bug#20472: 24.4; Cannot switch buffers in a dedicated window - report this error earlier

[martin rudalics]

> Sometimes Emacs creates a small window such as *log-edit-files*.
> If you go to that window and do C-x b, you enter the name of the buffer
> to switch to as usual, but then see the error
>
>      Cannot switch buffers in a dedicated window
>
> This error message should appear earlier, as soon as C-x b is given.
> Emacs should not ask you to type in the new buffer name before it tells
> you that switching buffers is not allowed.

Indeed.  Unless someone has a better idea I'll install something like the below.

martin


--- a/lisp/window.el
+++ b/lisp/window.el
@@ -6916,7 +6916,13 @@ window.

 Return the buffer switched to."
   (interactive
-   (list (read-buffer-to-switch "Switch to buffer: ") nil 'force-same-window))
+   (cond
+    ((eq (window-dedicated-p) t)
+     (user-error "Cannot switch buffers in a dedicated window"))
+    ((window-minibuffer-p)
+     (user-error "Cannot switch buffers in minibuffer window"))
+    (t
+     (list (read-buffer-to-switch "Switch to buffer: ") nil 
'force-same-window))))
   (let ((buffer (window-normalize-buffer-to-switch-to buffer-or-name)))
     (cond
      ;; Don't call set-window-buffer if it's not needed since it