bug#13663: 24.2.93; Why warn `flet' is an obsolete macro at runtime?

[Stefan Monnier]

> I am getting this when running emacs:
> /usr/local/emacs/share/emacs/24.2.93/lisp/gnus/message.elc:Warning:
>     `flet' is an obsolete macro (as of 24.3); use either `cl-flet' or
>     `cl-letf'.

> Why a user needs to care about this?

Good question.  Basically, the question is: why is this flet
macro-expanded so late (instead of during byte-compilation)?


        Stefan