From mboxrd@z Thu Jan 1 00:00:00 1970 Path: news.gmane.org!.POSTED!not-for-mail From: Stefan Monnier Newsgroups: gmane.emacs.devel Subject: Re: [Emacs-diffs] master 9c4e309: Check that variable lists are actually lists Date: Thu, 19 Jan 2017 11:40:16 -0500 Message-ID: References: <20170119161943.5234.63498@vcs.savannah.gnu.org> <20170119161943.49263220159@vcs.savannah.gnu.org> NNTP-Posting-Host: blaine.gmane.org Mime-Version: 1.0 Content-Type: text/plain X-Trace: blaine.gmane.org 1484844044 20303 195.159.176.226 (19 Jan 2017 16:40:44 GMT) X-Complaints-To: usenet@blaine.gmane.org NNTP-Posting-Date: Thu, 19 Jan 2017 16:40:44 +0000 (UTC) User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/26.0.50 (gnu/linux) Cc: Philipp Stephani To: emacs-devel@gnu.org Original-X-From: emacs-devel-bounces+ged-emacs-devel=m.gmane.org@gnu.org Thu Jan 19 17:40:40 2017 Return-path: Envelope-to: ged-emacs-devel@m.gmane.org Original-Received: from lists.gnu.org ([208.118.235.17]) by blaine.gmane.org with esmtp (Exim 4.84_2) (envelope-from ) id 1cUFlG-00048L-5k for ged-emacs-devel@m.gmane.org; Thu, 19 Jan 2017 17:40:30 +0100 Original-Received: from localhost ([::1]:49538 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1cUFlL-0001Mf-3s for ged-emacs-devel@m.gmane.org; Thu, 19 Jan 2017 11:40:35 -0500 Original-Received: from eggs.gnu.org ([2001:4830:134:3::10]:60562) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1cUFl9-0001L8-PM for emacs-devel@gnu.org; Thu, 19 Jan 2017 11:40:24 -0500 Original-Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1cUFl4-0007UG-Pa for emacs-devel@gnu.org; Thu, 19 Jan 2017 11:40:23 -0500 Original-Received: from chene.dit.umontreal.ca ([132.204.246.20]:41214) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1cUFl4-0007U2-KQ for emacs-devel@gnu.org; Thu, 19 Jan 2017 11:40:18 -0500 Original-Received: from pastel.home (lechon.iro.umontreal.ca [132.204.27.242]) by chene.dit.umontreal.ca (8.14.7/8.14.1) with ESMTP id v0JGeGdY029703; Thu, 19 Jan 2017 11:40:16 -0500 Original-Received: by pastel.home (Postfix, from userid 20848) id 810DF60657; Thu, 19 Jan 2017 11:40:16 -0500 (EST) In-Reply-To: <20170119161943.49263220159@vcs.savannah.gnu.org> (Philipp Stephani's message of "Thu, 19 Jan 2017 16:19:43 +0000 (UTC)") X-NAI-Spam-Flag: NO X-NAI-Spam-Threshold: 5 X-NAI-Spam-Score: 0 X-NAI-Spam-Rules: 2 Rules triggered EDT_SA_DN_PASS=0, RV5925=0 X-NAI-Spam-Version: 2.3.0.9418 : core <5925> : inlines <5636> : streams <1729772> : uri <2360671> X-detected-operating-system: by eggs.gnu.org: Genre and OS details not recognized. X-Received-From: 132.204.246.20 X-BeenThere: emacs-devel@gnu.org X-Mailman-Version: 2.1.21 Precedence: list List-Id: "Emacs development discussions." List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: emacs-devel-bounces+ged-emacs-devel=m.gmane.org@gnu.org Original-Sender: "Emacs-devel" Xref: news.gmane.org gmane.emacs.devel:211406 Archived-At: > 'let' and 'let*' document that their first argument has to be a list, > but don't check for that; instead, they allow (and silently ignore) > other types. Introduce an explicit type check. Notice that this may end up breaking currently working code :-( The way we've generally handled such issues is basically that if the programmer wants sanity checks, he should byte-compile his code. This has two corollaries: - We should make sure that the *byte-compiler* does warn about ill-formed code (we currently don't do a great job of that). - The interpreter can do whatever it wants with ill-formed code and doesn't need to go out of its way to detect it. Stefan