220 27151 <9e604034-9361-448a-a07f-04d0e61b4829@isocpp.org> article Path: news.gmane.org!not-for-mail From: Barry Revzin Newsgroups: gmane.comp.lang.c++.isocpp.proposals Subject: operator.() (R3) with deleted copy constructor Date: Sun, 17 Jul 2016 20:57:40 -0700 (PDT) Lines: 136 Approved: news@gmane.org Message-ID: <9e604034-9361-448a-a07f-04d0e61b4829@isocpp.org> Reply-To: std-proposals@isocpp.org NNTP-Posting-Host: plane.gmane.org Mime-Version: 1.0 Content-Type: multipart/mixed; boundary="----=_Part_1411_1403896651.1468814260132" X-Trace: ger.gmane.org 1468814270 7229 80.91.229.3 (18 Jul 2016 03:57:50 GMT) X-Complaints-To: usenet@ger.gmane.org NNTP-Posting-Date: Mon, 18 Jul 2016 03:57:50 +0000 (UTC) To: ISO C++ Standard - Future Proposals Original-X-From: std-proposals+bncBCJJTG7CS4ARBNNHWG6AKGQE7NKEV3A@isocpp.org Mon Jul 18 05:57:45 2016 Return-path: Envelope-to: gclcip-std-proposals@m.gmane.org Original-Received: from mail-it0-f70.google.com ([209.85.214.70]) by plane.gmane.org with esmtp (Exim 4.69) (envelope-from ) id 1bOzgd-0000tr-94 for gclcip-std-proposals@m.gmane.org; Mon, 18 Jul 2016 05:57:43 +0200 Original-Received: by mail-it0-f70.google.com with SMTP id i64sf175353980ith.2 for ; Sun, 17 Jul 2016 20:57:42 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=isocpp-org.20150623.gappssmtp.com; s=20150623; h=date:from:to:message-id:subject:mime-version:x-original-sender :reply-to:precedence:mailing-list:list-id:x-spam-checked-in-group :list-post:list-help:list-archive:list-subscribe:list-unsubscribe; bh=XGkBEeWsqx9ZMFvN1YI4Oz/BZWCIAXmg4WC9o7SGT5s=; b=XUeACxUe5/qCucMf9UCGv418U8lkrZdu2pS5Gz8q1DCAHpRsDA6Lav+ngxJaoEhTlc si/X5rAGLGGCxQgWbKVLdHbfeZe9Rh10hzN+nvLKVimL3nilrcq5cbD04oxgcCR/oXhw VVe8ZeDARhA7airlPWuvp7MfLzQwstisBYODbxgc2Uf7PTBM54fiDqgxB9drRkYF+3Sj GWDjD48WAItkK0UMdoYn5MvCsBpXlUP+J2Yika280MfTbWgTnE31YAQL/rg2SvBK+t2/ SB2R2h+T7IkEkKTuxEK8qnQozYtcDqLdU+R14k4tkdhOmh/acnnES7t+sh5qxs0rsMRO nMIg== DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20120113; h=date:from:to:message-id:subject:mime-version:x-original-sender :reply-to:precedence:mailing-list:list-id:x-spam-checked-in-group :list-post:list-help:list-archive:list-subscribe:list-unsubscribe; bh=XGkBEeWsqx9ZMFvN1YI4Oz/BZWCIAXmg4WC9o7SGT5s=; b=I0eQj5OYAlUFKHpupEgCZltLMzLB4q8ZlgaSPAuWZBHtXahwB14F9bonw5jql0eMdY v1M8urq2WSIsQzs1fsOz5psoRX0P6+06GK20b5+cfXisQ/wytI7yOzuPGMAn/Xk8nOEr ydBN1U4Ef4LRJcwJlZLQQ8QlZaTEAkZ95o8b4CnJTw/mXH9pRX/aRehbwHTOD3uPv9Gl g1k/x+o+mDC3db0M7F/Fc7myuyZJyyehRRD5h4piXxh/QH+s8UU7EOGXOQwS0snvlZ6B v5ol5gymB2dOEuI9/qZ049/bz+HqpoAQ9RGnwacLymOuWON5CB3gD13oE7uP1EV/zVyw xUXQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20130820; h=x-gm-message-state:date:from:to:message-id:subject:mime-version :x-original-sender:reply-to:precedence:mailing-list:list-id :x-spam-checked-in-group:list-post:list-help:list-archive :list-subscribe:list-unsubscribe; bh=XGkBEeWsqx9ZMFvN1YI4Oz/BZWCIAXmg4WC9o7SGT5s=; b=DAGTNX12RMBPJQcegeaWFLFJ5EKFGNIpUny8gDMi7Q+49y5fiQJdZsbPUe17xVvgH4 6wU0JoN++vo3PNt63/lLlwaVDToTQf0zgvRb8SKa3k9kkTExYuUQ1DW0og+OiqTmTCYl MEG3NVnaGOqnq204yPJXNEE8wq4ltkT0Yp9Q3GFB9IggtSfJjxyg1v4NYu+gf1ZXHOKy SVy0tFxaBnD0KsVpYW3AMPTCcWy3B0AhAAOrwQIyfVQGqBLVK0jiPrJToC6s/MFZlzAx eH31XiKFXQ0XU3B7th9EZyttWg5s9aNlVMxCxz1yp9jhTFGplQb0h/cv9wMcbApOb+B9 ivoQ== X-Gm-Message-State: ALyK8tKTutDPVC5PRHFTYR1m5Xh6WTasH0Wl7181UmAyCMrqAKGA12WqAcfYJIZn9eCTSg== X-Received: by 10.157.45.227 with SMTP id g90mr24543902otb.1.1468814261977; Sun, 17 Jul 2016 20:57:41 -0700 (PDT) X-BeenThere: std-proposals@isocpp.org Original-Received: by 10.36.67.208 with SMTP id s199ls2636868itb.1.gmail; Sun, 17 Jul 2016 20:57:41 -0700 (PDT) X-Received: by 10.36.123.135 with SMTP id q129mr373069itc.1.1468814261046; Sun, 17 Jul 2016 20:57:41 -0700 (PDT) X-Original-Sender: Barry.Revzin@gmail.com Precedence: list Mailing-list: list std-proposals@isocpp.org; contact std-proposals+owners@isocpp.org List-ID: X-Spam-Checked-In-Group: std-proposals@isocpp.org 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:27151 Archived-At: ------=_Part_1411_1403896651.1468814260132 Content-Type: multipart/alternative; boundary="----=_Part_1412_1591829672.1468814260133" ------=_Part_1412_1591829672.1468814260133 Content-Type: text/plain; charset=UTF-8 There's an example in the new paper (http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2016/p0416r0.pdf, page 11) that looks like this (reduced slightly ): template class Ref2 { public: Ref2(T& ); Ref2(const Ref2& ) = delete; T& operator.(); }; void f(Ref2 rr); X x; Ref2 r{x}; f(r);// OK: no copy constructor, but r.operator.() is an X so f(X{r.operator.()}) There's no wording paper yet, so maybe this is premature, but I wanted to ask what the intended changes to the conversion sequence rules would be that would allow this to happen? 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There's an example in the new paper (http://www.open-s= td.org/jtc1/sc22/wg21/docs/papers/2016/p0416r0.pdf, page 11) that looks lik= e this (reduced slightly ):

t= emplate <<= span style=3D"color: #008;" class=3D"styled-by-prettify">class T>
class Ref2 {
public:
=C2=A0 =C2=A0 = Ref2(T& );
=C2=A0 =C2=A0 Ref2(const= Ref2& ) =3D delete;
=C2=A0 =C2=A0 T& ope= rator.();<= /span>
= };

void f(Ref2<X> r= r);=

X x;
Ref2<X> r{x};

f= (r<= /span>);// OK: no copy cons= tructor, but r.operator.() is an X so f(X{r.operator.()})

There's no wording paper yet, = so maybe this is premature, but I wanted to ask what the intended changes t= o the conversion sequence rules would be that would allow this to happen?= =C2=A0

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