Use font-lock-comment-delimiter-face for "--" in interactive popups

Fixes #1741

Author: purcell

haskell-interactive-mode.el

@@ -645,7 +645,7 @@ wrapped in compiler directive at the top of FILE."
   (haskell-interactive-mode-prompt))
 
 (defun haskell-interactive-popup-error (response)
-  "Popup an error."
+  "Pop up an error."
   (if haskell-interactive-popup-errors
       (let ((buf (get-buffer-create "*HS-Error*")))
         (pop-to-buffer buf nil t)
@@ -659,12 +659,13 @@ wrapped in compiler directive at the top of FILE."
                                 'haskell-interactive-face-compile-error))
             (goto-char (point-min))
             (delete-blank-lines)
-            (insert (propertize "-- Hit `q' to close this window.\n\n"
-                                'font-lock-face 'font-lock-comment-face))
-            (save-excursion
-              (goto-char (point-max))
-              (insert (propertize "\n-- To disable popups, customize `haskell-interactive-popup-errors'.\n\n"
-                                  'font-lock-face 'font-lock-comment-face))))))
+            (let ((start-comment (propertize "-- " 'font-lock-face 'font-lock-comment-delimiter-face)))
+              (insert start-comment (propertize "Hit `q' to close this window.\n\n" 'font-lock-face 'font-lock-comment-face))
+              (save-excursion
+                (goto-char (point-max))
+                (insert "\n" start-comment
+                        (propertize "To disable popups, customize `haskell-interactive-popup-errors'.\n\n"
+                                    'font-lock-face 'font-lock-comment-face)))))))
     (haskell-interactive-mode-insert-error response)))
 
 (defun haskell-interactive-next-error-function (&optional n reset)