<table border="1" cellspacing="0" cellpadding="8">
    <tr>
        <th>Issue</th>
        <td>
            <a href=https://github.com/llvm/llvm-project/issues/140483>140483</a>
        </td>
    </tr>

    <tr>
        <th>Summary</th>
        <td>
            [Clang] `-Wdangling` does not emit warning when a dangerous call invoked in STL
        </td>
    </tr>

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

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

    <tr>
      <th>Reporter</th>
      <td>
          denzor200
      </td>
    </tr>
</table>

<pre>
    Please be patient reading all examples below - root of the evil hidden in the fact that `std::pair<const A, B>` not the same as `std::pair<A, B>` but the first one might be implicitly converted to the second one. Such implicit conversion might lead to hidden UB if not carefully coded.

Assume we have a `proj` lambda like this:
```
const auto proj = 
        [](const std::pair<std::string, int>& node [[clang::lifetimebound]])
         -> const std::pair<std::string, int>& {
            return node;
 };
```

Let's call this lambda directly by creating the problem with dangling reference artifically:
```
std::pair<const std::string, int> aa;
const auto& a = proj(aa);
```
Then we will watch `warning: temporary bound to local reference 'a' will be destroyed at the end of the full-expression [-Wdangling]` emited - that's fine.

Now let's create conditions under which the function will be called outside of user code, but the problem with the dangling reference will still be relevant:
```
std::map<std::string, int> counters = { {"hello", 5}, {"world", 5} };
for (const auto& node : counters | std::views::transform(proj)) {
    (void)node; // dangling
}
```

And here we will not see that warning emited - that's the problem that I am creating this issue about and which should be fixed.

The full snippet here: https://godbolt.org/z/1Yaj1s6Wf


</pre>
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