Highlight uninterned symbols.

* lisp/emacs-lisp/lisp-mode.el (lisp-cl-font-lock-keywords-2):
Highlight uninterned symbols, often used as string designators to
avoid namespace pollution (https://stackoverflow.com/a/46981940/850781).

1 files changed, 5 insertions, 0 deletions

diff --git a/lisp/emacs-lisp/lisp-mode.el b/lisp/emacs-lisp/lisp-mode.el
index fd12635d85c..0e1d3709194 100644
--- a/lisp/emacs-lisp/lisp-mode.el
+++ b/lisp/emacs-lisp/lisp-mode.el
@@ -491,6 +491,11 @@ This will generate compile-time constants from BINDINGS."
          (,(concat "[`‘]\\(\\(?:\\sw\\|\\s_\\|\\\\.\\)"
                    lisp-mode-symbol-regexp "\\)['’]")
           (1 font-lock-constant-face prepend))
+         ;; Uninterned symbols, e.g., (defpackage #:my-package ...)
+         ;; must come before keywords below to have effect
+         (,(concat "\\(#:\\)\\(" lisp-mode-symbol-regexp "\\)")
+           (1 font-lock-comment-delimiter-face)
+           (2 font-lock-doc-face))
          ;; Constant values.
          (,(concat "\\_<:" lisp-mode-symbol-regexp "\\_>")
           (0 font-lock-builtin-face))