Fix double negation issue in dot fontification

Author: gracjan

haskell-font-lock.el

@@ -304,10 +304,8 @@ like ::, class, instance, data, newtype, type."
     (conid (if (get-text-property (match-beginning 0) 'haskell-type)
                'haskell-type-face
              'haskell-constructor-face))
-    (varsym (when (and (not (member (match-string 0) '("-" "+" ".")))
-                       (not (save-excursion
-                              (goto-char (match-beginning 1))
-                              (looking-at-p "\\sw"))))
+    (varsym (unless (and (member (match-string 0) '("-" "+" "."))
+                         (equal (string-to-syntax "w") (syntax-after (match-beginning 0))))
               ;; We need to protect against the case of
               ;; plus, minus or dot inside a floating
               ;; point number.

tests/haskell-font-lock-tests.el

@@ -268,6 +268,7 @@
      " 9.9'r'"                          ; (9.9,'r')
      " 's'12e-34"                       ; ('s',1.2e-33)
      " 't'56.78"                        ; ('t',56.78)
+     " ."
      )
    '(("'a'" t font-lock-string-face)
      ("'b'" t font-lock-string-face)
@@ -294,6 +295,7 @@
      ("12e-34" t nil)
      ("'t'" t font-lock-string-face)
      ("56.78" t nil)
+     ("." t haskell-operator-face)
      )))