,7 +482,7 @@
   (let* ((firstsym (and listbeg
                         (save-excursion
                           (goto-char listbeg)
-                          (and (looking-at "([ \t\n]*\\(\\(\\sw\\|\\s_\\)+\\)")
+                          (and (looking-at "([ \t\n]*\\(\\(\\sw\\|\\s_\\|\\\\.\\)+\\)")
                                (match-string 1)))))
          (docelt (and firstsym
                       (function-get (intern-soft firstsym)

-- 
Alan Mackenzie (Nuremberg, Germany).