<!doctype html><html lang="en">
 <head>
  <meta content="text/html; charset=utf-8" http-equiv="Content-Type">
  <meta content="width=device-width, initial-scale=1, shrink-to-fit=no" name="viewport">
  <title>P2953R0: Forbid defaulting operator=(X&amp;&amp;) &amp;&amp;</title>
<style data-fill-with="stylesheet">/******************************************************************************
 *                   Style sheet for the W3C specifications                   *
 *
 * Special classes handled by this style sheet include:
 *
 * Indices
 *   - .toc for the Table of Contents (<ol class="toc">)
 *     + <span class="secno"> for the section numbers
 *   - #toc for the Table of Contents (<nav id="toc">)
 *   - ul.index for Indices (<a href="#ref">term</a><span>, in § N.M</span>)
 *   - table.index for Index Tables (e.g. for properties or elements)
 *
 * Structural Markup
 *   - table.data for general data tables
 *     -> use 'scope' attribute, <colgroup>, <thead>, and <tbody> for best results !
 *     -> use <table class='complex data'> for extra-complex tables
 *     -> use <td class='long'> for paragraph-length cell content
 *     -> use <td class='pre'> when manual line breaks/indentation would help readability
 *   - dl.switch for switch statements
 *   - ol.algorithm for algorithms (helps to visualize nesting)
 *   - .figure and .caption (HTML4) and figure and figcaption (HTML5)
 *     -> .sidefigure for right-floated figures
 *   - ins/del
 *     -> ins/del.c### for candidate and proposed changes (amendments)
 *
 * Code
 *   - pre and code
 *
 * Special Sections
 *   - .note       for informative notes             (div, p, span, aside, details)
 *   - .example    for informative examples          (div, p, pre, span)
 *   - .issue      for issues                        (div, p, span)
 *   - .advisement for loud normative statements     (div, p, strong)
 *   - .annoying-warning for spec obsoletion notices (div, aside, details)
 *   - .correction for "candidate corrections"       (div, aside, details, section)
 *   - .addition   for "candidate additions"         (div, aside, details, section)
 *   - .correction.proposed for "proposed corrections" (div, aside, details, section)
 *   - .addition.proposed   for "proposed additions"   (div, aside, details, section)
 *
 * Definition Boxes
 *   - pre.def   for WebIDL definitions
 *   - table.def for tables that define other entities (e.g. CSS properties)
 *   - dl.def    for definition lists that define other entitles (e.g. HTML elements)
 *
 * Numbering
 *   - .secno for section numbers in .toc and headings (<span class='secno'>3.2</span>)
 *   - .marker for source-inserted example/figure/issue numbers (<span class='marker'>Issue 4</span>)
 *   - ::before styled for CSS-generated issue/example/figure numbers:
 *     -> Documents wishing to use this only need to add
 *        figcaption::before,
 *        .caption::before { content: "Figure "  counter(figure) " ";  }
 *        .example::before { content: "Example " counter(example) " "; }
 *        .issue::before   { content: "Issue "   counter(issue) " ";   }
 *
 * Header Stuff (ignore, just don't conflict with these classes)
 *   - .head for the header
 *   - .copyright for the copyright
 *
 * Outdated warning for old specs
 *
 * Miscellaneous
 *   - .overlarge for things that should be as wide as possible, even if
 *     that overflows the body text area. This can be used on an item or
 *     on its container, depending on the effect desired.
 *     Note that this styling basically doesn't help at all when printing,
 *     since A4 paper isn't much wider than the max-width here.
 *     It's better to design things to fit into a narrower measure if possible.
 *
 *   - js-added ToC jump links (see fixup.js)
 *
 ******************************************************************************/

/* color variables included separately for reliability */

/******************************************************************************/
/*                                    Body                                    */
/******************************************************************************/

	html {
	}

	body {
		counter-reset: example figure issue;

		/* Layout */
		max-width: 50em;			  /* limit line length to 50em for readability   */
		margin: 0 auto;				/* center text within page                    */
		padding: 1.6em 1.5em 2em 50px; /* assume 16px font size for downlevel clients */
		padding: 1.6em 1.5em 2em calc(26px + 1.5em); /* leave space for status flag    */

		/* Typography */
		line-height: 1.5;
		font-family: sans-serif;
		widows: 2;
		orphans: 2;
		word-wrap: break-word;
		overflow-wrap: break-word;
		hyphens: auto;

		color: black;
		color: var(--text);
		background: white top left fixed no-repeat;
		background: var(--bg) top left fixed no-repeat;
		background-size: 25px auto;
	}


/******************************************************************************/
/*                         Front Matter & Navigation                          */
/******************************************************************************/

/** Header ********************************************************************/

	div.head { margin-bottom: 1em; }
	div.head hr { border-style: solid; }

	div.head h1 {
		font-weight: bold;
		margin: 0 0 .1em;
		font-size: 220%;
	}

	div.head h2 { margin-bottom: 1.5em;}

/** W3C Logo ******************************************************************/

	.head .logo {
		float: right;
		margin: 0.4rem 0 0.2rem .4rem;
	}

	.head img[src*="logos/W3C"] {
		display: block;
		border: solid #1a5e9a;
		border: solid var(--logo-bg);
		border-width: .65rem .7rem .6rem;
		border-radius: .4rem;
		background: #1a5e9a;
		background: var(--logo-bg);
		color: white;
		color: var(--logo-text);
		font-weight: bold;
	}

	.head a:hover > img[src*="logos/W3C"],
	.head a:focus > img[src*="logos/W3C"] {
		opacity: .8;
	}

	.head a:active > img[src*="logos/W3C"] {
		background: #c00;
		background: var(--logo-active-bg);
		border-color: #c00;
		border-color: var(--logo-active-bg);
	}

	/* see also additional rules in Link Styling section */

/** Copyright *****************************************************************/

	p.copyright,
	p.copyright small { font-size: small; }

/** Back to Top / ToC Toggle **************************************************/

	@media print {
		#toc-nav {
			display: none;
		}
	}
	@media not print {
		#toc-nav {
			position: fixed;
			z-index: 3;
			bottom: 0; left: 0;
			margin: 0;
			min-width: 1.33em;
			border-top-right-radius: 2rem;
			box-shadow: 0 0 2px;
			font-size: 1.5em;
		}
		#toc-nav > a {
			display: block;
			white-space: nowrap;

			height: 1.33em;
			padding: .1em 0.3em;
			margin: 0;

			box-shadow: 0 0 2px;
			border: none;
			border-top-right-radius: 1.33em;

			color: #707070;
			color: var(--tocnav-normal-text);
			background: white;
			background: var(--tocnav-normal-bg);
		}
		#toc-nav > a:hover,
		#toc-nav > a:focus {
			color: black;
			color: var(--tocnav-hover-text);
			background: #f8f8f8;
			background: var(--tocnav-hover-bg);
		}
		#toc-nav > a:active {
			color: #c00;
			color: var(--tocnav-active-text);
			background: white;
			background: var(--tocnav-active-bg);
		}

		#toc-nav > #toc-jump {
			padding-bottom: 2em;
			margin-bottom: -1.9em;
		}

		/* statusbar gets in the way on keyboard focus; remove once browsers fix */
		#toc-nav > a[href="#toc"]:not(:hover):focus:last-child {
			padding-bottom: 1.5rem;
		}

		#toc-nav:not(:hover) > a:not(:focus) > span + span {
			/* Ideally this uses :focus-within on #toc-nav */
			display: none;
		}
		#toc-nav > a > span + span {
			padding-right: 0.2em;
		}
	}

/** ToC Sidebar ***************************************************************/

	/* Floating sidebar */
	@media screen {
		body.toc-sidebar #toc {
			position: fixed;
			top: 0; bottom: 0;
			left: 0;
			width: 23.5em;
			max-width: 80%;
			max-width: calc(100% - 2em - 26px);
			overflow: auto;
			padding: 0 1em;
			padding-left: 42px;
			padding-left: calc(1em + 26px);
			color: black;
			color: var(--tocsidebar-text);
			background: inherit;
			background-color: #f7f8f9;
			background-color: var(--tocsidebar-bg);
			z-index: 1;
			box-shadow: -.1em 0 .25em rgba(0,0,0,.1) inset;
			box-shadow: -.1em 0 .25em var(--tocsidebar-shadow) inset;
		}
		body.toc-sidebar #toc h2 {
			margin-top: .8rem;
			font-variant: small-caps;
			font-variant: all-small-caps;
			text-transform: lowercase;
			font-weight: bold;
			color: gray;
			color: hsla(203,20%,40%,.7);
			color: var(--tocsidebar-heading-text);
		}
		body.toc-sidebar #toc-jump:not(:focus) {
			width: 0;
			height: 0;
			padding: 0;
			position: absolute;
			overflow: hidden;
		}
	}
	/* Hide main scroller when only the ToC is visible anyway */
	@media screen and (max-width: 28em) {
		body.toc-sidebar {
			overflow: hidden;
		}
	}

