Subject: bug#12895: 24.3.50; Replacement for flet

From: Stefan Monnier <[email-masked]>
Date: Thu, 15 Nov 2012 09:46:19 -0500

> (defun something ()
>   (message "hi"))
> (letf ((message (lambda () (&rest args) nil)))
>   (something))
> Is this because message is a built-in?

No, it's because what you want is not a local function, but an override
of an existing function.  Such override should be done with an advice.

        Stefan