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    CWG Issue 2760</TITLE>
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<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="2760"></A><H4>2760.
  
Defaulted constructor that is an immediate function
</H4>
<B>Section: </B>7.7&#160; [<A href="https://wg21.link/expr.const">expr.const</A>]
 &#160;&#160;&#160;

 <B>Status: </B>CD7
 &#160;&#160;&#160;

 <B>Submitter: </B>Corentin Jabot
 &#160;&#160;&#160;

 <B>Date: </B>2023-07-08<BR>


<P>[Accepted as a DR at the November, 2023 meeting.]</P>

<P>Consider:</P>

<PRE>
  consteval int f(int);
  struct S {
   int x = f(0);
   S() = default;
  };

  int main() {
    S s;     //<SPAN CLASS="cmnt"> OK?</SPAN>
  }
</PRE>

<P>Is <TT>S</TT> an immediate function?</P>

<P>The relevant specification is in 7.7 [<A href="https://wg21.link/expr.const#18">expr.const</A>] paragraph 18:</P>

<BLOCKQUOTE>

An immediate function is a function or constructor that is
<UL>
<LI>declared with the <TT>consteval</TT> specifier, or</LI>
<LI>an immediate-escalating function F whose function body contains an
immediate-escalating expression E such that E's innermost enclosing
non-block scope is F's function parameter scope.</LI>
</UL>

</BLOCKQUOTE>

<P><U>Suggested resolution [SUPERSEDED]:</U></P>

<P>Change in 7.7 [<A href="https://wg21.link/expr.const#18">expr.const</A>] paragraph 18 as follows:</P>

<BLOCKQUOTE>

An immediate function is a function or constructor that is
<UL>
<LI>declared with the <TT>consteval</TT> specifier, or</LI>
<LI>an immediate-escalating function F whose function body contains an
immediate-escalating expression E such that E's innermost enclosing
non-block scope is F's function parameter scope<INS>, or</INS>
</LI>
<LI class="ins">an immediate-escalating default constructor of a class
which has at least one non-static data member with an
immediate-escalating default member initializer.</LI>
</UL>

</BLOCKQUOTE>

<P><B>Proposed resolution (approved by CWG 2023-08-25):</B></P>

<OL>
<LI>
<P>Change in 7.7 [<A href="https://wg21.link/expr.const#18">expr.const</A>] paragraph 18 as follows:</P>

<BLOCKQUOTE>

An immediate function is a function or constructor that is
<UL>
<LI>declared with the <TT>consteval</TT> specifier, or</LI>
<LI>an immediate-escalating function F whose function body contains an
immediate-escalating expression E such that E's innermost enclosing
non-block scope is F's function parameter scope.
<INS>[ Note: Default member initializers used to initialize a base or
member subobject (11.9.3 [<A href="https://wg21.link/class.base.init">class.base.init</A>]) are considered to be
part of the function body (9.6.1 [<A href="https://wg21.link/dcl.fct.def.general">dcl.fct.def.general</A>]). -- end note
]</INS>
</LI>
</UL>

</BLOCKQUOTE>
</LI>

<LI>
<P>Change in 9.6.1 [<A href="https://wg21.link/dcl.fct.def.general#1">dcl.fct.def.general</A>] paragraph 1 as follows:</P>

<BLOCKQUOTE>

Any informal reference to the body of a function should be interpreted
as a reference to the non-terminal <I>function-body</I><INS>,
including, for a constructor, default member initializers or default
initialization used to initialize a base or member subobject in the
absence of a <I>mem-initializer-id</I>
(11.9.3 [<A href="https://wg21.link/class.base.init">class.base.init</A>])</INS>.

</BLOCKQUOTE>
</LI>

</OL>

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