Re: Is this a bug in while-let or do I missunderstand it?

["Alfred M. Szmidt" <ams@gnu.org>]

   > The scope of the let-binding is the same in both.

   I don't see how. With `while`, `result` is let-bound outside the loop, with
   `while-let` it's bound inside the loop, even after macroexpanding it:

And that is (again) the crux of the matter, one group thinks it is LET
bound outside of the loop, another inside.

Consider this, which will pass nil to BAR, but also reassign RESULT to
whatever FOO returns each iteration; which is the part that is
confusing for those who consider LET to be the binding and scope of
the variables (this also makes it much harder to debug code I think).

(while-let ((result (foo)))
  (setq result nil)
  (bar result))

Which expands to:
 
(catch 'done18
  (while t
    (let* ((result (and t (foo))))
      (if result
	  (progn
	    (setq result nil)
	    (bar result))
	(throw 'done18 nil)))))



   Mind you, what you want to do can still be done with `while-let`, provided
   you establish the relevant binding *outside* the loop:

Then what point is while-let?  Should there be a let-while? And a
let-while-let?  There are 20 occurences of while-let in Emacs ...