Subject: bug#9557: 24.0.50; "y-or-n-p" does not clear the echo area

From: Eli Zaretskii <[email-masked]>
Date: Tue, 20 Sep 2011 06:00:58 -0400

> Date: Tue, 20 Sep 2011 11:19:54 +0200
> From: Dani Moncayo <[email-masked]>
> 
> 1. Eval: (fset 'yes-or-no-p 'y-or-n-p)
> 2. Visit some file.
> 3. M-x revert-buffer <RET> y
> --> (Expected) The echo area ends up empty (as happens if you omit step #1).
> --> (Observed) The echo area remains with a residual text "Revert
> buffer from file <your-file>? (y or n)  y".

y-or-n-p deliberately displays the prompt with your response before it
returns to the caller, see the source.  It does that because
otherwise you would not have a chance of observing your response.