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    <head>
      <base href="https://bugs.llvm.org/">
    </head>
    <body><table border="1" cellspacing="0" cellpadding="8">
        <tr>
          <th>Bug ID</th>
          <td><a class="bz_bug_link 
          bz_status_NEW "
   title="NEW - Rewritten comparison expression is not checked for SFINAE"
   href="https://bugs.llvm.org/show_bug.cgi?id=47893">47893</a>
          </td>
        </tr>

        <tr>
          <th>Summary</th>
          <td>Rewritten comparison expression is not checked for SFINAE
          </td>
        </tr>

        <tr>
          <th>Product</th>
          <td>clang
          </td>
        </tr>

        <tr>
          <th>Version</th>
          <td>trunk
          </td>
        </tr>

        <tr>
          <th>Hardware</th>
          <td>PC
          </td>
        </tr>

        <tr>
          <th>OS</th>
          <td>Windows NT
          </td>
        </tr>

        <tr>
          <th>Status</th>
          <td>NEW
          </td>
        </tr>

        <tr>
          <th>Severity</th>
          <td>enhancement
          </td>
        </tr>

        <tr>
          <th>Priority</th>
          <td>P
          </td>
        </tr>

        <tr>
          <th>Component</th>
          <td>C++2a
          </td>
        </tr>

        <tr>
          <th>Assignee</th>
          <td>unassignedclangbugs@nondot.org
          </td>
        </tr>

        <tr>
          <th>Reporter</th>
          <td>igor.akhmetov@gmail.com
          </td>
        </tr>

        <tr>
          <th>CC</th>
          <td>blitzrakete@gmail.com, erik.pilkington@gmail.com, llvm-bugs@lists.llvm.org, richard-llvm@metafoo.co.uk
          </td>
        </tr></table>
      <p>
        <div>
        <pre><a href="https://gcc.godbolt.org/z/zsbc1Y">https://gcc.godbolt.org/z/zsbc1Y</a>
Clang fails to substitute foo here, while it should have picked the second
overload because of SFINAE:

#include <compare>

struct X
{
    void operator <=>(X const &) const {}
};

template<typename T, typename = decltype(T{} < T{})>
void foo(T t) {}

template<typename>
void foo(...);

void test()
{
    foo<X>(X{});
}</pre>
        </div>
      </p>


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