	/* Sidebar with its own space */
	@media screen and (min-width: 78em) {
		body:not(.toc-inline) #toc {
			position: fixed;
			top: 0; bottom: 0;
			left: 0;
			width: 23.5em;
			overflow: auto;
			padding: 0 1em;
			padding-left: 42px;
			padding-left: calc(1em + 26px);
			color: black;
			color: var(--tocsidebar-text);
			background: inherit;
			background-color: #f7f8f9;
			background-color: var(--tocsidebar-bg);
			z-index: 1;
			box-shadow: -.1em 0 .25em rgba(0,0,0,.1) inset;
			box-shadow: -.1em 0 .25em var(--tocsidebar-shadow) inset;
		}
		body:not(.toc-inline) #toc h2 {
			margin-top: .8rem;
			font-variant: small-caps;
			font-variant: all-small-caps;
			text-transform: lowercase;
			font-weight: bold;
			color: gray;
			color: hsla(203,20%,40%,.7);
			color: var(--tocsidebar-heading-text);
		}

		body:not(.toc-inline) {
			padding-left: 29em;
		}
		/* See also Overflow section at the bottom */

		body:not(.toc-inline) #toc-jump:not(:focus) {
			width: 0;
			height: 0;
			padding: 0;
			position: absolute;
			overflow: hidden;
		}
	}
	@media screen and (min-width: 90em) {
		body:not(.toc-inline) {
			margin: 0 4em;
		}
	}

/******************************************************************************/
/*                                Sectioning                                  */
/******************************************************************************/

/** Headings ******************************************************************/

	h1, h2, h3, h4, h5, h6, dt {
		page-break-after: avoid;
		page-break-inside: avoid;
		font: 100% sans-serif;   /* Reset all font styling to clear out UA styles */
		font-family: inherit;	/* Inherit the font family. */
		line-height: 1.2;		/* Keep wrapped headings compact */
		hyphens: manual;		/* Hyphenated headings look weird */
	}

	h2, h3, h4, h5, h6 {
		margin-top: 3rem;
	}

	h1, h2, h3 {
		color: #005A9C;
		color: var(--heading-text);
	}

	h1 { font-size: 170%; }
	h2 { font-size: 140%; }
	h3 { font-size: 120%; }
	h4 { font-weight: bold; }
	h5 { font-style: italic; }
	h6 { font-variant: small-caps; }
	dt { font-weight: bold; }

/** Subheadings ***************************************************************/

	h1 + h2,
	#profile-and-date {
		/* #profile-and-date is a subtitle in an H2 under the H1 */
		margin-top: 0;
	}
	h2 + h3,
	h3 + h4,
	h4 + h5,
	h5 + h6 {
		margin-top: 1.2em; /* = 1 x line-height */
	}

/** Section divider ***********************************************************/

	:not(.head) > :not(.head) + hr {
		font-size: 1.5em;
		text-align: center;
		margin: 1em auto;
		height: auto;
		color: black;
		color: var(--hr-text);
		border: transparent solid 0;
		background: transparent;
	}
	:not(.head) > hr::before {
		content: "\2727\2003\2003\2727\2003\2003\2727";
	}

/******************************************************************************/
/*                            Paragraphs and Lists                            */
/******************************************************************************/

	p {
		margin: 1em 0;
	}

	dd > p:first-child,
	li > p:first-child {
		margin-top: 0;
	}

	ul, ol {
		margin-left: 0;
		padding-left: 2em;
	}

	li {
		margin: 0.25em 0 0.5em;
		padding: 0;
	}

	dl dd {
		margin: 0 0 .5em 2em;
	}

	.head dd + dd { /* compact for header */
		margin-top: -.5em;
	}

	/* Style for algorithms */
	ol.algorithm ol:not(.algorithm),
	.algorithm > ol ol:not(.algorithm) {
	border-left: 0.5em solid #DEF;
	border-left: 0.5em solid var(--algo-border);
	}

	/* Put nice boxes around each algorithm. */
	[data-algorithm]:not(.heading) {
	 padding: .5em;
	 border: thin solid #ddd;
	 border: thin solid var(--algo-border);
	 border-radius: .5em;
	 margin: .5em calc(-0.5em - 1px);
	}
	[data-algorithm]:not(.heading) > :first-child {
	 margin-top: 0;
	}
	[data-algorithm]:not(.heading) > :last-child {
	 margin-bottom: 0;
	}

	/* Style for switch/case <dl>s */
	dl.switch > dd > ol.only,
	dl.switch > dd > .only > ol {
	margin-left: 0;
	}
	dl.switch > dd > ol.algorithm,
	dl.switch > dd > .algorithm > ol {
	margin-left: -2em;
	}
	dl.switch {
	padding-left: 2em;
	}
	dl.switch > dt {
	text-indent: -1.5em;
	margin-top: 1em;
	}
	dl.switch > dt + dt {
	margin-top: 0;
	}
	dl.switch > dt::before {
	content: '\21AA';
	padding: 0 0.5em 0 0;
	display: inline-block;
	width: 1em;
	text-align: right;
	line-height: 0.5em;
	}

/** Terminology Markup ********************************************************/


/******************************************************************************/
/*                                 Inline Markup                              */
/******************************************************************************/

/** Terminology Markup ********************************************************/
	dfn   { /* Defining instance */
		font-weight: bolder;
	}
	a > i { /* Instance of term */
		font-style: normal;
	}
	dt dfn code, code.idl {
		font-size: inherit;
	}
	dfn var {
		font-style: normal;
	}

/** Change Marking ************************************************************/

	del {
		color: #aa0000;
		color: var(--del-text);
		background: transparent;
		background: var(--del-bg);
		text-decoration: line-through;
	}
	ins {
		color: #006100;
		color: var(--ins-text);
		background: transparent;
		background: var(--ins-bg);
		text-decoration: underline;
	}

	/* for amendments (candidate/proposed changes) */

	.amendment ins, .correction ins, .addition ins,
	ins[class^=c] {
		text-decoration-style: dotted;
	}
	.amendment del, .correction del, .addition del,
	del[class^=c] {
		text-decoration-style: dotted;
	}
	.amendment.proposed ins, .correction.proposed ins, .addition.proposed ins,
	ins[class^=c].proposed {
		text-decoration-style: double;
	}
	.amendment.proposed del, .correction.proposed del, .addition.proposed del,
	del[class^=c].proposed {
		text-decoration-style: double;
	}

/** Miscellaneous improvements to inline formatting ***************************/

	sup {
		vertical-align: super;
		font-size: 80%
	}

/******************************************************************************/
/*                                    Code                                    */
/******************************************************************************/

/** General monospace/pre rules ***********************************************/

	pre, code, samp {
		font-family: Menlo, Consolas, "DejaVu Sans Mono", Monaco, monospace;
		font-size: .9em;
		hyphens: none;
		text-transform: none;
		text-align: left;
		text-align: start;
		font-variant: normal;
		orphans: 3;
		widows: 3;
		page-break-before: avoid;
	}
	pre code,
	code code {
		font-size: 100%;
	}

	pre {
		margin-top: 1em;
		margin-bottom: 1em;
		overflow: auto;
	}

/** Inline Code fragments *****************************************************/

	/* Do something nice. */

/******************************************************************************/
/*                                    Links                                   */
/******************************************************************************/

/** General Hyperlinks ********************************************************/

	/* We hyperlink a lot, so make it less intrusive */
	a[href] {
		color: #034575;
		color: var(--a-normal-text);
		text-decoration: underline #707070;
		text-decoration: underline var(--a-normal-underline);
		text-decoration-skip-ink: none;
	}
	a:visited {
		color: #034575;
		color: var(--a-visited-text);
		text-decoration-color: #bbb;
		text-decoration-color: var(--a-visited-underline);
	}

	/* Indicate interaction with the link */
	a[href]:focus,
	a[href]:hover {
		text-decoration-thickness: 2px;
	}
	a[href]:active {
		color: #c00;
		color: var(--a-active-text);
		text-decoration-color: #c00;
		text-decoration-color: var(--a-active-underline);
	}

	/* Backout above styling for W3C logo */
	.head .logo,
	.head .logo a {
		border: none;
		text-decoration: none;
		background: transparent;
	}

/******************************************************************************/
/*                                    Images                                  */
/******************************************************************************/

	img {
		border-style: none;
	}

	img, svg {
		/* Intentionally not color-scheme aware. */
		background: white;
	}

	/* For autogen numbers, add
	  .caption::before, figcaption::before { content: "Figure " counter(figure) ". "; }
	*/

	figure, .figure, .sidefigure {
		page-break-inside: avoid;
		text-align: center;
		margin: 2.5em 0;
	}
	.figure img,	.sidefigure img,	figure img,
	.figure object, .sidefigure object, figure object {
		max-width: 100%;
		margin: auto;
		height: auto;
	}
	.figure pre, .sidefigure pre, figure pre {
		text-align: left;
		display: table;
		margin: 1em auto;
	}
	.figure table, figure table {
		margin: auto;
	}
	@media screen and (min-width: 20em) {
		.sidefigure {
			float: right;
			width: 50%;
			margin: 0 0 0.5em 0.5em;
		}
	}
	.caption, figcaption, caption {
		font-style: italic;
		font-size: 90%;
	}
	.caption::before, figcaption::before, figcaption > .marker {
		font-weight: bold;
	}
	.caption, figcaption {
		counter-increment: figure;
	}

	/* DL list is indented 2em, but figure inside it is not */
	dd > .figure, dd > figure { margin-left: -2em; }

/******************************************************************************/
/*                             Colored Boxes                                  */
/******************************************************************************/

	.issue, .note, .example, .assertion, .advisement, blockquote,
	.amendment, .correction, .addition {
		margin: 1em auto;
		padding: .5em;
		border: .5em;
		border-left-style: solid;
		page-break-inside: avoid;
	}
	span.issue, span.note {
		padding: .1em .5em .15em;
		border-right-style: solid;
	}

	blockquote > :first-child,
	.note  > p:first-child,
	.issue > p:first-child,
	.amendment > p:first-child,
	.correction > p:first-child,
	.addition > p:first-child {
		margin-top: 0;
	}
	blockquote > :last-child,
	.note  > p:last-child,
	.issue > p:last-child,
	.amendment > p:last-child,
	.correction > p:last-child,
	.addition > p:last-child {
		margin-bottom: 0;
	}


