220 1495 article Path: news.gmane.org!not-for-mail From: Ville Voutilainen Newsgroups: gmane.comp.lang.c++.isocpp.proposals Subject: Re: making using declaration more precise Date: Mon, 7 Jan 2013 23:30:28 +0200 Lines: 34 Approved: news@gmane.org Message-ID: References: <738f626c-3b23-4c74-9eea-2c2246921a81@isocpp.org> Reply-To: std-proposals@isocpp.org NNTP-Posting-Host: plane.gmane.org Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 X-Trace: ger.gmane.org 1357594229 14419 80.91.229.3 (7 Jan 2013 21:30:29 GMT) X-Complaints-To: usenet@ger.gmane.org NNTP-Posting-Date: Mon, 7 Jan 2013 21:30:29 +0000 (UTC) To: std-proposals@isocpp.org Original-X-From: std-proposals+bncBC5JHI7A7ALRB5P4VSDQKGQEJFVIKZI@isocpp.org Mon Jan 07 22:30:47 2013 Return-path: Envelope-to: gclcip-std-proposals@m.gmane.org Original-Received: from mail-oa0-f72.google.com ([209.85.219.72]) by plane.gmane.org with esmtp (Exim 4.69) (envelope-from ) id 1TsKHO-00049S-3e for gclcip-std-proposals@m.gmane.org; Mon, 07 Jan 2013 22:30:46 +0100 Original-Received: by mail-oa0-f72.google.com with SMTP id h2sf83140125oag.11 for ; Mon, 07 Jan 2013 13:30:30 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20120113; h=x-received:x-beenthere:x-received:x-received:received-spf :mime-version:in-reply-to:references:date:message-id:subject:from:to :x-original-sender:x-original-authentication-results:reply-to :precedence:mailing-list:list-id:x-google-group-id:list-post :list-help:list-archive:list-subscribe:list-unsubscribe:content-type; bh=jnBPpUaVN7nK2R3Ou4XBrad80TShgFvA52STZe2SCC0=; b=uCAUF65X3SRVeau7RuLnWp3jXhXCWp5P6ix46NaAtYIRTZR/OewGmR/8u9gNHrtdIQ 6jgFWVNRemLXYZgZhlIH7itg11nF+j+Q4kOY4+8LYYFDKKVLF6nw0L9VvEpUcB3trgVK EsPD5oppIw7LmEXpNBaUNyhHeWafZdl8srxyZvCAHryKXY/aRH7FupFhO3GdIVpZKnwL T+OFTeURP6BDbbOdT59xTvwtt//v9AQHPa3ro9QLj+9pNqffyXnYP6vbDxu04LV5M3GK vIHTjE0MLXEQ7+QEQI01vTwqBd/0KoENQUT8CUvQoSQfqtSwustOYUMizHFoDhMk1trz X-Received: by 10.182.113.39 with SMTP id iv7mr8316414obb.32.1357594229846; Mon, 07 Jan 2013 13:30:29 -0800 (PST) X-BeenThere: std-proposals@isocpp.org Original-Received: by 10.182.131.38 with SMTP id oj6ls1328957obb.80.gmail; Mon, 07 Jan 2013 13:30:29 -0800 (PST) X-Received: by 10.60.32.67 with SMTP id g3mr33743445oei.77.1357594228982; Mon, 07 Jan 2013 13:30:28 -0800 (PST) X-Received: by 10.60.32.67 with SMTP id g3mr33743444oei.77.1357594228947; Mon, 07 Jan 2013 13:30:28 -0800 (PST) Original-Received: from mail-oa0-f50.google.com (mail-oa0-f50.google.com [209.85.219.50]) by mx.google.com with ESMTPS id y4si37113845obv.63.2013.01.07.13.30.28 (version=TLSv1/SSLv3 cipher=OTHER); Mon, 07 Jan 2013 13:30:28 -0800 (PST) Received-SPF: pass (google.com: domain of ville.voutilainen@gmail.com designates 209.85.219.50 as permitted sender) client-ip=209.85.219.50; Original-Received: by mail-oa0-f50.google.com with SMTP id n16so18218597oag.23 for ; Mon, 07 Jan 2013 13:30:28 -0800 (PST) Original-Received: by 10.60.7.67 with SMTP id h3mr33585648oea.31.1357594228705; Mon, 07 Jan 2013 13:30:28 -0800 (PST) Original-Received: by 10.76.108.82 with HTTP; Mon, 7 Jan 2013 13:30:28 -0800 (PST) In-Reply-To: X-Original-Sender: ville.voutilainen@gmail.com X-Original-Authentication-Results: mx.google.com; spf=pass (google.com: domain of ville.voutilainen@gmail.com designates 209.85.219.50 as permitted sender) smtp.mail=ville.voutilainen@gmail.com; dkim=pass header.i=@gmail.com Precedence: list Mailing-list: list std-proposals@isocpp.org; contact std-proposals+owners@isocpp.org List-ID: X-Google-Group-Id: 399137483710 List-Post: , List-Help: , List-Archive: List-Subscribe: , List-Unsubscribe: , Xref: news.gmane.org gmane.comp.lang.c++.isocpp.proposals:1495 Archived-At: On 7 January 2013 23:18, Nicol Bolas wrote: >> The work-around would, I think, be >> class B :public A >> { >> void f(int x) {A::f(x);} >> }; > It's not as maintainable. If the syntax in `A` changes, you don't get a > proper compiler error if the syntax happens to remain compatible with the > old one. If they change `f(int)` to `f(int64_t)` or something, the compiler > will silently let this work. Fine, a further work-around is to add another statement that gets a pointer to the base member, that'll fail to compile if the type of the argument in the base changes. > With the proposed syntax, if there is no `f(int)` in the base class, it > fails to compile. Which forces everyone to update to the new syntax. It's > also a lot more obvious what's going on. It's also yet another rule that is different from the existing using-declaration. The existing using-declaration will silently accept compatible calls (with implicit conversions, unfortunately), this new one wouldn't. I don't think it would be an improvement major enough to matter. I think it would be useful, but for quite narrow amounts of cases, and I don't think the use case is compelling enough to warrant an extension. -- .