bug#64294: 30.0.50; setf strange when lexical-binding is nil

[Katsumi Yamaoka]

Hi,

In the *scratch* buffer:

(setq lexical-binding nil)
(require 'nnheader)
(macroexpand '(setf (mail-header-date header) date))
 => (let* ((v #'(lambda (cl-x) (progn (progn (aref cl-x 3)))))
           (v header))
      (\(setf\ funcall\) date v v))

This looks broken, though it gets normal if lexical-binding is t.
Because of this, an old ELisp module doesn't work.  In addition,
the funny portion is replased with
\(setf\ internal--with-suppressed-warnings\)...
if the code is byte-compiled.

Thanks.

In GNU Emacs 30.0.50 (build 1, x86_64-pc-cygwin, GTK+ Version
 3.22.28, cairo version 1.17.4) of 2023-06-26 built on localhost