From 495963cfaf535646350051f47c085b84319572f0 Mon Sep 17 00:00:00 2001 From: Stefan Monnier Date: Fri, 20 Apr 2018 17:22:47 -0400 Subject: [PATCH] * lisp/emacs-lisp/bytecomp.el (byte-compile-file-form-defvar-function): Warn about defvaralias that follows instead of precedes its var. --- lisp/emacs-lisp/bytecomp.el | 9 +++++++++ 1 file changed, 9 insertions(+) diff --git a/lisp/emacs-lisp/bytecomp.el b/lisp/emacs-lisp/bytecomp.el index ea9e3f06555..50e67046e8b 100644 --- a/lisp/emacs-lisp/bytecomp.el +++ b/lisp/emacs-lisp/bytecomp.el @@ -2426,6 +2426,15 @@ list that represents a doc string reference. (defun byte-compile-file-form-defvar-function (form) (pcase-let (((or `',name (let name nil)) (nth 1 form))) (if name (byte-compile--declare-var name))) + ;; Variable aliases are better declared before the corresponding variable, + ;; since it makes it more likely that only one of the two vars has a value + ;; before the `defvaralias' gets executed, which avoids the need to + ;; merge values. + (pcase form + (`(defvaralias ,_ ',newname . ,_) + (when (memq newname byte-compile-bound-variables) + (byte-compile-warn + "Alias for `%S' should be declared before its referent" newname)))) (byte-compile-keep-pending form)) (put 'custom-declare-variable 'byte-hunk-handler -- 2.39.5