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    CWG Issue 2199</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="2199"></A><H4>2199.
  
Typedefs and tags
</H4>
<B>Section: </B>9.2.4&#160; [<A href="https://wg21.link/dcl.typedef">dcl.typedef</A>]
 &#160;&#160;&#160;

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

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

 <B>Date: </B>2015-11-12<BR>


<P>[Accepted at the November, 2020 meeting as part of paper P1787R6 and
moved to DR at the February, 2021 meeting.]</P>



<P>It is still unclear how typedefs
and <I>elaborated-type-specifier</I>s interact in some cases.
For example:</P>

<PRE>
    namespace A {
      struct S {};
    }
    namespace B {
      typedef int S;
    }
    namespace C {
      using namespace A;
      using namespace B;
      struct S s; //<SPAN CLASS="cmnt"> clearly ambiguous, </SPAN>S<SPAN CLASS="cmnt"> names different entities</SPAN>
    }
    namespace D {
      using A::S;
      typedef struct S S;
      struct S s; //<SPAN CLASS="cmnt"> OK under <A HREF="407.html">issue 407</A>: </SPAN>S<SPAN CLASS="cmnt"> could be used in an</SPAN>
                  //<SPAN CLASS="cmnt">  elaborated-type-specifier before the typedef, so still can be</SPAN>
    }
    namespace E {
      typedef A::S S;
      using A::S;
      struct S s; //<SPAN CLASS="cmnt"> ??? the identifier </SPAN>S<SPAN CLASS="cmnt"> could not have been used in an</SPAN>
                  //<SPAN CLASS="cmnt"> elaborated-type-specifier prior to the typedef, so is this lookup</SPAN>
                  //<SPAN CLASS="cmnt"> ill-formed because it finds a typedef-name?</SPAN>
    }
    namespace F {
      typedef A::S S;
    }
    namespace G {
      using namespace A;
      using namespace F;
      struct S s; //<SPAN CLASS="cmnt"> ??? </SPAN>F::S<SPAN CLASS="cmnt"> could not have been used as an</SPAN>
                  //<SPAN CLASS="cmnt"> elaborated-type-specifier before the typedef. is this ill-formed because</SPAN>
                  //<SPAN CLASS="cmnt"> the lookup finds a typedef-name?</SPAN>
    }
    namespace H {
      using namespace F;
      using namespace A;
      struct S s; //<SPAN CLASS="cmnt"> some implementations give different answers for </SPAN>G<SPAN CLASS="cmnt"> and </SPAN>H
    }
</PRE>

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