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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 - concepts: constrained member functions illegally instantiated during explicit class template instantiation"
   href="https://bugs.llvm.org/show_bug.cgi?id=45204">45204</a>
          </td>
        </tr>

        <tr>
          <th>Summary</th>
          <td>concepts: constrained member functions illegally instantiated during explicit class template instantiation
          </td>
        </tr>

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

        <tr>
          <th>Version</th>
          <td>10.0
          </td>
        </tr>

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

        <tr>
          <th>OS</th>
          <td>Linux
          </td>
        </tr>

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

        <tr>
          <th>Severity</th>
          <td>normal
          </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>akrzemi1@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>The following correct C++20 program fails to compile in clang.

```
template <typename T>
concept has_a = requires(T v) { v.a(); };

template<typename T>
struct X
{
  void fun(T) {}
  void gun(T v) requires has_a<T> { v.a(); }
};

template struct X<int>; 
```
member function `gun()` is instantiated which is a bug according to
<a href="http://eel.is/c++draft/temp.explicit#11">http://eel.is/c++draft/temp.explicit#11</a>


This works in the old experimental implementation of concepts in Clang by Saar
Raz: <a href="https://godbolt.org/z/K4SaCm">https://godbolt.org/z/K4SaCm</a></pre>
        </div>
      </p>


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