<table border="1" cellspacing="0" cellpadding="8">
    <tr>
        <th>Issue</th>
        <td>
            <a href=https://github.com/llvm/llvm-project/issues/143218>143218</a>
        </td>
    </tr>

    <tr>
        <th>Summary</th>
        <td>
            Wrong linkage and mangling for class-scope lambda expressions
        </td>
    </tr>

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

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

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

<pre>
    C++ allows lambdas to be defined directly in class scope. When this happens, the lambda should have the same linkage as the class, as it would if it appeared in a default argument or default member initializer or function body within the class, and it should be mangled [with the enclosing class as the mangling context](https://github.com/itanium-cxx-abi/cxx-abi/issues/165).

Example:
```c++
template <auto L> struct B {};
struct A { B<[] { return 0; }> b; };
void f(decltype(A::b) x) {}
```
This should result in an external linkage symbol for `f` being emitted. But Clang incorrectly gives the lambda internal linkage and a mangling involving `$_3`, resulting in no definition for `f` being emitted.

GCC appears to have implemented this in version 15 onwards. (In version 14 and before, GCC used internal linkage for the lambda, as Clang does.)
</pre>
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