Function: byte-compile-nilconstp

byte-compile-nilconstp is a byte-compiled function defined in byte-opt.el.gz.

Signature

(byte-compile-nilconstp FORM)

Documentation

Return non-nil if FORM always evaluates to a nil value.

Source Code

;; Defined in /usr/src/emacs/lisp/emacs-lisp/byte-opt.el.gz
(defsubst byte-compile-nilconstp (form)
  "Return non-nil if FORM always evaluates to a nil value."
  (while (eq (car-safe form) 'progn)
    (setq form (car (last (cdr form)))))
  (cond ((consp form)
         (pcase (car form)
           ('quote (null (cadr form)))
           ;; Can't use recursion in a defsubst.
           ;; (`progn (byte-compile-nilconstp (car (last (cdr form)))))
           ))
        ((not (symbolp form)) nil)
        ((null form))))