	.issue::before, .issue > .marker,
	.example::before, .example > .marker,
	.note::before, .note > .marker,
	details.note > summary > .marker,
	.amendment::before, .amendment > .marker,
	details.amendment > summary > .marker,
	.addition::before, .addition > .marker,
	addition.amendment > summary > .marker,
	.correction::before, .correction > .marker,
	correction.amendment > summary > .marker
	{
		text-transform: uppercase;
		padding-right: 1em;
	}

	.example::before, .example > .marker {
		display: block;
		padding-right: 0em;
	}

/** Blockquotes ***************************************************************/

	blockquote {
		border-color: silver;
		border-color: var(--blockquote-border);
		background: transparent;
		background: var(--blockquote-bg);
		color: currentcolor;
		color: var(--blockquote-text);
	}

/** Open issue ****************************************************************/

	.issue {
		border-color: #e05252;
		border-color: var(--issue-border);
		background: #fbe9e9;
		background: var(--issue-bg);
		color: black;
		color: var(--issue-text);
		counter-increment: issue;
		overflow: auto;
	}
	.issue::before, .issue > .marker {
		color: #831616;
		color: var(--issueheading-text);
	}
	/* Add .issue::before { content: "Issue " counter(issue) " "; } for autogen numbers,
	  or use class="marker" to mark up the issue number in source. */

/** Example *******************************************************************/

	.example {
		border-color: #e0cb52;
		border-color: var(--example-border);
		background: #fcfaee;
		background: var(--example-bg);
		color: black;
		color: var(--example-text);
		counter-increment: example;
		overflow: auto;
		clear: both;
	}
	.example::before, .example > .marker {
		color: #574b0f;
		color: var(--exampleheading-text);
	}
	/* Add .example::before { content: "Example " counter(example) " "; } for autogen numbers,
	  or use class="marker" to mark up the example number in source. */

/** Non-normative Note ********************************************************/

	.note {
		border-color: #52e052;
		border-color: var(--note-border);
		background: #e9fbe9;
		background: var(--note-bg);
		color: black;
		color: var(--note-text);
		overflow: auto;
	}

	.note::before, .note > .marker,
	details.note > summary {
		color: hsl(120, 70%, 30%);
		color: var(--noteheading-text);
	}
	/* Add .note::before { content: "Note "; } for autogen label,
	  or use class="marker" to mark up the label in source. */

	details.note[open] > summary {
		border-bottom: 1px silver solid;
		border-bottom: 1px var(--notesummary-underline) solid;
	}

/** Assertion Box *************************************************************/
	/*  for assertions in algorithms */

	.assertion {
		border-color: #AAA;
		border-color: var(--assertion-border);
		background: #EEE;
		background: var(--assertion-bg);
		color: black;
		color: var(--assertion-text);
	}

/** Advisement Box ************************************************************/
	/*  for attention-grabbing normative statements */

	.advisement {
		border-color: orange;
		border-color: var(--advisement-border);
		border-style: none solid;
		background: #fec;
		background: var(--advisement-bg);
		color: black;
		color: var(--advisement-text);
	}
	strong.advisement {
		display: block;
		text-align: center;
	}
	.advisement::before, .advisement > .marker {
		color: #b35f00;
		color: var(--advisementheading-text);
	}

/** Amendment Box *************************************************************/

	.amendment, .correction, .addition {
		border-color: #330099;
		border-color: var(--amendment-border);
		background: #F5F0FF;
		background: var(--amendment-bg);
		color: black;
		color: var(--amendment-text);
	}
	.amendment.proposed, .correction.proposed, .addition.proposed {
		border-style: solid;
		border-block-width: 0.25em;
	}
	.amendment::before, .amendment > .marker,
	details.amendment > summary::before, details.amendment > summary > .marker,
	.correction::before, .correction > .marker,
	details.correction > summary::before, details.correction > summary > .marker,
	.addition::before, .addition > .marker,
	details.addition > summary::before, details.addition > summary > .marker {
		color: #220066;
		color: var(--amendmentheading-text);
	}
	.amendment.proposed::before, .amendment.proposed > .marker,
	details.amendment.proposed > summary::before, details.amendment.proposed > summary > .marker,
	.correction.proposed::before, .correction.proposed > .marker,
	details.correction.proposed > summary::before, details.correction.proposed > summary > .marker,
	.addition.proposed::before, .addition.proposed > .marker,
	details.addition.proposed > summary::before, details.addition.proposed > summary > .marker {
		font-weight: bold;
	}

/** Spec Obsoletion Notice ****************************************************/
	/* obnoxious obsoletion notice for older/abandoned specs. */

	details {
		display: block;
	}
	summary {
		font-weight: bolder;
	}

	.annoying-warning:not(details),
	details.annoying-warning:not([open]) > summary,
	details.annoying-warning[open] {
		background: hsla(40,100%,50%,0.95);
		background: var(--warning-bg);
		color: black;
		color: var(--warning-text);
		padding: .75em 1em;
		border: red;
		border: var(--warning-border);
		border-style: solid none;
		box-shadow: 0 2px 8px black;
		text-align: center;
	}
	.annoying-warning :last-child {
		margin-bottom: 0;
	}

@media not print {
	details.annoying-warning[open] {
		position: fixed;
		left: 0;
		right: 0;
		bottom: 2em;
		z-index: 1000;
	}
}

	details.annoying-warning:not([open]) > summary {
		text-align: center;
	}

/** Entity Definition Boxes ***************************************************/

	.def {
		padding: .5em 1em;
		background: #def;
		background: var(--def-bg);
		margin: 1.2em 0;
		border-left: 0.5em solid #8ccbf2;
		border-left: 0.5em solid var(--def-border);
		color: black;
		color: var(--def-text);
	}

/******************************************************************************/
/*                                    Tables                                  */
/******************************************************************************/

	th, td {
		text-align: left;
		text-align: start;
	}

/** Property/Descriptor Definition Tables *************************************/

	table.def {
		/* inherits .def box styling, see above */
		width: 100%;
		border-spacing: 0;
	}

	table.def td,
	table.def th {
		padding: 0.5em;
		vertical-align: baseline;
		border-bottom: 1px solid #bbd7e9;
		border-bottom: 1px solid var(--defrow-border);
	}

	table.def > tbody > tr:last-child th,
	table.def > tbody > tr:last-child td {
		border-bottom: 0;
	}

	table.def th {
		font-style: italic;
		font-weight: normal;
		padding-left: 1em;
		width: 3em;
	}

	/* For when values are extra-complex and need formatting for readability */
	table td.pre {
		white-space: pre-wrap;
	}

	/* A footnote at the bottom of a def table */
	table.def td.footnote {
		padding-top: 0.6em;
	}
	table.def td.footnote::before {
		content: " ";
		display: block;
		height: 0.6em;
		width: 4em;
		border-top: thin solid;
	}

/** Data tables (and properly marked-up index tables) *************************/
	/*
		<table class="data"> highlights structural relationships in a table
		when correct markup is used (e.g. thead/tbody, th vs. td, scope attribute)

		Use class="complex data" for particularly complicated tables --
		(This will draw more lines: busier, but clearer.)

		Use class="long" on table cells with paragraph-like contents
		(This will adjust text alignment accordingly.)
		Alternately use class="longlastcol" on tables, to have the last column assume "long".
	*/

	table {
		word-wrap: normal;
		overflow-wrap: normal;
		hyphens: manual;
	}

	table.data,
	table.index {
		margin: 1em auto;
		border-collapse: collapse;
		border: hidden;
		width: 100%;
	}
	table.data caption,
	table.index caption {
		max-width: 50em;
		margin: 0 auto 1em;
	}

	table.data td,  table.data th,
	table.index td, table.index th {
		padding: 0.5em 1em;
		border-width: 1px;
		border-color: silver;
		border-color: var(--datacell-border);
		border-top-style: solid;
	}

	table.data thead td:empty {
		padding: 0;
		border: 0;
	}

	table.data  thead,
	table.index thead,
	table.data  tbody,
	table.index tbody {
		border-bottom: 2px solid;
	}

	table.data colgroup,
	table.index colgroup {
		border-left: 2px solid;
	}

	table.data  tbody th:first-child,
	table.index tbody th:first-child  {
		border-right: 2px solid;
		border-top: 1px solid silver;
		border-top: 1px solid var(--datacell-border);
		padding-right: 1em;
	}

	table.data th[colspan],
	table.data td[colspan] {
		text-align: center;
	}

	table.complex.data th,
	table.complex.data td {
		border: 1px solid silver;
		border: 1px solid var(--datacell-border);
		text-align: center;
	}

	table.data.longlastcol td:last-child,
	table.data td.long {
		vertical-align: baseline;
		text-align: left;
	}

	table.data img {
		vertical-align: middle;
	}


/*
Alternate table alignment rules

	table.data,
	table.index {
		text-align: center;
	}

	table.data  thead th[scope="row"],
	table.index thead th[scope="row"] {
		text-align: right;
	}

	table.data  tbody th:first-child,
	table.index tbody th:first-child  {
		text-align: right;
	}

Possible extra rowspan handling

	table.data  tbody th[rowspan]:not([rowspan='1']),
	table.index tbody th[rowspan]:not([rowspan='1']),
	table.data  tbody td[rowspan]:not([rowspan='1']),
	table.index tbody td[rowspan]:not([rowspan='1']) {
		border-left: 1px solid silver;
	}

	table.data  tbody th[rowspan]:first-child,
	table.index tbody th[rowspan]:first-child,
	table.data  tbody td[rowspan]:first-child,
	table.index tbody td[rowspan]:first-child{
		border-left: 0;
		border-right: 1px solid silver;
	}
*/

