Rollup merge of #99026 - anall:buffix/clippy-9131, r=xFrednet

Add test for and fix rust-lang/rust-clippy#9131

This lint seems to have been broken by #98446 -- but of course, there was no clippy test for this case at the time.

`expr.span.ctxt().outer_expn_data()` now has `MacroKind::Derive` instead of `MacroKind::Attr` for something like:

```
#[derive(Clone, Debug)]
pub struct UnderscoreInStruct {
    _foo: u32,
}
```

---

changelog: none

closes: https://github.com/rust-lang/rust-clippy/issues/9131

1 files changed, 6 insertions, 0 deletions

diff --git a/tests/ui/used_underscore_binding.rs b/tests/ui/used_underscore_binding.rs
index 21d66d5df79..d20977d55d2 100644
--- a/tests/ui/used_underscore_binding.rs
+++ b/tests/ui/used_underscore_binding.rs
@@ -44,6 +44,12 @@ fn in_struct_field() {
     s._underscore_field += 1;
 }
 
+/// Tests that we do not lint if the struct field is used in code created with derive.
+#[derive(Clone, Debug)]
+pub struct UnderscoreInStruct {
+    _foo: u32,
+}
+
 /// Tests that we do not lint if the underscore is not a prefix
 fn non_prefix_underscore(some_foo: u32) -> u32 {
     some_foo + 1