I quite often get the following messages:

Warning: Unknown defun property ‘compiler-macro’ in ...

As far as I could trace it, the problem is indirectly caused by
`define-inline'. While definition of `defun-declarations-alist' does
contain `compiler-macro' in its init form, it can be removed later.
E.g. when I evaluated the variable, it was not there anymore, only
`gv-setter' was there.

It seems this is done unintentionally by `elisp-completion-at-point':

                       (`declare
                        (list t (mapcar (lambda (x) (symbol-name (car x)))
                                        (delete-dups
                                         ;; FIXME: We should include some
                                         ;; docstring with each entry.
                                         (append
                                          macro-declarations-alist
                                          defun-declarations-alist)))))

Here `delete-dups' destructively modifies a list that includes
`defun-declarations-alist' as its tail verbatim, not as a copy.
Attached patch should fix that.

Paul

* elisp-mode.el (elisp-completion-at-point): Fix to not alter
`defun-declarations-alist' by side effect.