Don't call syntax-ppss twice for raw strings.

Author: kurnevsky

rust-mode.el

@@ -1105,32 +1105,32 @@ should be considered a paired angle bracket."
 	 (group "'")))
     "A regular expression matching a character literal."))
 
-(defun rust--syntax-propertize-raw-string (end)
+(defun rust--syntax-propertize-raw-string (str-start end)
   "A helper for rust-syntax-propertize.
 
-If point is already in a raw string, this will apply the
-appropriate string syntax to the character up to the end of the
-raw string, or to END, whichever comes first."
-  (let ((str-start (nth 8 (syntax-ppss))))
-    (when str-start
-      (when (save-excursion
-	      (goto-char str-start)
-	      (looking-at "r\\(#*\\)\\(\"\\)"))
-	;; In a raw string, so try to find the end.
-	(let ((hashes (match-string 1)))
-	  ;; Match \ characters at the end of the string to suppress
-	  ;; their normal character-quote syntax.
-	  (when (re-search-forward (concat "\\(\\\\*\\)\\(\"" hashes "\\)") end t)
-	    (put-text-property (match-beginning 1) (match-end 1)
-			       'syntax-table (string-to-syntax "_"))
-	    (put-text-property (1- (match-end 2)) (match-end 2)
-			       'syntax-table (string-to-syntax "|"))
-	    (goto-char (match-end 0))))))))
+This will apply the appropriate string syntax to the character
+from the STR-START up to the end of the raw string, or to END,
+whichever comes first."
+  (when (save-excursion
+	  (goto-char str-start)
+	  (looking-at "r\\(#*\\)\\(\"\\)"))
+    ;; In a raw string, so try to find the end.
+    (let ((hashes (match-string 1)))
+      ;; Match \ characters at the end of the string to suppress
+      ;; their normal character-quote syntax.
+      (when (re-search-forward (concat "\\(\\\\*\\)\\(\"" hashes "\\)") end t)
+	(put-text-property (match-beginning 1) (match-end 1)
+			   'syntax-table (string-to-syntax "_"))
+	(put-text-property (1- (match-end 2)) (match-end 2)
+			   'syntax-table (string-to-syntax "|"))
+	(goto-char (match-end 0))))))
 
 (defun rust-syntax-propertize (start end)
   "A `syntax-propertize-function' to apply properties from START to END."
   (goto-char start)
-  (rust--syntax-propertize-raw-string end)
+  (let ((str-start (rust-in-str-or-cmnt)))
+    (when str-start
+      (rust--syntax-propertize-raw-string str-start end)))
   (funcall
    (syntax-propertize-rules
     ;; Character literals.
@@ -1142,7 +1142,7 @@ raw string, or to END, whichever comes first."
           (unless (save-excursion (nth 8 (syntax-ppss (match-beginning 0))))
             (put-text-property (match-beginning 1) (match-end 1)
 			       'syntax-table (string-to-syntax "|"))
-            (rust--syntax-propertize-raw-string end)))))
+            (rust--syntax-propertize-raw-string (match-beginning 0) end)))))
     ("[<>]"
      (0 (ignore
 	 (when (save-match-data