<table border="1" cellspacing="0" cellpadding="8">
    <tr>
        <th>Issue</th>
        <td>
            <a href=https://github.com/llvm/llvm-project/issues/62880>62880</a>
        </td>
    </tr>

    <tr>
        <th>Summary</th>
        <td>
            [c++20] Clang doesn't show an error for defaulted comparison operators with mixed parameters
        </td>
    </tr>

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

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

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

<pre>
    By the standard both parameters of a defaulted comparison operator for a class `C` should be either of type `const C&` or type `C` but not mixed, see https://eel.is/c++draft/class.compare.default#1.

However, Clang accepts the following example which is declined by GCC and MSCV:

```
#include <compare>

template <class C>
struct Bar {
  C i;
  friend bool operator==(const Bar&, Bar) = default;
};
```

See https://gcc.godbolt.org/z/M7Y9qGrsE

Note that an error is printed if it is class without a template https://gcc.godbolt.org/z/4sb5hMn3M
</pre>
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