Advise symbol-file to return doom-file property

...if it exists. Otherwise fall back on original functionality. This
allows certain symbols to overwrite where Emacs thinks they were
defined.

Warning: only use this for autodefs! It may have unintended side-effects
for other symbols.

core/core.el

@@ -213,6 +213,13 @@ with functions that require it (like modeline segments)."
     buffer))
 (advice-add #'make-indirect-buffer :around #'doom*set-indirect-buffer-filename)
 
+(defun doom*symbol-file (orig-fn symbol &optional type)
+  "If a `doom-file' symbol property exists on SYMBOL, use that instead of the
+original value of `symbol-file'."
+  (or (get symbol 'doom-file)
+      (funcall orig-fn symbol type)))
+(advice-add #'symbol-file :around #'doom*symbol-file)
+
 ;; Truly silence startup message
 (fset #'display-startup-echo-area-message #'ignore)