(defun preserved-symbol-p (sym)
  (and (slime-eval `(cl:let ((sym (cl:find-symbol
                                   (cl:format nil "~A" (cl:read-from-string ',sym))
                                   :cl)))
                            (cl:and sym
                                    (cl:eq sym
                                           (cl:find-symbol
                                            (cl:format nil "~A" (cl:read-from-string ',sym))
                                            (cl:read-from-string ,(slime-current-package))))))
                   (slime-current-package))
       t))


(defun slime-upcase-preserved-symbol ()
  (interactive)
  (and (preserved-symbol-p
        (substring-no-properties (thing-at-point 'symbol)))
       (save-excursion
         (let ((beg (point)))
           (backward-sexp 1)
           (upcase-region beg (point))))))


(defun slime-upcase-preserved-symbol/slime-autodoc-space (&rest args)
  (slime-upcase-preserved-symbol))


(advice-add 'slime-autodoc-space :before #'slime-upcase-preserved-symbol/slime-autodoc-space)