<table border="1" cellspacing="0" cellpadding="8">
    <tr>
        <th>Issue</th>
        <td>
            <a href=https://github.com/llvm/llvm-project/issues/115347>115347</a>
        </td>
    </tr>

    <tr>
        <th>Summary</th>
        <td>
            Unsafe buffer usage: constructing [[clang::unsafe_buffer_usage]] fields are not warned on
        </td>
    </tr>

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

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

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

<pre>
    Similar to https://github.com/llvm/llvm-project/issues/80482 but splitting this off as it's about fields annotated with `[[clang::unsafe_buffer_usage]]`.

Godbolt example: https://godbolt.org/z/9v9EsPej6
```cc
struct S {
 [[clang::unsafe_buffer_usage]] int i;
};

class C {
public:
 C() : i(1) {}  // no error?
    C(int j) : i(j) {}  // no error?
private:
    [[clang::unsafe_buffer_usage]] int i;
};

int main(){
    S s = { .i = 1 };  // no error?
    s.i = 2;  // error ^_^b
    S s2(1);  // no error?
    C c;
    C c2(1);
}
```

In the above example only `s.i = 2` causes an unsafe-buffer-usage warning. Constructing a type with `[[unsafe_buffer_usage]]` fields does not produce any warning.

cc: @haoNoQ @ziqingluo-90
</pre>
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