/******************************************************************************/
/*                                  Indices                                   */
/******************************************************************************/


/** Table of Contents *********************************************************/

	.toc a {
		/* More spacing; use padding to make it part of the click target. */
		padding: 0.1rem 1px 0;
		/* Larger, more consistently-sized click target */
		display: block;
		/* Switch to using border-bottom for underlines */
		text-decoration: none;
		border-bottom: 1px solid;
		/* Reverse color scheme */
		color: black;
		color: var(--toclink-text);
		border-color: #3980b5;
		border-color: var(--toclink-underline);
	}
	.toc a:visited {
		color: black;
		color: var(--toclink-visited-text);
		border-color: #054572;
		border-color: var(--toclink-visited-underline);
	}
	.toc a:focus,
	.toc a:hover {
		background: rgba(75%, 75%, 75%, .25);
		background: var(--a-hover-bg);
		border-bottom-width: 3px;
		margin-bottom: -2px;
	}
	.toc a:not(:focus):not(:hover) {
		/* Allow colors to cascade through from link styling */
		border-bottom-color: transparent;
	}

	.toc, .toc ol, .toc ul, .toc li {
		list-style: none; /* Numbers must be inlined into source */
		/* because generated content isn't search/selectable and markers can't do multilevel yet */
		margin:  0;
		padding: 0;
	}
	.toc {
		line-height: 1.1em;
	}

	/* ToC not indented until third level, but font style & margins show hierarchy */
	.toc > li			{ font-weight: bold;   }
	.toc > li li		 { font-weight: normal; }
	.toc > li li li	  { font-size:   95%;	}
	.toc > li li li li	{ font-size:   90%;	}
	.toc > li li li li li { font-size:   85%;	}

	/* @supports not (display:grid) { */
		.toc > li			{ margin: 1.5rem 0;	}
		.toc > li li		 { margin: 0.3rem 0;	}
		.toc > li li li	  { margin-left: 2rem;   }

		/* Section numbers in a column of their own */
		.toc .secno {
			float: left;
			width: 4rem;
			white-space: nowrap;
		}
		.toc > li li li li .secno { font-size: 85%; }
		.toc > li li li li li .secno { font-size: 100%; }

		.toc li {
			clear: both;
		}

		:not(li) > .toc			 { margin-left:  5rem; }
		.toc .secno				 { margin-left: -5rem; }
		.toc > li li li .secno	  { margin-left: -7rem; }
		.toc > li li li li .secno	{ margin-left: -9rem; }
		.toc > li li li li li .secno { margin-left: -11rem; }

		/* Tighten up indentation in narrow ToCs */
		@media (max-width: 30em) {
			:not(li) > .toc			 { margin-left:  4rem; }
			.toc .secno				 { margin-left: -4rem; }
			.toc > li li li			 { margin-left:  1rem; }
			.toc > li li li .secno	  { margin-left: -5rem; }
			.toc > li li li li .secno	{ margin-left: -6rem; }
			.toc > li li li li li .secno { margin-left: -7rem; }
		}
		/* Loosen it on wide screens */
		@media screen and (min-width: 78em) {
			body:not(.toc-inline) :not(li) > .toc			 { margin-left:  4rem; }
			body:not(.toc-inline) .toc .secno				 { margin-left: -4rem; }
			body:not(.toc-inline) .toc > li li li			 { margin-left:  1rem; }
			body:not(.toc-inline) .toc > li li li .secno	  { margin-left: -5rem; }
			body:not(.toc-inline) .toc > li li li li .secno	{ margin-left: -6rem; }
			body:not(.toc-inline) .toc > li li li li li .secno { margin-left: -7rem; }
	}
	/* } */

	@supports (display:grid) and (display:contents) {
		/* Use #toc over .toc to override non-@supports rules. */
		#toc {
			display: grid;
			align-content: start;
			grid-template-columns: auto 1fr;
			grid-column-gap: 1rem;
			column-gap: 1rem;
			grid-row-gap: .6rem;
			row-gap: .6rem;
		}
		#toc h2 {
			grid-column: 1 / -1;
			margin-bottom: 0;
		}
		#toc ol,
		#toc li,
		#toc a {
			display: contents;
			/* Switch <a> to subgrid when supported */
		}
		#toc span {
			margin: 0;
		}
		#toc > .toc > li > a > span {
			/* The spans of the top-level list,
			  comprising the first items of each top-level section. */
			margin-top: 1.1rem;
		}
		#toc#toc .secno { /* Ugh, need more specificity to override base.css */
			grid-column: 1;
			width: auto;
			margin-left: 0;
		}
		#toc .content {
			grid-column: 2;
			width: auto;
			margin-right: 1rem;
			border-bottom: 3px solid transparent;
			margin-bottom: -3px;
		}
		#toc .content:hover,
		#toc .content:focus {
			background: rgba(75%, 75%, 75%, .25);
			background: var(--a-hover-bg);
			border-bottom-color: #054572;
			border-bottom-color: var(--toclink-underline);
		}
		#toc li li li .content {
			margin-left: 1rem;
		}
		#toc li li li li .content {
			margin-left: 2rem;
		}
	}


/** Index *********************************************************************/

	/* Index Lists: Layout */
	ul.index	  { margin-left: 0; columns: 15em; text-indent: 1em hanging; }
	ul.index li	{ margin-left: 0; list-style: none; break-inside: avoid; }
	ul.index li li { margin-left: 1em; }
	ul.index dl	{ margin-top: 0; }
	ul.index dt	{ margin: .2em 0 .2em 20px;}
	ul.index dd	{ margin: .2em 0 .2em 40px;}
	/* Index Lists: Typography */
	ul.index ul,
	ul.index dl { font-size: smaller; }
	@media not print {
		ul.index li a + span {
			white-space: nowrap;
			color: transparent; }
		ul.index li a:hover + span,
		ul.index li a:focus + span {
			color: #707070;
			color: var(--indexinfo-text);
		}
	}

/** Index Tables *****************************************************/
	/* See also the data table styling section, which this effectively subclasses */

	table.index {
		font-size: small;
		border-collapse: collapse;
		border-spacing: 0;
		text-align: left;
		margin: 1em 0;
	}

	table.index td,
	table.index th {
		padding: 0.4em;
	}

	table.index tr:hover td:not([rowspan]),
	table.index tr:hover th:not([rowspan]) {
		color: black;
		color: var(--indextable-hover-text);
		background: #f7f8f9;
		background: var(--indextable-hover-bg);
	}

	/* The link in the first column in the property table (formerly a TD) */
	table.index th:first-child a {
		font-weight: bold;
	}

/** Outdated warning **********************************************************/

.outdated-spec {
	color: black;
	color: var(--outdatedspec-text);
	background-color: rgba(0,0,0,0.5);
	background-color: var(--outdatedspec-bg);
}

.outdated-warning {
	position: fixed;
	bottom: 50%;
	left: 0;
	right: 0;
	margin: 0 auto;
	width: 50%;
	background: maroon;
	background: var(--outdated-bg);
	color: white;
	color: var(--outdated-text);
	border-radius: 1em;
	box-shadow: 0 0 1em red;
	box-shadow: 0 0 1em var(--outdated-shadow);
	padding: 2em;
	text-align: center;
	z-index: 2;
}

.outdated-warning a {
	color: currentcolor;
	background: transparent;
}

.edited-rec-warning {
	background: darkorange;
	background: var(--editedrec-bg);
	box-shadow: 0 0 1em;
}

.outdated-warning button {
	color: var(--outdated-text);
	border-radius: 1em;
	box-shadow: 0 0 1em red;
	box-shadow: 0 0 1em var(--outdated-shadow);
	padding: 2em;
	text-align: center;
	z-index: 2;
}

.outdated-warning a {
	color: currentcolor;
	background: transparent;
}

.edited-rec-warning {
	background: darkorange;
	background: var(--editedrec-bg);
	box-shadow: 0 0 1em;
}

.outdated-warning button {
	position: absolute;
	top: 0;
	right:0;
	margin: 0;
	border: 0;
	padding: 0.25em 0.5em;
	background: transparent;
	color: white;
	color: var(--outdated-text);
	font:1em sans-serif;
	text-align:center;
}

.outdated-warning span {
	display: block;
}

.outdated-collapsed {
	bottom: 0;
	border-radius: 0;
	width: 100%;
	padding: 0;
}

/******************************************************************************/
/*                                    Print                                   */
/******************************************************************************/

	@media print {
		/* Pages have their own margins. */
		html {
			margin: 0;
		}
		/* Serif for print. */
		body {
			font-family: serif;
		}

		.outdated-warning {
			position: absolute;
			border-style: solid;
			border-color: red;
		}

		.outdated-warning input {
			display: none;
		}
	}
	@page {
		margin: 1.5cm 1.1cm;
	}



/******************************************************************************/
/*                             Overflow Control                               */
/******************************************************************************/

	.figure .caption, .sidefigure .caption, figcaption {
		/* in case figure is overlarge, limit caption to 50em */
		max-width: 50rem;
		margin-left: auto;
		margin-right: auto;
	}
	.overlarge {
		/* Magic to create good item positioning:
		  "content column" is 50ems wide at max; less on smaller screens.
		  Extra space (after ToC + content) is empty on the right.

