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    CWG Issue 2506</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="2506"></A><H4>2506.
  
Structured bindings and array cv-qualifiers
</H4>
<B>Section: </B>9.7&#160; [<A href="https://wg21.link/dcl.struct.bind">dcl.struct.bind</A>]
 &#160;&#160;&#160;

 <B>Status: </B>CD6
 &#160;&#160;&#160;

 <B>Submitter: </B>Barry Revzin
 &#160;&#160;&#160;

 <B>Date: </B>2018-12-11<BR>


<P>[Accepted at the February, 2022 meeting.]</P>



<P>According to 9.7 [<A href="https://wg21.link/dcl.struct.bind#1">dcl.struct.bind</A>] paragraph 1,</P>

<BLOCKQUOTE>

<P>A structured binding declaration introduces the
identifiers <TT>v<SUB>0</SUB></TT>, <TT>v<SUB>1</SUB></TT>,
<TT>v<SUB>2</SUB></TT>, ... of the <I>identifier-list</I> as
names of <I>structured bindings</I>. Let <I>cv</I> denote
the <I>cv-qualifier</I>s in the <I>decl-specifier-seq</I>
and <I>S</I> consist of the <I>storage-class-specifier</I>s
of the <I>decl-specifier-seq</I> (if any). A <I>cv</I> that
includes volatile is deprecated; see
D.4 [<A href="https://wg21.link/depr.volatile.type">depr.volatile.type</A>]. First, a variable with a unique
name <I>e</I> is introduced. If
the <I>assignment-expression</I> in the initializer has
array type <TT>A</TT> and no <I>ref-qualifier</I> is
present, <I>e</I> is defined by</P>

<UL>
<I>attribute-specifier-seq<SUB>opt</SUB> S cv</I> <TT>A</TT> <I>e</I> <TT>;</TT>
</UL>

<P>and each element is copy-initialized or direct-initialized
from the corresponding element of
the <I>assignment-expression</I> as specified by the form of
the initializer.</P>

</BLOCKQUOTE>

<P>This means that in an example like</P>

<PRE>
  const int arr[1]{};
  auto [i] = arr;
</PRE>

<P>
<TT>i</TT> is a reference to <TT>const int</TT>. Presumably
the fact that the array is copied should drop the array's
cv-qualification.</P>

<P><B>Proposed resolution (December, 2021):</B></P>

<P>Change 9.7 [<A href="https://wg21.link/dcl.struct.bind#1">dcl.struct.bind</A>] paragraph 1 as follows:</P>

<BLOCKQUOTE>

<P>If the <I>assignment-expression</I> in the initializer
has array type <INS><I>cv1</I></INS> <TT>A</TT> and
no <I>ref-qualifier</I> is present, <I>e</I> is defined
by...</P>

</BLOCKQUOTE>

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