<table border="1" cellspacing="0" cellpadding="8">
    <tr>
        <th>Issue</th>
        <td>
            <a href=https://github.com/llvm/llvm-project/issues/96638>96638</a>
        </td>
    </tr>

    <tr>
        <th>Summary</th>
        <td>
            Optimize `decltype(T){}` to `T` in compiler error messages
        </td>
    </tr>

    <tr>
      <th>Labels</th>
      <td>
      </td>
    </tr>

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

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

<pre>
    In many cases clang generates an error like:

```
note: because 'implicitly_convertible(kind_of_<decltype(struct time{{{}}})>{{{}, {}}}, kind_of_<decltype(derived_quantity_spec<power<length, 2>, per<time> >{{{}, {{}}}})>{{{}}})' evaluated to false
```

besides the #88502 issue the `decltype(T){}` also does not help in readability here. The above message could be simplified to:

```
note: because 'implicitly_convertible(kind_of_<struct time>{}, kind_of_<derived_quantity_spec<power<length, 2>, per<time> >>{})' evaluated to false
```

Those two issues would help libraries like mp-units provide users with much easier-to-understand diagnostics.
</pre>
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