		  1. When item < content column, centers item in column.
		  2. When content < item < available, left-aligns.
		  3. When item > available, fills available + scroll bar.
		*/
		display: grid;
		grid-template-columns: minmax(0, 50em);
	}
	.overlarge > table {
		/* limit preferred width of table */
		max-width: 50em;
		margin-left: auto;
		margin-right: auto;
	}

	@media (min-width: 55em) {
		.overlarge {
			margin-right: calc(13px + 26.5rem - 50vw);
			max-width: none;
		}
	}
	@media screen and (min-width: 78em) {
		body:not(.toc-inline) .overlarge {
			/* 30.5em body padding 50em content area */
			margin-right: calc(40em - 50vw) !important;
		}
	}
	@media screen and (min-width: 90em) {
		body:not(.toc-inline) .overlarge {
			/* 4em html margin 30.5em body padding 50em content area */
			margin-right: calc(84.5em - 100vw) !important;
		}
	}

	@media not print {
		.overlarge {
			overflow-x: auto;
			/* See Lea Verou's explanation background-attachment:
			* http://lea.verou.me/2012/04/background-attachment-local/
			*
			background: top left  / 4em 100% linear-gradient(to right,  #ffffff, rgba(255, 255, 255, 0)) local,
						top right / 4em 100% linear-gradient(to left, #ffffff, rgba(255, 255, 255, 0)) local,
						top left  / 1em 100% linear-gradient(to right,  #c3c3c5, rgba(195, 195, 197, 0)) scroll,
						top right / 1em 100% linear-gradient(to left, #c3c3c5, rgba(195, 195, 197, 0)) scroll,
						white;
			background-repeat: no-repeat;
			*/
		}
	}
</style>
<style>
    table, th, td {
      border: 1px solid black;
      border-collapse: collapse;
      vertical-align: top;
    }
    th, td {
      border-left: none;
      border-right: none;
      padding: 0px 10px;
    }
    th {
      text-align: center;
    }

    del { background: #fcc; color: #000; text-decoration: line-through; }
    ins { background: #cfc; color: #000; }
    blockquote .highlight:not(.idl) { background: initial; margin: initial; padding: 0.5em }
    blockquote ul { background: inherit; }
    blockquote code.highlight:not(.idl) { padding: initial; }
    blockquote c-[a] { color: inherit; } /* Keyword.Declaration */
    blockquote c-[b] { color: inherit; } /* Keyword.Type */
    blockquote c-[c] { color: inherit; } /* Comment */
    blockquote c-[d] { color: inherit; } /* Comment.Multiline */
    blockquote c-[e] { color: inherit; } /* Name.Attribute */
    blockquote c-[f] { color: inherit; } /* Name.Tag */
    blockquote c-[g] { color: inherit; } /* Name.Variable */
    blockquote c-[k] { color: inherit; } /* Keyword */
    blockquote c-[l] { color: inherit; } /* Literal */
    blockquote c-[m] { color: inherit; } /* Literal.Number */
    blockquote c-[n] { color: inherit; } /* Name */
    blockquote c-[o] { color: inherit; } /* Operator */
    blockquote c-[p] { color: inherit; } /* Punctuation */
    blockquote c-[s] { color: inherit; } /* Literal.String */
    blockquote c-[t] { color: inherit; } /* Literal.String.Single */
    blockquote c-[u] { color: inherit; } /* Literal.String.Double */
    blockquote c-[cp] { color: inherit; } /* Comment.Preproc */
    blockquote c-[c1] { color: inherit; } /* Comment.Single */
    blockquote c-[cs] { color: inherit; } /* Comment.Special */
    blockquote c-[kc] { color: inherit; } /* Keyword.Constant */
    blockquote c-[kn] { color: inherit; } /* Keyword.Namespace */
    blockquote c-[kp] { color: inherit; } /* Keyword.Pseudo */
    blockquote c-[kr] { color: inherit; } /* Keyword.Reserved */
    blockquote c-[ld] { color: inherit; } /* Literal.Date */
    blockquote c-[nc] { color: inherit; } /* Name.Class */
    blockquote c-[no] { color: inherit; } /* Name.Constant */
    blockquote c-[nd] { color: inherit; } /* Name.Decorator */
    blockquote c-[ni] { color: inherit; } /* Name.Entity */
    blockquote c-[ne] { color: inherit; } /* Name.Exception */
    blockquote c-[nf] { color: inherit; } /* Name.Function */
    blockquote c-[nl] { color: inherit; } /* Name.Label */
    blockquote c-[nn] { color: inherit; } /* Name.Namespace */
    blockquote c-[py] { color: inherit; } /* Name.Property */
    blockquote c-[ow] { color: inherit; } /* Operator.Word */
    blockquote c-[mb] { color: inherit; } /* Literal.Number.Bin */
    blockquote c-[mf] { color: inherit; } /* Literal.Number.Float */
    blockquote c-[mh] { color: inherit; } /* Literal.Number.Hex */
    blockquote c-[mi] { color: inherit; } /* Literal.Number.Integer */
    blockquote c-[mo] { color: inherit; } /* Literal.Number.Oct */
    blockquote c-[sb] { color: inherit; } /* Literal.String.Backtick */
    blockquote c-[sc] { color: inherit; } /* Literal.String.Char */
    blockquote c-[sd] { color: inherit; } /* Literal.String.Doc */
    blockquote c-[se] { color: inherit; } /* Literal.String.Escape */
    blockquote c-[sh] { color: inherit; } /* Literal.String.Heredoc */
    blockquote c-[si] { color: inherit; } /* Literal.String.Interpol */
    blockquote c-[sx] { color: inherit; } /* Literal.String.Other */
    blockquote c-[sr] { color: inherit; } /* Literal.String.Regex */
    blockquote c-[ss] { color: inherit; } /* Literal.String.Symbol */
    blockquote c-[vc] { color: inherit; } /* Name.Variable.Class */
    blockquote c-[vg] { color: inherit; } /* Name.Variable.Global */
    blockquote c-[vi] { color: inherit; } /* Name.Variable.Instance */
    blockquote c-[il] { color: inherit; } /* Literal.Number.Integer.Long */
  </style>
  <meta content="Bikeshed version d29f71adb, updated Wed Jul 19 11:08:56 2023 -0700" name="generator">
  <link href="https://isocpp.org/favicon.ico" rel="icon">
<style>
hilite  {background-color: #FFFF00; font-weight: bold;}
ins  {background-color: #CCFFCC; text-decoration: underline;}
del  {background-color: #FFCACA; text-decoration: line-through;}
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 <body class="h-entry">
  <div class="head">
   <p data-fill-with="logo"></p>
   <h1 class="p-name no-ref" id="title">P2953R0<br>Forbid defaulting operator=(X&amp;&amp;) &amp;&amp;</h1>
   <h2 class="no-num no-toc no-ref heading settled" id="profile-and-date"><span class="content">Published Proposal, <time class="dt-updated" datetime="2023-08-10">2023-08-10</time></span></h2>
   <div data-fill-with="spec-metadata">
    <dl>
     <dt class="editor">Author:
     <dd class="editor p-author h-card vcard"><a class="p-name fn u-email email" href="mailto:arthur.j.odwyer@gmail.com">Arthur O'Dwyer</a>
     <dt>Audience:
     <dd>EWG
     <dt>Project:
     <dd>ISO/IEC 14882 Programming Languages — C++, ISO/IEC JTC1/SC22/WG21
     <dt>Draft Revision:
     <dd>4
    </dl>
   </div>
   <div data-fill-with="warning"></div>
   <hr title="Separator for header">
  </div>
  <div class="p-summary" data-fill-with="abstract">
   <h2 class="no-num no-toc no-ref heading settled" id="abstract"><span class="content">Abstract</span></h2>
   <p>Current C++ permits explicitly-defaulted special members to differ from their

