 (defface fstar-subscript-face
   '((t :height 0.8))
   "Face used to use for subscripts"
+  :group 'fstar)
+
+(defface fstar-ambiguous-face
+  '((t :inherit font-lock-negation-char-face))
+  "Face used to use for /\\ and \//."
   :group 'fstar)
 
 (defun fstar-group-pre-matcher (prefix-len allowed-newlines)

      (,fstar-syntax-builtins     . 'font-lock-builtin-face)
      (,fstar-syntax-preprocessor . 'font-lock-preprocessor-face)
      (,fstar-syntax-structure    . 'fstar-structure-face)
      ,@fstar-syntax-additional)
     nil nil))
  (font-lock-set-defaults)

                "effect" "new_effect" "sub_effect")
              'symbols))

(defconst fstar-syntax-ambiguous
  (regexp-opt `("\\/" "/\\")))

;; (defconst fstar-syntax-types
;;   (regexp-opt '("Type")
;;               'symbols))
