Refactor +evil:mc

+ Improve error handling when no PATTERN is given (reported by @ar1a)
+ Report correct number of resulting cursors
+ Handle edge case where only one cursor is created
+ Report edge case where no cursors are created

modules/feature/evil/autoload/evil-mc.el

@@ -50,16 +50,24 @@ cursor at the final match. If BANG, then treat PATTERN as literal."
   :move-point nil
   :evil-mc t
   (interactive "<R><//g><!>")
+  (unless (and (stringp pattern)
+               (not (string-empty-p pattern)))
+    (user-error "A regexp pattern is required"))
   (require 'evil-mc)
-  (setq evil-mc-pattern (cons (evil-mc-make-pattern (if bang (regexp-quote pattern) pattern) nil)
+  (setq evil-mc-pattern
+        (cons (evil-mc-make-pattern (if bang (regexp-quote pattern) pattern)
+                                    nil)
               (list beg end type)))
   (save-excursion
     (evil-with-restriction beg end
-      (evil-mc-make-cursors-for-all)
-      (evil-mc-print-cursors-info "Created")))
+      (evil-mc-make-cursors-for-all)))
   (evil-exit-visual-state)
   (evil-mc-goto-cursor
    (if (= (evil-visual-direction) 1)
        (evil-mc-find-last-cursor)
      (evil-mc-find-first-cursor))
-   nil))
+   nil)
+  (evil-mc-undo-cursor-at-pos (point))
+  (if (evil-mc-has-cursors-p)
+      (evil-mc-print-cursors-info "Created")
+    (evil-mc-message "No cursors were created")))