  implicitly-defaulted counterparts in various ways, including parameter type and
  ref-qualification. This permits implausible
  signatures like <code class="highlight"><c- n>A</c-><c- o>&amp;</c-> <c- k>operator</c-><c- o>=</c-><c- p>(</c-><c- k>const</c-> <c- n>A</c-><c- o>&amp;</c-><c- p>)</c-> <c- o>&amp;&amp;</c-> <c- o>=</c-> <c- k>default</c-></code>, where the left-hand
  operand is rvalue-ref-qualified. We propose to forbid such signatures.</p>
  </div>
  <nav data-fill-with="table-of-contents" id="toc">
   <h2 class="no-num no-toc no-ref" id="contents">Table of Contents</h2>
   <ol class="toc" role="directory">
    <li><a href="#changelog"><span class="secno">1</span> <span class="content">Changelog</span></a>
    <li>
     <a href="#proposal"><span class="secno">2</span> <span class="content">Motivation and proposal</span></a>
     <ol class="toc">
      <li><a href="#p2952"><span class="secno">2.1</span> <span class="content">Interaction with P2952</span></a>
      <li><a href="#deleted-versus-ill-formed"><span class="secno">2.2</span> <span class="content">"Deleted" versus "ill-formed"</span></a>
      <li><a href="#corner-cases"><span class="secno">2.3</span> <span class="content">Existing corner cases</span></a>
      <li><a href="#impact"><span class="secno">2.4</span> <span class="content">Impact on existing code</span></a>
     </ol>
    <li><a href="#experience"><span class="secno">3</span> <span class="content">Implementation experience</span></a>
    <li>
     <a href="#wording"><span class="secno">4</span> <span class="content">Proposed wording</span></a>
     <ol class="toc">
      <li><a href="#wording-dcl.fct.def.default"><span class="secno">4.1</span> <span class="content">[dcl.fct.def.default]</span></a>
      <li><a href="#wording-class.copy.assign"><span class="secno">4.2</span> <span class="content">[class.copy.assign]</span></a>
     </ol>
    <li><a href="#straw-polls"><span class="secno">5</span> <span class="content">Proposed straw polls</span></a>
    <li>
     <a href="#references"><span class="secno"></span> <span class="content">References</span></a>
     <ol class="toc">
      <li><a href="#informative"><span class="secno"></span> <span class="content">Informative References</span></a>
     </ol>
   </ol>
  </nav>
  <main>
   <h2 class="heading settled" data-level="1" id="changelog"><span class="secno">1. </span><span class="content">Changelog</span><a class="self-link" href="#changelog"></a></h2>
   <ul>
    <li data-md>
     <p>R0:</p>
     <ul>
      <li data-md>
       <p>Initial revision.</p>
     </ul>
   </ul>
   <h2 class="heading settled" data-level="2" id="proposal"><span class="secno">2. </span><span class="content">Motivation and proposal</span><a class="self-link" href="#proposal"></a></h2>
   <p>Currently, <a href="https://eel.is/c++draft/dcl.fct.def.default#2.5">[dcl.fct.def.default]/2.5</a> permits an explicitly defaulted special member function to differ from the
implicit one by adding <i>ref-qualifiers</i>, but not <i>cv-qualifiers</i>.</p>
   <p>For example, the signature <code class="highlight"><c- k>const</c-> <c- n>A</c-><c- o>&amp;</c-> <c- k>operator</c-><c- o>=</c-><c- p>(</c-><c- k>const</c-> <c- n>A</c-><c- o>&amp;</c-><c- p>)</c-> <c- k>const</c-><c- o>&amp;</c-> <c- o>=</c-> <c- k>default</c-></code> is forbidden
because it is additionally const-qualified, and also because its return type differs
from the implicitly-defaulted <code class="highlight"><c- n>A</c-><c- o>&amp;</c-></code>. This might be considered unfortunate, because that’s
a reasonable signature for a const-assignable proxy-reference type.
But programmers aren’t clamoring for that signature to be supported, so we do not propose to support it here.</p>
   <p>Our concern is that the <em>unrealistic</em> signature <code class="highlight"><c- n>A</c-><c- o>&amp;</c-> <c- k>operator</c-><c- o>=</c-><c- p>(</c-><c- k>const</c-> <c- n>A</c-><c- o>&amp;</c-><c- p>)</c-> <c- o>&amp;&amp;</c-> <c- o>=</c-> <c- k>default</c-></code> is <em>permitted!</em> This has three minor drawbacks:</p>
   <ul>
    <li data-md>
     <p>The possibility of these unrealistic signatures makes C++ harder to understand.
Before writing <a data-link-type="biblio" href="#biblio-p2952" title="auto&amp; operator=(X&amp;&amp;) = default">[P2952]</a>, Arthur didn’t know such signatures were possible.</p>
    <li data-md>
     <p>The wording to permit these signatures is at least a tiny bit more complicated than
if they weren’t permitted.</p>
    <li data-md>
     <p>The quirky interaction with <a data-link-type="biblio" href="#biblio-cwg2586" title="Explicit object parameter for assignment and comparison">[CWG2586]</a> and <a data-link-type="biblio" href="#biblio-p2952" title="auto&amp; operator=(X&amp;&amp;) = default">[P2952]</a> discussed in the next subsection.</p>
   </ul>
   <p>To eliminate all three drawbacks,
we propose that a defaulted copy/move assignment operator should not be permitted to add
to its implicit signature an <em>rvalue</em> ref-qualifier (nor an explicit object parameter
of rvalue reference type).</p>
   <h3 class="heading settled" data-level="2.1" id="p2952"><span class="secno">2.1. </span><span class="content">Interaction with P2952</span><a class="self-link" href="#p2952"></a></h3>
   <p><a data-link-type="biblio" href="#biblio-cwg2586" title="Explicit object parameter for assignment and comparison">[CWG2586]</a> (adopted for C++23) permits <code class="highlight"><c- k>operator</c-><c- o>=</c-></code> to have an explicit object parameter.</p>
   <p><a data-link-type="biblio" href="#biblio-p2952" title="auto&amp; operator=(X&amp;&amp;) = default">[P2952]</a> proposes that <code class="highlight"><c- k>operator</c-><c- o>=</c-></code> should (also) be allowed to have a placeholder return type.
If P2952 is adopted without P2953, then we will have the following pub-quiz fodder:</p>
<pre class="language-cpp highlight"><c- k>struct</c-> <c- nc>C</c-> <c- p>{</c->
  <c- k>auto</c-><c- o>&amp;&amp;</c-> <c- k>operator</c-><c- o>=</c-><c- p>(</c-><c- k>this</c-> <c- n>C</c-><c- o>&amp;&amp;</c-> <c- n>self</c-><c- p>,</c-> <c- k>const</c-> <c- n>C</c-><c- o>&amp;</c-><c- p>)</c-> <c- p>{</c-> <c- k>return</c-> <c- n>self</c-><c- p>;</c-> <c- p>}</c->
    <c- c1>// Today: OK, deduces C&amp;&amp;</c->
    <c- c1>// After P2952: Still OK, still deduces C&amp;&amp;</c->
    <c- c1>// Proposed: Still OK, still deduces C&amp;&amp;</c->

  <c- k>auto</c-><c- o>&amp;&amp;</c-> <c- k>operator</c-><c- o>=</c-><c- p>(</c-><c- k>this</c-> <c- n>C</c-><c- o>&amp;&amp;</c-> <c- n>self</c-><c- p>,</c-> <c- k>const</c-> <c- n>C</c-><c- o>&amp;</c-><c- p>)</c-> <c- o>=</c-> <c- k>default</c-><c- p>;</c->
    <c- c1>// Today: Ill-formed, return type involves placeholder</c->
    <c- c1>// After P2952: OK, deduces C&amp;</c->
    <c- c1>// Proposed: Deleted, object parameter is not C&amp;</c->
<c- p>};</c->
</pre>
   <p>The first, non-defaulted, operator "does the natural thing" by returning its left-hand operand,
and deduces <code class="highlight"><c- n>C</c-><c- o>&amp;&amp;</c-></code>. The second operator also "does the natural thing" by being defaulted; but
after P2952 it will deduce <code class="highlight"><c- n>C</c-><c- o>&amp;</c-></code>. (For rationale, see <a data-link-type="biblio" href="#biblio-p2952" title="auto&amp; operator=(X&amp;&amp;) = default">[P2952]</a> §3.3 "Deducing <code class="highlight"><c- k>this</c-></code> and CWG2586.")
The two "natural" implementations deduce different types! This might be perceived as inconsistency.</p>
   <p>If we adopt P2953 alongside P2952, then the second <code class="highlight"><c- k>operator</c-><c- o>=</c-></code> will go back to being unusable,
which reduces the perception of inconsistency.</p>
   <table>
    <tbody>
     <tr>
      <td>
      <th>Today
      <th>P2952
     <tr>
      <th>Today
      <td><code class="highlight"><c- n>C</c-><c- o>&amp;&amp;</c-></code>/ill-formed
      <td><code class="highlight"><c- n>C</c-><c- o>&amp;&amp;</c-></code>/<code class="highlight"><c- n>C</c-><c- o>&amp;</c-></code>
     <tr>
      <th>P2953
      <td><code class="highlight"><c- n>C</c-><c- o>&amp;&amp;</c-></code>/ill-formed
      <td><code class="highlight"><c- n>C</c-><c- o>&amp;&amp;</c-></code>/deleted
   </table>
   <h3 class="heading settled" data-level="2.2" id="deleted-versus-ill-formed"><span class="secno">2.2. </span><span class="content">"Deleted" versus "ill-formed"</span><a class="self-link" href="#deleted-versus-ill-formed"></a></h3>
   <p><a href="https://eel.is/c++draft/dcl.fct.def.default">[dcl.fct.def.default]</a> goes out of its way
to make many explicitly defaulted assignment operators "defaulted as deleted," rather than ill-formed.
I think I understand the reason for this in the case of <em>comparison operators</em> (see <a data-link-type="biblio" href="#biblio-p2952" title="auto&amp; operator=(X&amp;&amp;) = default">[P2952]</a> §3.2 "Defaulted as deleted"), but it’s non-obvious why we should care about
the corresponding cases for constructors, destructors, and assignment operators.
(Clang handles this example correctly; GCC, MSVC, and EDG
already non-conformingly treat <em>both</em> <code class="highlight"><c- n>cl</c-></code> and <code class="highlight"><c- n>cr</c-></code> as ill-formed.)</p>
<pre class="language-cpp highlight"><c- k>template</c-><c- o>&lt;</c-><c- k>template</c-><c- o>&lt;</c-><c- k>class</c-><c- o>></c-> <c- k>class</c-> <c- nc>TT</c-><c- o>></c->
<c- k>struct</c-> <c- nc>C</c-> <c- p>{</c->
  <c- n>C</c-><c- o>&amp;</c-> <c- k>operator</c-><c- o>=</c-><c- p>(</c-><c- n>TT</c-><c- o>&lt;</c-><c- k>const</c-> <c- n>C</c-><c- o>></c-><c- p>)</c-> <c- o>=</c-> <c- k>default</c-><c- p>;</c->
<c- p>};</c->

<c- n>C</c-><c- o>&lt;</c-><c- n>std</c-><c- o>::</c-><c- n>add_lvalue_reference_t</c-><c- o>></c-> <c- n>cl</c-><c- p>;</c->
  <c- c1>// OK, operator= is defaulted</c->
  <c- c1>// (and GCC/MSVC/EDG have a bug)</c->

