Prettify Haskell types in eldoc support.

Replaces some substrings like "::" with Unicode characters.

Author: ikirill

haskell-customize.el

@@ -77,6 +77,13 @@ a per-project basis."
 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
 ;; Configuration
 
+(defcustom haskell-doc-prettify-types t
+  "Replace some parts of types with Unicode characters like \"∷\"
+when showing type information about symbols."
+  :group 'haskell-doc
+  :type 'boolean
+  :safe 'booleanp)
+
 (defvar haskell-process-end-hook nil
   "Hook for when the haskell process ends.")
 

haskell-doc.el

@@ -1648,7 +1648,11 @@ CALLBACK will be called with a formatted type string."
                       (type (propertize
                              (substring response (match-end 0))
                              'face 'eldoc-highlight-function-argument)))
-                  (setq response (concat name type))))))
+                  (setq response (concat name type)))))
+            (when haskell-doc-prettify-types
+              (dolist (re '(("::" . "∷") ("=>" . "⇒") ("->" . "→")))
+                (setq response
+                      (replace-regexp-in-string (car re) (cdr re) response)))))
           (when callback (funcall callback response))))))))
 
 (defun haskell-doc-sym-doc (sym)