Auto merge of #34654 - jseyfried:configure_multi_modified, r=nrc

Perform `cfg` attribute processing on `MultiModifier`-generated items

Fixes https://users.rust-lang.org/t/unused-attribute-warning-for-custom-derive-attribute/6180.
r? @nrc

1 files changed, 5 insertions, 1 deletions

diff --git a/src/libsyntax/ext/expand.rs b/src/libsyntax/ext/expand.rs
index c670283e559..877293bac54 100644
--- a/src/libsyntax/ext/expand.rs
+++ b/src/libsyntax/ext/expand.rs
@@ -769,7 +769,11 @@ fn expand_annotatable(mut item: Annotatable, fld: &mut MacroExpander) -> SmallVe
             };
 
             fld.cx.bt_pop();
-            modified.into_iter().flat_map(|it| expand_annotatable(it, fld)).collect()
+            let configured = modified.into_iter().flat_map(|it| {
+                it.fold_with(&mut fld.strip_unconfigured())
+            }).collect::<SmallVector<_>>();
+
+            configured.into_iter().flat_map(|it| expand_annotatable(it, fld)).collect()
         }
     }
 }