<c- n>C</c-><c- o>&lt;</c-><c- n>std</c-><c- o>::</c-><c- n>add_rvalue_reference_t</c-><c- o>></c-> <c- n>cr</c-><c- p>;</c->
  <c- c1>// OK, operator= is defaulted as deleted</c->
  <c- c1>// (but why not just make it ill-formed?)</c->
</pre>
   <p>P2953 isn’t yet proposing to change the complicated status quo, but Arthur would certainly like
to learn the status quo’s rationale. If we were willing to aggressively change the status quo,
we could simplify <a href="https://eel.is/c++draft/dcl.fct.def.default">[dcl.fct.def.default]</a> something like this:</p>
   <p><small></small></p>
   <blockquote><small> 1․ A function definition whose <i>function-body</i> is of the form <code class="highlight"><c- o>=</c-> <c- k>default</c-> <c- p>;</c-></code> is called an <i>explicitly-defaulted</i> definition.
A function that is explicitly defaulted shall<p></p> <ul><li data-md><p>(1.1) be a special member function or a comparison operator function ([over.binary]), and</p> </li><li data-md><p>(1.2) not have default arguments.</p> </li></ul> <p>2․ An explicitly defaulted special member function <code class="highlight"><c- n>F</c-></code><sub>1</sub> is allowed to differ
from the corresponding special member function <code class="highlight"><c- n>F</c-></code><sub>2</sub> that would have been implicitly declared, as follows: </p><ul><li data-md><p>(2.1) <ins>if <code class="highlight"><c- n>F</c-></code><sub>2</sub> is an assignment operator,</ins> <del><code class="highlight"><c- n>F</c-></code><sub>1</sub> and <code class="highlight"><c- n>F</c-></code><sub>2</sub> may have differing <i>ref-qualifiers</i></del> <ins><code class="highlight"><c- n>F</c-></code><sub>1</sub> may have an lvalue <i>ref-qualifier</i></ins>;</p> </li><li data-md><p>(2.2) if <code class="highlight"><c- n>F</c-></code><sub>2</sub> <del>has an implicit object parameter of type “reference to C”</del> <ins>is
an assignment operator with an implicit object parameter of type <code class="highlight"><c- n>C</c-><c- o>&amp;</c-></code></ins>, <code class="highlight"><c- n>F</c-></code><sub>1</sub> may <del>be an explicit object member function whose</del> <ins>have an</ins> explicit
object parameter <del>is</del> of type <del>(possibly
different) “reference to C”</del> <ins><code class="highlight"><c- n>C</c-><c- o>&amp;</c-></code></ins>, in which case the type of <code class="highlight"><c- n>F</c-></code><sub>1</sub> would differ from the type of <code class="highlight"><c- n>F</c-></code><sub>2</sub> in that the type of <code class="highlight"><c- n>F</c-></code><sub>1</sub> has an additional parameter; <ins>and</ins></p> </li><li data-md><p>(2.3) <code class="highlight"><c- n>F</c-></code><sub>1</sub> and <code class="highlight"><c- n>F</c-></code><sub>2</sub> may have differing exception specifications<ins>.</ins> <del>; and</del></p> </li><li data-md><del>(2.4) if <code class="highlight"><c- n>F</c-></code><sub>2</sub> has a non-object parameter of type <code class="highlight"><c- k>const</c-> <c- n>C</c-><c- o>&amp;</c-></code>, the corresponding
non-object parameter of <code class="highlight"><c- n>F</c-></code><sub>1</sub> may be of type <code class="highlight"><c- n>C</c-><c- o>&amp;</c-></code>.</del> </li></ul> <p>If the type of <code class="highlight"><c- n>F</c-></code><sub>1</sub> differs from the type of <code class="highlight"><c- n>F</c-></code><sub>2</sub> in a way other than as allowed by the preceding rules, then: </p><ul><li data-md><del>(2.5) if <code class="highlight"><c- n>F</c-></code><sub>1</sub> is an assignment operator, and the return type of <code class="highlight"><c- n>F</c-></code><sub>1</sub> differs from the return type of <code class="highlight"><c- n>F</c-></code><sub>2</sub> or <code class="highlight"><c- n>F</c-></code><sub>1</sub>’s non-object parameter type is not a reference, the program is ill-formed;</del> </li><li data-md><p>(2.6) <del>otherwise,</del> if <code class="highlight"><c- n>F</c-></code><sub>1</sub> is <ins>a three-way comparison operator</ins> explicitly
defaulted on its first declaration, it is defined as deleted;</p> </li><li data-md><p>(2.7) otherwise, the program is ill-formed.</p> </li></ul> <p>[...] </p></small></blockquote>
   <p>Again, P2953 doesn’t yet propose the above change; but it would be good to know why we shouldn’t.</p>
   <h3 class="heading settled" data-level="2.3" id="corner-cases"><span class="secno">2.3. </span><span class="content">Existing corner cases</span><a class="self-link" href="#corner-cases"></a></h3>
   <p>There is vendor divergence in some corner cases. Here is a table of the divergences we found,
plus our opinion as to the conforming behavior, and our proposed behavior.</p>
   <p><small></small></p>
   <p></p>
   <table>
    <tbody>
     <tr>
      <th>URL
      <th>Code
      <th>Clang
      <th>GCC
      <th>MSVC
      <th>EDG
      <th>Correct
     <tr>
      <td><a href="https://godbolt.org/z/WezedYYE3">link</a>
      <td>
<pre class="highlight"><c- n>C</c-><c- o>&amp;</c-> <c- k>operator</c-><c- o>=</c-><c- p>(</c-><c- n>C</c-><c- o>&amp;</c-><c- p>)</c-> <c- o>=</c-> <c- k>default</c-><c- p>;</c-></pre>
      <td>✓
      <td>✓
      <td>✓
      <td>✓
      <td>✓<br>(§2.2: ✗)
     <tr>
      <td><a href="https://godbolt.org/z/hxc9za5KT">link</a>
      <td>
<pre class="highlight"><c- n>C</c-><c- o>&amp;</c-> <c- k>operator</c-><c- o>=</c-><c- p>(</c-><c- k>const</c-> <c- n>C</c-><c- o>&amp;&amp;</c-><c- p>)</c-> <c- o>=</c-> <c- k>default</c-><c- p>;</c-></pre>
      <td>deleted
      <td bgcolor="#FFCACA">✗
      <td bgcolor="#FFCACA">✗
      <td>deleted
      <td><a href="https://eel.is/c++draft/dcl.fct.def.default#2.6">deleted</a><br>(§2.2: ✗)
     <tr>
      <td><a href="https://godbolt.org/z/ojM541bTM">link</a>
      <td>
<pre class="highlight"><c- n>C</c-><c- o>&amp;</c-> <c- k>operator</c-><c- o>=</c-><c- p>(</c-><c- k>const</c-> <c- n>C</c-><c- o>&amp;</c-><c- p>)</c-> <c- k>const</c-> <c- o>=</c-> <c- k>default</c-><c- p>;</c-></pre>
      <td>deleted
      <td bgcolor="#FFCACA">✗
      <td bgcolor="#FFCACA">✗
      <td>deleted
      <td><a href="https://eel.is/c++draft/dcl.fct.def.default#2.6">deleted</a><br>(§2.2: ✗)
     <tr>
      <td><a href="https://godbolt.org/z/hchco3rcK">link</a>
      <td>
<pre class="highlight"><c- n>C</c-><c- o>&amp;</c-> <c- k>operator</c-><c- o>=</c-><c- p>(</c-><c- k>const</c-> <c- n>C</c-><c- o>&amp;</c-><c- p>)</c-> <c- o>&amp;&amp;</c-> <c- o>=</c-> <c- k>default</c-><c- p>;</c-></pre>
      <td>✓
      <td>✓
      <td>✓
      <td>✓
      <td>Today: <a href="https://eel.is/c++draft/dcl.fct.def.default#2.1">✓</a><br>Proposed: deleted<br>(§2.2: ✗)
     <tr>
      <td><a href="https://godbolt.org/z/5P6EKrGjo">link</a>
      <td>
<pre class="highlight"><c- n>C</c-><c- o>&amp;&amp;</c-> <c- k>operator</c-><c- o>=</c-><c- p>(</c-><c- k>const</c-> <c- n>C</c-><c- o>&amp;</c-><c- p>)</c-> <c- o>&amp;&amp;</c-> <c- o>=</c-> <c- k>default</c-><c- p>;</c-></pre>
      <td>✗
      <td>✗
      <td>✗
      <td>✗
      <td><a href="https://eel.is/c++draft/dcl.fct.def.default#2.5">✗</a>
     <tr>
      <td><a href="https://godbolt.org/z/Th33Meeez">link</a>
      <td>
<pre class="highlight"><c- k>template</c-><c- o>&lt;</c-><c- k>class</c-><c- o>></c->
<c- k>struct</c-> <c- nc>C</c-> <c- p>{</c->
  <c- n>C</c-><c- o>&amp;</c-> <c- k>operator</c-><c- o>=</c-><c- p>(</c-><c- n>std</c-><c- o>::</c-><c- n>add_lvalue_reference_t</c-><c- o>&lt;</c-><c- k>const</c-> <c- n>C</c-><c- o>></c-><c- p>)</c-> <c- o>=</c-> <c- k>default</c-><c- p>;</c->
<c- p>};</c-></pre>
      <td>✓
      <td bgcolor="#FFCACA">✗
      <td bgcolor="#FFCACA">✗
      <td bgcolor="#FFCACA">✗
      <td>✓
   </table>
   <h3 class="heading settled" data-level="2.4" id="impact"><span class="secno">2.4. </span><span class="content">Impact on existing code</span><a class="self-link" href="#impact"></a></h3>
   <p>This proposal takes code that was formerly well-formed C++23, and makes it ill-formed.
The affected constructs are extremely implausible in Arthur’s opinion; but of course we
need some implementation and usage experience in a real compiler before adopting this proposal.</p>
<pre class="language-cpp highlight"><c- k>struct</c-> <c- nc>C</c-> <c- p>{</c->
  <c- n>C</c-><c- o>&amp;</c-> <c- k>operator</c-><c- o>=</c-><c- p>(</c-><c- k>const</c-> <c- n>C</c-><c- o>&amp;</c-><c- p>)</c-> <c- o>&amp;&amp;</c-> <c- o>=</c-> <c- k>default</c-><c- p>;</c->
    <c- c1>// Today: Well-formed</c->
    <c- c1>// Tomorrow: Deleted</c->
<c- p>};</c->

