<HTML>
<HEAD>
<meta http-equiv="Content-Type" content="text/html; charset=us-ascii">
<TITLE>
    CWG Issue 2651</TITLE>
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<STYLE TYPE="text/css">
  INS { text-decoration:none; font-weight:bold; background-color:#A0FFA0 }
  .INS { text-decoration:none; background-color:#D0FFD0 }
  DEL { text-decoration:line-through; background-color:#FFA0A0 }
  .DEL { text-decoration:line-through; background-color: #FFD0D0 }
  @media (prefers-color-scheme: dark) {
    HTML { background-color:#202020; color:#f0f0f0; }
    A { color:#5bc0ff; }
    A:visited { color:#c6a8ff; }
    A:hover, a:focus { color:#afd7ff; }
    INS { background-color:#033a16; color:#aff5b4; }
    .INS { background-color: #033a16; }
    DEL { background-color:#67060c; color:#ffdcd7; }
    .DEL { background-color:#67060c; }
  }
  SPAN.cmnt { font-family:Times; font-style:italic }
</STYLE>
</HEAD>
<BODY>
<P><EM>This is an unofficial snapshot of the ISO/IEC JTC1 SC22 WG21
  Core Issues List revision 118b.
  See http://www.open-std.org/jtc1/sc22/wg21/ for the official
  list.</EM></P>
<P>2025-09-28</P>
<HR>
<A NAME="2651"></A><H4>2651.
  
Conversion function templates and "noexcept"
</H4>
<B>Section: </B>13.10.3.4&#160; [<A href="https://wg21.link/temp.deduct.conv">temp.deduct.conv</A>]
 &#160;&#160;&#160;

 <B>Status: </B>C++23
 &#160;&#160;&#160;

 <B>Submitter: </B>US
 &#160;&#160;&#160;

 <B>Date: </B>2022-11-03<BR><BR>


<A href="http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2022/p2720r0.pdf#US29-069">P2720R0 comment
  US&#160;29-069<BR></A>

<P>[Accepted as a DR at the November, 2022 meeting.]</P>

<P>The rule in 13.10.3.4 [<A href="https://wg21.link/temp.deduct.conv#5.2">temp.deduct.conv</A>] bullet 5.2 seems to allow</P>

<PRE>
template&lt;class T,bool B&gt;
using get=T(*)() noexcept(B);

struct A {
 template&lt;class T&gt;
 operator get&lt;T,false&gt;() const;
};

auto *p=A().operator get&lt;int,true&gt;();
</PRE>

<P><B>Proposed resolution (approved by CWG 2022-11-09):</B></P>

<P>Change in 13.10.3.4 [<A href="https://wg21.link/temp.deduct.conv#1">temp.deduct.conv</A>] paragraph 1 as follows:</P>

<BLOCKQUOTE>
... If the <I>conversion-function-id</I> is constructed during overload
resolution ([over.match.funcs]), the <DEL>following transformations</DEL>
<INS>rules in the remainder of this subclause</INS> apply.
</BLOCKQUOTE>

<P>Change in 13.10.3.4 [<A href="https://wg21.link/temp.deduct.conv#5.2">temp.deduct.conv</A>] bullet 5.2 as follows:</P>

<BLOCKQUOTE>

However, certain attributes of A may be ignored:

<UL>
<LI>...</LI>

<LI>If the original A is a function pointer or
pointer-to-member-function type <INS>with a potentially-throwing exception
specification (14.5 [<A href="https://wg21.link/except.spec">except.spec</A>])</INS>, <DEL>its
noexcept</DEL> <INS>the exception specification</INS>.</LI>

<LI>...</LI>

</UL>

</BLOCKQUOTE>

<BR><BR>
</BODY>
</HTML>
