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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 - Clang should warn on what appear to be buggy friend declarations"
   href="https://bugs.llvm.org/show_bug.cgi?id=50648">50648</a>
          </td>
        </tr>

        <tr>
          <th>Summary</th>
          <td>Clang should warn on what appear to be buggy friend declarations
          </td>
        </tr>

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

        <tr>
          <th>Version</th>
          <td>unspecified
          </td>
        </tr>

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

        <tr>
          <th>OS</th>
          <td>All
          </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>Frontend
          </td>
        </tr>

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

        <tr>
          <th>Reporter</th>
          <td>rnk@google.com
          </td>
        </tr>

        <tr>
          <th>CC</th>
          <td>llvm-bugs@lists.llvm.org, neeilans@live.com, richard-llvm@metafoo.co.uk
          </td>
        </tr></table>
      <p>
        <div>
        <pre>Consider code like this:

<a href="https://gcc.godbolt.org/z/EEe8xWrzj">https://gcc.godbolt.org/z/EEe8xWrzj</a>

class Bar;
namespace foo {
class Foo {
  friend class Bar; // forward declares ::foo::Bar
  Foo();
  int x;
};
}
class Bar {
  Bar() {}
  foo::Foo m; // error
};

It seems like clang should be able to warn and say, "hey, you probably say
`friend class ::Bar;`".

We accept this code in MSVC mode with a warning, so it shouldn't be too hard to
detect when we would do that and provide a warning in that case:
<a href="https://reviews.llvm.org/D4443">https://reviews.llvm.org/D4443</a>
See `bool FriendSawTagOutsideEnclosingNamespace` in SemaDecl.cpp.</pre>
        </div>
      </p>


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