Re: Template types not correctly highlighted in C++

[Alan M. <ac...@mu...>]

Hello, Ludwig.

On Tue, Mar 28, 2017 at 08:14:29 +0100, Lud wrote:
> Alan,


>  > Yes, this seems to be a bug.  ;-)  That sequence of operations shouldn't
>  > cause the fontification of "NotHighlighted".  I'm trying to track this
>  > down at the moment.

>  > CC Mode maintains a collection of "known types" for each buffer -
>  > identifiers which are known from their contexts to be types.  Somehow,
>  > "NotHighlighted" has got into this collection.  I will figure out soon
>  > how and why.

> Let me know when I can help for testing.

Please apply the patch below.  I think it works on the test code in your
original bug report, but would you please try it out on your normal code,
and either let me know that it works, or tell me what still needs fixing.

This patch attempts to remove the "ambiguity" of font locking which
happened with deleting and reinserting the ">", and such like.

>  > The more fundamental question is whether an ambiguous template argument
>  > should be fontified as a type or not.  Doing so will inevitably lead to
>  > errors in places where the identifier actually isn't a type.

> I think it is better to not font lock ambiguous template arguments, 
> because of the following reasons:

> 1. correctness - as you said, "errors [...] where the identifier 
> actually isn't a type"
> 2. less font lock is a speedup to render the source file because it is a 
> heavy process which can be annoying for large files.

I agree with you there, I think, except it won't really help the speedup,
much.

Anyway, here is the patch.  (Feel free to send me private mail if you
want any help applying it).  After applying it, just byte-compile
cc-engine.el and cc-mode.el the usual way, and restart Emacs.  (Or
however you usually do it.  ;-)



diff -r 79b94d28dad4 cc-engine.el
--- a/cc-engine.el	Sun Mar 19 16:33:03 2017 +0000
+++ b/cc-engine.el	Tue Apr 04 20:32:35 2017 +0000
@@ -6005,6 +6005,13 @@
   ;; Clears `c-found-types'.
   (setq c-found-types (make-vector 53 0)))
 
+(defun c-copy-found-types ()
+  (let ((copy (make-vector 53 0)))
+    (mapatoms (lambda (sym)
+		(intern (symbol-name sym) copy))
+	      c-found-types)
+    copy))
+
 (defun c-add-type (from to)
   ;; Add the given region as a type in `c-found-types'.  If the region
   ;; doesn't match an existing type but there is a type which is equal
@@ -6965,6 +6972,7 @@
   ;; This function might do hidden buffer changes.
 
   (let ((start (point))
+	(old-found-types (c-copy-found-types))
 	;; If `c-record-type-identifiers' is set then activate
 	;; recording of any found types that constitute an argument in
 	;; the arglist.
@@ -6980,6 +6988,7 @@
 		  (nconc c-record-found-types c-record-type-identifiers)))
 	  t)
 
+      (setq c-found-types old-found-types)
       (goto-char start)
       nil)))
 
diff -r 79b94d28dad4 cc-mode.el
--- a/cc-mode.el	Sun Mar 19 16:33:03 2017 +0000
+++ b/cc-mode.el	Tue Apr 04 20:32:35 2017 +0000
@@ -429,27 +429,36 @@
 	t))))
 
 (defun c-unfind-coalesced-tokens (beg end)
-  ;; unless the non-empty region (beg end) is entirely WS and there's at
-  ;; least one character of WS just before or after this region, remove
-  ;; the tokens which touch the region from `c-found-types' should they
-  ;; be present.
-  (or (c-partial-ws-p beg end)
-      (save-excursion
-	(progn
-	  (goto-char beg)
-	  (or (eq beg (point-min))
-	      (c-skip-ws-backward (1- beg))
-	      (/= (point) beg)
-	      (= (c-backward-token-2) 1)
-	      (c-unfind-type (buffer-substring-no-properties
-			      (point) beg)))
-	  (goto-char end)
-	  (or (eq end (point-max))
-	      (c-skip-ws-forward (1+ end))
-	      (/= (point) end)
-	      (progn (forward-char) (c-end-of-current-token) nil)
-	      (c-unfind-type (buffer-substring-no-properties
-			      end (point))))))))
+  ;; If removing the region (beg end) would coalesce an identifier ending at
+  ;; beg with an identifier (fragment) beginning at end, or an identifier
+  ;; fragment ending at beg with an identifier beginning at end, remove the
+  ;; pertinent identifier(s) from `c-found-types'.
+  (save-excursion
+    (when (< beg end)
+      (goto-char beg)
+      (when
+	  (and (not (bobp))
+	       (progn (c-backward-syntactic-ws) (eq (point) beg))
+	       (/= (skip-chars-backward c-symbol-chars (1- (point))) 0)
+	       (progn (goto-char beg) (c-forward-syntactic-ws) (<= (point) end))
+	       (> (point) beg)
+	       (goto-char end)
+	       (looking-at c-symbol-char-key))
+	(goto-char beg)
+	(c-simple-skip-symbol-backward)
+	(c-unfind-type (buffer-substring-no-properties (point) beg)))
+
+      (goto-char end)
+      (when
+	  (and (not (eobp))
+	       (progn (c-forward-syntactic-ws) (eq (point) end))
+	       (looking-at c-symbol-char-key)
+	       (progn (c-backward-syntactic-ws) (>= (point) beg))
+	       (< (point) end)
+	       (/= (skip-chars-backward c-symbol-chars (1- (point))) 0))
+	(goto-char (1+ end))
+	(c-end-of-current-token)
+	(c-unfind-type (buffer-substring-no-properties end (point)))))))
 
 ;; c-maybe-stale-found-type records a place near the region being
 ;; changed where an element of `found-types' might become stale.  It



> Ludwig

-- 
Alan Mackenzie (Nuremberg, Germany).