Subject: 27.2; `cl-macs.el' no longer provides `cl-macs'

From: Drew Adams <[email-masked]>
Date: Tue, 4 Jan 2022 21:14:08 +0000

Presumably a design bug, i.e., intentional.

Until Emacs 27, code could use this to load the macros defining things
like `cl-case' (which has  l o n g  been aliased to `case', and which
should even be in Emacs Lisp itself, as is `push'):

(eval-when-compile (require 'cl-macs))

Emacs 27 breaks that.  Now, if you need only CL macros, you need to
require `cl-lib.el' instead.  So any library that needs something like
`case', and needs to support both Emacs 27+ and older Emacs versions,
needs to jump through a hoop such as this (or another, using
`load-library'):

(eval-when-compile 
  (require (if (< emacs-major-version 27) 'cl-macs 'cl-lib)))

Gratuitous bother.  Or was there some real need for introducing the
incompatibility?

In GNU Emacs 27.2 (build 1, x86_64-w64-mingw32)
 of 2021-03-26 built on CIRROCUMULUS
Repository revision: deef5efafb70f4b171265b896505b92b6eef24e6
Repository branch: HEAD
Windowing system distributor 'Microsoft Corp.', version 10.0.19042
System Description: Microsoft Windows 10 Pro (v10.0.2009.19042.1348)