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    CWG Issue 1892</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="1892"></A><H4>1892.
  
Use of <TT>auto</TT> in function type
</H4>
<B>Section: </B>9.2.9.7&#160; [<A href="https://wg21.link/dcl.spec.auto">dcl.spec.auto</A>]
 &#160;&#160;&#160;

 <B>Status: </B>CD4
 &#160;&#160;&#160;

 <B>Submitter: </B>Richard Smith
 &#160;&#160;&#160;

 <B>Date: </B>2014-03-12<BR>


<P>[Moved to DR at the November, 2014 meeting.]</P>



<P>There appear to be no restrictions against using the <TT>auto</TT>
specifier in examples like the following:</P>

<PRE>
  template&lt;typename T&gt; using X = T;
  X&lt;auto()&gt; f_with_deduced_return_type; //<SPAN CLASS="cmnt"> ok</SPAN>
  std::vector&lt;auto(*)()&gt; v; //<SPAN CLASS="cmnt"> ok?!</SPAN>
  void f(auto (*)()); //<SPAN CLASS="cmnt"> ok?!</SPAN>
</PRE>

<P><B>Proposed resolution (June, 2014):</B></P>

<P>Change 9.2.9.7 [<A href="https://wg21.link/dcl.spec.auto#2">dcl.spec.auto</A>] paragraph 2 as follows:</P>

<BLOCKQUOTE>

The placeholder type can appear with a function declarator in
the <I>decl-specifier-seq</I>, <I>type-specifier-seq</I>,
<I>conversion-function-id</I>, or <I>trailing-return-type</I>, in any
context where such a declarator is valid. If the function declarator
includes a <I>trailing-return-type</I> (9.3.4.6 [<A href="https://wg21.link/dcl.fct">dcl.fct</A>]), that
specifies the declared return type of the function. <INS>Otherwise, the
function declarator shall declare a function.</INS> If the declared return
type of the function contains a placeholder type, the return type of the
function is deduced from return statements in the body of the function, if
any.

</BLOCKQUOTE>

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