<table border="1" cellspacing="0" cellpadding="8">
    <tr>
        <th>Issue</th>
        <td>
            <a href=https://github.com/llvm/llvm-project/issues/77583>77583</a>
        </td>
    </tr>

    <tr>
        <th>Summary</th>
        <td>
            conversion function depended on template cannot be rebuild during instantiating class
        </td>
    </tr>

    <tr>
      <th>Labels</th>
      <td>
            new issue
      </td>
    </tr>

    <tr>
      <th>Assignees</th>
      <td>
      </td>
    </tr>

    <tr>
      <th>Reporter</th>
      <td>
          HerrCai0907
      </td>
    </tr>
</table>

<pre>
    part of #76837

https://godbolt.org/z/Wba7qdYM9
```
struct a {
 operator int();
};

template <typename A> struct b {
  template <typename B> using C = decltype(A{}.operator B());
};

b<a> v{};
```
</pre>
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