<html>
    <head>
      <base href="http://llvm.org/bugs/" />
    </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 --- - bad diagnostic on conflicting forward declaration"
   href="http://llvm.org/bugs/show_bug.cgi?id=19216">19216</a>
          </td>
        </tr>

        <tr>
          <th>Summary</th>
          <td>bad diagnostic on conflicting forward declaration
          </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>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++
          </td>
        </tr>

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

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

        <tr>
          <th>CC</th>
          <td>dgregor@apple.com, llvmbugs@cs.uiuc.edu
          </td>
        </tr>

        <tr>
          <th>Classification</th>
          <td>Unclassified
          </td>
        </tr></table>
      <p>
        <div>
        <pre>This has a great diagnostic:

namespace llvm {
  struct StringRef {};
}
namespace clang {
  struct StringRef;
  using llvm::StringRef;

  void f(StringRef sr);
}

x.cc:6:15: error: target of using declaration conflicts with declaration
already
      in scope
  using llvm::StringRef;
              ^
x.cc:2:10: note: target of using declaration
  struct StringRef {};
         ^
x.cc:5:10: note: conflicting declaration
  struct StringRef;
         ^
1 error generated.

We should do something like that when we have a forward declaration that
conflicts with a using declaration. Here's what we get instead:

x.cc:8:10: error: reference to 'StringRef' is ambiguous
  void f(StringRef sr);
         ^
x.cc:6:10: note: candidate found by name lookup is 'clang::StringRef'
  struct StringRef;
         ^
x.cc:5:15: note: candidate found by name lookup is 'clang::StringRef'
  using llvm::StringRef;
              ^
1 error generated.

That's confusing.</pre>
        </div>
      </p>
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