<c- k>struct</c-> <c- nc>D</c-> <c- p>{</c->
  <c- n>D</c-><c- o>&amp;</c-> <c- k>operator</c-><c- o>=</c-><c- p>(</c-><c- k>this</c-> <c- n>D</c-><c- o>&amp;&amp;</c-> <c- n>self</c-><c- p>,</c-> <c- k>const</c-> <c- n>C</c-><c- o>&amp;</c-><c- p>)</c-> <c- o>=</c-> <c- k>default</c-><c- p>;</c->
    <c- c1>// Today: Well-formed</c->
    <c- c1>// Tomorrow: Deleted</c->
<c- p>};</c->
</pre>
   <h2 class="heading settled" data-level="3" id="experience"><span class="secno">3. </span><span class="content">Implementation experience</span><a class="self-link" href="#experience"></a></h2>
   <p>None yet.</p>
   <h2 class="heading settled" data-level="4" id="wording"><span class="secno">4. </span><span class="content">Proposed wording</span><a class="self-link" href="#wording"></a></h2>
   <h3 class="heading settled" data-level="4.1" id="wording-dcl.fct.def.default"><span class="secno">4.1. </span><span class="content">[dcl.fct.def.default]</span><a class="self-link" href="#wording-dcl.fct.def.default"></a></h3>
   <p class="note" role="note"><span class="marker">Note:</span> The only defaultable special member functions are default constructors,
copy/move constructors, copy/move assignment operators, and destructors. Of these,
only the assignment operators can ever be cvref-qualified at all.</p>
   <p>Modify <a href="https://eel.is/c++draft/dcl.fct.def.default">[dcl.fct.def.default]</a> as follows:</p>
   <p><small></small></p>
   <blockquote><small> 1․ A function definition whose <i>function-body</i> is of the form <code class="highlight"><c- o>=</c-> <c- k>default</c-> <c- p>;</c-></code> is called an <i>explicitly-defaulted</i> definition.
A function that is explicitly defaulted shall<p></p> <ul><li data-md><p>(1.1) be a special member function or a comparison operator function ([over.binary]), and</p> </li><li data-md><p>(1.2) not have default arguments.</p> </li></ul> <p>2․ An explicitly defaulted special member function <code class="highlight"><c- n>F</c-></code><sub>1</sub> is allowed to differ
from the corresponding special member function <code class="highlight"><c- n>F</c-></code><sub>2</sub> that would have been implicitly declared, as follows: </p><ul><li data-md><p>(2.1) <ins>if <code class="highlight"><c- n>F</c-></code><sub>2</sub> is an assignment operator,</ins> <del><code class="highlight"><c- n>F</c-></code><sub>1</sub> and <code class="highlight"><c- n>F</c-></code><sub>2</sub> may have differing <i>ref-qualifiers</i></del> <ins><code class="highlight"><c- n>F</c-></code><sub>1</sub> may have an lvalue <i>ref-qualifier</i></ins>;</p> </li><li data-md><p>(2.2) if <code class="highlight"><c- n>F</c-></code><sub>2</sub> <del>has an implicit object parameter of type “reference to C”</del> <ins>is
an assignment operator with an implicit object parameter of type <code class="highlight"><c- n>C</c-><c- o>&amp;</c-></code></ins>, <code class="highlight"><c- n>F</c-></code><sub>1</sub> may <del>be an explicit object member function whose</del> <ins>have an</ins> explicit
object parameter <del>is</del> of type <del>(possibly
different) “reference to C”</del> <ins><code class="highlight"><c- n>C</c-><c- o>&amp;</c-></code></ins>, in which case the type of <code class="highlight"><c- n>F</c-></code><sub>1</sub> would differ from the type of <code class="highlight"><c- n>F</c-></code><sub>2</sub> in that the type of <code class="highlight"><c- n>F</c-></code><sub>1</sub> has an additional parameter;</p> </li><li data-md><p>(2.3) <code class="highlight"><c- n>F</c-></code><sub>1</sub> and <code class="highlight"><c- n>F</c-></code><sub>2</sub> may have differing exception specifications; and</p> </li><li data-md><p>(2.4) if <code class="highlight"><c- n>F</c-></code><sub>2</sub> has a non-object parameter of type <code class="highlight"><c- k>const</c-> <c- n>C</c-><c- o>&amp;</c-></code>, the corresponding
non-object parameter of <code class="highlight"><c- n>F</c-></code><sub>1</sub> may be of type <code class="highlight"><c- n>C</c-><c- o>&amp;</c-></code>.</p> </li></ul> <p>If the type of <code class="highlight"><c- n>F</c-></code><sub>1</sub> differs from the type of <code class="highlight"><c- n>F</c-></code><sub>2</sub> in a way other than as allowed by the preceding rules, then: </p><ul><li data-md><p>(2.5) if <del><code class="highlight"><c- n>F</c-></code><sub>1</sub></del> <ins><code class="highlight"><c- n>F</c-></code><sub>2</sub></ins> is an assignment operator, and the return type of <code class="highlight"><c- n>F</c-></code><sub>1</sub> differs from the return type of <code class="highlight"><c- n>F</c-></code><sub>2</sub> or <code class="highlight"><c- n>F</c-></code><sub>1</sub>’s non-object parameter type is not a reference, the program is ill-formed;</p> </li><li data-md><p>(2.6) otherwise, if <code class="highlight"><c- n>F</c-></code><sub>1</sub> is explicitly defaulted on its first declaration, it is defined as deleted;</p> </li><li data-md><p>(2.7) otherwise, the program is ill-formed.</p> </li></ul> <p>[...] </p></small></blockquote>
   <h3 class="heading settled" data-level="4.2" id="wording-class.copy.assign"><span class="secno">4.2. </span><span class="content">[class.copy.assign]</span><a class="self-link" href="#wording-class.copy.assign"></a></h3>
   <p class="note" role="note"><span class="marker">Note:</span> If we do the wording patch above, then I think nothing in [class.copy.assign] needs
to change. But much of the wording above is concerned specifically with copy/move assignment operators,
so it might be nice to move that wording out of [dcl.fct.def.default] and into [class.copy.assign].
Also note that right now a difference in <code class="highlight"><c- k>noexcept</c-></code>-ness is handled explicitly by [dcl.fct.def.default]
for special member functions but only by omission-and-note in <a href="https://eel.is/c++draft/class.compare#default-note-1">[class.compare]</a> for comparison operators.</p>
   <p>Modify <a href="https://eel.is/c++draft/class.copy.assign">[class.copy.assign]</a> as follows:</p>
   <p><small></small></p>
   <blockquote><small> TODO FIXME BUG HACK<p></p> </small></blockquote>
   <h2 class="heading settled" data-level="5" id="straw-polls"><span class="secno">5. </span><span class="content">Proposed straw polls</span><a class="self-link" href="#straw-polls"></a></h2>
   <p>The next revision of this paper (if any) will be guided by the outcomes of these two straw polls.</p>
   <table class="def">
    <tbody>
     <tr>
      <th style="width: 70%;">
      <th><strong>SF</strong>
      <th><strong>F</strong>
      <th><strong>N</strong>
      <th><strong>A</strong>
      <th><strong>SA</strong>
     <tr>
      <th><small>EWG would like to forbid rvalue-ref-qualified assignment operators (by any means, not necessarily by this proposed wording).</small>
      <th> – 
      <th> — 
      <th> — 
      <th> — 
      <th> — 
     <tr>
      <th><small>P2953R1 should pursue §2.2’s wording, making some "defaulted-as-deleted" operators into hard errors.</small>
      <th> – 
      <th> — 
      <th> — 
      <th> — 
      <th> — 
   </table>
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  <h2 class="no-num no-ref heading settled" id="references"><span class="content">References</span><a class="self-link" href="#references"></a></h2>
  <h3 class="no-num no-ref heading settled" id="informative"><span class="content">Informative References</span><a class="self-link" href="#informative"></a></h3>
  <dl>
   <dt id="biblio-cwg2586">[CWG2586]
   <dd>Barry Revzin. <a href="https://cplusplus.github.io/CWG/issues/2586.html"><cite>Explicit object parameter for assignment and comparison</cite></a>. May–July 2022. URL: <a href="https://cplusplus.github.io/CWG/issues/2586.html">https://cplusplus.github.io/CWG/issues/2586.html</a>
   <dt id="biblio-p2952">[P2952]
   <dd>Arthur O'Dwyer; Matthew Taylor. <a href="https://www.open-std.org/jtc1/sc22/wg21/docs/papers/2023/p2952r0.html"><cite>auto&amp; operator=(X&amp;&amp;) = default</cite></a>. August 2023. URL: <a href="https://www.open-std.org/jtc1/sc22/wg21/docs/papers/2023/p2952r0.html">https://www.open-std.org/jtc1/sc22/wg21/docs/papers/2023/p2952r0.html</a>
  </dl>