<table border="1" cellspacing="0" cellpadding="8">
    <tr>
        <th>Issue</th>
        <td>
            <a href=https://github.com/llvm/llvm-project/issues/94764>94764</a>
        </td>
    </tr>

    <tr>
        <th>Summary</th>
        <td>
            Improve error message for invalid lambda captures
        </td>
    </tr>

    <tr>
      <th>Labels</th>
      <td>
            clang:diagnostics
      </td>
    </tr>

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

    <tr>
      <th>Reporter</th>
      <td>
          ilya-biryukov
      </td>
    </tr>
</table>

<pre>
    For the following code (https://gcc.godbolt.org/z/GGoWq45hs) Clang produces an error message that some people find confusing:
```cpp
struct X {
 int x;
    void foo() {
        [x](){};
    }
};
// <source>:4:10: error: 'x' in capture list does not name a variable
```

It seems that the error message could indeed be improved, a few ideas that come to mind:
- mentioning what kind of symbol we are actually referring to: `'class member 'x' cannot appear in capture list as it is not a variable'`
- we could suggest fixes in some situations `did you mean to capture 'this'?` or `did you mean to use a capture with initializer?`
- `variable` is technically correct and what Clang is using, but maybe it would be better to say`local variable or parameter`? I might be missing some cases, but it sounds more user-friendly than the [similar error](https://gcc.godbolt.org/z/q7aen8azc) about "automatic storage duration` that we have today: 
```
<source>:4:10: error: 'x' cannot be captured because it does not have automatic storage duration
```
</pre>
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