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    <body><span class="vcard"><a class="email" href="mailto:richard-llvm@metafoo.co.uk" title="Richard Smith <richard-llvm@metafoo.co.uk>"> <span class="fn">Richard Smith</span></a>
</span> changed
          <a class="bz_bug_link 
          bz_status_RESOLVED  bz_closed"
   title="RESOLVED INVALID - "too many template arguments for class template" disallows sensible empty-parameter-pack instantiation"
   href="https://bugs.llvm.org/show_bug.cgi?id=38431">bug 38431</a>
          <br>
             <table border="1" cellspacing="0" cellpadding="8">
          <tr>
            <th>What</th>
            <th>Removed</th>
            <th>Added</th>
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         <tr>
           <td style="text-align:right;">CC</td>
           <td>
                
           </td>
           <td>richard-llvm@metafoo.co.uk
           </td>
         </tr>

         <tr>
           <td style="text-align:right;">Status</td>
           <td>NEW
           </td>
           <td>RESOLVED
           </td>
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           <td style="text-align:right;">Resolution</td>
           <td>---
           </td>
           <td>INVALID
           </td>
         </tr></table>
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        <div>
            <b><a class="bz_bug_link 
          bz_status_RESOLVED  bz_closed"
   title="RESOLVED INVALID - "too many template arguments for class template" disallows sensible empty-parameter-pack instantiation"
   href="https://bugs.llvm.org/show_bug.cgi?id=38431#c1">Comment # 1</a>
              on <a class="bz_bug_link 
          bz_status_RESOLVED  bz_closed"
   title="RESOLVED INVALID - "too many template arguments for class template" disallows sensible empty-parameter-pack instantiation"
   href="https://bugs.llvm.org/show_bug.cgi?id=38431">bug 38431</a>
              from <span class="vcard"><a class="email" href="mailto:richard-llvm@metafoo.co.uk" title="Richard Smith <richard-llvm@metafoo.co.uk>"> <span class="fn">Richard Smith</span></a>
</span></b>
        <pre>(In reply to tonyelewis from <a href="show_bug.cgi?id=38431#c0">comment #0</a>)
<span class="quote">> I'm guessing that this
> code is valid because f() and A can be reasonably instantiated with an empty
> parameter pack</span >

Your guess turns out to be incorrect. See <a href="http://eel.is/c++draft/temp#res-8.3">http://eel.is/c++draft/temp#res-8.3</a>:

"The program is ill-formed, no diagnostic required, if [...] every valid
specialization of a variadic template requires an empty template parameter
pack"

So Clang is correct to diagnose this. (And the other compilers are correct to
accept it if they so choose.)</pre>
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