<table border="1" cellspacing="0" cellpadding="8">
    <tr>
        <th>Issue</th>
        <td>
            <a href=https://github.com/llvm/llvm-project/issues/55962>55962</a>
        </td>
    </tr>

    <tr>
        <th>Summary</th>
        <td>
            [Clang] Poor diagnostics for use of a template class without providing parameters in some contexts
        </td>
    </tr>

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

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

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

<pre>
    [Godbolt](https://godbolt.org/z/Y4YY6Gj5W)

```
template <typename T>
struct x;

template <typename T>
constexpr int y = x::a; // Clang diagnostic doesn't mention that `x` is a template.

using z = x; // Clang diagnostic mentions that `x` is a template.
```

In the definition of `y`, Clang complains that `x` isn't a "class, namespace, or enumeration", but fails to mention that it is a class template and no template parameters have been provided.

In other simpler contexts, such as the definition of the using alias `y`, Clang does explain that `x` is a class template and template parameters need to be provided.

We should improve the quality of the diagnostic for the `y` case - it should explain that `x` is a class template and template parameters are missing.

</pre>
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